Facial expression processing in developmental prosopagnosia

<p>Individuals with developmental prosopagnosia experience lifelong deficits recognising facial identity, but whether their ability to process facial expression is also impaired is unclear. Addressing this issue is key for understanding the core deficit in developmental prosopagnosia, and for advancing knowledge about the mechanisms and development of normal face processing. In this thesis, I report two online studies on facial expression processing with large samples of prosopagnosics. In Study 1, I compared facial expression and facial identity perception in 124 prosopagnosics and 133 controls. I used three perceptual tasks including simultaneous matching, sequential matching, and sorting. I also measured inversion effects to examine whether prosopagnosics rely on typical face mechanisms. Prosopagnosics showed subtle deficits with facial expression, but they performed worse with facial identity. Prosopagnosics also showed reduced inversion effects for facial identity but normal inversion effects for facial expression, suggesting they use atypical mechanisms for facial identity but normal mechanisms for facial expression. In Study 2, I extended the findings of Study 1 by assessing facial expression recognition in 78 prosopagnosics and 138 controls. I used four labelling tasks that varied on whether the facial expressions were basic (e.g., happy) or complex (e.g., elated), and whether they were displayed via static (i.e., images) or dynamic (i.e., video clips) stimuli. Prosopagnosics showed subtle deficits with basic expressions but performed normally with complex expressions. Further, prosopagnosics did not show reduced inversion effects for both types of expressions, suggesting they use similar recognition mechanisms as controls. Critically, the subtle expression deficits that prosopagnosics showed in both studies can be accounted for by autism traits, suggesting that expression deficits are not a feature of prosopagnosia per se. I also provide estimates of the prevalence of deficits in facial expression perception (7.70%) and recognition (2.56% - 5.13%) in prosopagnosia, both of which suggest that facial expression processing is normal in the majority of prosopagnosics. Overall, my thesis demonstrates that facial expression processing is not impaired in developmental prosopagnosia, and suggests that facial expression and facial identity processing rely on separate mechanisms that dissociate in development.</p>

Facial expression processing in developmental prosopagnosia

<p>Individuals with developmental prosopagnosia experience lifelong deficits recognising facial identity, but whether their ability to process facial expression is also impaired is unclear. Addressing this issue is key for understanding the core deficit in developmental prosopagnosia, and for advancing knowledge about the mechanisms and development of normal face processing. In this thesis, I report two online studies on facial expression processing with large samples of prosopagnosics. In Study 1, I compared facial expression and facial identity perception in 124 prosopagnosics and 133 controls. I used three perceptual tasks including simultaneous matching, sequential matching, and sorting. I also measured inversion effects to examine whether prosopagnosics rely on typical face mechanisms. Prosopagnosics showed subtle deficits with facial expression, but they performed worse with facial identity. Prosopagnosics also showed reduced inversion effects for facial identity but normal inversion effects for facial expression, suggesting they use atypical mechanisms for facial identity but normal mechanisms for facial expression. In Study 2, I extended the findings of Study 1 by assessing facial expression recognition in 78 prosopagnosics and 138 controls. I used four labelling tasks that varied on whether the facial expressions were basic (e.g., happy) or complex (e.g., elated), and whether they were displayed via static (i.e., images) or dynamic (i.e., video clips) stimuli. Prosopagnosics showed subtle deficits with basic expressions but performed normally with complex expressions. Further, prosopagnosics did not show reduced inversion effects for both types of expressions, suggesting they use similar recognition mechanisms as controls. Critically, the subtle expression deficits that prosopagnosics showed in both studies can be accounted for by autism traits, suggesting that expression deficits are not a feature of prosopagnosia per se. I also provide estimates of the prevalence of deficits in facial expression perception (7.70%) and recognition (2.56% - 5.13%) in prosopagnosia, both of which suggest that facial expression processing is normal in the majority of prosopagnosics. Overall, my thesis demonstrates that facial expression processing is not impaired in developmental prosopagnosia, and suggests that facial expression and facial identity processing rely on separate mechanisms that dissociate in development.</p>

Measurement of individual differences in face-identity processing abilities in older adults

Background Face-identity processing declines with age. Few studies have examined whether face-identity processing abilities can be measured independently from general cognitive abilities in older adults (OA). This question has practical implications for the assessment of face-identity processing abilities in OA and theoretical implications for the notion of face processing as a specific ability. The present study examined the specificity of face memory and face matching abilities in OA aged 50 + . Methods Performance of younger adults (YA) and OA was measured on face tasks: Cambridge Face Memory Task (CFMT), the Glasgow Face Matching Task (GFMT), holistic processing; and tasks of general cognition: fluid intelligence, selective attention, and mental rotation. Data were analyzed using multiple regression models encompassing (i) the CFMT/GFMT and measures of general cognition; and (ii) all face processing tasks. Results Across the two age groups, models encompassing all face tasks were significant and accounted for more variance in the data than models encompassing the CFMT/GFMT and measures of general cognition. General cognitive abilities accounted for 17% of variance for the GFMT (p < 0.01) and 3% for the CFMT (p > 0.05). Discussion Our results suggest that face memory can be measured independently from general cognition using the CFMT in OA. Implications for the notion of a general face processing factor across the adult lifespan are discussed.

The impact of facemasks on emotion recognition, trust attribution and re-identification

Covid-19 pandemics has fostered a pervasive use of facemasks all around the world. While they help in preventing infection, there are concerns related to the possible impact of facemasks on social communication. The present study investigates how emotion recognition, trust attribution and re-identification of faces differ when faces are seen without mask, with a standard medical facemask, and with a transparent facemask restoring visual access to the mouth region. Our results show that, in contrast to standard medical facemasks, transparent masks significantly spare the capability to recognize emotional expressions. Moreover, transparent masks spare the capability to infer trustworthiness from faces with respect to standard medical facemasks which, in turn, dampen the perceived untrustworthiness of faces. Remarkably, while transparent masks (unlike standard masks) do not impair emotion recognition and trust attribution, they seemingly do impair the subsequent re-identification of the same, unmasked, face (like standard masks). Taken together, this evidence supports a dissociation between mechanisms sustaining emotion and identity processing. This study represents a pivotal step in the much-needed analysis of face reading when the lower portion of the face is occluded by a facemask.

Talker and accent familiarity yield advantages for voice identity perception: a voice sorting study

Familiarity benefits in voice identity perception have been frequently described in the literature. Typically, studies have contrasted listeners who were either familiar or unfamiliar with the target voices, thus manipulating talker familiarity. In these studies, familiarity with a voice results in more accurate voice identity perception. Such talker familiarity is, however, only one way in which listeners can be familiar the stimuli used: Another type of familiarity that has been shown to benefit voice identity perception is language or accent familiarity. In the current study, we examine and compare the effects of talker and accent familiarity in the context of a voice identity sorting task, using naturally varying voice recording samples from the TV show “Derry Girls”. Voice samples were thus all spoken with a regional accent of UK/Irish English (Northern Irish). We tested four listeners groups: Listeners were either familiar or unfamiliar with the TV show (and therefore the talker identities) and were either highly familiar or relatively less familiar with the accent. We find that both talker and accent familiarity significantly improve accuracy of voice identity perception. However, the effect sizes for effects of talker familiarity are overall larger. We discuss our findings in light of existing models of voice perception, arguing that they provide evidence for interactions of speech and identity processing pathways in voice perception. We conclude that voice perception is a highly interactive process, during which listeners make use of any available information to achieve their perceptual goals.