Chabris, C.F., & Simons, D.J. (2010). The Invisible Gorilla, and Other Ways Our Intuitions Deceive Us. New York: Crown. Book website
My Google Scholar Profile
The largest reported sex difference in human cognition is found on mental rotation tests,
which ask participants to compare pictures of three-dimensional objects and decide whether they
depict the same or different objects. When the objects are the same, one can be rotated two- or
three-dimensionally to match the other. Across cultures, males score up to one standard deviation
higher than females on these tests. We administered two mental rotation tests to 123 participants
and found that these higher scores likely do not reflect superiority in the process of mental
rotation per se, but rather in other aspects of task performance. We found: (1) men are more
likely than women to answer correctly when two objects are different, whereas women are more
likely to answer incorrectly that they are the same; and (2) individual differences in confidence
explain a considerable portion of the male advantage, but differences in spatial encoding ability
do not. These results suggest more attention should be paid to individual differences in the
various components of spatial ability and task performance, and have implications for
evolutionary theories of sex differences in spatial cognition and for efforts to reduce sex
differences in spatial ability, especially via training interventions.
Hart, J.J., & Chabris, C.F. (2016). Does a "triple package" of traits predict success?
Personality and Individual Differences, 94, 216-222.
PDF file of
What individual factors predict success? We tested Chua and Rubenfeld's (2014) widely publicized "Triple Package" hypothesis that a tendency toward impulse control, personal insecurity, and a belief in the superiority of one's cultural or ethnic group combine to increase the odds that individuals will attain exceptional achievement. Consistent with previous research, we found in two sizable samples (combined N=1258) that parents' level of education and individuals' own cognitive ability robustly predicted a composite measure of success that included income, education, and awards. Other factors such as impulse control and emotional stability also appeared to be salutary. But despite measuring personal insecurity in four different ways and measuring success in three different ways, we did not find support for any plausible version of Chua and Rubenfeld's proposed synergistic trinity of success-engendering personality traits.
Chabris, C.F.,* Lee, J.J.,* Cesarini, D., Benjamin, D.J., & Laibson, D.I. (2015). The Fourth Law of Behavior Genetics.
Current Directions in Psychological Science, 24(4), 304-312. [*These authors contributed equally to the work.] Article online at SAGE (open-access)
Behavior genetics is the study of the relationship between genetic variation and psychological traits. Turkheimer (2000) proposed "Three Laws of Behavior Genetics" based on empirical regularities observed in studies of twins and other kinships. On the basis of molecular studies that have measured DNA variation directly, we propose a Fourth Law of Behavior Genetics: "A typical human behavioral trait is associated with very many genetic variants, each of which accounts for a very small percentage of the behavioral variability." This law explains several consistent patterns in the results of gene-discovery studies, including the failure of candidate-gene studies to robustly replicate, the need for genome-wide association studies (and why such studies have a much stronger replication record), and the crucial importance of extremely large samples in these endeavors. We review the evidence in favor of the Fourth Law and discuss its implications for the design and interpretation of gene-behavior research.
Chabris, C.F. (2013). The Goliath of nonfiction. [Review of the book
David and Goliath: Underdogs, misfits, and the art of battling giants by Malcolm Gladwell.]
Wall Street Journal, 28 September.
Article online at wsj.com | PDF file of review | Followup blog post
Chabris, C.F., Lee, J.J., Benjamin, D.J., Beauchamp, J.P., Glaeser, E.L., Borst, G., Pinker, S., & Laibson, D.I. (2013). Why it is hard to find genes associated with social science traits: Theoretical and empirical considerations. American Journal of Public Health, 103(S1), S152-S166. PDF file of article | PDF file of supplemental material
Objectives. We explain why traits of interest to behavioral scientists may have
a genetic architecture featuring hundreds or thousands of loci with tiny individual
effects rather than a few with large effects and why such an architecture
makes it difficult to find robust associations between traits and genes.
Methods. We conducted a genome-wide association study at 2 sites, Harvard
University and Union College, measuring more than 100 physical and behavioral
traits with a sample size typical of candidate gene studies. We evaluated
predictions that alleles with large effect sizes would be rare and most traits of
interest to social science are likely characterized by a lack of strong directional
selection. We also carried out a theoretical analysis of the genetic architecture of
traits based on R.A. Fisher’s geometric model of natural selection and empirical
analyses of the effects of selection bias and phenotype measurement stability on
the results of genetic association studies.
Results. Although we replicated several known genetic associations with
physical traits, we found only 2 associations with behavioral traits that met the
nominal genome-wide significance threshold, indicating that physical and
behavioral traits are mainly affected by numerous genes with small effects.
Conclusions. The challenge for social science genomics is the likelihood that
genes are connected to behavioral variation by lengthy, nonlinear, interactive
causal chains, and unraveling these chains requires allying with personal
genomics to take advantage of the potential for large sample sizes as well as
continuing with traditional epidemiological studies.
Chabris, C.F., Hebert, B.M., Benjamin, D.J., Beauchamp, J.P., Cesarini,
D., van der Loos, M.J.H.M., Johannesson, M., Magnusson, P.K.E.,
Lichtenstein, P., Atwood, C.S., Freese, J., Hauser, T.S., Hauser, R.M.,
Christakis, N.A., & Laibson, D. (2012). Most reported genetic
associations with general intelligence are probably false positives.
Psychological Science, 23(11), 1314-1323. PDF file of
article | PDF file of
General intelligence (g) and virtually all other behavioral traits are
heritable. Associations between g and specific single-nucleotide
polymorphisms (SNPs) in several candidate genes involved in brain function
have been reported. We sought to replicate published associations between
g and 12 specific genetic variants (in the genes DTNBP1, CTSD, DRD2, ANKK1,
CHRM2, SSADH, COMT, BDNF, CHRNA4, DISC1, APOE, and SNAP25) using data sets from
independent, well-characterized, longitudinal studies with samples of 5571,
1759, and 2441
individuals. Of 32 independent tests across all three datasets, only one
was nominally significant. By contrast, power
analyses showed that we should have expected 10 to 15 significant
associations, given reasonable assumptions for genotype effect sizes. For
positive controls, we confirmed accepted genetic associations for
Alzheimer's disease and body mass index, and we used SNP-based
calculations of genetic relatedness to replicate previous estimates that about
half of the variance in g
is accounted for by common genetic variation among individuals. We
conclude that the
molecular genetics of psychology and social science requires approaches that go
beyond the examination of candidate genes.
Simons, D.J., & Chabris, C.F. (2012). Do our gadgets really threaten
planes? The Wall Street Journal, 8 September.
online at wsj.com
Chabris, C.F., & Simons, D.J. (2012). Why we should scam the scammers. The Wall Street Journal, 3 August. Article online at wsj.com
Chabris, C.F. (2012). Go ahead, think it over. [Review of the book Wait: The Art and Science of Delay by Frank Partnoy.] The Wall Street Journal, 22 June. Article online at wsj.com
Chabris, C.F. (2012). Boggle the mind. [Review of the book Imagine: How Creativity Works by Jonah Lehrer.] The New York Times, 13 May. Article online at nytimes.com | Reply by Jonah Lehrer at wired.com | My rebuttal to Lehrer's reply (PDF) | Jonah Lehrer Interviews Christopher Chabris
Benjamin, D.J., Cesarini, D., Chabris, C.F., Glaeser, E.L., Laibson, D.I., Gudnason, V., Harris, T.B., Launer, L.J., Purcell, S., Smith, A.V., Johannesson, M., Magnusson, P.K.E., Beauchamp, J.P., Christakis, N.A., Atwood, C.S., Hebert, B., Freese, J., Hauser, R.M., Hauser, T.S., Grankvist, A., Hultman, C., & Lichtenstein, P. (2012). The promises and pitfalls of genoeconomics. Annual Review of Economics, 4, 627-662. PDF file of article
This article reviews existing research at the intersection of genetics and
economics, presents some new findings that illustrate the state of
genoeconomics research, and surveys the prospects of this emerging
field. Twin studies suggest that economic outcomes and preferences, once
corrected for measurement error, appear to be about as heritable as many
medical conditions and personality traits. Consistent with this pattern,
we present new evidence on the heritability of permanent income and
wealth. Turning to genetic association studies, we survey the main ways
that direct measurement of genetic variation across individuals is likely
to contribute to economics, and we outline the challenges that have slowed
progress in making these contributions. The most urgent problem facing
researchers in this field is that most existing efforts to find
associations between genetic variation and economic behavior are based on
samples that are too small to ensure adequate statistical power. This has
led to many false positives in the literature. We suggest a number of
possible strategies to improve power and remedy this problem: (a)
pooling datasets; (b) using statistical techniques that exploit the
greater information content of many genes considered jointly; and (c)
focusing on economically-relevant traits that are most proximate to known
Benjamin, D.J., Cesarini, D., van der Loos, M.J.H.M., Dawes, C.T.,
Koellinger, P.D., Magnusson, P.K.E., Chabris, C.F., Conley, D., Laibson,
D., & Johannesson, M., & Visscher, P.M. (2012). The genetic architecture
of economic and political preferences. Proceedings of the National
of Sciences, 109(21), 8026-8031.
