Buyun Xu

Does face inversion qualitatively change face processing: An eye movement study using a face change detection task

Understanding the Face Inversion Effect is important for the study of face processing. Some researchers believe that the processing of inverted faces is qualitatively different from the processing of upright faces because inversion leads to a disproportionate performance decrement on the processing of different kinds of face information. Other researchers believe that the difference is quantitative because the processing of all kinds of facial information is less efficient due to the change in orientation and thus, the performance decrement is not disproportionate. To address the Qualitative and Quantitative debate, the current study employed a response-contingent, change detection paradigm to study eye movement during the processing of upright and inverted faces. In this study, configural and featural information were parametrically and independently manipulated in the eye and mouth region of the face. The manipulations for configural information involved changing the interocular distance between the eyes or the distance between the mouth and the nose. The manipulations for featural information involved changing the size of the eyes or the size of the mouth. The main results showed that change detection was more difficult in inverted than upright faces. Specifically, performance declined when the manipulated change occurred in the mouth region, despite the greater efforts allocated to the mouth region. Moreover, compared to upright faces where fixations were concentrated on the eyes and nose regions, inversion produced a higher concentration of fixations on the nose and mouth regions. Finally, change detection performance was better when the last fixation prior to response was located on the region of change, and the relationship between last fixation location and accuracy was stronger for inverted than upright faces. These findings reinforce the connection between eye movements and face processing strategies, and suggest that face inversion produces a qualitative disruption of looking behavior in the mouth region.

Individual Differences in Face Identity Processing with Fast Periodic Visual Stimulation

A growing body of literature suggests that human individuals differ in their ability to process face identity. These findings mainly stem from explicit behavioral tasks, such as the Cambridge Face Memory Test (CFMT). However, it remains an open question whether such individual differences can be found in the absence of an explicit face identity task and when faces have to be individualized at a single glance. In the current study, we tested 49 participants with a recently developed fast periodic visual stimulation (FPVS) paradigm [Liu-Shuang, J., Norcia, A. M., & Rossion, B. An objective index of individual face discrimination in the right occipitotemporal cortex by means of fast periodic oddball stimulation. Neuropsychologia, 52, 57–72, 2014] in EEG to rapidly, objectively, and implicitly quantify face identity processing. In the FPVS paradigm, one face identity (A) was presented at the frequency of 6 Hz, allowing only one gaze fixation, with different face identities (B, C, D) presented every fifth face (1.2 Hz; i.e., AAAABAAAACAAAAD…). Results showed a face individuation response at 1.2 Hz and its harmonics, peaking over occipitotemporal locations. The magnitude of this response showed high reliability across different recording sequences and was significant in all but two participants, with the magnitude and lateralization differing widely across participants. There was a modest but significant correlation between the individuation response amplitude and the performance of the behavioral CFMT task, despite the fact that CFMT and FPVS measured different aspects of face identity processing. Taken together, the current study highlights the FPVS approach as a promising means for studying individual differences in face identity processing.

Investigating the face inversion effect in a deaf population using the Dimensions Tasks

ABSTRACT Early experience can change the way people process faces. Early deafness provides deaf children with the opportunity to learn sign language, which is likely to alter their face processing strategy. The goal of the current study was to investigate whether early deafness, combined with the sign language experience, was able to change the face processing strategy using the Dimensions Task. In the Face Dimensions Task, configural and featural information were parametrically and independently manipulated in the eye and mouth region of the face. The manipulations for configural information involved changing the distance between the eyes or the distance between the mouth and the nose. The manipulations for featural information involved changing the size of the eyes or the size of the mouth. Similar manipulations were applied in the House Dimensions Task, with top and bottom windows treated as eyes and mouth. In the Face Dimensions Task, both the signing deaf and hearing participants showed a larger inversion effect in the mouth condition than the eye condition. However, as compared to hearing participants, deaf participants showed smaller inversion effect in the mouth condition, because their performance in the inverted mouth condition was not compromised by inversion to the same extent as the hearing participants. In the House Dimensions Task, this effect was not present, suggesting that it was face specific. This effect could be explained by the redistributed attentional resources from the centre to peripheral visual fields of deaf participants.

Investigating the perception of face identity in adults on the autism spectrum using behavioural and electrophysiological measures

In the present study, we investigated face processing in individuals with self-reported Autism Spectrum Disorder (ASD, n = 16) and typically developing control participants (n = 16) using behavioural and electrophysiological measures. As a measure of their face memory, we administered the Cambridge Face Memory Test to participants in the ASD group. The results showed that the scores of the ASD participants were reliably below the age- and gender-matched norms of neurotypical individuals. To measure brain responses to faces, we used the fast periodic visual stimulation method, presenting photographs of a same-identity face (i.e., base face) at a constant frequency of 6 Hz (F) interleaved with different-identity faces (i.e., the oddball faces) presented at 1.2 Hz. The 6 Hz presentation of the base face and 1.2 Hz presentation of the oddball face elicited periodic brain responses corresponding to face detection and face individuation processes, respectively. Participants viewed four blocks of upright faces and four blocks of inverted faces. The results showed an enhanced EEG response to upright base faces at 6 Hz frequency and its harmonics compared to inverted faces, and the response was most focal over medial occipital channels. An enhanced response was found to upright oddball faces at 1.2 Hz and its harmonics compared to the inverted faces, and the response was centred over occipito-temporal channels in the right hemisphere. Critically, no differences or interactions were found between the ASD and typically developing groups in the responses to either the 6 Hz base faces or the 1.2 oddball faces. These results suggest that in individuals with ASD, the earlier stage of face perception, as measured by the fast periodic visual stimulation paradigm, can be dissociated from the later memory stage of face processing, as assessed by the Cambridge Face Memory Test.

Investigating the face inversion effect in adults with Autism Spectrum Disorder using the fast periodic visual stimulation paradigm

Fast periodic visual stimulation (FPVS) is a powerful method for investigating the brain activity underlying human face processing. Previous studies have shown that FPVS provides a reliable index of the face inversion effect (FIE) (Liu-Shuang et al., 2013) and individual differences in face recognition ability (Xu et al., 2014). In the current study, the FPVS method was used to compare the discrimination of upright and inverted faces of 6 adults with Autism Spectrum Disorder (ASD) and 6 age-matched typically developed (TD) control participants. A repeated face stimulus (A) was presented at a frequency of 6Hz (F) for a 60-second block with a different oddball face (B, C, D) interspersed at every 5th cycle of presentation (F/5=1.2Hz) (i.e., AAAABAAAACAAAAD....). Faces within each 60-second block were presented either in their upright or inverted orientations. It is hypothesized that the 6Hz response reflects sensitivity to stimuli belonging to the generic face category whereas the 1.2Hz oddball response indicates sensitivity to a particular individuated face. The results showed that the repeated face stimuli produced an enhanced EEG signal at the fundamental 6Hz frequency and its harmonics (12Hz, 18Hz, etc.) with the largest activation found at medial-occipital electrode sites. Both the ASD and TD groups showed the FIE in which upright faces elicited a greater EEG amplitude than inverted faces. At the 1.2Hz frequency and its harmonics (2.4Hz, 3.6Hz, etc.) , participants in the TD group showed the FIE where a greater signal was generated by the upright oddball face than the inverted oddball face. In contrast, participants in the ASD group exhibited the same EEG response to the upright and inverted oddball face. The lack of the FIE to the individuated oddball face in the ASD group is consistent with the behavioral findings indicating that adults with ASD have difficulty discriminating individual faces. Meeting abstract presented at VSS 2015.