Correction: Bayesian regression explains how human participants handle parameter uncertainty.

[This corrects the article DOI: 10.1371/journal.pcbi.1007886.].

Bayesian regression explains how human participants handle parameter uncertainty.

Accumulating evidence indicates that the human brain copes with sensory uncertainty in accordance with Bayes' rule. However, it is unknown how humans make predictions when the generative model of the task at hand is described by uncertain parameters. Here, we tested whether and how humans take parameter uncertainty into account in a regression task. Participants extrapolated a parabola from a limited number of noisy points, shown on a computer screen. The quadratic parameter was drawn from a bimodal prior distribution. We tested whether human observers take full advantage of the given information, including the likelihood of the quadratic parameter value given the observed points and the quadratic parameter's prior distribution. We compared human performance with Bayesian regression, which is the (Bayes) optimal solution to this problem, and three sub-optimal models, which are simpler to compute. Our results show that, under our specific experimental conditions, humans behave in a way that is consistent with Bayesian regression. Moreover, our results support the hypothesis that humans generate responses in a manner consistent with probability matching rather than Bayesian decision theory.

The Bandwidth of Diagnostic Horizontal Structure for Face Identification.

Horizontally oriented spatial frequency components are a diagnostic source of face identity information, and sensitivity to this information predicts upright identification accuracy and the magnitude of the face-inversion effect. However, the bandwidth at which this information is conveyed, and the extent to which human tuning matches this distribution of information, has yet to be characterized. We designed a 10-alternative forced choice face identification task in which upright or inverted faces were filtered to retain horizontal or vertical structure. We systematically varied the bandwidth of these filters in 10° steps and replaced the orientation components that were removed from the target face with components from the average of all possible faces. This manipulation created patterns that looked like faces but contained diagnostic information in orientation bands unknown to the observer on any given trial. Further, we quantified human performance relative to the actual information content of our face stimuli using an ideal observer with perfect knowledge of the diagnostic band. We found that the most diagnostic information for face identification is conveyed by a narrow band of orientations along the horizontal meridian, whereas human observers use information from a wide range of orientations.

Personal familiarity enhances sensitivity to horizontal structure during processing of face identity.

What makes identification of familiar faces seemingly effortless? Recent studies using unfamiliar face stimuli suggest that selective processing of information conveyed by horizontally oriented spatial frequency components supports accurate performance in a variety of tasks involving matching of facial identity. Here, we studied upright and inverted face discrimination using stimuli with which observers were either unfamiliar or personally familiar (i.e., friends and colleagues). Our results reveal increased sensitivity to horizontal spatial frequency structure in personally familiar faces, further implicating the selective processing of this information in the face processing expertise exhibited by human observers throughout their daily lives.

Psychophysical profiles in super-recognizers.

Facial identity matching ability varies widely, ranging from prosopagnosic individuals (who exhibit profound impairments in face cognition/processing) to so-called super-recognizers (SRs), possessing exceptional capacities. Yet, despite the often consequential nature of face matching decisions-such as identity verification in security critical settings-ability assessments tendentially rely on simple performance metrics on a handful of heterogeneously related subprocesses, or in some cases only a single measured subprocess. Unfortunately, methodologies of this ilk leave contributions of stimulus information to observed variations in ability largely un(der)specified. Moreover, they are inadequate for addressing the qualitative or quantitative nature of differences between SRs' abilities and those of the general population. Here, therefore, we sought to investigate individual differences-among SRs identified using a novel conservative diagnostic framework, and neurotypical controls-by systematically varying retinal availability, bandwidth, and orientation of faces' spatial frequency content in two face matching experiments. Psychophysical evaluations of these parameters' contributions to ability reveal that SRs more consistently exploit the same spatial frequency information, rather than suggesting qualitatively different profiles between control observers and SRs. These findings stress the importance of optimizing procedures for SR identification, for example by including measures quantifying the consistency of individuals' behavior.

The effect of training with inverted faces on the selective use of horizontal structure.

A growing body of evidence demonstrates that selective processing of structure conveyed by horizontally oriented spatial frequency components is associated with upright face discrimination accuracy and the magnitude of the face inversion effect. In this study, we examined whether the increase in discrimination accuracy for inverted faces that is known to result from practice would coincide with more selective processing of horizontal structure in inverted faces. To assess this hypothesis, our observers practiced discrimination of inverted faces for three training sessions and we measured accuracy, efficiency relative to an ideal observer, and horizontal selectivity before and after training. As hypothesized, we observed more efficient discrimination and more selective processing of horizontal structure after training. However, the effects of training did not generalize reliably to novel face exemplars.

The role of horizontal facial structure on the N170 and N250.