Article online at PNAS
Preferences are fundamental building blocks in all models of economic and
political behavior. We study a new sample of comprehensively genotyped
subjects with data on economic and political preferences and educational
attainment. We use dense single nucleotide polymorphism (SNP) data to
estimate the proportion of variation in these traits explained by common
SNPs and to conduct genome-wide association study (GWAS) and prediction
analyses. The pattern of results is consistent with findings for other
complex traits. First, the estimated fraction of phenotypic variation that
could, in principle, be explained by dense SNP arrays is around one-half
of the narrow heritability estimated using twin and family samples. The
molecular-genetic–based heritability estimates, therefore, partially
corroborate evidence of significant heritability from behavior genetic
studies. Second, our analyses suggest that these traits have a polygenic
architecture, with the heritable variation explained by many genes with
small effects. Our results suggest that most published genetic association
studies with economic and political traits are dramatically underpowered,
which implies a high false discovery rate. These results convey a
cautionary message for whether, how, and how soon molecular genetic data
can contribute to, and potentially transform, research in social science.
We propose some constructive responses to the inferential challenges posed
by the small explanatory power of individual SNPs.
Germine, L., Nakayama, K., Duchaine, B.C., Chabris, C.F., Chatterjee, G., &
Wilmer, J.B. (2012). Is the Web as good as the lab? Comparable performance from
Web and lab in cognitive/perceptual experiments. Psychonomic Bulletin and
Review, 19(5), 847-857.
PDF file of article
With the increasing sophistication and ubiquity of the Internet, behavioral
research is on the cusp of a revolution that will do for population sampling what
the computer did for stimulus control and measurement. It remains a common
assumption, however, that data from self-selected Web samples must involve a
trade-off between participant numbers and data quality. Concerns about data
quality are heightened for performance-based cognitive and perceptual measures,
particularly those that are timed or that involve complex stimuli. In experiments
run with uncompensated, anonymous participants whose motivation for participation
is unknown, reduced conscientiousness or lack of focus could produce results that
would be difficult to interpret due to decreased overall performance, increased
variability of performance, or increased measurement noise. Here, we addressed the
question of data quality across a range of cognitive and perceptual tests. For
three key performance metrics -- mean performance, performance variability, and
internal reliability -- the results from self-selected Web samples did not differ
systematically from those obtained from traditionally recruited and/or lab-tested
samples. These findings demonstrate that collecting data from uncompensated,
anonymous, unsupervised, self-selected participants need not reduce data quality,
even for demanding cognitive and perceptual experiments.
Chabris, C.F., Weinberger, A., Fontaine, M., & Simons, D.J. (2011). You do
not talk about fight club if you do not notice fight club: Inattentional
blindness for a simulated real-world assault.
i-Perception, 2, 150-153.
Article online at i-Perception
Inattentional blindness -- the failure to see visible and otherwise
salient events when one is paying attention to something else -- has
as an explanation for various real-world events. In one such event, a
Boston police officer chasing a suspect ran past a brutal assault and was
prosecuted for perjury when he claimed not to have seen it. However, there
have been no experimental studies of inattentional blindness in real-world
conditions. We simulated the Boston incident by having subjects run after
a confederate along a route near which three other confederates staged a
fight. At night only 35% of subjects noticed the fight; during the day 56%
noticed. We manipulated the attentional load on the subjects and found
that increasing the load significantly decreased noticing. These results
provide evidence that inattentional blindness can occur during real-world
situations, including the Boston case.
Simons, D.J., & Chabris, C.F. (2011). What people believe about how memory
works: A representative survey of the U.S. population. PLoS ONE,
Article online at PLoS ONE
Incorrect beliefs about the properties of memory have broad implications:
The media conflate normal forgetting and inadvertent memory distortion
with intentional deceit, juries issue verdicts based on flawed intuitions
about the accuracy and confidence of testimony, and students misunderstand
the role of memory in learning. We conducted a large representative
telephone survey of the U.S. population to assess common beliefs about the
properties of memory. Substantial numbers of respondents agreed with
propositions that conflict with expert consensus: Amnesia results in the
inability to remember one's own identity (83% of respondents agreed),
unexpected objects generally grab attention (78%), memory works like a
video camera (63%), memory can be enhanced through hypnosis (55%), memory
is permanent (48%), and the testimony of a single confident eyewitness
should be enough to convict a criminal defendant (37%). This discrepancy
between popular belief and scientific consensus has implications from the
classroom to the courtroom.
Chabris, C.F. (2011). Why the grass seems greener. [Review of the book
Thinking, Fast and Slow by Daniel Kahneman.]
Wall Street Journal, 22 October.
Article online at wsj.com
Chabris, C.F. (2011). Think again. [Review of the books Brain Bugs by Dean Buonomano, Now You See It by Cathy N. Davidson, and The Compass of Pleasure by David J. Linden.] The New York Times, 16 October. Article online at nytimes.com
Chabris, C.F. (2011). The stranger within. [Review of the book Incognito: The Secret Lives of the Brain by David Eagleman.] The Wall Street Journal, 15 June.
Chabris, C.F. (2011). Knowing what isn't so. [Review of the book Everything is Obvious: Once You Know the Answer by Duncan Watts.] The Wall Street Journal, 9 April.
Chabris, C.F. (2011). The mind readers. [Review of the book The Social Animal: The Hidden Sources of Love, Character, and Achievement by David Brooks.] The Wall Street Journal, 5 March.
Wolley, A.W., Chabris, C.F., Pentland, A., Hashmi, N., & Malone, T.W. (2010). Evidence for a collective intelligence factor in the performance of human groups. Science, 330, 686-688.
Psychologists have repeatedly shown that a single statistical factor --
often called "general intelligence" -- emerges from the correlations among
people's performance on a wide variety of cognitive tasks. But no one has
systematically examined whether a similar kind of "collective
intelligence" exists for groups of people. In two studies with 699 people,
working in groups of two to five, we find converging evidence of a general
collective intelligence factor that explains a group's performance on a
wide variety of tasks. This "c factor" is not strongly correlated with the
average or maximum individual intelligence of group members but is
correlated with the average social sensitivity of group members, the
equality in distribution of conversational turn-taking, and the proportion
of females in the group.
PDF file of
article | Supporting
Chabris, C.F. (2010). The other "g" spot. [Review of the book How
Intelligence Happens by John Duncan.]
Wall Street Journal, 23 October.
Article online at wsj.com
Abstract: Psychologists have repeatedly shown that a single statistical factor -- often called "general intelligence" -- emerges from the correlations among people's performance on a wide variety of cognitive tasks. But no one has systematically examined whether a similar kind of "collective intelligence" exists for groups of people. In two studies with 699 people, working in groups of two to five, we find converging evidence of a general collective intelligence factor that explains a group's performance on a wide variety of tasks. This "c factor" is not strongly correlated with the average or maximum individual intelligence of group members but is correlated with the average social sensitivity of group members, the equality in distribution of conversational turn-taking, and the proportion of females in the group.
Chabris, C.F. (2010). Hard questions from "soft" sciences. The Wall Street Journal, 16 April. Article online at wsj.com
Chabris, C.F. (2010). Pick an ordeal, any ordeal. [Review of the book The Art of Choosing by Sheena Iyengar.] The Wall Street Journal, 16 April. Article online at wsj.com
Wilmer, J.B., Germine, L., Chabris, C.F., Chatterjee, G., Williams, M., Nakayama, K., & Duchaine, B. (2010). Human face recognition is specific and highly heritable: A twin study. Proceedings of the National Academy of Sciences, 107(11), 5238-5241. Article online at PNAS
Compared with notable successes in the genetics of basic sensory
transduction, progress on the genetics of higher level perception and
cognition has been limited. We propose that investigating specific
cognitive abilities with well-defined neural substrates, such as face
recognition, may yield additional insights. In a twin study of face
recognition, we found that the correlation of scores between monozygotic
twins (0.70) was more than double the dizygotic twin correlation (0.29),
evidence for a high genetic contribution to face recognition ability. Low
correlations between face recognition scores and visual and verbal
recognition scores indicate that both face recognition ability itself and
its genetic basis are largely attributable to face-specific mechanisms.
The present results therefore identify an unusual phenomenon: a highly
specific cognitive ability that is highly heritable. Our results establish
a clear genetic basis for face recognition, opening this intensively
studied and socially advantageous cognitive trait to genetic
Chabris, C.F. (2010). Old habits die hard. [Review of the book Switch:
to Change Things When Change is Hard by Chip Heath and Dan Heath.]
Wall Street Journal, 19 February.
