Normal recognition of famous voices in developmental prosopagnosia

This condition impacts every aspect of my life: A survey to understand the experience of living with developmental prosopagnosia

This mixed methods study examined the real-world experiences of living with developmental prosopagnosia (face blindness), a lifelong neurodevelopmental condition that severely affects the ability to recognise faces despite otherwise normal vision, IQ and memory. Twenty-nine UK based adults with confirmed face recognition difficulties completed an online survey describing and quantifying their experiences of living with poor face recognition. Although the majority (62%) of participants reported being able to recognise their immediate family, e.g., parent, partner, or child, strikingly 35% reported being unable to reliably recognise their immediate family members out of context. Even fewer (45%), reported always being able to recognise their three closest friends when encountering them unexpectedly, highlighting that DP commonly affects the recognition of highly familiar faces with whom individuals have close emotional relationships. Furthermore, participants who reported being able or unable to recognise their immediate family showed no significant difference in objective face memory ability. More than two thirds of participants (65.5%) reported being able to recognise fewer than 10 familiar faces (with the most common response being none), far below typical abilities. Thematic framework analysis highlighted how low public, professional, and employer awareness of developmental prosopagnosia presented challenges across multiple domains including seeking diagnosis, social and family relationships and workplaces. Driven largely by concerns about negative evaluation by others, most participants employed a range of highly effortful, though error prone, strategies to disguise and compensate for their face recognition difficulties. Some of the strategies described may help explain why many individuals can perform within typical norms on laboratory face processing tests despite their clear difficulties in everyday life and highlight the need for ecologically valid tests. Participants' highest priorities for future research were improved awareness of developmental prosopagnosia and interventions to improve their face recognition ability.

A taxometric analysis of developmental prosopagnosia: Evidence for a categorically distinct impairment

Poor performance on cognitive assessment tasks may indicate a selective 'impairment'. However, it is unclear whether such difficulties separate the individual from the general population qualitatively (i.e., they form a discrete group) or quantitatively (i.e., they represent the lower end of a continuous distribution). Taxometric methods address this question but have rarely been applied to cognitive disorders. This study examined the latent structure of developmental prosopagnosia (DP) - a relatively selective deficit in face recognition that occurs in the absence of neurological injury. Multiple taxometric procedures were applied to dominant diagnostic indices of face recognition ability across two independent datasets. All analyses supported a categorical outcome, even for mild cases of DP, suggesting that it is a qualitatively distinct condition. This finding has significant implications for our understanding of DP given it has traditionally been viewed as a continuous impairment. In particular, existing (arbitrary) diagnostic cut-offs may be too conservative, underestimating prevalence rates and prohibiting big-data approaches to theoretical study. More broadly, these conclusions support application of the taxometric method to many other cognitive processes where weaknesses are predominantly assumed to reside on a continuous distribution.

Face naming and recollection represent key memory deficits in developmental prosopagnosia

Previous studies have found that face perception deficits do not fully account for the severity of face recognition deficits in developmental prosopagnosia (DP). Researchers have begun identifying deficient memory mechanisms such as impaired face recollection, but these findings require replication, and further characterization of additional memory deficits is necessary. Our goals were to replicate prior findings of face recollection impairment in DP and extend these findings to assess different types of face associative memory. We had 69 DPs and 99 controls perform a face perception battery as well as three face memory tasks: 1) Old/New task with confidence ratings to calculate recollection and familiarity using ROC analysis, 2) Face/Scene task to examine remember-know judgments and contextual memory for faces, and 3) Face-Name/Occupation task to assess the ability to learn semantic associations with faces. Compared to controls, DPs showed poorer recollection and familiarity across both Old/New and Face/Scene tasks as well as reduced scene accuracy for correct faces. Of these differences, only Old/New recollection remained significant after controlling for group differences in face perception abilities. In the Face-Name/Occupation task, after controlling for face perception, DPs showed poorer recall of names than controls but performed similarly in recalling occupations. Finally, we found that DPs with major, mild, and no face perception deficits showed consistent impairments in Old/New recollection and face-naming, and larger perceptual deficits were associated with larger memory deficits. Together, these results provide several mechanistic insights into the nature of memory deficits in DPs and have diagnostic and treatment implications.

