Functional MRI studies have uncovered a number of brain areas that demonstrate highly specific functional patterns. In the case of visual object recognition, small, focal regions have been characterized with selectivity for visual categories such as human faces. In this paper, we develop an algorithm that automatically learns patterns of functional specificity from fMRI data in a group of subjects. The method does not require spatial alignment of functional images from different subjects. The algorithm is based on a generative model that comprises two main layers. At the lower level, we express the functional brain response to each stimulus as a binary activation variable. At the next level, we define a prior over sets of activation variables in all sub- jects. We use a Hierarchical Dirichlet Process as the prior in order to learn the patterns of functional specific- ity shared across the group, which we call functional systems, and estimate the number of these systems. Inference based on our model enables automatic discovery and characterization of dominant and consistent functional systems. We apply the method to data from a visual fMRI study comprised of 69 distinct stimulus images. The discovered system activation profiles correspond to selectivity for a number of image categories such as faces, bodies, and scenes. Among systems found by our method, we identify new areas that are deac- tivated by face stimuli. In empirical comparisons with previously proposed exploratory methods, our results appear superior in capturing the structure in the space of visual categories of stimuli.
 

Lashkari D., Sridharan R., Vul E., Hsieh P-J., Kanwisher N. & Golland P. (in-p) Search for patterns of functional specificity in the brain: a nonparametric hierarchical Bayesian model for group fMRI data., NeuroImage, (),
 

no bibtex style for type
 

Ambiguous images present a challenge to the visual system: how can uncertainty about the causes of visual inputs be represented when there are multiple equally plausible causes? A Bayesian ideal observer should represent uncertainty in the form of a pos- terior probability distribution over causes. However, in many real-world situations, computing this distribution is intractable and requires some form of approximation. We argue that the visual system approximates the posterior over underlying causes with a set of samples and that this approximation strategy produces perceptual multistability— stochastic alternation between percepts in consciousness. Under our analysis, multi- stability arises from a dynamic sample-generating process that explores the posterior through stochastic diffusion, implementing a rational form of approximate Bayesian inference known as Markov chain Monte Carlo (MCMC). We examine in detail the most extensively studied form of multistability, binocular rivalry, showing how a va- riety of experimental phenomena—Gamma-like stochastic switching, patchy percepts, fusion, and traveling waves—can be understood in terms of MCMC sampling over sim- ple graphical models of the underlying perceptual tasks. We conjecture that the stochas- tic nature of spiking neurons may lend itself to implementing sample-based posterior approximations in the brain.
 

Gershman S., Vul E. & Tenenbaum JB. (in-p) Multistability and perceptual inference., Neural Computation, (),
 

no bibtex style for type
 

How do young children direct their attention to other people in the natural world? Although many studies have examined the perception of faces and of goal-directed actions, relatively little work has focused on what children will look at in complex and unconstrained viewing environments. To address this question, we showed videos of objects, faces, children playing with toys, and complex social scenes to a large sample of infants and toddlers between 3 and 30 months old. We found systematic developmental changes in what children looked at. When viewing faces alone, younger children looked more at eyes and older children more at mouths, especially when the faces were making expressions or talking. In the more complex videos, older children looked more at hands than younger children, especially when the hands were performing actions. Our results suggest that as children develop they become better able to direct their attention to the parts of complex scenes that are most interesting socially.
 

Frank MC., Vul E. & Saxe R. (2011) Measuring the development of social attention using free-viewing, Infancy, (), 1-21
 

@article{2011,
Author = {MC Frank and E Vul and R Saxe},
Title = {Measuring the development of social attention using free-viewing},
Journal = {Infancy},
Volume = {},
Number = {},
Pages = {1-21},
Year = {2011}}
 

Many organisms can predict future events from the statistics of past experience, but humans also excel at making predictions by pure reasoning: integrating multiple sources of information, guided by abstract knowledge, to form rational expectations about novel situations, never directly experienced. Here, we show that this reasoning is surprisingly rich, powerful, and coherent even in preverbal infants. When 12-month-old infants view complex displays of multiple moving objects, they form time-varying expectations about future events that are a systematic and rational function of several stimulus variables. Infants’ looking times are consistent with a Bayesian ideal observer embodying abstract principles of object motion. The model explains infants’ statistical expectations and classic qualitative findings about object cognition in younger babies, not originally viewed as probabilistic inferences.
 