Article online at wsj.com
Banerjee, K., Chabris, C.F., Lee, J.J., Johnson, V.E., Tsao, F., & Hauser, M.D. (2009). General intelligence in another primate: Individual differences across cognitive task performance in a New World monkey (Saguinus oedipus). PLoS ONE, 4(6), e5883. Article online at PLoS ONE
Background: Individual differences in human cognitive abilities show
consistently positive correlations across diverse domains, providing the
basis for the trait of "general intelligence" (g). At present,
little is known about the evolution of g, in part because most
comparative studies focus on rodents or on differences across higher-level
taxa. What is needed, therefore, are experiments targeting nonhuman
primates, focusing on individual differences within a single species,
using a broad battery of tasks. To this end, we administered a large
battery of tasks, representing a broad range of cognitive domains, to a
population of captive cotton-top tamarin monkeys (Saguinus
oedipus). Methodology and Results: Using a Bayesian latent variable
model, we show that the pattern of correlations among tasks is consistent
with the existence of a general factor accounting for a small but
significant proportion of the variance in each task (the lower bounds of
95% Bayesian credibility intervals for correlations between g and
task performance all exceed 0.12). Conclusion: Individual differences in
cognitive abilities within at least one other primate species can be
characterized by a general intelligence factor, supporting the hypothesis
that important aspects of human cognitive function most likely evolved
from ancient neural substrates.
Chabris, C.F. (2009). Information, please. [Review of the book
Reading in the brain: The science and evolution of a human
invention by Stanislas Dehaene.] The Wall Street Journal, 18
Article online at wsj.com
Chabris, C.F. (2009). Why the eyes have it. [Review of the book The vision revolution: How the latest research overturns everything we thought we knew about human vision by Mark Changizi.] The Wall Street Journal, 19 June. Article online at wsj.com
Chabris, C.F., Laibson, D.I., Morris, C.L., Schuldt, J.P., & Taubinsky, D. (2009). The allocation of time in decision-making. Journal of the European Economic Association, 7(2-3), 628-637. PDF file of manuscript
We study the allocation of time across decision problems. If a
decision-maker (1) has noisy estimates of value, (2) improves those
estimates the longer he or she analyzes a choice problem, and (3)
allocates time optimally, then the decision-maker should spend less time
choosing when the difference in value between two options is relatively
large. To test this prediction we ask subjects to make 27 binary
incentive-compatible intertemporal choices, and measure response time for
each decision. Our time allocation model explains 54% of the variance in
average decision time. These results support the view that decision-making
is a cognitively costly activity that uses time as an input allocated
according to cost-benefit principles.
Glickman, M.E., & Chabris, C.F. (2009). Comparing extreme members is a
low-power method of comparing groups: An example using sex differences in
chess performance. Unpublished paper. PDF file of
Chabris, C.F. (2009). How to wake up slumbering minds. [Review of the book Why don't students like school? A cognitive scientist answers questions about how the mind works and what it means for the classroom by Daniel T. Willingham.] The Wall Street Journal, 27 April. Article online at wsj.com
Chabris, C.F. (2009). Last-minute changes. [Review of the book The 10,000 year explosion: How civilization accelerated human evolution by Gregory Cochran and Henry Harpending.] The Wall Street Journal, 12 February. Article online at wsj.com
Chabris, C.F. (2008). You have too much mail. [Review of the book The overflowing brain: Information overload and the limits of working memory by Torkel Klingberg.] The Wall Street Journal, 15 December. Article online at wsj.com
Chabris, C.F., Laibson, D.I., Morris, C.L., Schuldt, J.P., & Taubinsky, D. (2008). Individual laboratory-measured discount rates predict field behavior. Journal of Risk and Uncertainty, 37(2-3), 237-269. PDF file of manuscript
We estimate discount rates of 555 subjects using a laboratory task and
find that these individual discount rates predict inter-individual
variation in field behaviors (e.g., exercise, BMI, smoking). The
correlation between the discount rate and each field behavior is small:
none exceeds 0.28 and many are near 0. However, the discount rate has at
least as much predictive power as any variable in our dataset (e.g., sex,
age, education). The correlation between the discount rate and field
behavior rises when field behaviors are aggregated: these correlations
range from 0.09-0.38. We present a model that explains why specific
intertemporal choice behaviors are only weakly correlated with discount
rates, even though discount rates robustly predict aggregates of
Chabris, C.F., Laibson, D.I., & Schuldt, J.P. (2008). Intertemporal
choice. In Durlauf, S., & Blume, L. (Eds.), The New Palgrave Dictionary
of Economics (2nd ed.). London: Palgrave Macmillan. PDF file of manuscript
Woolley, A.W., Gerbasi, M., Chabris, C.F., Kosslyn, S.M., & Hackman, J.R.
(2008). Bringing in the experts: How team
ability composition and collaborative planning jointly shape analytic
effectiveness. Small Group Research, 39(3), 352-371. [Group Brain
Project Technical Report #4.]
PDF file of article
Abstract: This study investigates the separate and joint effects of the inclusion of experts and collaborative planning on the performance of analytic teams. Teams either did or did not include members with expert-level task-relevant cognitive abilities, and either did or did not receive an intervention that fostered collaborative planning. Results support the authors' hypothesis that analytic performance requires both task-appropriate expertise and collaborative planning to identify strategies for optimally using that expertise. Indeed, high expertise in the absence of collaborative planning actually decreased team performance. Teams engaging in collaborative planning were more likely to effectively integrate their information on key aspects of the analytic problem, which significantly enhanced their analytic performance. Furthermore, information integration mediated the effects of the interaction of expertise and collaboration on performance. The implications of the findings for the optimal use of team member skills and the development of team performance strategies are discussed.Chabris, C.F. (2008). The reflection reflex: How brain researchers pinpointed the inextricable link between seeing and doing. [Review of two books: (1) Mirroring people: The new science of how we connect with others by Marco Iacoboni; (2) Mirrors in the brain: How our minds share actions, emotions, and experience by Giacomo Rizzolatti and Corrado Sinigaglia.] The Wall Street Journal, 31 May. Article online at wsj.com
Chabris, C.F. (2007). Cognitive and neurobiological mechanisms of the Law of General Intelligence. In Roberts, M.J. (Ed.), Integrating the mind: Domain general versus domain specific processes in higher cognition (pp. 449-491). Hove, UK: Psychology Press. PDF file of chapter
Benjamin, D.J., Chabris, C.F., Glaeser, E.L., Gudnason, V.L., Harris, T.B., Laibson, D.I., Launer, L.J., & Purcell, S. (2007). Genoeconomics. In Weinstein, M., Vaupel, J.W., & Wachter, K.W. (Eds.), Biosocial surveys (pp. 304-335). Washington, DC: The National Academies Press. PDF file of chapter
Woolley, A.W., Hackman, J.R., Jerde, T.E., Chabris, C.F., Bennett, S.L., &
Kosslyn, S.M. (2007). Using brain-based measures to compose teams: How
individual capabilities and team collaboration strategies jointly shape
performance. Social Neuroscience, 2(2), 96-105.
Project Technical Report #1.]
PDF file of article
Abstract: Advances in understanding neural processes open the possibility of using brain-based measures to compose collaborative work teams. Neuroimaging studies have shown that individual differences in patterns of brain activity can predict differences in performance of specific tasks. We extended this finding by examining performance not simply by a single brain, but by pairs of brains. We used measures derived from brain-based studies to compose 100 two-person teams in which members' roles were either congruent or incongruent with their individual abilities. The assessed abilities are rooted in the visual system, which comprises independent "spatial" and "object" subsystems. The team task required one member to navigate through a virtual maze (a spatial task) and the other to "tag" repetitions of complex "greebles" (an object-properties task). Teams in which members' role assignments were congruent with their abilities performed better than incongruent teams and teams in which both members were high on only one of the abilities. In addition, verbal collaboration enabled members of incongruent teams to overcome their compositional disadvantage but did not enhance the performance of congruent teams -- and actually impaired performance when both members were adept in only one of the two necessary abilities. The findings show that knowledge about brain systems can not only be used to compose teams, but also provides insight into how teams can best perform.Chabris, C.F., Jerde, T.E., Woolley, A.W., Gerbasi, M.E., Schuldt, J.P., Bennett, S.L., Hackman, J.R., & Kosslyn, S.M. (2006). Spatial and object visualization cognitive styles: Validation studies in 3800 individuals. Submitted for publication. [Group Brain Project Technical Report #2.]
PDF file of manuscript
Abstract: The well-established dissociation between the ventral object and dorsal spatial processing streams within the visual system suggests a contrast between object and spatial visual cognitive styles. We assessed the validity of this distinction using a self-report questionnaire in a sample of 3839 online participants, and laboratory cognitive tests in a subsample of 196. We found that (1) object and spatial processing preferences were virtually uncorrelated (r = -.05); (2) men, science majors, and people with videogame experience preferred spatial visualization, whereas women, humanities majors, and people with visual arts experience preferred object visualization; and (3) spatial visualizers performed better on tests of mental rotation and virtual maze navigation, whereas object visualizers performed better on a difficult test of picture recognition. Interestingly, the associations among the spatial measures were stronger than those among the object measures, suggesting that spatial visualization may be the more unitary cognitive ability and style.Chabris, C.F., & Glickman, M.E. (2006). Sex differences in intellectual performance: Analysis of a large cohort of competitive chess players. Psychological Science, 17(12), 1040-1046.
