Publications by authors named "Laurence T Maloney"

96 Publications

Two sources of uncertainty independently modulate temporal expectancy.

Proc Natl Acad Sci U S A 2021 Apr;118(16)

Department of Neuroscience, Max-Planck-Institute for Empirical Aesthetics, Frankfurt 60322, Germany.

The environment is shaped by two sources of temporal uncertainty: the discrete probability of whether an event will occur and-if it does-the continuous probability of when it will happen. These two types of uncertainty are fundamental to every form of anticipatory behavior including learning, decision-making, and motor planning. It remains unknown how the brain models the two uncertainty parameters and how they interact in anticipation. It is commonly assumed that the discrete probability of whether an event will occur has a fixed effect on event expectancy over time. In contrast, we first demonstrate that this pattern is highly dynamic and monotonically increases across time. Intriguingly, this behavior is independent of the continuous probability of when an event will occur. The effect of this continuous probability on anticipation is commonly proposed to be driven by the hazard rate (HR) of events. We next show that the HR fails to account for behavior and propose a model of event expectancy based on the probability density function of events. Our results hold for both vision and audition, suggesting independence of the representation of the two uncertainties from sensory input modality. These findings enrich the understanding of fundamental anticipatory processes and have provocative implications for many aspects of behavior and its neural underpinnings.
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http://dx.doi.org/10.1073/pnas.2019342118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8072397PMC
April 2021

The bounded rationality of probability distortion.

Proc Natl Acad Sci U S A 2020 09 25;117(36):22024-22034. Epub 2020 Aug 25.

Department of Psychology, New York University, New York, NY 10003.

In decision making under risk (DMR) participants' choices are based on probability values systematically different from those that are objectively correct. Similar systematic distortions are found in tasks involving relative frequency judgments (JRF). These distortions limit performance in a wide variety of tasks and an evident question is, Why do we systematically fail in our use of probability and relative frequency information? We propose a bounded log-odds model (BLO) of probability and relative frequency distortion based on three assumptions: 1) log-odds: probability and relative frequency are mapped to an internal log-odds scale, 2) boundedness: the range of representations of probability and relative frequency are bounded and the bounds change dynamically with task, and 3) variance compensation: the mapping compensates in part for uncertainty in probability and relative frequency values. We compared human performance in both DMR and JRF tasks to the predictions of the BLO model as well as 11 alternative models, each missing one or more of the underlying BLO assumptions (factorial model comparison). The BLO model and its assumptions proved to be superior to any of the alternatives. In a separate analysis, we found that BLO accounts for individual participants' data better than any previous model in the DMR literature. We also found that, subject to the boundedness limitation, participants' choice of distortion approximately maximized the mutual information between objective task-relevant values and internal values, a form of bounded rationality.
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http://dx.doi.org/10.1073/pnas.1922401117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7486738PMC
September 2020

Measuring and Modeling Visual Appearance.

Annu Rev Vis Sci 2020 09 18;6:519-537. Epub 2020 May 18.

Université Lyon, Université Claude Bernard Lyon 1, INSERM, Stem Cell and Brain Research Institute U1208, 69500 Bron, France; email:

In studying visual perception, we seek to develop models of processing that accurately predict perceptual judgments. Much of this work is focused on judgments of discrimination, and there is a large literature concerning models of visual discrimination. There are, however, non-threshold visual judgments, such as judgments of the magnitude of differences between visual stimuli, that provide a means to bridge the gap between threshold and appearance. We describe two such models of suprathreshold judgments, maximum likelihood difference scaling and maximum likelihood conjoint measurement, and review recent literature that has exploited them.
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http://dx.doi.org/10.1146/annurev-vision-030320-041152DOI Listing
September 2020

The anticipation of events in time.

Nat Commun 2019 12 20;10(1):5802. Epub 2019 Dec 20.

Neuroscience Department, Max-Planck-Institute for Empirical Aesthetics, Grüneburgweg 14, 60322, Frankfurt, Germany.

Humans anticipate events signaled by sensory cues. It is commonly assumed that two uncertainty parameters modulate the brain's capacity to predict: the hazard rate (HR) of event probability and the uncertainty in time estimation which increases with elapsed time. We investigate both assumptions by presenting event probability density functions (PDFs) in each of three sensory modalities. We show that perceptual systems use the reciprocal PDF and not the HR to model event probability density. We also demonstrate that temporal uncertainty does not necessarily grow with elapsed time but can also diminish, depending on the event PDF. Previous research identified neuronal activity related to event probability in multiple levels of the cortical hierarchy (sensory (V4), association (LIP), motor and other areas) proposing the HR as an elementary neuronal computation. Our results-consistent across vision, audition, and somatosensation-suggest that the neurobiological implementation of event anticipation is based on a different, simpler and more stable computation than HR: the reciprocal PDF of events in time.
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http://dx.doi.org/10.1038/s41467-019-13849-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6925136PMC
December 2019

Sub-optimality in motor planning is not improved by explicit observation of motor uncertainty.

