Matthew V. Pachai

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.

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.

Masking of individual facial features reveals the use of horizontal structure in the eyes

3) Pachai et al. (2013). Front Psych, 4. 4) Goffaux & Dakin (2010). Front Psych, 1. 1) Sekuler et al. (2004). Curr Biol, 5. 2) Gold et al. (2012). Psych Sci, 23. This work was supported by NSERC and the Canada Research Chair program. The authors would like to thank Donna Waxman for her assistance and support. Simulated observer  Higher overall masking for the eyes relative to the nose and mouth suggests these features are maximally diagnostic.  Higher masking for horizontal relative to vertical suggests the eyes and mouth contain diagnostic horizontal structure.

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.

The N170 is driven by the presence of horizontal facial structure

Behaviour Results 2 x 5 repeated-measures ANOVA • Base, F(1,10) = 180, p < 0.0001 • Band, F(4,40) = 189, p < 0.0001 • Base x Band, F(4,40) = 37, p < 0.0001 N170 Amplitude Results 2 x 5 x 2 repeated-measures ANOVA • Base, F(1,10) = 10.1, p = 0.0098 • Band, F(4,40) = 6.1, p = 0.0006 • Base x Band, F(4,40) = 8.8, p < 0.0001 • Hemisphere, F(1,10) = 1.8, p = 0.2117 • Base x Hemi, F(1,10) = 0.04, p = 0.839 • Band x Hemi, F(4,40) = 3.04, p = 0.0281 N170 Latency Results 2 x 5 x 2 repeated-measures ANOVA • Base, F(1,10) = 1.1, p = 0.3252 • Band, F(4,40) = 25.9, p < 0.0001 • Base x Band, F(4,40) = 9.7, p < 0.0001 • Hemisphere, F(1,10) = 1.1, p = 0.3194 • Base x Hemi, F(1,10) = 4.5, p = 0.0597 • Band x Hemi, F(4,40) = 3.0, p = 0.0285 Conclusions • Behaviourally, horizontal structure drives face identification • N170 is are more full-face-like with increasing horizontal structure • Next: What orientation content is required to observe an N170? What is the role of facial context? right latency v: r=0.98, p<0.01 h: r=0.91, p=0.03 le ft

Effects of size, fixation location, and inversion on face identification

One possible explanation for the face inversion effect (FIE) is that inversion swaps the eye and mouth locations relative to fixation, and attention typically is directed to the top of a stimulus for faces. As the eye region is the most informative for face discrimination, automatically attending to the upper-half of a face would cause observers to use less diagnostic regions for inverted faces. Consistent with this hypothesis, cueing attention to the eyes modulates the FIE measured both behaviourally (Hills et al. , JEP: HPP 2011) and with EEG (de Lissa et al., Neuropsychologia 2014). However, past studies used old/new recognition or gender discrimination tasks rather than identification tasks, and they did not consider the effects of stimulus size. The size manipulation is interesting in light of a recent suggestion that specialized face processing is engaged only by large stimuli (Yang et al., J Vis 2014). To address these issues, we measured accuracy and ERPs in a 6-AFC identification task that varied fixation location (center, left eye, right eye, mouth), orientation (upright or inverted), and face width (3.2 or 8.1 deg). Behavioural results showed significant main effects of: i) face size (higher accuracy for large faces), ii) fixation location (lower accuracy for mouth fixations), and iii) orientation (lower accuracy for inverted faces). However, we observed no fixation x orientation interaction, thus fixation location did not modulate the FIE. The size x orientation interaction also was not significant, which is inconsistent with the suggestion that small and large faces differentially recruit face-specific mechanisms. Finally, we found a significant N170 latency FIE that, consistent with previous studies, was larger with eye fixations. Together, these results clarify the roles of size and fixation in identification tasks, and further implicate the eyes in both behavioural and electrophysiological markers of face processing. Meeting abstract presented at VSS 2015.

Age-related effects on selective processing of horizontal structure in whole-face context

Age X Viewpoint: F(1,44) = 0.99, p = 0.3241 Context X Viewpoint: F(1,44) = 3.87, p = 0.0556 Age X Context X Viewpoint: F(1,44) = 0.43, p = 0.5147 Age: F(1,48) = 11.08, p = 0.0017 Context: F(1,48) = 0.54, p = 0.4676 Age X Context: F(1,48) = 7.94, p = 0.007 Age: F(1,44) = 11.09, p = 0.0018 Context: F(1,44) = 0.86, p = 0.3591 View: F(1,44) = 15.61, p = 0.0003 Age-related effects on selective processing of horizontal structure in a whole-face context

The effect of practice with inverted faces on behavioural and ERP horizontal bias.

1.Goffaux & Dakin, (2010). Horizontal information drives the behavioural signatures of face processing. Front. Psychol. 2.Pachai et al. (2013). Sensitivity to information conveyed by horizontal contours is correlated with face identification accuracy. Front. Psychol. 3.Pachai et al.,(2017). Personal familiarity enhances sensitivity to horizontal structure during processing of face identity. J. Vis. 4.Pachai et al., (2018). The effect of training with inverted faces on the selective use of horizontal structure. Vis. Res. 5.Hashemi, et al., (2018). The role of horizontal facial structure on the N170 and N250. Vis. Res. 6.Jacques et al., (2014). Face perception is tuned to horizontal orientation in the N170 time window. J. Vis. Practice with inverted faces improves face identification and strengthens horizontal bias.4 ERPs to inverted faces are more negative after training, but, like upright faces5, they are sensitive to orientation structure before training. Behaviour and N250 amplitude sensitivity to horizontal structure are good measures of horizontal bias.5 ho riz on ta l b ia s 4.6 dva 3. Rotman Research Institute, Baycrest Health Sciences 
 4. Department of Psychology, University of Toronto 1. Department of Psychology, Neuroscience & Behaviour, McMaster University 
 2. Department of Psychology, York University

Learning to generalize stimulus-specific learning across contexts

Perceptual Learning (PL) in a texture identification task reflects observers becoming more sensitive to diagnostic stimulus components, and the learned components vary across observers1. Discrimination of a particular orientation component is difficult when 
 orthogonal, uninformative orientation components (i.e., context) are visible2. Learning to discriminate particular orientation components in a texture 
 identification task is highly specific to the context presented during training3. Can we reduce the influence of context on learning to discriminate 
 particular orientation components in a texture identification task? Learning to generalize stimulus-specific learning across contexts Ali Hashemi1, Matthew V. Pachai2, Allison B. Sekuler1, and Patrick J. Bennett1 1Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, Canada
 2Brain Mind Institute, School of Life Sciences, École Polytechnique Fédérale de Lausanne