PDF file of article
Abstract: Only 1% of the world's chess grandmasters are women. This underrepresentation is unlikely to be caused by discrimination, because chess ratings objectively reflect competitive results. Using data on the ratings of more than 250,000 tournament players over 13 years, we investigated several potential explanations for the male domination of elite chess. We found that: (a) the ratings of men are higher on average than those of women, but no more variable; (b) matched boys and girls improve and drop out at equal rates, but boys begin chess competition in greater numbers and at higher performance levels than girls; and (c) in locales where at least 50% of the new young players are girls, their initial ratings are not lower than those of boys. We conclude that the greater number of men at the highest levels in chess can be explained by the greater number of boys who enter chess at the lowest levels.Harris, G.J., Chabris, C.F., Clark, J., Urban, T., Aharon, I., Steele, S., McGrath, L., Condouris, K., & Tager-Flusberg, H. (2006). Brain activation during semantic processing in autism spectrum disorders via functional magnetic resonance imaging. Brain and Cognition, 61(1), 54-68.
PDF file of article
Abstract: Language and communication deficits are core features of autism spectrum disorders (ASD), even in high-functioning adults with ASD. This study investigated brain activation patterns using functional magnetic resonance imaging in right-handed adult males with ASD and a control group, matched on age, handedness, and verbal IQ. Semantic processing in the controls produced robust activation in Broca's area (left inferior frontal gyrus) and in superior medial frontal gyrus and right cerebellum. The ASD group had substantially reduced Broca's activation, but increased left temporal (Wernicke's) activation. Furthermore, the ASD group showed diminished activation differences between concrete and abstract words, consistent with behavioral studies. The current study suggests Broca's area is a region of abnormal neurodevelopment in ASD, which may be linked with semantic and related language deficits frequently observed in ASD.Aharon, I., Becerra, L., Chabris, C.F., & Borsook, D. (2006). Noxious heat induces fMRI activation in two anatomically distinct clusters within the nucleus accumbens. Neuroscience Letters, 392(3), 159-164.
PDF file of article
Abstract: Using functional magnetic resonance imaging (fMRI) we found that a noxious thermal stimulus (46 degrees C) to the hand activates the nucleus accumbens (NAc) in humans, while a non-noxious warm stimulus (41 degrees C) does not. Following the noxious stimulus, two distinct foci of decreased activation were observed showing distinct time course profiles. One focus was anterior, superior, and lateral and the second that was more posterior, inferior, and medial. The anatomical segregation may correlate with the functional components of the NAc, i.e., shell and core. The results support heterogeneity of function within the NAc and have implications for the understanding the contribution of NAc function to processing of pain and analgesia.Chabris, C.F. (2005). Marked by genius. [Review of the book The creating brain: The neuroscience of genius by Nancy Andreasen.] The Wall Street Journal, 30 December. View HTML reprint
Chabris, C.F., & Hearst, E.S. (2005). Search, recognition, and visualization in chess: Rebuttal to Gobet's critique of Chabris & Hearst (2003). Unpublished paper. PDF file of paper
Chabris, C.F., & Kosslyn, S.M. (2005). Representational correspondence
as a basic principle of diagram design. In Tergan, S-O., & Keller, T.
(Eds.), Knowledge and information visualization: Searching for
synergies (pp. 36-57). Berlin: Springer.
PDF file of chapter
Abstract: The timeworn claim that a picture is worth a thousand words is generally well-supported by empirical evidence, suggesting that diagrams and other information graphics can enhance human cognitive capacities in a wide range of contexts and applications. But not every picture is worth the space it occupies. What qualities make a diagram an effective and efficient conduit of information to the human mind? In this article we argue that the best diagrams systems depict information the same way that our internal mental representations do. That is, "visual thinking" operates largely on relatively sketchy, cartoon-like representations of the physical world, translating sensory input into efficient codes before storing and manipulating it. Effective diagrams will assist this process by stripping away irrelevant detail while preserving or highlighting essential information about objects and their spatial relations. We discuss several examples that illustrate this "Representational Correspondence Principle," and we consider its implications for the design of systems that use diagrams to represent abstract, conceptual knowledge, such as social networks, financial markets, or web content hierarchies.Chabris, C.F. (2004). Molecules of desire. [Review of the book Why we love: The nature and chemistry of romantic love by Helen Fisher.] The Wall Street Journal, 13 February. View HTML reprint
Note: The authors thank Justin Ocean and Brooks Newkirk for their invaluable assistance with the figures in this chapter. This acknowledgement was inadvertently left out of the published chapter.
Hadjikhani, N., Joseph, R.M., Snyder. J., Chabris, C.F., Clark, J.,
Steele, S., McGrath, L., Vangel, M., Aharon, I., Feczko, E., Harris, G.J.,
& Tager-Flusberg, H. (2004). Activation of the fusiform gyrus when
individuals with autism spectrum disorder view faces. Neuroimage,
PDF file of article
Abstract: Prior imaging studies have failed to show activation of the fusiform gyrus in response to emotionally neutral faces in individuals with autism spectrum disorder (ASD) [Critchley et al., Brain 124 (2001) 2059; Schultz et al., Arch. Gen. Psychiatry 57 (2000) 331]. However, individuals with ASD do not typically exhibit the striking behavioral deficits that might be expected to result from fusiform gyrus damage, such as those seen in prosopagnosia, and their deficits appear to extend well beyond face identification to include a wide range of impairments in social perceptual processing. In this study, our goal was to further assess the question of whether individuals with ASD have abnormal fusiform gyrus activation to faces. We used high-field (3T) functional magnetic resonance imaging to study face perception in 11 adult individuals with autism spectrum disorder (ASD) and 10 normal controls. We used face stimuli, object stimuli, and sensory control stimuli (Fourier scrambled versions of the face and object stimuli) containing a fixation point in the center to ensure that participants were looking at and attending to the images as they were presented. We found that individuals with ASD activated the fusiform face area and other brain areas normally involved in face processing when they viewed faces as compared to non-face stimuli. These data indicate that the face-processing deficits encountered in ASD are not due to a simple dysfunction of the fusiform area, but to more complex anomalies in the distributed network of brain areas involved in social perception and cognition.Hadjikhani, N., Chabris, C.F., Joseph, R.M., Clark, J., McGrath, L., Aharon, I., Feczko, E., Tager-Flusberg, H., & Harris, G.J. (2004). Early visual cortex organization in autism: An fMRI study. Neuroreport, 15, 267-270.
PDF file of article
Abstract: Autism is a neurodevelopmental disorder characterized by preserved visual abilities as well as a special profile for visual cognition. We examined the visual cortex of high-ability individuals with autism in order to assess whether the presence of abnormalities at the primary sensory level in autism could be the basis of their unusual pattern of visual cognitive abilities. We found that the early sensory visual areas are normally organized in individuals with autism, with a normal ratio between central versus peripheral visual field representation. We conclude that the differences observed in the visual capacities of individuals with autism are likely to arise from higher-level cognitive areas and functions, and are the result of top-down processes.Hooven, C.K., Chabris, C.F., Ellison, P.T., & Kosslyn, S.M. (2004). The relationship of testosterone to components of mental rotation. Neuropsychologia, 42, 782-790.
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Abstract: Studies suggest that higher levels of testosterone (T) in males contribute to their advantage over females in tests of spatial ability. However, the mechanisms that underlie the effects of T on spatial ability are not understood. We investigated the relationship of salivary T in men to performance on a computerized version of the MRT (MRT) developed by Shepard and Metzler. We studied whether T is associated specifically with the ability to mentally rotate objects or with other aspects of the task. We collected hormonal and cognitive data from 27 college-age men on two days of testing. Subjects evaluated whether two block objects presented at different orientations were the same or different. We recorded each subject's mean response time (RT) and error rate (ER) and computed the slopes and intercepts of the functions relating performance to angular disparity. T level was negatively correlated with ER and RT; these effects arose from correlations with the intercepts but not the slopes of the rotation functions. These results suggest that T may facilitate male performance on MRTs by affecting cognitive processes unrelated to changing the orientation of imagined objects, including encoding stimuli, initiating the transformation processes, making a comparison and decision, or producing a response.Chabris, C.F., & Hearst, E.S. (2003). Visualization, pattern recognition, and forward search: Effects of playing speed and sight of the position on grandmaster chess errors. Cognitive Science, 27, 637-648.
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Abstract: A new approach examined two aspects of chess skill, long a popular topic in cognitive science. A powerful computer-chess program calculated the number and magnitude of blunders made by the same 23 grandmasters in hundreds of serious games of slow ("classical") chess, regular "rapid" chess, and rapid "blindfold" chess, in which opponents transmit moves without ever seeing the actual position. Rapid chess led to substantially more and larger blunders than classical chess. Perhaps more surprisingly, the frequency and magnitude of blunders did not differ in rapid versus blindfold play, despite the additional memory and visualization load imposed by the latter. We discuss the involvement of various cognitive processes in human problem-solving and expertise, especially with respect to chess. Prior opposing views about the basis of general chess skill have emphasized the dominance of either (a) swift pattern recognition or (b) analyzing ahead, but both seem important and the controversy appears currently unresolvable and perhaps fruitless.Gray, J.R., Chabris, C.F., & Braver, T.S. (2003). Neural mechanisms of general fluid intelligence. Nature Neuroscience, 6(3), 316-322 (cover article, with accompanying commentary).