Sci Rep 2019 10 16;9(1):14850. Epub 2019 Oct 16.

Laboratory of Sports Sciences, Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan.

To make optimal decisions under risk, one must correctly weight potential rewards and penalties by the probabilities of receiving them. In motor decision tasks, the uncertainty in outcome is a consequence of motor uncertainty. When participants perform suboptimally as they often do in such tasks, it could be because they have insufficient information about their motor uncertainty: with more information, their performance could converge to optimal as they learn their own motor uncertainty. Alternatively, their suboptimal performance may reflect an inability to make use of the information they have or even to perform the correct computations. To discriminate between these two possibilities, we performed an experiment spanning two days. On the first day, all participants performed a reaching task with trial-by-trial feedback of motor error. At the end of the day, their aim points were still typically suboptimal. On the second day participants were divided into two groups one of which repeated the task of the first day and the other of which repeated the task but were intermittently given additional information summarizing their motor errors. Participants receiving additional information did not perform significantly better than those who did not.
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http://dx.doi.org/10.1038/s41598-019-50901-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6795881PMC
October 2019

Generality of likelihood ratio decisions.

Cognition 2019 10 2;191:103931. Epub 2019 Jul 2.

Department of Psychology, New York University, USA; Center for Neural Science, New York University, USA.

A basic assumption of Signal Detection Theory - a special case of Bayesian Decision Theory - is that decisions are based on likelihood ratios (the likelihood ratio hypothesis). In a preceding paper, Glanzer et al. (2009) tested this assumption in recognition memory tasks. The tests consisted of formal proofs and computational demonstrations that decisions based on likelihood ratios produce three regularities (1. the Mirror Effect, 2. the Variance Effect, and 3. the z-ROC Length Effect). Glanzer et al. found that the three implied regularities do indeed hold for a wide range of item recognition memory studies taken from the literature. We now claim that the likelihood ratio regularities hold for decisions generally: decisions about sensory events, reasoning, weather forecasting, etc. An examination of past decision studies supports the generalization. We also report new experimental studies of decisions in two additional areas, semantic memory and mental rotation, further supporting the generalization. The results highlight the optimal characteristics of decision making in contrast to the current emphasis on its inefficiencies.
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http://dx.doi.org/10.1016/j.cognition.2019.03.023DOI Listing
October 2019

Efficient visual information sampling develops late in childhood.

J Exp Psychol Gen 2019 Jul;148(7):1138-1152

Institute of Ophthalmology, University College London.

It is often unclear which course of action gives the best outcome. We can reduce this uncertainty by gathering more information, but gathering information always comes at a cost. For example, a sports player waiting too long to judge a ball's trajectory will run out of time to intercept it. Efficient samplers must therefore optimize a trade-off: when the costs of collecting further information exceed the expected benefits, they should stop sampling and start acting. In visually guided tasks, adults can make these trade-offs efficiently, correctly balancing any reductions in visuomotor uncertainty against cost factors associated with increased sampling. To investigate how this ability develops during childhood, we tested 6- to 11-year-olds, adolescents, and adults on a visual localization task in which the costs and benefits of sampling were formalized in a quantitative framework. This allowed us to compare participants to each other and to an ideal observer who maximizes expected reward. Visual sampling became substantially more efficient between 6 and 11 years, converging onto adult performance in adolescence. Younger children systematically undersampled information relative to the ideal observer and varied their sampling strategy more. Further analyses suggested that young children used a suboptimal decision rule that insufficiently accounted for the chance of task failure, in line with a late developing ability to compute with probabilities and costs. We therefore propose that late development of efficient information sampling, a crucial element of real-world decision-making under risk, may form an important component of suboptimality in child perception, action, and decision-making. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
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http://dx.doi.org/10.1037/xge0000629DOI Listing
July 2019

One mirror effect: The regularities of recognition memory.

Mem Cognit 2019 02;47(2):266-278

Department of Psychology, New York University, New Yotablerk, NY, USA.