Teglas E., Vul E., Girotto V., Gonzalez M., Tenenbaum JB. & Bonatti LL. (2011) Pure reasoning in 12-month-olds as probabilistic inference., Science, 332(6033), 1054-1059
 

@article{2011,
Author = {E Teglas and E Vul and V Girotto and M Gonzalez and JB Tenenbaum and LL Bonatti},
Title = {Pure reasoning in 12-month-olds as probabilistic inference.},
Journal = {Science},
Volume = {332},
Number = {6033},
Pages = {1054-1059},
Year = {2011}}
 

In three experiments, we used face–name learning to examine the puzzling feedback delay benefit—the tendency for feedback to be more effective when it is delayed rather than presented immediately. In Experiment 1, we found that feedback presented after a 3-s blank screen was more effective than feedback presented immediately, even after controlling for the exposure time to the material. In Experiment 2, we replicated the benefit of a feedback delay even when participants were given extra time to view the feedback or to try to retrieve the answer, indicating that this benefit is specific to a delay before feedback. Finally, in Experiment 3, we showed that the 3-s delay is beneficial only if it involves a blank screen, not if the delay is filled with an unrelated distracter task. These results suggest that the feedback delay benefit in this paradigm could arise from an active anticipatory process that occurs during the delay.
 

Carpenter SK. & Vul E. (2011) Delaying feedback by three seconds benefits retention of face-name pairs: The role of active anticipatory processing. , Memory & Cognition, 39(7), 1211-1221
 

@article{2011,
Author = {SK Carpenter and E Vul},
Title = {Delaying feedback by three seconds benefits retention of face-name pairs: The role of active anticipatory processing. },
Journal = {Memory & Cognition},
Volume = {39},
Number = {7},
Pages = {1211-1221},
Year = {2011}}
 

 

Vul E. (2011) Reductionism and practicality, Psychological Inquiry, 22(2), 137-138
 

@article{2011,
Author = {E Vul},
Title = {Reductionism and practicality},
Journal = {Psychological Inquiry},
Volume = {22},
Number = {2},
Pages = {137-138},
Year = {2011}}
 

Unlike laboratory experiments, real-world visual search can contain multiple targets. Searching for an unknown number of targets creates a unique set of challenges for the observer, and often produces serious errors. We propose a Bayesian op- timal foraging model to predict and describe behavior in such search scenarios, and investigate whether people adapt their search strategies based on complex statistics of target distribu- tions. Separate groups searched arrays drawn from three target distributions with the same average number of targets per dis- play, but different target-clustering properties. As predicted, participants searched longer when they expected more targets to remain and adjusted their expectations as searches unfolded, indicating that searchers are sensitive to the target distribution, consistent with both an optimal foraging framework and an ideal Bayesian observer. However, compared to the ideal ob- servers, searchers systematically under-adjusted to the target distribution, suggesting that training could improve multiple- target search in radiology and other crucial applications.
 

Cain M., Vul E., Clark K. & Mittroff SA. (2011) Optimal models of human multiple-target visual search., Proceedings of the 33 Annual Meetings of the Cognitive Science Society, (),
 

@inproceedings{2011,
Author = {M Cain and E Vul and K Clark and SA Mittroff},
Title = {Optimal models of human multiple-target visual search.},
Booktitle = {Proceedings of the 33 Annual Meetings of the Cognitive Science Society},
Pages = {},
Address = {},
Year = {2011}}
 

We develop a method for unsupervised analysis of functional brain images that learns group-level patterns of functional response. Our algorithm is based on a generative model that comprises two main layers. At the lower level, we express the functional brain response to each stimulus as a binary activation variable. At the next level, we define a prior over the sets of activation variables in all subjects. We use a Hierarchical Dirichlet Process as the prior in order to simultaneously learn the patterns of response that are shared across the group, and to estimate the number of these patterns supported by data. Inference based on this model enables automatic discovery and characterization of salient and consistent patterns in functional signals. We apply our method to data from a study that explores the response of the visual cortex to a collection of images. The discovered profiles of activation correspond to selectivity to a number of image categories such as faces, bodies, and scenes. More generally, our results appear superior to the results of alternative data-driven methods in capturing the category structure in the space of stimuli.
 

Lashkari D., Sridharan R., Vul E., Hsieh P-J., Kanwisher N. & Golland P. (2010) Nonparametric hierarchical Bayesian model for functional brain parcellation, MMBIA: IEEE Workshop on Mathematical Methods in Biomedical Image Analysis, (),
 

@inproceedings{2010,
Author = {D Lashkari and R Sridharan and E Vul and P-J Hsieh and N Kanwisher and P Golland},
Title = {Nonparametric hierarchical Bayesian model for functional brain parcellation},
Booktitle = {MMBIA: IEEE Workshop on Mathematical Methods in Biomedical Image Analysis},
Pages = {},
Address = {},
Year = {2010}}
 