PDF file of article
Abstract: We used an individual-differences approach to test whether general fluid intelligence (gF) is mediated by brain regions that support attentional (executive) control, including subregions of the prefrontal cortex. Forty-eight participants first completed a standard measure of gF (Raven's Advanced Progressive Matrices). They then performed verbal and nonverbal versions of a challenging working-memory task (three-back) while their brain activity was measured using functional magnetic resonance imaging (fMRI). Trials within the three-back task varied greatly in the demand for attentional control because of differences in trial-to-trial interference. On high-interference trials specifically, participants with higher gF were more accurate and had greater event-related neural activity in several brain regions. Multiple regression analyses indicated that lateral prefrontal and parietal regions may mediate the relation between ability (gF) and performance (accuracy despite interference), providing constraints on the neural mechanisms that support gF.Laeng, B., Chabris, C.F., & Kosslyn, S.M. (2003). Asymmetries in encoding spatial relations. In Hugdahl, K., & Davidson, R.J. (Eds.), The asymmetrical brain (pp. 303-339). Cambridge, MA: MIT Press. PDF file of chapter
Elman, I., Karlsgodt, K.H., Gastfriend, D.R., Chabris, C.F., & Breiter,
H.C. (2002). Cocaine-primed craving and its relationship to depressive
symptomatology in individuals with cocaine dependence. Journal of
Psychopharmacology, 16(2), 163-167.
PDF file of article
Abstract: Several lines of evidence suggest a link between cocaine-primed craving and depressive symptomatology. The purpose of this study was to directly relate these two clinical phenomena. Thirty-three cocaine-dependent subjects were rated on the Hamilton Rating Scale for Depression (HRSD) at baseline and then administered an i.v. bolus of cocaine (0.2 mg/kg). Multiple regression analysis revealed that only the HRSD score was an independent predictor of cocaine-primed craving (F= 4.09; d.f. = 10,22; r = 0.81, p < 0.003) when baseline spontaneous craving during early withdrawal, age, gender, frequency of use, time since last use, monetary expenditure on cocaine and the Addiction Severity Index Drug Composite Scores were considered. These data support the hypothesis that depressive symptomatology affects cocaine-primed craving and that this relationship is relatively specific to symptoms defined by the HRSD and is not seen with a number of other clinical and demographic variables.Herbert, M.R., Harris, G.J., Adrien, K.T., Ziegler, D.A., Makris, N., Kennedy, D.N., Lange, N.T., Chabris, C.F., Bakardjiev, A., Hodgson, J., Takeoka, M., Tager-Flusberg, H., & Caviness, V.S. (2002). Abnormal asymmetry in language association cortex in autism. Annals of Neurology, 52(5), 588-596.
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Abstract: Autism is a neurodevelopmental disorder affecting cognitive, language, and social functioning. Although language and social communication abnormalities are characteristic, prior structural imaging studies have not examined language-related cortex in autistic and control subjects. Subjects included 16 boys with autism (aged 7-11 years), with nonverbal IQ greater than 80, and 15 age- and handedness-matched controls. Magnetic resonance brain images were segmented into gray and white matter; cerebral cortex was parcellated into 48 gyral-based divisions per hemisphere. Asymmetry was assessed a priori in language-related inferior lateral frontal and posterior superior temporal regions and assessed post hoc in all regions to determine specificity of asymmetry abnormalities. Boys with autism had significant asymmetry reversal in frontal language-related cortex: 27% larger on the right in autism and 17% larger on the left in controls. Only one additional region had significant asymmetry differences on post hoc analysis: posterior temporal fusiform gyrus (more left-sided in autism), whereas adjacent fusiform gyrus and temporooccipital inferior temporal gyrus both approached significance (more right-sided in autism). These inferior temporal regions are involved in visual face processing. In boys with autism, language and social/face processing-related regions displayed abnormal asymmetry. These structural abnormalities may relate to language and social disturbances observed in autism.Levin, D.T., Simons, D.J., Angelone, B.L., & Chabris, C.F. (2002). Memory for centrally attended changing objects in an incidental real-world change detection paradigm. British Journal of Psychology, 93(3), 289-302.
PDF file of article
Abstract: People often have difficulty detecting visual changes in scenes, a phenomenon referred to as 'change blindness'. Although change blindness is usually observed in pictures of objects that are not the focus of attention, it also occurs for attended objects in the real world. Here, we further explore the finding that many participants fail to detect the unexpected substitution of one conversation partner for another. We show that change blindness for a conversation partner occurs in a variety of situations. Furthermore, when tested with a photographic lineup following the change, participants who noticed the substitution showed better memory for both pre- and post-change experimenters than participants who did not detect the change. We conclude that change blindness in this case is associated with relatively ineffective or inaccessible representations of previously attended objects, and we contrast these results with others indicating that change blindness arises from a failure to compare the original and changed object.Simons, D.J., Chabris, C.F., Schnur, T., & Levin, D.T. (2002). Evidence for preserved representations in change blindness. Consciousness & Cognition, 11(1), 78-97.
PDF file of article
Abstract: People often fail to detect large changes to scenes, provided that the changes occur during a visual disruption. This phenomenon, known as "change blindness," occurs both in the laboratory and in real-world situations in which changes occur unexpectedly. The pervasiveness of the inability to detect changes is consistent with the theoretical notion that we internally represent relatively little information from our visual world from one glance at a scene to the next. However, evidence for change blindness does not necessarily imply the absence of such a representation -- people could also miss changes if they fail to compare an existing representation of the pre-change scene to the post-change scene. In three experiments, we show that people often do have a representation of some aspects of the pre-change scene even when they fail to report the change. And, in fact, they appear to "discover" this memory and can explicitly report details of a changed object in response to probing questions. The results of these real-world change detection studies are discussed in the context of broader claims about change blindness.Aharon, I.,* Etcoff, N.,* Ariely, D.,* Chabris, C.F.,* O'Connor, E., & Breiter, H.C. (2001). Beautiful faces have variable reward value: Behavioral and FMRI evidence. Neuron, 32, 537-551. [*These authors contributed equally to the work.]
PDF file of article
Abstract: The brain circuitry processing rewarding and aversive stimuli is hypothesized to be at the core of motivated behavior. In this study, discrete categories of beautiful faces are shown to have differing reward values and to differentially activate reward circuitry in human subjects. In particular, young heterosexual males rate pictures of beautiful males and females as attractive, but exert effort via a keypress procedure only to view pictures of attractive females. Functional magnetic resonance imaging at 3 T shows that passive viewing of beautiful female faces activates reward circuitry, in particular the nucleus accumbens. An extended set of subcortical and paralimbic reward regions also appear to follow aspects of the keypress rather than the rating procedures, suggesting that reward circuitry function does not include aesthetic assessment.Huffman, E.K.,* Chabris, C.F.,* Ariely, D., Aharon, I., Kaplan, L.M., & Breiter, H.C. (2001). Pictures of food have reward value that varies according to appetitive state. Unpublished paper. [*These authors contributed equally to the work.]
PDF file of paper
Abstract: A stimulus is considered a reward if an animal will perform work in order to receive it. In this study we asked whether pictures of food can be rewards for human subjects, with reward value operationalized as the physical effort the subjects would exert to continue viewing the pictures. We designed a procedure, modeled on the animal literature of operant conditioning, under which subjects viewed two sets of pictures of appetizing and unappetizing food items, and controlled how long each picture remained in view by repeatedly pressing pairs of keys on a computer. Subjects performed this procedure twice, once while hungry and once after consuming a meal. We found that in general, appetizing food pictures were viewed longer than unappetizing food pictures. When subjects were hungry (in a deficit state specific to food reward), this difference in favor of appetizing food pictures was even greater than when subjects were satiated. These results show that pictures of food items do indeed have reward value in the absence of the food items themselves, and more generally, that pictures of rewards can stand in for actual rewards.Most, S.B., Simons, D.J., Scholl, B.J., Jimenez, R., Clifford, E., & Chabris, C.F. (2001). How not to be seen: The contribution of similarity and selective ignoring to sustained inattentional blindness. Psychological Science, 12(1), 9-17.
PDF file of article
Abstract: When people attend to objects or events in a visual display, they often fail to notice an additional, unexpected, but fully visible object or event in the same display. This phenomenon is now known as inattentional blindness. We present a new approach to the study of sustained inattentional blindness for dynamic events, in order to explore the roles of similarity, distinctiveness, and attentional set in the detection of unexpected objects. In Experiment 1, we found that the similarity of an unexpected object to other objects in the display influences attentional capture: The more similar an unexpected object is to the attended items, and the greater its difference from the ignored items, the more likely it is that people will notice it. Experiment 2 explored whether this effect of similarity is driven by selective ignoring of irrelevant items or by selective focusing on attended items. The results of Experiment 3 suggest that the distinctiveness of the unexpected object alone cannot entirely account for the similarity effects found in the first two experiments; when attending to black items or white items in a dynamic display, nearly 30% of observers failed to notice a bright red cross move across the display, even though it had a unique color, luminance, shape, and motion trajectory and was visible for 5 seconds. Together, the results suggest that inattentional blindness for ongoing dynamic events depends both on the similarity of the unexpected object to the other objects in the display and on the observer's attentional set.Most, S.B., Simons, D.J., Scholl, B.J., & Chabris, C.F. (2000). Sustained inattentional blindness: The role of location in the detection of unexpected dynamic events. Psyche, 6(14).