The mirror effect is a pattern of results generally found in two-condition recognition memory experiments that is consistent with normative signal detection theory as a model of recognition. However, the claim has been made that there is a distinct mirror effect, the "strength mirror effect," that differs from the normative one. This claim is based on experiments on recognition memory in which repetition or study time is varied to produce differences in accuracy, where typically the ordinary mirror effect pattern is absent. If this claim is correct, it has major implications for theories of recognition memory. Therefore, a full examination of the data that support the claim was called for. To do that, we replicated the basic demonstration of the no-mirror-effect data and analyzed it further in a series of experiments. The analysis showed the following: (1) Whether or not the mirror effect occurs is determined by whether the experimenter furnishes effective discriminanda that distinguish the weak and strong conditions for the participant. (2) Once Finding 1 is taken into account, no adjustments of or additions to the normative signal detection theory explanations are necessary. (3) There is only one mirror effect, and no separate "strength mirror effect."
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http://dx.doi.org/10.3758/s13421-018-0864-yDOI Listing
February 2019

Information sampling behavior with explicit sampling costs.

Decision (Wash D C ) 2016 Jul;3(3):147-168

Department of Psychology, New York University; Center for Neural Science, New York University.

The decision to gather information should take into account both the value of information and its accrual costs in time, energy and money. Here we explore how people balance the monetary costs and benefits of gathering additional information in a perceptual-motor estimation task. Participants were rewarded for touching a hidden circular target on a touch-screen display. The target's center coincided with the mean of a circular Gaussian distribution from which participants could sample repeatedly. Each "cue" - sampled one at a time - was plotted as a dot on the display. Participants had to repeatedly decide, after sampling each cue, whether to stop sampling and attempt to touch the hidden target or continue sampling. Each additional cue increased the participants' probability of successfully touching the hidden target but reduced their potential reward. Two experimental conditions differed in the initial reward associated with touching the hidden target and the fixed cost per cue. For each condition we computed the optimal number of cues that participants should sample, before taking action, to maximize expected gain. Contrary to recent claims that people gather less information than they objectively should before taking action, we found that participants over-sampled in one experimental condition, and did not significantly under- or over-sample in the other. Additionally, while the ideal observer model ignores the current sample dispersion, we found that participants used it to decide whether to stop sampling and take action or continue sampling, a possible consequence of imperfect learning of the underlying population dispersion across trials.
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http://dx.doi.org/10.1037/dec0000045DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4942190PMC
July 2016

Gambling on visual performance: neural correlates of metacognitive choice between visual lotteries.

Front Neurosci 2015 3;9:314. Epub 2015 Sep 3.

Department of Psychology, New York University New York, NY, USA ; Center for Neural Science, New York University New York, NY, USA.

A lottery is a list of mutually exclusive outcomes together with their associated probabilities of occurrence. Decision making is often modeled as choices between lotteries and-in typical research on decision under risk-the probabilities are given to the subject explicitly in numerical form. In this study, we examined lottery decision task where the probabilities of receiving various rewards are contingent on the subjects' own visual performance in a random-dot-motion (RDM) discrimination task, a metacognitive or second order judgment. While there is a large literature concerning the RDM task and there is also a large literature on decision under risk, little is known about metacognitive decisions when the source of uncertainty is visual. Using fMRI with humans, we found distinct fronto-striatal and fronto-parietal networks representing subjects' estimates of his or her performance, reward value, and the expected value (EV) of the lotteries. The fronto-striatal network includes the dorsomedial prefrontal cortex and the ventral striatum, involved in reward processing and value-based decision-making. The fronto-parietal network includes the intraparietal sulcus and the ventrolateral prefrontal cortex, which was shown to be involved in the accumulation of sensory evidence during visual decision making and in metacognitive judgments on visual performance. These results demonstrate that-while valuation of performance-based lotteries involves a common fronto-striatal valuation network-an additional network unique to the estimation of task-related performance is recruited for the integration of probability and reward information when probability is inferred from visual performance.
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http://dx.doi.org/10.3389/fnins.2015.00314DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4558824PMC
September 2015

Allocentric kin recognition is not affected by facial inversion.

J Vis 2015 ;15(13)

Typical judgments involving faces are disrupted by inversion, with the Thatcher illusion serving as a compelling example. In two experiments, we examined how inversion affects allocentric kin recognition-the ability to judge the degree of genetic relatedness of others. In the first experiment, participants judged whether pairs of photographs of children portrayed siblings or unrelated children. Half of the pairs were siblings, half were unrelated. In three experimental conditions, photographs were viewed in upright orientation, flipped around a horizontal axis, or rotated 180°. Neither rotation nor flipping had any detectable effect on allocentric kin recognition. In the second experiment, participants judged pairs of photographs of adult women. Half of the pairs were sisters, half were unrelated. We again found no significant effect of facial inversion. Unlike almost all other face judgments, judgments of kinship from facial appearance do not rely on perceptual cues disrupted by inversion, suggesting that they rely more on spatially localized cues rather than "holistic" cues. We conclude that kin recognition is not simply a byproduct of other face perception abilities. We discuss the implications for cue combination models of other facial judgments that are affected by inversion.
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http://dx.doi.org/10.1167/15.13.5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4578574PMC
December 2015

Human representation of visuo-motor uncertainty as mixtures of orthogonal basis distributions.