The study of cognition, perception, and behavior often requires the estimation of thresholds as a function of continuous independent variables (e.g., contrast threshold as a function of spatial frequency, subjective value as a function of reward delay, tracking speed as a function of the number of objects tracked). Unidimensional adaptive testing methods make estimation of single threshold values faster and more efficient, but substantial efficiency can be further gained by taking into account the relationship between thresholds at different values of an independent variable. Here we present a generic method -- Functional Adaptive Sequential Testing (FAST) -- for estimating thresholds as a function of another variable. This method allows efficient estimation of parameters relating an independent variable (e.g., stimulus spatial frequency; or reward delay) to the measured threshold along a stimulus strength dimension (e.g., contrast; or present monetary value). We formally describe the FAST algorithm and introduce a Matlab toolbox implementation thereof; we then evaluate several possible sampling and estimation algorithms for such two-dimensional functions. Our results demonstrate that efficiency can be substantially increased by considering the functional relationship between thresholds at different values of the independent variable of interest.
 

Vul E., Bergsma J. & MacLeod D.I.A. (2010) Functional Adaptive Sequential Testing, Seeing and Perceiving, (),
 

@article{2010,
Author = {E Vul and J Bergsma and D I A MacLeod},
Title = {Functional Adaptive Sequential Testing},
Journal = {Seeing and Perceiving},
Volume = {},
Number = {},
Pages = {},
Year = {2010}}
 

Decades of research suggest that selective attention is critical for binding the features of objects together for conscious perception. A fundamental question, however, remains unresolved: How do people perceive objects, albeit with binding errors (illusory conjunctions), when attentional resolution is poor? We used a novel technique to investigate how features are selected to create percepts of bound objects. We measured the correlation of errors (intrusions) in color and identity reports in spatial and temporal selection tasks under conditions of varying spatial or temporal uncertainty. Our findings suggest that attention selects each feature independently by randomly sampling from a probability distribution over space or time. Thus, veridical perception of bound object features arises only when attentional selection is sufficiently precise that the independently sampled features originate from a single object.
 

Vul E. & Rich A. (2010) Independent sampling of features enables conscious perception of bound objects, Psychological Science, (),
 

@article{2010,
Author = {E Vul and A Rich},
Title = {Independent sampling of features enables conscious perception of bound objects},
Journal = {Psychological Science},
Volume = {},
Number = {},
Pages = {},
Year = {2010}}
 

Over the past year, a heated discussion about 'circular' or 'nonindependent' analysis in brain imaging has emerged in the literature. An analysis is circular (or nonindependent) if it is based on data that were selected for showing the effect of interest or a related effect. The authors of this paper are researchers who have contributed to the discussion and span a range of viewpoints. To clarify points of agreement and disagreement in the community, we collaboratively assembled a series of questions on circularity herein, to which we provide our individual current answers in  

Kriegeskorte N., Lindquist M.A., Nichols T.E., Poldrack R.A. & Vul E. (2010) Everything you never wanted to know about circular analysis, but were afraid to ask, Journal of Cerebral Blood Flow and Metabolism, (), 1-7
 

@article{2010,
Author = {N Kriegeskorte and M A Lindquist and T E Nichols and R A Poldrack and E Vul},
Title = {Everything you never wanted to know about circular analysis, but were afraid to ask},
Journal = {Journal of Cerebral Blood Flow and Metabolism},
Volume = {},
Number = {},
Pages = {1-7},
Year = {2010}}
 

We present a method for discovering patterns of selectivity in fMRI data for experiments with multiple stimuli/tasks. We introduce a representation of the data as profiles of selectivity using linear regression estimates, and employ mixture model density estimation to identify functional systems with distinct types of selectivity. The method characterizes these systems by their selectivity patterns and spatial maps, both estimated simultaneously via the EM algorithm. We demonstrate a corresponding method for group analysis that avoids the need for spatial correspondence among subjects. Consistency of the selectivity profiles across subjects provides a way to assess the validity of the discovered systems. We validate this model in the context of category selectivity in visual cortex, demonstrating good agreement with the findings based on prior hypothesis-driven methods.
 

Lashkari D., Vul E., Kanwisher N. & Golland P. (2010) Discovering structure in the space of fMRI selectivity profiles, NeuroImage, 80(), 1085-1098
 

@article{2010,
Author = {D Lashkari and E Vul and N Kanwisher and P Golland},
Title = {Discovering structure in the space of fMRI selectivity profiles},
Journal = {NeuroImage},
Volume = {80},
Number = {},
Pages = {1085-1098},
Year = {2010}}
 

 

Vul E. & Kanwisher N. (2010) On the advantages of not having to rely on multiple comparison corrections, Foundational issues in Human Brain Mapping, (), 97-98
 

no bibtex style for type incollection
 

 