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Abstract: Attempts to understand visual attention have produced models based on location, in which attention selects particular regions of space, and models based on other visual attributes (e.g., in which attention selects discrete objects or specific features). Previous studies of inattentional blindness have contributed to our understanding of attention by suggesting that the detection of an unexpected object depends on the distance of that object from the spatial focus of attention. When the distance of a briefly flashed object from both fixation and the focus of attention is systematically varied, detection appears to have a location-based component. However, the likelihood that people will detect an unexpected event in sustained and dynamic displays may depend on more than just spatial location. We investigated the influence of spatial location on inattentional blindness under precisely controlled, sustained and dynamic conditions. We found that although location-based models cannot fully account for the detection of unexpected objects, spatial location does play a role even when displays are visible for an extended period.Baker, D.P., Chabris, C.F., & Kosslyn, S.M. (1999). Encoding categorical and coordinate spatial relations without input-output correlations: New simulation models. Cognitive Science, 23(1), 33-51.
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Abstract: Cook (1995) has criticized Kosslyn, Chabris, Marsolek, & Koenig's (1992) network simulation models of spatial relations encoding in part because the absolute position of a stimulus in the input array was correlated with its spatial relation to a landmark; thus, on at least some trials, the networks did not need to compute spatial relations. The network models reported here include larger input arrays, which allow stimuli to appear in a large range of locations with equal probability of being above or below a "bar," thus eliminating the confound present in earlier models. The results confirm the original hypothesis that as the size of the network's receptive fields increases, performance on a coordinate spatial relations task (which requires computing precise, metric distance) will be relatively better than on a categorical spatial relations task (which requires computing above/below relative to a landmark).Chabris, C.F. (1999). Braintwisters. [Review of the book The myth of the first three years: A new understanding of early brain development and lifelong learning by John T. Bruer.] Commentary, 108(5), 74-77. View HTML reprint
Chabris, C.F. (1999). Prelude or requiem for the "Mozart effect"?
Nature, 400, 826-827.
PDF file of article (includes article by K.M. Steele et al. and reply by F.H. Rauscher)
PDF file of unpublished rebuttal to Rauscher's reply
First paragraph: Rauscher et al. [Nature, 1993] reported that listening to ten minutes of Mozart's music increased the abstract reasoning ability of college students, as measured by IQ scores, by 8 or 9 points compared with listening to relaxation instructions or silence, respectively. This startling finding became known as the "Mozart effect," and has since been explored by several research groups. Here I use a meta-analysis to demonstrate that any cognitive enhancement is small and does not reflect any change in IQ or reasoning ability in general, but instead derives entirely from performance on one specific type of cognitive task and has a simple neuropsychological explanation.Chabris, C.F. (1999). Cognitive and neuropsychological mechanisms of expertise: Studies with chess masters. Doctoral dissertation, Harvard University.
PDF file of dissertation
Abstract: Research on expertise in visual-spatial tasks such as chess has ignored the introspective reports of top-level practitioners, overemphasized pattern recognition as the sole mechanism underlying skilled performance, and neglected the role of mental imagery in the thinking process. In addressing these limitations I propose a new theory of expertise, the "mental cartoons hypothesis," and illustrate its properties by application to chess, which has historically been the primary domain for psychological studies of human expertise. Experiment 1 uses a classic image-scanning paradigm to show that chess masters and novices differ substantially in their ability to visualize chess moves, even in semantically impoverished contexts, extending the range of novice-expert differences from pattern recognition and knowledge representation to mental imagery processing. Experiments 2 and 3 exploit original very-long-term memory recognition and recall tasks to show that the memory representations of famous chess positions held by chess masters include both pattern and conceptual information, supporting a key distinction between this theory and its predecessors. Experiment 4 uses computer analysis of 1188 chess games between grandmasters to show that when players have additional time to think ahead, the quality of their decisions improves significantly, refuting a claim extrapolated from theories that emphasize fast pattern recognition over slow search processes. Experiments 5 and 6 investigate hemispheric specialization for chess perception, an issue not addressed by previous theories, and find that chess masters have a right-hemisphere advantage for recognizing previously studied normal chess positions and for parsing normal chess positions into component patterns. This is consistent with other neuropsychological evidence that ties the right hemisphere to chess skill. I also discuss more specific brain mechanisms that may support chess expertise, compare the mental cartoons hypothesis to other theories, suggest several specific experiments and general directions for future research, and argue that the study of expertise is relevant to a broad range of issues in human cognition.Simons, D.J., & Chabris, C.F. (1999). Gorillas in our midst: Sustained inattentional blindness for dynamic events. Perception, 28, 1059-1074.
PDF file of article
Abstract: With each eye fixation, we experience a richly detailed visual world. Yet recent work on visual integration and change detection reveals that we are surprisingly unaware of the details of our environment from one view to the next: we often do not detect large changes to objects and scenes ("change blindness"). Furthermore, without attention, we may not even perceive objects ("inattentional blindness"). Taken together, these findings suggest that we perceive and remember only those objects and details that receive focused attention. In this paper, we briefly review and discuss evidence for these cognitive forms of "blindness." We then present a new study that builds on classic studies of divided visual attention to examine inattentional blindness for complex objects and events in dynamic scenes. Our results suggest that the likelihood of noticing an unexpected object depends on the similarity of that object to other objects in the display and on how difficult the primary monitoring task is. Interestingly, spatial proximity of the critical unattended object to attended locations does not appear to affect detection, suggesting that observers attend to objects and events, not spatial positions. We discuss the implications of these results for visual representations and awareness of our visual environment.Chabris, C.F. (1998). IQ since "The Bell Curve." Commentary, 106(2), 33-40. View HTML reprint
Chabris, C.F., et al. (1998). Does IQ matter? Commentary, 106(5), 13-23. View HTML reprint
Chabris, C.F., & Kosslyn, S.M. (1998). How do the cerebral hemispheres contribute to encoding spatial relations? Current Directions in Psychological Science, 7(1), 8-14. PDF file of article
Mijovic-Prelec, D., Chabris, C.F., Shin, L.M., Kosslyn, S.M., & Wray,
S. (1998). The judgment of absence in neglect.
Neuropsychologia, 36(8), 797-802.
PDF file of article
Abstract: The usual way of looking at neglect is by investigating how neglect patients fail to detect that something is there. In this study, we look at how neglect patients correctly detect that something is not there. Patients with parietal lesions (11 with and 16 without neglect) and 23 control subjects indicated whether a dot target was or was not present in a geometrical display. While control subjects were consistently (and unexpectedly) faster in the no-dot than in the dot condition, the distinguishing response time pattern of right parietal patients with neglect was not -- as one might expect -- a relatively longer response time to left vs right targets, but a longer response time to target absence vs presence. This may be due to a serial search or, alternatively, it might result from double-checking for target absence, produced by lowered perceptual confidence. Since this "wariness" about stimulus absence seems to operate in parallel with neglect patients' denial of the deficit, we conclude that the response time pattern observed in this study could be used as a measure of subjective (un)awareness of neglect.Glickman, M.E., & Chabris, C.F. (1996). Using chess ratings as data in psychological research. Unpublished paper. PDF file of paper
Chabris, C.F., & Kosslyn, S.M. (1995). Illustrated editorial is value-added text. Folio, February, 28-29. [Reprinted, as "A picture is worth 1,000 words," in Folio Special Sourcebook Issue, 1996.] PDF file of article
Kosslyn, S.M., Chabris, C.F., & Baker, D.P. (1995). Neural network
models as evidence for different types of visual representations.
Cognitive Science, 19(4), 575-579.
PDF file of article
Abstract: Cook (1995) criticizes the work of Jacobs and Kosslyn (1994) on spatial relations, shape representations, and receptive fields in neural network models on the grounds that first-order correlations between input and output unit activities can explain the results. We reply briefly to Cook's arguments here (and in Kosslyn, Chabris, Marsolek, Jacobs, & Koenig, 1995) and discuss how new simulations can confirm the importance of receptive field size as a crucial variable in the encoding of categorical and coordinate spatial relations and the corresponding shape representations; such simulations would testify to the computational distinction between the different types of representations.Kosslyn, S.M., Chabris, C.F., Marsolek, C.J., Jacobs, R.A., & Koenig, O. (1995). On computational evidence for different types of spatial relations encoding: Reply to Cook et al. (1995). Journal of Experimental Psychology: Human Perception and Performance, 21(2), 423-431.