Nat Neurosci 2015 Aug 29;18(8):1152-8. Epub 2015 Jun 29.

1] Department of Psychology, New York University, New York, New York, USA. [2] Center for Neural Science, New York University, New York, New York, USA. [3] Institute for the Interdisciplinary Study of Decision Making, New York University, New York, New York, USA.

In many laboratory visuo-motor decision tasks, subjects compensate for their own visuo-motor error, earning close to the maximum reward possible. To do so, they must combine information about the distribution of possible error with values associated with different movement outcomes. The optimal solution is a potentially difficult computation that presupposes knowledge of the probability density function (pdf) of visuo-motor error associated with each possible planned movement. It is unclear how the brain represents such pdfs or computes with them. In three experiments, we used a forced-choice method to reveal subjects' internal representations of their spatial visuo-motor error in a speeded reaching movement. Although subjects' objective distributions were unimodal, close to Gaussian, their estimated internal pdfs were typically multimodal and were better described as mixtures of a small number of distributions differing only in location and scale. Mixtures of a small number of uniform distributions outperformed other mixture distributions, including mixtures of Gaussians.
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http://dx.doi.org/10.1038/nn.4055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4487408PMC
August 2015

The efficiency of vision and action.

Vision Res 2015 Aug 18;113(Pt B):113-5. Epub 2015 Jun 18.

Department of Psychology and Center for Neural Science, New York University, New York, NY, USA.

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http://dx.doi.org/10.1016/j.visres.2015.06.003DOI Listing
August 2015

Acquisition, representation, and transfer of models of visuo-motor error.

J Vis 2015 ;15(8)

We examined how human subjects acquire and represent models of visuo-motor error and how they transfer information about visuo-motor error from one task to a closely related one. The experiment consisted of three phases. In the training phase, subjects threw beanbags underhand towards targets displayed on a wall-mounted touch screen. The distribution of their endpoints was a vertically elongated bivariate Gaussian. In the subsequent choice phase, subjects repeatedly chose which of two targets varying in shape and size they would prefer to attempt to hit. Their choices allowed us to investigate their internal models of visuo-motor error distribution, including the coordinate system in which they represented visuo-motor error. In the transfer phase, subjects repeated the choice phase from a different vantage point, the same distance from the screen but with the throwing direction shifted 45°. From the new vantage point, visuo-motor error was effectively expanded horizontally by √2. We found that subjects incorrectly assumed an isotropic distribution in the choice phase but that the anisotropy they assumed in the transfer phase agreed with an objectively correct transfer. We also found that the coordinate system used in coding two-dimensional visuo-motor error in the choice phase was effectively one-dimensional.
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http://dx.doi.org/10.1167/15.8.6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4461894PMC
December 2015

Three regularities of recognition memory: the role of bias.

Psychon Bull Rev 2015 Dec;22(6):1646-64

Department of Psychology, Iona College, New Rochelle, NY, USA.

A basic assumption of Signal Detection Theory is that decisions are made on the basis of likelihood ratios. In a preceding paper, Glanzer, Hilford, and Maloney (Psychonomic Bulletin & Review, 16, 431-455, 2009) showed that the likelihood ratio assumption implies that three regularities will occur in recognition memory: (1) the Mirror Effect, (2) the Variance Effect, (3) the normalized Receiver Operating Characteristic (z-ROC) Length Effect. The paper offered formal proofs and computational demonstrations that decisions based on likelihood ratios produce the three regularities. A survey of data based on group ROCs from 36 studies validated the likelihood ratio assumption by showing that its three implied regularities are ubiquitous. The study noted, however, that bias, another basic factor in Signal Detection Theory, can obscure the Mirror Effect. In this paper we examine how bias affects the regularities at the theoretical level. The theoretical analysis shows: (1) how bias obscures the Mirror Effect, not the other two regularities, and (2) four ways to counter that obscuring. We then report the results of five experiments that support the theoretical analysis. The analyses and the experimental results also demonstrate: (1) that the three regularities govern individual, as well as group, performance, (2) alternative explanations of the regularities are ruled out, and (3) that Signal Detection Theory, correctly applied, gives a simple and unified explanation of recognition memory data.
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http://dx.doi.org/10.3758/s13423-015-0829-0DOI Listing
December 2015

Revealing individual differences in strategy selection through visual motion extrapolation.

