Fakhri Shafai

Size determines whether specialized expert processes are engaged for recognition of faces

Many influential models of face recognition postulate specialized expert processes that are engaged when viewing upright, own-race faces, as opposed to a general-purpose recognition route used for nonface objects and inverted or other-race faces. In contrast, others have argued that empirical differences do not stem from qualitatively distinct processing. We offer a potential resolution to this ongoing controversy. We hypothesize that faces engage specialized processes at large sizes only. To test this, we measured recognition efficiencies for a wide range of sizes. Upright face recognition efficiency increased with size. This was not due to better visibility of basic image features at large sizes. We ensured this by calculating efficiency relative to a specialized ideal observer unique to each individual that incorporated size-related changes in visibility and by measuring inverted efficiencies across the same range of face sizes. Inverted face recognition efficiencies did not change with size. A qualitative face inversion effect, defined as the ratio of relative upright and inverted efficiencies, showed a complete lack of inversion effects for small sizes up to 6°. In contrast, significant face inversion effects were found for all larger sizes. Size effects may stem from predominance of larger faces in the overall exposure to faces, which occur at closer viewing distances typical of social interaction. Our results offer a potential explanation for the contradictory findings in the literature regarding the special status of faces.

Visual orientation processing in autism spectrum disorder: No sign of enhanced early cortical function

It has been suggested that enhanced perceptual processing underlies some of the social difficulties associated with autism spectrum disorder (ASD). While a variety of visual tasks have been reported in which individuals with ASD outperform neurotypical individuals in control groups, the precise origin of such effects within the visual pathway remains unclear. It has recently been established that visual acuity is intact yet unremarkable in ASD. This suggests that the earliest levels of retinal processing are an unlikely candidate as the source of differences. The next potential levels for divergent visual processing are those involved in processing simple aspects of visual stimuli, such as orientation and spatial frequency, considered to be functions of early visual cortex. Here we focused on the basic processing of orientation. In three experiments, we assessed three basic aspects of orientation processing-discrimination, veridical perception, and detection-in participants with ASD in comparison to age-, gender-, and IQ-matched adults without ASD. Each experiment allowed for both qualitative and quantitative comparisons between the two groups. These provided a dense array of data indicating that participants with ASD perceive orientation of low-level stimuli in a qualitatively (as well as quantitatively) similar manner to participants without ASD in control groups, with no evidence of superior processing in detection, precision, or accuracy aspects of orientation perception. These results suggest that the source for altered perceptual abilities should be sought elsewhere, possibly in specific subgroups of people with ASD, other aspects of low-level vision such as spatial frequency, or subsequent levels of visual processing.

Qualitatively similar processing for own- and other-race faces: Evidence from efficiency and equivalent input noise

ABSTRACT The other‐race effect is the finding of diminished performance in recognition of other‐race faces compared to those of own‐race. It has been suggested that the other‐race effect stems from specialized expert processes being tuned exclusively to own‐race faces. In the present study, we measured recognition contrast thresholds for own‐ and other‐race faces as well as houses for Caucasian observers. We have factored face recognition performance into two invariant aspects of visual function: efficiency, which is related to neural computations and processing demanded by the task, and equivalent input noise, related to signal degradation within the visual system. We hypothesized that if expert processes are available only to own‐race faces, this should translate into substantially greater recognition efficiencies for own‐race compared to other‐race faces. Instead, we found similar recognition efficiencies for both own‐ and other‐race faces. The other‐race effect manifested as increased equivalent input noise. These results argue against qualitatively distinct perceptual processes. Instead they suggest that for Caucasian observers, similar neural computations underlie recognition of own‐ and other‐race faces.

Link Between Facial Identity and Expression Abilities Suggestive of Origins of Face Impairments in Autism: Support for the Social-Motivation Hypothesis:

Individuals with autism spectrum disorder (ASD) often have difficulties with processing identity and expression in faces. This is at odds with influential models of face processing that propose separate neural pathways for the identity and expression domains. The social-motivation hypothesis of ASD posits a lack of visual experience with faces as the root cause of face impairments in autism. A direct prediction is that identity and expression abilities should be related in ASD, reflecting the common origin of face impairment in this population. We tested adults with and without ASD (ns = 34) in identity and expression tasks. Our results showed that performance in the two domains was significantly correlated in the ASD group but not in the comparison group. These results suggest that the most likely origin for face impairments in ASD stems from the input stage impacting development of identity and expression domains alike, consistent with the social-motivation hypothesis.