Disentangling developmental prosopagnosia: A scoping review of terms, tools and topics

The goal of this preregistered scoping review is to create an overview of the research on developmental prosopagnosia (DP). Through analysis of all empirical studies of DP in adults, we investigate 1) how DP is conceptualized and defined, 2) how individuals are classified with DP and 3) which aspects of DP are investigated in the literature. We reviewed 224 peer-reviewed studies of DP. Our analysis of the literature reveals that while DP is predominantly defined as a lifelong face recognition impairment in the absence of acquired brain injury and intellectual/cognitive problems, there is far from consensus on the specifics of the definition with some studies emphasizing e.g., deficits in face perception, discrimination and/or matching as core characteristics of DP. These differences in DP definitions is further reflected in the vast heterogeneity in classification procedures. Only about half of the included studies explicitly state how they classify individuals with DP, and these studies adopt 40 different assessment tools. The two most frequently studied aspects of DP are the role of holistic processing and the specificity of face processing, and alongside a substantial body of neuroimaging studies of DP, this paints a picture of a research field whose scientific interests and aims are rooted in cognitive neuropsychology and neuroscience. We argue that these roots - alongside the heterogeneity in DP definition and classification - may have limited the scope and interest of DP research unnecessarily, and we point to new avenues of research for the field.

The neuropsychological evaluation of face identity recognition

Facial identity recognition (FIR) is arguably the ultimate form of recognition for the adult human brain. Even if the term prosopagnosia is reserved for exceptionally rare brain-damaged cases with a category-specific abrupt loss of FIR at adulthood, subjective and objective impairments or difficulties of FIR are common in the neuropsychological population. Here we provide a critical overview of the evaluation of FIR both for clinicians and researchers in neuropsychology. FIR impairments occur following many causes that should be identified objectively by both general and specific, behavioral and neural examinations. We refute the commonly used dissociation between perceptual and memory deficits/tests for FIR, since even a task involving the discrimination of unfamiliar face images presented side-by-side relies on cortical memories of faces in the right-lateralized ventral occipito-temporal cortex. Another frequently encountered confusion is between specific deficits of the FIR function and a more general impairment of semantic memory (of people), the latter being most often encountered following anterior temporal lobe damage. Many computerized tests aimed at evaluating FIR have appeared over the last two decades, as reviewed here. However, despite undeniable strengths, they often suffer from ecological limitations, difficulties of instruction, as well as a lack of consideration for processing speed and qualitative information. Taking into account these issues, a recently developed behavioral test with natural images manipulating face familiarity, stimulus inversion, and correct response times as a key variable appears promising. The measurement of electroencephalographic (EEG) activity in the frequency domain from fast periodic visual stimulation also appears as a particularly promising tool to complete and enhance the neuropsychological assessment of FIR.

Familial Transmission of Developmental Prosopagnosia: New Case Reports from an Extended Family and Identical Twins

Existing evidence suggests that developmental prosopagnosia (DP) is a surprisingly prevalent condition, with some individuals describing lifelong difficulties with facial identity recognition. Together with case reports of multiple family members with the condition, this evidence suggests that DP is inherited in at least some instances. Here, we offer some novel case series that further support the heritability of the condition. First, we describe five adult siblings who presented to our lab with symptoms of DP. Second, for the first known time in the literature, we describe a pair of adult identical twins who contacted us in the belief that they both experience DP. The condition was confirmed in three of the five siblings (with minor symptoms observed in the remaining two) and in both twins. Supplementary assessments suggested that all individuals also experienced some degree of difficulty with facial identity perception, but that object recognition was preserved. These findings bolster the evidence supporting the heritability of DP and suggest that it can be a specific impairment in some cases.

A new approach to diagnosing and researching developmental prosopagnosia: Excluded cases are impaired too

Developmental prosopagnosia is characterized by severe, lifelong difficulties when recognizing facial identity. Unfortunately, the most common diagnostic assessment (Cambridge Face Memory Test) misses 50-65% of individuals who believe that they have this condition. This results in such excluded cases' absence from scientific knowledge, effect sizes of impairment potentially overestimated, treatment efficacy underrated, and may elicit in them a negative experience of research. To estimate their symptomology and group-level impairments in face processing, we recruited a large cohort who believes that they have prosopagnosia. Matching prior reports, 56% did not meet criteria on the Cambridge Face Memory Test. However, the severity of their prosopagnosia symptoms and holistic perception deficits were comparable to those who did meet criteria. Excluded cases also exhibited face perception and memory impairments that were roughly one standard deviation below neurotypical norms, indicating the presence of objective problems. As the prosopagnosia index correctly classified virtually every case, we propose it should be the primary method for providing a diagnosis, prior to subtype categorization. We present researchers with a plan on how they can analyze these excluded prosopagnosia cases in their future work without negatively impacting their traditional findings. We anticipate such inclusion will enhance scientific knowledge, more accurately estimate effect sizes of impairments and treatments, and identify commonalities and distinctions between these different forms of prosopagnosia. Owing to their atypicalities in visual perception, we recommend that the prosopagnosia index should be used to screen out potential prosopagnosia cases from broader vision research.