Cogn Neurosci 2015 5;6(4):169-79. Epub 2015 Feb 5.

e Department of Psychology , University of Minnesota , Minneapolis , MN 55455 , USA.

Humans are constantly challenged to make use of internal models to fill in missing sensory information. We measured human performance in a simple motion extrapolation task where no feedback was provided in order to elucidate the models of object motion incorporated into observers' extrapolation strategies. There was no "right" model for extrapolation in this task. Observers consistently adopted one of two models, linear or quadratic, but different observers chose different models. We further demonstrate that differences in motion sensitivity impact the choice of internal models for many observers. These results demonstrate that internal models and individual differences in those models can be elicited by unconstrained, predictive-based psychophysical tasks.
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http://dx.doi.org/10.1080/17588928.2014.1003181DOI Listing
June 2016

Neural mechanisms for integrating prior knowledge and likelihood in value-based probabilistic inference.

J Neurosci 2015 Jan;35(4):1792-805

Institute of Neuroscience and Brain Research Center, National Yang-Ming University, Taipei, 112 Taiwan, Institute for the Interdisciplinary Study of Decision Making, New York University, New York, New York 10003

In Bayesian decision theory, knowledge about the probabilities of possible outcomes is captured by a prior distribution and a likelihood function. The prior reflects past knowledge and the likelihood summarizes current sensory information. The two combined (integrated) form a posterior distribution that allows estimation of the probability of different possible outcomes. In this study, we investigated the neural mechanisms underlying Bayesian integration using a novel lottery decision task in which both prior knowledge and likelihood information about reward probability were systematically manipulated on a trial-by-trial basis. Consistent with Bayesian integration, as sample size increased, subjects tended to weigh likelihood information more compared with prior information. Using fMRI in humans, we found that the medial prefrontal cortex (mPFC) correlated with the mean of the posterior distribution, a statistic that reflects the integration of prior knowledge and likelihood of reward probability. Subsequent analysis revealed that both prior and likelihood information were represented in mPFC and that the neural representations of prior and likelihood in mPFC reflected changes in the behaviorally estimated weights assigned to these different sources of information in response to changes in the environment. Together, these results establish the role of mPFC in prior-likelihood integration and highlight its involvement in representing and integrating these distinct sources of information.
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http://dx.doi.org/10.1523/JNEUROSCI.3161-14.2015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4308614PMC
January 2015

Decision from Models: Generalizing Probability Information to Novel Tasks.

Decision (Wash D C ) 2015 Jan;2(1):39-53

Department of Psychology and Center for Neural Science, New York University.

We investigate a new type of decision under risk where-to succeed-participants must generalize their experience in one set of tasks to a novel set of tasks. We asked participants to trade distance for reward in a virtual minefield where each successive step incurred the same fixed probability of failure (referred to as ). With constant hazard, the probability of success (the survival function) decreases exponentially with path length. On each trial, participants chose between a shorter path with smaller reward and a longer (more dangerous) path with larger reward. They received feedback in 160 training trials: encountering a mine along their chosen path resulted in zero reward and successful completion of the path led to the reward associated with the path chosen. They then completed 600 no-feedback test trials with novel combinations of path length and rewards. To maximize expected gain, participants had to learn the correct exponential model in training and generalize it to the test conditions. We compared how participants discounted reward with increasing path length to the predictions of nine choice models including the correct exponential model. The choices of a majority of the participants were best accounted for by a model of the correct exponential form although with marked overestimation of the hazard rate. The decision-from-models paradigm differs from experience-based decision paradigms such as decision-from-sampling in the importance assigned to generalizing experience-based information to novel tasks. The task itself is representative of everyday tasks involving repeated decisions in stochastically invariant environments.
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http://dx.doi.org/10.1037/dec0000022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4300983PMC
January 2015

The irrationality of categorical perception.

J Neurosci 2013 Dec;33(49):19060-70

Department of Psychology and Center for Neural Science, New York University, New York, New York 10003, and Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, United Kingdom.

Perception is often categorical: the perceptual system selects one interpretation of a stimulus even when evidence in favor of other interpretations is appreciable. Such categorization is potentially in conflict with normative decision theory, which mandates that the utility of various courses of action should depend on the probabilities of all possible states of the world, not just that of the one perceived. If these probabilities are lost as a result of categorization, choice will be suboptimal. Here we test for such irrationality in a task that requires human observers to combine perceptual evidence with the uncertain consequences of action. Observers made rapid pointing movements to targets on a touch screen, with rewards determined by perceptual and motor uncertainty. Across both visual and auditory decision tasks, observers consistently placed too much weight on perceptual uncertainty relative to action uncertainty. We show that this suboptimality can be explained as a consequence of categorical perception. Our findings indicate that normative decision making may be fundamentally constrained by the architecture of the perceptual system.
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http://dx.doi.org/10.1523/JNEUROSCI.1263-13.2013DOI Listing
December 2013

Inferred motion perception of light sources in 3D scenes is color-blind.