Vul E. & Kanwisher N. (2010) Begging the question: The non-independence error in fMRI data analysis, Foundational issues for human brain mapping, (),
 

no bibtex style for type incollection
 

When individuals learn facts (e.g., foreign language vocabulary) over multiple study sessions, the temporal spacing of study has a significant impact on memory retention. Behavioral experiments have shown a nonmonotonic relationship between spacing and retention: short or long intervals between study sessions yield lower cued-recall accuracy than intermediate intervals. Appropriate spacing of study can double retention on educationally relevant time scales. We introduce a Multiscale Context Model (MCM) that is able to predict the influence of a particular study schedule on retention for specific material. MCM’s prediction is based on empirical data characterizing forgetting of the material following a single study session. MCM is a synthesis of two existing memory models (Staddon, Chelaru, & Higa, 2002; Raaijmakers, 2003). On the surface, these models are unrelated and incompatible, but we show they share a core feature that allows them to be integrated. MCM can determine study schedules that maximize the durability of learning, and has implications for education and training. MCM can be cast either as a neural network with inputs that fluctuate over time, or as a cascade of leaky integrators. MCM is intriguingly similar to a Bayesian multiscale model of memory (Kording, Tenenbaum, & Shadmehr, 2007), yet MCM is better able to account for human declarative memory.
 

Mozer M.C., Pashler H., Cepeda N., Lindsey R. & Vul E. (2010) Predicting the optimal spacing of study: A multiscale context model of memory, Advances in Neural Information Processing Systems 22, (),
 

@inproceedings{2010,
Author = {M C Mozer and H Pashler and N Cepeda and R Lindsey and E Vul},
Title = {Predicting the optimal spacing of study: A multiscale context model of memory},
Booktitle = {Advances in Neural Information Processing Systems 22},
Pages = {},
Address = {},
Year = {2010}}
 

While many perceptual and cognitive phenomena are well described in terms of Bayesian inference, the necessary computations are intractable at the scale of real-world tasks, and it remains unclear how the human mind approximates Bayesian inference algorithmically. We explore the proposal that for some tasks, humans use a form of Markov Chain Monte Carlo to approximate the posterior distribution over hidden variables. As a case study, we show how several phenomena of perceptual multistability can be explained as MCMC inference in simple graphical models for low-level vision.
 

Gershman S.J., Vul E. & Tenenbaum J.B. (2010) Perceptual multistability as Marko Chain Monte Carlo inference, Advances in Neural Information Processing Systems 22, (),
 

@inproceedings{2010,
Author = {S J Gershman and E Vul and J B Tenenbaum},
Title = {Perceptual multistability as Marko Chain Monte Carlo inference},
Booktitle = {Advances in Neural Information Processing Systems 22},
Pages = {},
Address = {},
Year = {2010}}
 

Multiple object tracking is a task commonly used to investigate the architecture of human visual attention. Human participants show a distinctive pattern of successes and failures in tracking experiments that is often attributed to limits on an object system, a tracking module, or other specialized cognitive structures. Here we use a computational analysis of the task of object tracking to ask which human failures arise from cognitive limitations and which are consequences of inevitable perceptual uncertainty in the tracking task. We find that many human performance phenomena, measured through novel behavioral experiments, are naturally produced by the operation of our ideal observer model (a Rao-Blackwelized particle filter). The tradeoff between the speed and number of objects being tracked, however, can only arise from the allocation of a flexible cognitive resource, which can be formalized as either memory or attention.
 

Vul E., Frank M.C., Alvarez G.A. & Tenenbaum J.B. (2010) Explaining human multiple object tracking as resource-constrained approximate inference in a dynamic probabilistic model, Advances in Neural Information Processing Systems 22, (),
 

@inproceedings{2010,
Author = {E Vul and M C Frank and G A Alvarez and J B Tenenbaum},
Title = {Explaining human multiple object tracking as resource-constrained approximate inference in a dynamic probabilistic model},
Booktitle = {Advances in Neural Information Processing Systems 22},
Pages = {},
Address = {},
Year = {2010}}
 

Theories of probabilistic cognition postulate that internal representations are made up of multiple simultaneously held hypotheses, each with its own probability of being correct (henceforth, “probability distributions”). However, subjects make discrete responses and report the phenomenal contents of their mind to be all-or-none states rather than graded probabilities. How can these 2 positions be reconciled? Selective attention tasks, such as those used to study crowding, the attentional blink, rapid serial visual presentation, and so forth, were recast as probabilistic inference problems and used to assess how graded, probabilistic representations may produce discrete subjective states. The authors asked subjects to make multiple guesses per trial and used 2nd-order statistics to show that (a) visual selective attention operates in a graded fashion in time and space, selecting multiple targets to varying degrees on any given trial; and (b) responses are generated by a process of sampling from the probabilistic states that result from graded selection. The authors concluded that although people represent probability distributions, their discrete responses and conscious states are products of a process that samples from these probabilistic representations.
 