Recent studies have shown that horizontal facial structure is important for face identification (Dakin and Watt, 2009; Goffaux and Dakin, 2010). Also, sensitivity to horizontal structure is associated with the size of the face inversion effect (Pachai et al., 2013). However, it is unclear how the N170 and N250, two components of visual event-related potentials ERPs that have been implicated in face perception, are modulated by oriented facial structure in an upright face identification task. Here, we recorded ERPs and behavioural accuracy from adult observers performing a 1-of-6 face identification task in conditions that parametrically manipulated the orientation structure of upright faces. Faces were filtered with ideal orientation filters centred on either 0 (horizontal) or 90 deg (vertical). Filter bandwidth was varied across conditions from ±45 to ±90 deg in steps of ±9 deg. As has been reported previously, response accuracy was significantly higher for faces that contained horizontal structure than vertical structure, and the horizontal-vertical difference was correlated with accuracy for unfiltered faces. In addition, the N170 and N250 were affected by the manipulation of horizontal facial structure. Furthermore, for the N250, but not the N170, the relative sensitivity to horizontal compared to vertical facial structure was significantly correlated with identification accuracy for unfiltered faces. We suggest that in a face identification task, the N250 but not the N170 is modulated by the amount of diagnostic information conveyed by horizontal structure.

How best to unify crowding?

In crowding, the perception of an object deteriorates in the presence of nearby elements. Obviously, crowding is a ubiquitous phenomenon, as elements are rarely seen in isolation. One of the main characteristics of crowding is that the elements themselves are not rendered invisible, but their features are averaged[1] or substituted[2] with those of neighboring elements. Recently, Harrison and Bex [3] presented "A Unifying Model of Orientation Crowding in Peripheral Vision", which elegantly explains these two characteristics of crowding with one unifying mechanism. They tested their model using a new crowding paradigm and demonstrated an excellent match between human and model results. A key prediction of their model is that a higher number of flankers leads to stronger crowding, simply because more non-target features contribute to the model's output and thus deteriorate performance. However, several recent studies have shown that increasing the number of flankers can actually improve performance [4-9]. Using the same experimental design as Harrison and Bex [3], we report here that adding more flankers can also improve performance in their paradigm, whereas their model predicts the opposite result. We propose that a truly unified model of crowding must include a grouping stage.

An attentional bias for LEGO® people using a change detection task: Are LEGO® people animate?

Animate objects have been shown to elicit attentional priority in a change detection task. This benefit has been seen for both human and nonhuman animals compared with inanimate objects. One explanation for these results has been based on the importance animate objects have served over the course of our species' history. In the present set of experiments, we present stimuli, which could be perceived as animate, but with which our distant ancestors would have had no experience, and natural selection could have no direct pressure on their prioritization. In the first experiment, we compared LEGO® "people" with LEGO "nonpeople" in a change detection task. In a second experiment, we attempt to control the heterogeneity of the nonanimate objects by using LEGO blocks, matched in size and colour to LEGO people. In the third experiment, we occlude the faces of the LEGO people to control for facial pattern recognition. In the final 2 experiments, we attempt to obscure high-level categorical information processing of the stimuli by inverting and blurring the scenes. (PsycINFO Database Record

Sensitivity to Information Conveyed by Horizontal Contours is Correlated with Face Identification Accuracy.

We measured thresholds in a 1-of-10 face identification task in which stimuli were embedded in orientation-filtered Gaussian noise. For upright faces, the threshold elevation produced by the masking noise varied as a function of noise orientation: significantly greater masking was obtained with horizontal noise than with vertical noise. However, the orientation selectivity of masking was significantly less with inverted faces. The performance of an ideal observer was qualitatively similar to human observers viewing upright faces: the masking function exhibited a peak for horizontally oriented noise although the selectivity of masking was greater than what was observed in human observers. These results imply that significantly more information about facial identity was conveyed by horizontal contours than by vertical contours, and that human observers use this information more efficiently to identify upright faces than inverted faces. We also found a significant positive correlation between selectivity for horizontal information and face identification accuracy for upright, but not inverted faces. Finally, there was a significant positive correlation between horizontal tuning and the size of the face inversion effect. These results demonstrate that the use of information conveyed by horizontal contours is associated with face identification accuracy and the magnitude of the face inversion effect.

The influences of face inversion and facial expression on sensitivity to eye contact in high-functioning adults with autism spectrum disorders.

We examined the influences of face inversion and facial expression on sensitivity to eye contact in high-functioning adults with and without an autism spectrum disorder (ASD). Participants judged the direction of gaze of angry, fearful, and neutral faces. In the typical group only, the range of directions of gaze leading to the perception of eye contact (the cone of gaze) was narrower for upright than inverted faces. In both groups, the cone of gaze was wider for angry faces than for fearful or neutral faces. These results suggest that in high-functioning adults with ASD, the perception of eye contact is not tuned to be finer for upright than inverted faces, but that information is nevertheless integrated across expression and gaze direction.