Iperception 2013 8;4(2):98-100. Epub 2013 Mar 8.

Department of Psychology, New York University, 6 Washington Place, New York, NY 10003, USA; Werner Reichardt Centre for Integrative Neuroscience, Otfried-Mueller-Strasse 25, Tuebingen 72076, Germany; e-mail:

In everyday scenes, the illuminant can vary spatially in chromaticity and luminance, and change over time (e.g. sunset). Such variation generates dramatic image effects too complex for any contemporary machine vision system to overcome, yet human observers are remarkably successful at inferring object properties separately from lighting, an ability linked with estimation and tracking of light field parameters. Which information does the visual system use to infer light field dynamics? Here, we specifically ask whether color contributes to inferred light source motion. Observers viewed 3D surfaces illuminated by an out-of-view moving collimated source (sun) and a diffuse source (sky). In half of the trials, the two sources differed in chromaticity, thereby providing more information about motion direction. Observers discriminated light motion direction above chance, and only the least sensitive observer benefited slightly from the added color information, suggesting that color plays only a very minor role for inferring light field dynamics.
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http://dx.doi.org/10.1068/i0591sasDOI Listing
June 2013

Testing whether humans have an accurate model of their own motor uncertainty in a speeded reaching task.

PLoS Comput Biol 2013 23;9(5):e1003080. Epub 2013 May 23.

Department of Psychology, New York University, New York, NY, USA.

In many motor tasks, optimal performance presupposes that human movement planning is based on an accurate internal model of the subject's own motor error. We developed a motor choice task that allowed us to test whether the internal model implicit in a subject's choices differed from the actual in isotropy (elongation) and variance. Subjects were first trained to hit a circular target on a touch screen within a time limit. After training, subjects were repeatedly shown pairs of targets differing in size and shape and asked to choose the target that was easier to hit. On each trial they simply chose a target - they did not attempt to hit the chosen target. For each subject, we tested whether the internal model implicit in her target choices was consistent with her true error distribution in isotropy and variance. For all subjects, movement end points were anisotropic, distributed as vertically elongated bivariate Gaussians. However, in choosing targets, almost all subjects effectively assumed an isotropic distribution rather than their actual anisotropic distribution. Roughly half of the subjects chose as though they correctly estimated their own variance and the other half effectively assumed a variance that was more than four times larger than the actual, essentially basing their choices merely on the areas of the targets. The task and analyses we developed allowed us to characterize the internal model of motor error implicit in how humans plan reaching movements. In this task, human movement planning - even after extensive training - is based on an internal model of human motor error that includes substantial and qualitative inaccuracies.
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http://dx.doi.org/10.1371/journal.pcbi.1003080DOI Listing
March 2014

Very slow search and reach: failure to maximize expected gain in an eye-hand coordination task.

PLoS Comput Biol 2012 11;8(10):e1002718. Epub 2012 Oct 11.

Department of Psychology, New York University, New York, New York, United States of America.

We examined an eye-hand coordination task where optimal visual search and hand movement strategies were inter-related. Observers were asked to find and touch a target among five distractors on a touch screen. Their reward for touching the target was reduced by an amount proportional to how long they took to locate and reach to it. Coordinating the eye and the hand appropriately would markedly reduce the search-reach time. Using statistical decision theory we derived the sequence of interrelated eye and hand movements that would maximize expected gain and we predicted how hand movements should change as the eye gathered further information about target location. We recorded human observers' eye movements and hand movements and compared them with the optimal strategy that would have maximized expected gain. We found that most observers failed to adopt the optimal search-reach strategy. We analyze and describe the strategies they did adopt.
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http://dx.doi.org/10.1371/journal.pcbi.1002718DOI Listing
May 2013

Speeded reaching movements around invisible obstacles.

PLoS Comput Biol 2012 20;8(9):e1002676. Epub 2012 Sep 20.

Department of Psychology, New York University, New York, New York, USA.