Vul E., Hanus D. & Kanwisher N. (2009) Attention as inference: Selection is probabilistic; Responses are all-or-none samples, Journal of Experimental Psychology: General, 138(4), 540-560
 

@article{2009,
Author = {E Vul and D Hanus and N Kanwisher},
Title = {Attention as inference: Selection is probabilistic; Responses are all-or-none samples},
Journal = {Journal of Experimental Psychology: General},
Volume = {138},
Number = {4},
Pages = {540-560},
Year = {2009}}
 

In many situations human behavior approximates that of a Bayesian ideal observer, suggesting that, at some level, cognition can be described as Bayesian inference. However, a number of findings have highlighted an intriguing mismatch between human behavior and that predicted by Bayesian inference: people often appear to make judgments based on a few samples from a probability distribution, rather than the full distribution. Although sample-based approximations are a common implementation of Bayesian inference, the very limited number of samples used by humans seems to be insufficient to approximate the required probability distributions. Here we consider this discrepancy in the broader framework of statistical decision theory, and ask: if people were making decisions based on samples, but samples were costly, how many samples should people use? We find that under reasonable assumptions about how long it takes to produce a sample, locally suboptimal decisions based on few samples are globally optimal. These results reconcile a large body of work showing sampling, or probability-matching, behavior with the hypothesis that human cognition is well described as Bayesian inference, and suggest promising future directions for studies of resource-constrained cognition.
 

Vul E., Goodman N.D., Griffiths T.L. & Tenenbaum J.B. (2009) One and Done? Optimal decisions from very few samples, Proceedings of the 31st Annual Conference of the Cognitive Science Society, (),
 

@inproceedings{2009,
Author = {E Vul and N D Goodman and T L Griffiths and J B Tenenbaum},
Title = {One and Done? Optimal decisions from very few samples},
Booktitle = {Proceedings of the 31st Annual Conference of the Cognitive Science Society},
Pages = {},
Address = {Amsterdam, Netherlands},
Year = {2009}}
 

We are grateful to the commentators for providing many stimulating and valuable observations. The main point of our article was to call attention to the overestimation of individual differences correlations in a subset of neuroimaging papers. To structure our discussion of these comments, we list the main points from our paper, note where commentators have agreed or disagreed with each, and provide our own reactions to their comments.
 

Vul E., Harris C., Winkielman P. & Pashler H. (2009) Reply to comments on Puzzlingly high correlations in fMRI studies of emotion, personality, and social cognition, Perspectives on Psychological Science, 4(3), 319-324
 

@article{2009,
Author = {E Vul and C Harris and P Winkielman and H Pashler},
Title = {Reply to comments on Puzzlingly high correlations in fMRI studies of emotion, personality, and social cognition},
Journal = {Perspectives on Psychological Science},
Volume = {4},
Number = {3},
Pages = {319-324},
Year = {2009}}
 

In simple tests of preference, infants as young as newborns prefer faces and face-like stimuli over distractors. Little is known, however, about the development of attention to faces in complex scenes. We recorded eye-movements of 3-, 6-, and 9-month-old infants and adults during free-viewing of clips from A Charlie Brown Christmas (an animated film). The tendency to look at faces increased with age. Using novel computational tools, we found that 3-month-olds were less consistent (across individuals) in where they looked than were older infants. Moreover, younger infants’ fixations were best predicted by low-level image salience, rather than the locations of faces. Between 3 and 9 months of age, infants gradually focused their attention on faces. We discuss several possible interpretations of this shift in terms of social development, cross-modal integration, and attentional/executive control.
 

Frank M.C., Vul E. & Johnson S.P. (2009) Development of infants attention to faces during the first year, Cognition, 110(), 160-170
 

@article{2009,
Author = {M C Frank and E Vul and S P Johnson},
Title = {Development of infants attention to faces during the first year},
Journal = {Cognition},
Volume = {110},
Number = {},
Pages = {160-170},
Year = {2009}}
 

Functional magnetic resonance imaging (fMRI) studiesofemotion, personality, and social cognition have drawn much attention in recent years, with high-profile studies frequently reporting extremely high (e.g., >.8) correlations between brain activation and personality measures. We show that these correlations are higher than should be expected given the (evidently limited) reliability of both fMRI and personality measures. The high correlations are all the more puzzling because method sections rarely contain much detail about how the correlations were obtained. We surveyed authors of 55 articles that reported findings of this kind to determine a few details on how these correlations were computed. More than half acknowledged using a strategy that computes separate correlations for individual voxels and reports means of only those voxels exceeding chosen thresholds. We show how this nonindependent analysis inflates correlations while yielding reassuring-looking scattergrams. This analysis technique was used to obtain the vast majority of the implausibly high correlations in our survey sample. In addition, we argue that, in some cases, other analysis problems likely created entirely spurious correlations. We outline how the data from these studies could be reanalyzed with unbiased methods to provide accurate estimates of the correlations in question and urge authors to perform such reanalyses. The underlying problems described here appear to be common in fMRI research of many kinds—not just in studies of emotion, personality, and social cognition.
 