PDF file of article
Abstract: Computational models in psychology play an increasingly important role in characterizing theoretical distinctions, understanding empirical results, and formulating new predictions. However, the proper use of models is subject to debate and interpretations, as Cook, Fruh, and Landis (1995) have demonstrated in a critique of neural network simulations reported by Kosslyn, Chabris, Marsolek, and Koenig (1992). These simulation results supported a distinction between two types of spatial relations encoding. Cook et al. argue that Kosslyn et al.'s models did not process "spatial" representations and that input-output correlations rather than properties of spatial relations encoding processes explain the performance of the models. This article provides conceptual and analytic rebuttals of those criticisms.Kosslyn, S.M., Alpert, N.M., Thompson, W.L., Chabris, C.F., Rauch, S.L., & Anderson, A.K. (1994). Identifying objects seen from different viewpoints: A PET investigation. Brain, 117(5), 1055-1071.
PDF file of article
Abstract: Positron emission tomography scans were acquired when subjects performed three tasks, each in a separate block of trials. They decided whether words named pictures of objects viewed from a canonical perspective, decided whether words named pictures of objects viewed from a non-canonical (unusual) perspective, or saw random patterns of lines and pressed a pedal when they heard the word (this was a baseline condition). The dorsolateral prefrontal region was activated when subjects identified objects seen from non-canonical perspectives, as expected if the frontal lobes are involved in top-down perceptual processing. In addition, several areas in the occipital, temporal, and parietal lobes were selectively activated when subjects identified objects seen from non-canonical perspectives, as specifically predicted by a recent theory. Overall, the pattern of results supported the view that the human brain identifies objects by using a system of areas similar to that suggested by studies of other primates.Mijovic-Prelec, D., Shin, L.M., Chabris, C.F., & Kosslyn, S.M. (1994). When does "no" really mean "yes"? A case study in unilateral visual neglect. Neuropsychologia, 32(2), 151-158.
PDF file of article
Abstract: A patient with unilateral visual neglect indicated whether a dot was or was not present in a display. When present, the dot appeared equally often in the left and right visual fields. Although he typically denied having seen dots in his left visual field, he was able to make this judgment much more quickly than when no dot was in fact present. The mean response times when the dot was present (1135 and 1004 msec, for left and right) were almost twice as fast as the response times when no dot was present (2025 msec). This result suggests that the patient searched the visual fields individually, and in fact generated a "No" response based on detecting the dot in his neglected field. Thus, the mechanisms used to detect stimuli apparently are not rigidly linked to those used to classify them or to produce a response.Kosslyn, S.M., Alpert, N.M., Thompson, W.L., Maljkovic, V., Weise, S.B., Chabris, C.F., Hamilton, S.E., Rauch, S.L., & Buonanno, F.S. (1993). Visual mental imagery activates topographically organized visual cortex: PET investigations. Journal of Cognitive Neuroscience, 5(3), 263-287.
PDF file of article
Abstract: Cerebral blood flow was measured using positron emission tomography (PET) in three experiments while subjects performed mental imagery or analogous perceptual tasks. In Experiment 1, the subjects either visualized letters in grids and decided whether an X mark would have fallen on each letter if it were actually in the grid, or they saw letters in grids and decided whether an X mark fell on each letter. A region identified as part of area 17 by the Talairach and Tournoux (1988) atlas, in addition to other areas involved in vision, was activated more in the mental imagery task than in the perception task. In Experiment 2, the identical stimuli were presented in imagery and baseline conditions, but subjects were asked to form images only in the imagery condition; the portion of area 17 that was more active in the imagery condition of Experiment 1 was also more activated in imagery than in the basline condition, as was part of area 18. Subjects also were tested with degraded perceptual stimuli, which caused the visual cortex to be activated to the same degree in imagery and perception. In both Experiments 1 and 2, however, imagery selectively activated the extreme anterior part of what was identified as area 17, which is inconsistent with the relatively small size of the imaged stimuli. These results, then, suggest that imagery may have activated another region just anterior to area 17. In Experiment 3, subjects were instructed to close their eyes and evaluate visual mental images of upper case letters that were formed at a small size or a large size. The small mental images engendered more activation in the posterior portion of visual cortex, and the large mental images engendered more activation in anterior portions of visual cortex. This finding is strong evidence that imagery activates topographically mapped cortex. The activated regions were also consistent with their being localized in area 17. Finally, additional results were consistent with the existence of two types of imagery, one that rests on allocating attention to form a pattern and one that rests on activating stored visual memories.Kosslyn, S.M., & Chabris, C.F. (1993). The mind is not a camera, the brain is not a VCR: Some psychological guidelines for designing charts and graphs. Aldus Magazine, September/October, 35-38. PDF file of article
Chabris, C.F., & Hamilton, S.E. (1992). Hemispheric
specialization for skilled perceptual organization by chessmasters.
Neuropsychologia, 30(1), 47-57.
PDF file of article
Abstract: The right cerebral hemisphere may be relatively specialized for parsing simple visual stimuli according to default rules, such as the Gestalt laws of perceptual organization, whereas the left cerebral hemisphere may be relatively specialized for overriding such default rules. We extend this model to "semantically rich domains" by performing a divided-visual-field experiment on 16 chessmasters. Such subjects are able to recall and recognize complex chess positions by chunking the basic elements of the stimuli -- the chess pieces -- into meaningful groupings according to certain rules that are specific to the semantic structure of the chess domain. We show that the right hemisphere is superior to the left at parsing according to the default rules of chess chunking, but that the left hemisphere is superior to the right at grouping pieces together in violation of those rules. These results suggest that the right hemisphere is better able to acquire and apply new sets of default parsing rules for specific contexts. We conclude, consistent with other neuropsychological evidence, that the right hemisphere is critical for chess skill.Kosslyn, S.M., & Chabris, C.F. (1992). Minding information graphics. Folio, February, 69-71. PDF file of article
Erratum: In Figure 1, there should be no black bishop on c8.
Kosslyn, S.M., Chabris, C.F., Marsolek, C.J., & Koenig, O. (1992).
Categorical versus coordinate spatial relations: Computational analyses
and computer simulations. Journal of Experimental Psychology: Human
Perception and Performance, 18(2), 562-577.
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Abstract: Results of four sets of neural network simulations support the distinction between categorical and coordinate spatial relations representations: (a) Networks that were split so that different hidden units contributed to each type of judgment performed better than unsplit networks; the reverse was observed when they made two coordinate judgments. (b) Both computations were more difficult when finer discriminations were required; this result mirrored findings with human subjects. (c) Networks with large, overlapping "receptive fields" performed the coordinate task better than did networks with smaller, less overlapping receptive fields, but vice versa for the categorical task; this suggests a possible basis for the observed cerebral lateralization of the two kinds of processing. (d) The previously observed effect of stimulus contrast on this hemispheric asymmetry could reflect contributions of more neuronal input in high-contrast conditions.Kosslyn, S.M.,* & Chabris, C.F.* (1990). Naming pictures. Journal of Visual Languages and Computing, 1, 77-95. [*These authors contributed equally to the work.]
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Abstract: Pictures are inherently ambiguous but people categorize and name pictured objects with remarkable consistency. However, the time to assign a name to a picture depends on a large number of variables, ranging from the quality of the picture itself to the level of hierarchy and frequency of the name. We review the empirical results in the psychological literature on how people name pictured objects, summarizing the major variables that affect the name assigned and the time spent assigning it. The underlying regularities in these data are explained by properties of three mechanisms used in picture naming: bottom-up perceptual encoding; hierarchical associative memory; and top-down knowledge-based search. The properties ascribed to these mechanisms are hypothesized on the basis of computational analyses and considerations of characteristics of the neural systems underlying vision.Kosslyn, S.M., Chabris, C.F., & Hamilton, S.E. (1990). Designing for the mind: Five psychological principles of articulate graphics. Multimedia Review, 1(3), 23-29. PDF file of article
O'Reilly, R.C., Kosslyn, S.M., Marsolek, C.J., & Chabris, C.F.
(1990). Receptive field characteristics that allow parietal lobe neurons
to encode spatial properties of visual input: A computational analysis.
Journal of Cognitive Neuroscience, 2(2), 141-155.
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Abstract: A subset of visually sensitive neurons in the parietal lobe apparently can encode the locations of stimuli, whereas visually sensitive neurons in the inferotemporal cortex (area IT) cannot. This finding is puzzling because both sorts of neurons have large receptive fields, and yet location can be encoded in one case, but not in the other. The experiments reported here investigated the hypothesis that a crucial difference between the IT and parietal neurons is the spatial distribution of their response profiles. In particular, IT neurons typically respond maximally when stimuli are presented at the fovea, whereas parietal neurons do not. We found that a parallel-distributed-processing network could map a point in an array to a coordinate representation more easily when a greater proportion of its input units had response peaks off the center of the input array. Furthermore, this result did not depend on potentially implausible assumptions about the regularity of the overlap in receptive fields or the homogeneity of the response profiles of different units. Finally, the internal representations formed within the network had receptive fields resembling those found in area 7a of the parietal lobe.