We analyze the problem of obstacle avoidance from a Bayesian decision-theoretic perspective using an experimental task in which reaches around a virtual obstacle were made toward targets on an upright monitor. Subjects received monetary rewards for touching the target and incurred losses for accidentally touching the intervening obstacle. The locations of target-obstacle pairs within the workspace were varied from trial to trial. We compared human performance to that of a Bayesian ideal movement planner (who chooses motor strategies maximizing expected gain) using the Dominance Test employed in Hudson et al. (2007). The ideal movement planner suffers from the same sources of noise as the human, but selects movement plans that maximize expected gain in the presence of that noise. We find good agreement between the predictions of the model and actual performance in most but not all experimental conditions.
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http://dx.doi.org/10.1371/journal.pcbi.1002676DOI Listing
January 2013

Effective integration of serially presented stochastic cues.

J Vis 2012 Aug 21;12(8). Epub 2012 Aug 21.

Department of Psychology, New York University, New York, NY, USA.

This study examines how people deal with inherently stochastic cues when estimating a latent environmental property. Seven cues to a hidden location were presented one at a time in rapid succession. The seven cues were sampled from seven different Gaussian distributions that shared a common mean but differed in precision (the reciprocal of variance). The experimental task was to estimate the common mean of the Gaussians from which the cues were drawn. Observers ran in two conditions on separate days. In the "decreasing precision" condition the seven cues were ordered from most precise to least precise. In the "increasing precision" condition this ordering was reversed. For each condition, we estimated the weight that each cue in the sequence had on observers' estimates and compared human performance to that of an ideal observer who maximizes expected gain. We found that observers integrated information from more than one cue, and that they adaptively gave more weight to more precise cues and less weight to less precise cues. However, they did not assign weights that would maximize their expected gain, even over the course of several hundred trials with corrective feedback. The cost to observers of their suboptimal performance was on average 16% of their maximum possible winnings.
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http://dx.doi.org/10.1167/12.8.12DOI Listing
August 2012

Optimizing multiscale SSIM for compression via MLDS.

IEEE Trans Image Process 2012 Dec 30;21(12):4682-94. Epub 2012 Jul 30.

Université de Caen-Basse Normandie, GREYC Laboratory, Equipe Image, ENSICAEN, Caen 14050, France.

A crucial step in the assessment of an image compression method is the evaluation of the perceived quality of the compressed images. Typically, researchers ask observers to rate perceived image quality directly and use these rating measures, averaged across observers and images, to assess how image quality degrades with increasing compression. These ratings in turn are used to calibrate and compare image quality assessment algorithms intended to predict human perception of image degradation. There are several drawbacks to using such omnibus measures. First, the interpretation of the rating scale is subjective and may differ from one observer to the next. Second, it is easy to overlook compression artifacts that are only present in particular kinds of images. In this paper, we use a recently developed method for assessing perceived image quality, maximum likelihood difference scaling (MLDS), and use it to assess the performance of a widely-used image quality assessment algorithm, multiscale structural similarity (MS-SSIM). MLDS allows us to quantify supra-threshold perceptual differences between pairs of images and to examine how perceived image quality, estimated through MLDS, changes as the compression rate is increased. We apply the method to a wide range of images and also analyze results for specific images. This approach circumvents the limitations inherent in the use of rating methods, and allows us also to evaluate MS-SSIM for different classes of visual image. We show how the data collected by MLDS allow us to recalibrate MS-SSIM to improve its performance.
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http://dx.doi.org/10.1109/TIP.2012.2210723DOI Listing
December 2012

Comparison of the distortion of probability information in decision under risk and an equivalent visual task.

Psychol Sci 2012 Apr 6;23(4):419-26. Epub 2012 Mar 6.

Department of Psychology, New York University, USA.

Decision makers typically overweight small probabilities and underweight large probabilities. However, there are recent reports that when probability is presented in the form of relative frequencies, this typical pattern reverses. We tested this hypothesis by comparing decision making in two tasks: In one task, probability was stated numerically, and in the other task, it was conveyed through a visual representation. In the visual task, participants chose whether a "stochastic bullet" should be fired at either a large target for a small reward or a small target for a large reward. Participants' knowledge of probability in the visual task was the result of extensive practice firing bullets at targets. In the classical numerical task, participants chose between pairs of lotteries with probabilities and rewards matched to the probabilities and rewards in the visual task. We found that participants' probability-weighting functions were significantly different in the two tasks, but the pattern for the visual task was the typical, not the reversed, pattern.
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http://dx.doi.org/10.1177/0956797611429798DOI Listing
April 2012

Human visual search does not maximize the post-saccadic probability of identifying targets.

PLoS Comput Biol 2012 Feb 2;8(2):e1002342. Epub 2012 Feb 2.

Department of Psychology, New York University, New York, New York, USA.