Vul E., Harris C., Winkielman P. & Pashler H. (2009) Puzzlingly high correlations in fMRI studies of emotion, personality, and social cognition, Perspectives on Psychological Science, 4(3), 274-290
 

@article{2009,
Author = {E Vul and C Harris and P Winkielman and H Pashler},
Title = {Puzzlingly high correlations in fMRI studies of emotion, personality, and social cognition},
Journal = {Perspectives on Psychological Science},
Volume = {4},
Number = {3},
Pages = {274-290},
Year = {2009}}
 

We develop a method for unsupervised analysis of functional brain images that learns group-level patterns of functional response. Our algorithm is based on a generative model that comprises two main layers. At the lower level, we express the functional brain response to each stimulus as a binary activation variable. At the next level, we de- fine a prior over the sets of activation variables in all subjects. We use a Hierarchical Dirichlet Process as the prior in order to simultaneously learn the patterns of response that are shared across the group, and to estimate the number of these patterns supported by data. Inference based on this model enables automatic discovery and characterization of salient and consistent patterns in functional signals. We apply our method to data from a study that explores the response of the visual cortex to a collection of images. The discovered profiles of activation correspond to selectivity to a number of image categories such as faces, bodies, and scenes. More generally, our results appear superior to the results of alternative data-driven methods in capturing the category structure in the space of stimuli.
 

Lashkari D., Vul E., Kanwisher N. & Golland P. (2008) Discovering structure in the space of activation profiles in fMRI, MICCAI, Part 1(LNCS), 52411016-102
 

@article{2008,
Author = {D Lashkari and E Vul and N Kanwisher and P Golland},
Title = {Discovering structure in the space of activation profiles in fMRI},
Journal = {MICCAI},
Volume = {Part 1},
Number = {LNCS},
Pages = {52411016-102},
Year = {2008}}
 

To achieve enduring retention, people must usually study information on multiple occasions. How does the timing of study events affect retention? Prior research has examined this issue only in a spotty fashion, usually with very short time intervals. In a study aimed at characterizing spacing effects over significant durations, more than 1,350 individuals were taught a set of facts and--after a gap of up to 3.5 months--given a review. A final test was administered at a further delay of up to 1 year. At any given test delay, an increase in the interstudy gap at first increased, and then gradually reduced, final test performance. The optimal gap increased as test delay increased. However, when measured as a proportion of test delay, the optimal gap declined from about 20 to 40% of a 1-week test delay to about 5 to 10% of a 1-year test delay. The interaction of gap and test delay implies that many educational practices are highly inefficient.
 

Cepeda N.J., Vul E., Rohrer D., Wixted J.T. & Pashler H. (2008) Spacing effects in learning: A temporal ridgeline of optimal retention, Psychological Science, 19(11), 1095-1102
 

@article{2008,
Author = {N J Cepeda and E Vul and D Rohrer and J T Wixted and H Pashler},
Title = {Spacing effects in learning: A temporal ridgeline of optimal retention},
Journal = {Psychological Science},
Volume = {19},
Number = {11},
Pages = {1095-1102},
Year = {2008}}
 

The attentional blink is the inability to report the second of two targets in an RSVP stream when they are separated by 200-500 ms. Recent evidence shows that this failure results from three dissociable changes to the properties of temporal selective attention. During the attentional blink, selection is suppressed (items are selected less effectively, resulting in greater levels of random guessing), diffused (more letters around the target are selected), and delayed (the items that are selected tend to be later in the RSVP stream relative to the cue) [Vul, E., Nieuwenstein, M., & Kanwisher, N. (2008). Temporal selection is suppressed, delayed, and diffused during the attentional blink. Psychological Science, 19(1), 55-61]. Here we assess the properties of the delay in selection and evaluate how the delay contributes to the attentional blink. First, by pre-cueing, we manipulate the delay of selective attention and show that neither delay nor suppression alone is sufficient to account for the failure to report the second target; thus both play a role in the usual attentional blink. Second, we explore the persistence of the delay effect over much longer T1-T2 SOAs and show that the effect remains strong at lags of 1,400 ms and appears to subside with a time-constant of roughly 500 ms. Third, we manipulate RSVP rate and find that the "delay" of selection is a delay in time, independent of the number of items.
 