Abstract: Over the past 60 years, approximately 100 cases of acquired prosopagnosia have been reported. Such cases are frequently accompanied by cortical color blindness and upper visual field defects. Damage to right ventral occipital temporal cortex is often implicated. More recently, it has become evident that prosopagnosic symptoms as severe as that seen with acquired prosopagnosia can occur without any evident brain damage. Reports of these cases, called either developmental or congenital prosopagnosia, are rapidly increasing. Using a web based portal (faceblind.org), over 900 such individuals have contacted us, and we have conducted in-depth testing with 75 of them, showing that an overwhelming majority of the individuals have severe prosopagnosic symptoms. In general, these individuals show strong deficits when tested for face memory, moderate to strong deficits in perceiving similarities and differences in faces, but only very rarely do they have deficits in detecting faces. In addition, most of these individuals have normal emotion recognition and can judge attractiveness and gender from closely cropped faces. Such individuals are much less rare than has been previously assumed. Web based testing of a general population of 1600 observers using our Cambridge Face Memory Test indicates that 2% of this population have deficits as severe as our sample of self-reported and tested prosopagnosics. It is thus conceivable that millions of individuals have symptoms as severe as the classical cases of prosopagnosia. Approximately 20% of our prosopagnosic respondents report relatives with similar difficulties. We have tested the face recognition in three such families, one with 6 affected cases (USA), one with 3 cases (Canada) and 2 cases (UK). These subjects show the same pattern of deficits as mentioned above, and allow us to begin exploring possible genetic determinants of developmental prosopagnosia.Chabris, C.F., Schuldt, J., & Woolley, A.W. (2006). Individual differences in confidence affect judgments made collectively by groups. Presented at the Annual Convention of the Association for Psychological Science, New York, 25-28 May.
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We developed a reliable measure of confidence and had participants with
different individual confidence levels collaborate on a decision-making
task. Group confidence exceeded individual confidence, mainly because
low-confidence individuals showed much greater confidence when working
together than as individuals. These results underscore the influence of
individual differences on collective decision-making.
Chabris, C.F., Aharon, I., Clark, J.A., McGrath, L., Steele, S.,
Tager-Flusberg, H., & Harris, G.J. (2002). A region in right prefrontal
cortex is activated selectively by semantic processing of words about the
mind in normal but not autistic individuals. Presented at the
International Meeting for Autism Research, Orlando, FL, 1-2 November.
The right prefrontal cortex plays a critical role in the cognitive system
that represents and reasons about the mental states of others; e.g.,
damage here impairs performance on tests of theory-of-mind ability more
severely than does damage elsewhere in the brain. We compared processing
of words about the mind (e.g., think, believe, confusion) and other
abstract words (e.g., cause, attempt, liberty) that were matched for
frequency, length, and reading level. Groups of normal and
high-functioning autistic adult males performed semantic ("Is the word
positive or negative?") and perceptual ("Is the word in upper or lower
case letters?") tasks while viewing blocks of these words (and a set of
matched concrete words) during whole-brain FMRI at 1.5T over four runs
totaling approximately 18 minutes. As predicted, in the normal group, a
cluster in the right inferior and orbital frontal gyri was more active
during semantic processing of words about the mind than other abstract
words. Critically, the autistic group did not show the same activation
difference, and neither group showed it during perceptual processing.
These results suggest that (1) different categories of abstract words and
concepts are processed in different brain regions, (2) neural systems
involved in understanding the minds of others are also involved in
understanding words about the mind, and (3) underuse of words about the
mind by autistic individuals is related to their impaired theory-of-mind
ability by a common neural locus.
Chabris, C.F., Aharon, I., Clark, J., Nakayama, K., Sepeta, L.,
A., Joseph, R., McGrath, L., Tager-Flusberg, H., & Harris, G.J. (2002).
Processing of facial expressions by autistic and normal adults: Behavioral
and FMRI studies. Presented at the Annual Meeting of the Cognitive
Neuroscience Society, San Francisco, 14-16 April.
Autism involves social deficits that may include abnormal processing of
the human face. We compared the abilities of high-functioning adult
autistic males and control subjects to label facial expressions of basic
emotions (anger, disgust, fear, happiness, sadness, surprise, neutral) and
to discriminate between facial morphs showing different intensities of
emotion. We used 70 of the Ekman and Friesen Pictures of Facial Affect,
preprocessed to align the eyes and mouths to common coordinates, equalize
contrast, and mask out non-face information. Results suggest that autistic
subjects have no gross deficits in labeling emotions or discriminating
emotional intensity. Separately, we characterized neural activation during
passive viewing of the same faces, using whole-brain BOLD-contrast FMRI at
1.5T with blocked presentation of the emotion categories. Results suggest
that amygdala activation is comparable between groups, but while control
subjects strongly activate the cerebellum bilaterally during emotional
faces compared to neutral faces, autistic subjects show little cerebellum
activation. Based on previous behavioral findings by our group, we
examined activation separately for emotions that can be identified based
on the mouth region of the face (disgust, happiness) and the eye region
(anger, fear, sadness). Activation to mouth emotions (relative to neutral)
was greater than activation to eye emotions for both groups, and the
autistic group showed almost no activation to eye emotions. It is possible
that autistic adults are able to recognize emotional information in faces,
but have difficulty in fluently using such information to guide social
interaction, a possible function for the cerebellum and its cortical
Chabris, C.F., Benjamin, D.J., & Simons, D.J. (1998). How well do
chess masters remember famous chess positions? Implications for
theories of spatial expertise. Presented at the Workshop on
Object Perception and Memory, Dallas, 19 November.
Two experiments tested whether the memory representations used by
chess masters (1) are lists of familiar clusters or chunks of
chess pieces or (2) include only information about important or
relevant pieces. First, 24 masters recognized famous chess
positions they were likely to have previously studied. When a
position was modified from the correct one, participants detected
the change more often if it affected the "meaning" of the position
than if it did not, even if the non-meaningful change affected
more pieces. Second, two grandmasters recalled a similar set of
positions without prior study; most of their errors did not alter
the meaning of the positions. In each experiment memory for unimportant
pieces was retained as well, though not as strongly as for
important pieces. These results support a hybrid model in which
chunks of pieces, global categories, and meaning are all
represented in the visual memory of chess masters.
Chabris, C.F. (2007). It's your move. [Review of the book How life imitates chess by Garry Kasparov.] The Wall Street Journal, 25 October. Article online at wsj.com
Chabris, C.F. (2006). How chess became the king of games. [Review of the book The immortal game: A history of chess by David Shenk.] The Wall Street Journal, 4 November. View HTML reprint
Chabris, C.F. (2005). The other American game. [Review of four books: (1) Moneymaker: How an amateur poker player turned $40 into $2.5 million at the World Series of Poker, (2) One of a kind: The Rise and fall of Stuey "The Kid" Ungar, the world's greatest poker player, (3) The professor, the banker, and the suicide king: Inside the richest poker game of all time, (4) The making of a poker player: How an Ivy League math geek learned to play championship poker.] The Wall Street Journal, 8 July. View HTML reprint
Chabris, C.F. (2002). A match for all seasons. [Review of the book Behind Deep Blue: Building the computer that defeated the world chess champion by Feng-Hsiung Hsu.] The Wall Street Journal, 27 December. View HTML reprint
Chabris, C.F. (2000). Checkmate for a champion. The Wall Street Journal, 7 November. View HTML reprint
Chabris, C.F. (1997). Licao historica. Veja, 21 May, 104-105. (Reprinted in English translation as "Brave new chess world," Chess Horizons, September-October.)
Wolff, P., & Chabris, C.F. (1997). The complete idiot's guide to chess. New York: Alpha Books.
Chabris, C.F. (1996). The last human champion? Games, August, 10-12, 14, 63.
Chabris, C.F. (1994). The girl who would be king. Games, February, 12-14, 65-66. (Best Human Interest Story, 1994 Chess Journalists of America awards.)
Chabris, C.F. (1993). Kasparov revealed. [Review of the book Mortal games: The turbulent genius of Garry Kasparov by Fred Waitzkin.] American Chess Journal, 2, 109-114. (Best Review [Honorable Mention], 1994 Chess Journalists of America awards.)
Chabris, C.F. (1993). The Harvard Cup man-versus-machine chess challenge. ICCA Journal, 16(1), 57-61.
Chabris, C.F. (1992). "The Polgar sisters" -- facts or rumors? [Review of the book The Polgar sisters: Training or genius? by Cathy Forbes.] American Chess Journal, 1, 120-127.
Hoechst, T., Melander, N., & Chabris, C.F. (1990). Guide to ORACLE. New York: McGraw-Hill.
Chabris, C.F. (1989). Artificial intelligence and Turbo C. Homewood, IL: Dow Jones-Irwin. Japanese translation by the Kogaku-Sha Group, Tokyo, 1990.
Chabris, C. F. (1987). Artificial intelligence and Turbo Pascal. Homewood, IL: Dow Jones-Irwin. British reprint by Chapman & Hall, London, 1989. Indian reprint by Galgotia, New Delhi, 1989.
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