Researchers have conjectured that eye movements during visual search are selected to minimize the number of saccades. The optimal Bayesian eye movement strategy minimizing saccades does not simply direct the eye to whichever location is judged most likely to contain the target but makes use of the entire retina as an information gathering device during each fixation. Here we show that human observers do not minimize the expected number of saccades in planning saccades in a simple visual search task composed of three tokens. In this task, the optimal eye movement strategy varied, depending on the spacing between tokens (in the first experiment) or the size of tokens (in the second experiment), and changed abruptly once the separation or size surpassed a critical value. None of our observers changed strategy as a function of separation or size. Human performance fell far short of ideal, both qualitatively and quantitatively.
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http://dx.doi.org/10.1371/journal.pcbi.1002342DOI Listing
February 2012

Visual extrapolation under risk: human observers estimate and compensate for exogenous uncertainty.

Proc Biol Sci 2012 Jun 1;279(1736):2171-9. Epub 2012 Feb 1.

School of Psychological Sciences, University of Manchester, Manchester M13 9PL, UK.

Humans commonly face choices between multiple options with uncertain outcomes. Such situations occur in many contexts, from purely financial decisions (which shares should I buy?) to perceptuo-motor decisions between different actions (where should I aim my shot at goal?). Regardless of context, successful decision-making requires that the uncertainty at the heart of the decision-making problem is taken into account. Here, we ask whether humans can recover an estimate of exogenous uncertainty and then use it to make good decisions. Observers viewed a small dot that moved erratically until it disappeared behind an occluder. We varied the size of the occluder and the unpredictability of the dot's path. The observer attempted to capture the dot as it emerged from behind the occluded region by setting the location and extent of a 'catcher' along the edge of the occluder. The reward for successfully catching the dot was reduced as the size of the catcher increased. We compared human performance with that of an agent maximizing expected gain and found that observers consistently selected catcher size close to this theoretical solution. These results suggest that humans are finely tuned to exogenous uncertainty information and can exploit it to guide action.
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http://dx.doi.org/10.1098/rspb.2011.2527DOI Listing
June 2012

Ubiquitous log odds: a common representation of probability and frequency distortion in perception, action, and cognition.

Front Neurosci 2012 19;6. Epub 2012 Jan 19.

Department of Psychology and Center for Neural Science, New York University New York, NY, USA.

In decision from experience, the source of probability information affects how probability is distorted in the decision task. Understanding how and why probability is distorted is a key issue in understanding the peculiar character of experience-based decision. We consider how probability information is used not just in decision-making but also in a wide variety of cognitive, perceptual, and motor tasks. Very similar patterns of distortion of probability/frequency information have been found in visual frequency estimation, frequency estimation based on memory, signal detection theory, and in the use of probability information in decision-making under risk and uncertainty. We show that distortion of probability in all cases is well captured as linear transformations of the log odds of frequency and/or probability, a model with a slope parameter, and an intercept parameter. We then consider how task and experience influence these two parameters and the resulting distortion of probability. We review how the probability distortions change in systematic ways with task and report three experiments on frequency distortion where the distortions change systematically in the same task. We found that the slope of frequency distortions decreases with the sample size, which is echoed by findings in decision from experience. We review previous models of the representation of uncertainty and find that none can account for the empirical findings.
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http://dx.doi.org/10.3389/fnins.2012.00001DOI Listing
October 2012

The neural correlates of subjective utility of monetary outcome and probability weight in economic and in motor decision under risk.

J Neurosci 2011 Jun;31(24):8822-31

Institute of Neuroscience, National Yang-Ming University, Taipei 112, Taiwan.

In decision under risk, people choose between lotteries that contain a list of potential outcomes paired with their probabilities of occurrence. We previously developed a method for translating such lotteries to mathematically equivalent "motor lotteries." The probability of each outcome in a motor lottery is determined by the subject's noise in executing a movement. In this study, we used functional magnetic resonance imaging in humans to compare the neural correlates of monetary outcome and probability in classical lottery tasks in which information about probability was explicitly communicated to the subjects and in mathematically equivalent motor lottery tasks in which probability was implicit in the subjects' own motor noise. We found that activity in the medial prefrontal cortex (mPFC) and the posterior cingulate cortex quantitatively represent the subjective utility of monetary outcome in both tasks. For probability, we found that the mPFC significantly tracked the distortion of such information in both tasks. Specifically, activity in mPFC represents probability information but not the physical properties of the stimuli correlated with this information. Together, the results demonstrate that mPFC represents probability from two distinct forms of decision under risk.
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http://dx.doi.org/10.1523/JNEUROSCI.0540-11.2011DOI Listing
June 2011
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