Vul E., Hanus D. & Kanwisher N. (2008) Delay os selective attention during the attentional blink, Vision Research, 48(18), 1902-1909
 

@article{2008,
Author = {E Vul and D Hanus and N Kanwisher},
Title = {Delay os selective attention during the attentional blink},
Journal = {Vision Research},
Volume = {48},
Number = {18},
Pages = {1902-1909},
Year = {2008}}
 

The brain encounters input varying with many different time courses. Given such temporal variability, it would seem practical for adaptation to operate at multiple timescales. Indeed, to account for peculiar effects such as spacing, savings, and spontaneous recovery, many recent models of learning and adaptation have postulated multiple mechanisms operating at different timescales. However, despite this assumption, and compelling modelling results, different timescales of cortical adaptation and learning are rarely isolated in behaving animals. Here we demonstrate in a series of experiments that early visual cortex adapts at two distinct and separable timescales: fast (saturating with a time constant of roughly 30 seconds) and infinite (a perfect integrator: exhibiting no signs of decay or diminishing returns within the range of intervals tested). We further demonstrate that these two timescales sum linearly and appear to be operating independently and in parallel.
 

Vul E., Krizay E. & MacLeod D.I.A. (2008) The McCollough effect reflects permanent and transient adaptation in early visual cortex, Journal of Vision, 8(12), 1-12
 

@article{2008,
Author = {E Vul and E Krizay and D I A MacLeod},
Title = {The McCollough effect reflects permanent and transient adaptation in early visual cortex},
Journal = {Journal of Vision},
Volume = {8},
Number = {12},
Pages = {1-12},
Year = {2008}}
 

A crowd often possesses better information than do the individuals it comprises. For example, if people are asked to guess the weight of a prize-winning ox, the error of the average response is substantially smaller than the average error of individual estimates. This fact, which Galton interpreted as support for democratic governance, is responsible for the success of polling the audience in the television program "Who Wants to be a Millionaire" and for the superiority of combined over individual financial forecasts. Researchers agree that this wisdom-of-crowds effect depends on a statistical fact: The crowd's average will be more accurate as long as some of the error of one individual is statistically independent of the error of other individuals--as seems almost guaranteed to be the case. We recruited 428 participants from an Internet-based subject pool and asked them eight questions probing their real-world knowledge. Although people assume that their first guess about a matter of fact exhausts the best information available to them, a forced second guess contributes additional information, such that the average of two guesses is better than either guess alone. This observed benefit of averaging multiple responses from the same person suggests that responses made by a subject are sampled from an internal probability distribution, rather than deterministically selected on the basis of all the knowledge a subject has.
 

Vul E. & Pashler H. (2008) Measuring the crowd within: Probabilistic representations within individuals, Psychological Science, 19(7), 645-647
 

@article{2008,
Author = {E Vul and H Pashler},
Title = {Measuring the crowd within: Probabilistic representations within individuals},
Journal = {Psychological Science},
Volume = {19},
Number = {7},
Pages = {645-647},
Year = {2008}}
 

How does temporal selection work, and along what dimensions does it vary from one instance to the next? We explored these questions using a phenomenon in which temporal selection goes awry. In the attentional blink, subjects fail to report the second of a pair of targets (T1 and T2) when they are presented at stimulus onset asyn-chronies (SOAs) of roughly 200 to 500 ms. We directly tested the properties of temporal selection during the blink by analyzing distractor intrusions at a fast rate of item presentation. Our analysis shows that attentional selection is (a) suppressed, (b) delayed, and (c) diffused in time during the attentional blink. These effects are dissociated by their time course: The measure of each effect returns to the baseline value at a different SOA. Our results constrain theories of the attentional blink and indicate that temporal selection varies along at least three dissociable dimensions: efficacy, latency, and precision.
 

Vul E., Nieuwenstein M. & Kanwisher N. (2008) Temporal selection is suppressed, delayed, and diffused during the attentional blink, Psychological Science, 19(1), 55-61
 

@article{2008,
Author = {E Vul and M Nieuwenstein and N Kanwisher},
Title = {Temporal selection is suppressed, delayed, and diffused during the attentional blink},
Journal = {Psychological Science},
Volume = {19},
Number = {1},
Pages = {55-61},
Year = {2008}}
 

Incubation refers to the popular idea that stopping work on a problem may, at times, be a more efficient means by which to reach a solution than continuing to work. Empirical studies of incubation have used few participants and have provided ambiguous and discrepant results. We investigated three potential accounts of incubation in retrieval and search problems (subconscious work, spreading activation, and fixation forgetting) with the help of a large Internet-based participant pool. The amount of time allotted for explicit work on each of 12 problems was controlled, while the distribution of that time was manipulated in several incubation conditions. When problems were presented by themselves, none of the incubation conditions aided in the solution of either anagram or remote associate test problems. However, incubation benefits arose when participants were given misdirecting clues (probably because time delays facilitated forgetting of these clues).
 

Vul E. & Pashler H. (2007) Incubation is helpful only when people have been misdirected, Memory and Cognition, 35(4), 701-710
 

@article{2007,
Author = {E Vul and H Pashler},
Title = {Incubation is helpful only when people have been misdirected},
Journal = {Memory and Cognition},
Volume = {35},
Number = {4},
Pages = {701-710},
Year = {2007}}
 

In two experiments, we investigated what types of learning benefit from a cued recall test. After initial exposure to a word pair (A+B), subjects experienced either an intervening cued recall test (A-->?) with feedback, or a restudy presentation (A-->B). The final test could be cued recall in the same (A-->?) or opposite (?-->B) direction, or free recall of just the cues (Recall As) or just the targets (Recall Bs). All final tests revealed a benefit for testing as opposed to restudying. Tests produced a direct benefit for information that was retrieved on the intervening test (B). This benefit also "spilled over" to facilitate recall of information that was present on the test but not retrieved (A). Both theoretical and practical implications are discussed.
 

Carpenter S.K., Pashler H. & Vul E. (2006) What type of learning is enhanced by a cued recall test?, Psychonomic Bulletin and Review, 13(5), 826-830
 

@article{2006,
Author = {S K Carpenter and H Pashler and E Vul},
Title = {What type of learning is enhanced by a cued recall test?},
Journal = {Psychonomic Bulletin and Review},
Volume = {13},
Number = {5},
Pages = {826-830},
Year = {2006}}
 

Basic geometric patterns like straight lines and circles seem fundamental to human perception and mental imagery. In this study we examined subjects' ability to interpolate circular curves-to derive the whole circle from an arc of 180 degrees or less. Specifically, we tested how the center point is utilized during such visual interpolation. Naturally, a mechanism that interpolates by extending the curvature of the visible arc will be unaffected by the presence or absence of the center point. On the other hand, a mechanism that achieves the same end by completing the circle from estimates of the center and radius will be significantly aided by the presence of the center. We found that when the visible arc was long (180 degrees), presenting the circle's center did not affect the precision with which subjects localized the invisible section. However, when the visible arc was relatively short (90 degrees or 45 degrees), displaying the center point significantly increased spatial precision. Thus, both computational mechanisms appear to exist.
 

Huang L. & Vul E. (2006) Role of a circle's center to visual interpolation, Vision Research, 46(15), 2311-2314
 

@article{2006,
Author = {L Huang and E Vul},
Title = {Role of a circle's center to visual interpolation},
Journal = {Vision Research},
Volume = {46},
Number = {15},
Pages = {2311-2314},
Year = {2006}}
 

The authors performed a meta-analysis of the distributed practice effect to illuminate the effects of temporal variables that have been neglected in previous reviews. This review found 839 assessments of distributed practice in 317 experiments located in 184 articles. Effects of spacing (consecutive massed presentations vs. spaced learning episodes) and lag (less spaced vs. more spaced learning episodes) were examined, as were expanding interstudy interval (ISI) effects. Analyses suggest that ISI and retention interval operate jointly to affect final-test retention; specifically, the ISI producing maximal retention increased as retention interval increased. Areas needing future research and theoretical implications are discussed.
 

Cepeda N., Pashler H., Vul E., Wixted J. & Rohrer D. (2006) Distribution of practice in verbal recall tasks: a review and quantitative synthesis, Psychological Bulletin, 132(3), 354-380
 

@article{2006,
Author = {N Cepeda and H Pashler and E Vul and J Wixted and D Rohrer},
Title = {Distribution of practice in verbal recall tasks: a review and quantitative synthesis},
Journal = {Psychological Bulletin},
Volume = {132},
Number = {3},
Pages = {354-380},
Year = {2006}}
 

The brain can process input without perception, but what distinguishes conscious from preconscious processing? Using aftereffects induced by quickly alternating images, we show that cortical mechanisms track color much faster than perception, responding well to color alternations that are too rapid to be perceptible. The more restricted frequency response of the conscious perception of color suggests that extra integrative steps give conscious color perception a time course substantially slower than that of early cortical mechanisms.
 

Vul E. & MacLeod D.I.A. (2006) Contingent after-effects distinguish conscious and pre-conscious colour processing, Nature Neuroscience, 9(7), 873-874
 

@article{2006,
Author = {E Vul and D I A MacLeod},
Title = {Contingent after-effects distinguish conscious and pre-conscious colour processing},
Journal = {Nature Neuroscience},
Volume = {9},
Number = {7},
Pages = {873-874},
Year = {2006}}