Neural Correlates of Voice Learning with Distinctive and Non-Distinctive Faces

Recognizing people from their voices may be facilitated by a voice's distinctiveness, in a manner similar to that which has been reported for faces. However, little is known about the neural time-course of voice learning and the role of facial information in voice learning. Based on evidence for audiovisual integration in the recognition of familiar people, we studied the behavioral and electrophysiological correlates of voice learning associated with distinctive or non-distinctive faces. We repeated twelve unfamiliar voices uttering short sentences, together with either distinctive or non-distinctive faces (depicted before and during voice presentation) in six learning-test cycles. During learning, distinctive faces increased early visually-evoked (N170, P200, N250) potentials relative to non-distinctive faces, and face distinctiveness modulated voice-elicited slow EEG activity at the occipito-temporal and fronto-central electrodes. At the test, unimodally-presented voices previously learned with distinctive faces were classified more quickly than were voices learned with non-distinctive faces, and also more quickly than novel voices. Moreover, voices previously learned with faces elicited an N250-like component that was similar in topography to that typically observed for facial stimuli. The preliminary source localization of this voice-induced N250 was compatible with a source in the fusiform gyrus. Taken together, our findings provide support for a theory of early interaction between voice and face processing areas during both learning and voice recognition.

The impact of low vision on social function: The potential importance of lost visual social cues

Visual cues usually play a vital role in social interaction. As well as being the primary cue for identifying other people, visual cues also provide crucial non-verbal social information via both facial expressions and body language. One consequence of vision loss is the need to rely on non-visual cues during social interaction. Although verbal cues can carry a significant amount of information, this information is often not available to an untrained listener. Here, we review the current literature examining potential ways that the loss of social information due to vision loss might impact social functioning. A large number of studies suggest that low vision and blindness is a risk factor for anxiety and depression. This relationship has been attributed to multiple factors, including anxiety about disease progression, and impairments to quality of life that include difficulties reading, and a lack of access to work and social activities. However, our review suggests a potential additional contributing factor to reduced quality of life that has been hitherto overlooked: blindness may make it more difficult to effectively engage in social interactions, due to a loss of visual information. The current literature suggests it might be worth considering training in voice discrimination and/or recognition when carrying out rehabilitative training in late blind individuals.

New evidence of impaired expression recognition in developmental prosopagnosia

Developmental prosopagnosia (DP) is a neurodevelopmental condition characterized by lifelong face recognition difficulties. To date, it remains unclear whether or not individuals with DP experience impaired recognition of facial expressions. It has been proposed that DPs may have sufficient perceptual ability to correctly interpret facial expressions when tasks are relatively easy (e.g., the stimuli are unambiguous and viewing conditions are optimal), but exhibit subtle impairments when tested under more challenging conditions. In the present study, we sought to take advantage of the COVID-19 pandemic to test this view. It is well-established that the surgical-type masks worn during the pandemic hinder the recognition and interpretation of facial emotion in typical participants. Relative to typical participants, we hypothesized that DPs may be disproportionately impaired when asked to interpret the facial emotion of people wearing face masks. We compared the ability of 34 DPs and 60 age-matched typical controls to recognize facial emotions i) when the whole face is visible, and ii) when the lower portion of the face is covered with a surgical mask. When expression stimuli were viewed without a mask, the DPs and typical controls exhibited similar levels of performance. However, when expression stimuli were shown with a mask, the DPs showed signs of subtle expression recognition deficits. The DPs were particularly prone to mislabeling masked expressions of happiness as emotion neutral. These results add to a growing body of evidence that under some conditions, DPs do exhibit subtle deficits of expression recognition.

Atypical prosopagnosia following right hemispheric stroke: A 23-year follow-up study with M.T

Most findings on prosopagnosia to date suggest preserved voice recognition in prosopagnosia (except in cases with bilateral lesions). Here we report a follow-up examination on M.T., suffering from acquired prosopagnosia following a large unilateral right-hemispheric lesion in frontal, parietal, and anterior temporal areas excluding core ventral occipitotemporal face areas. Twenty-three years after initial testing we reassessed face and object recognition skills [Henke, K., Schweinberger, S. R., Grigo, A., Klos, T., & Sommer, W. (1998). Specificity of face recognition: Recognition of exemplars of non-face objects in prosopagnosia. Cortex, 34(2), 289-296]; [Schweinberger, S. R., Klos, T., & Sommer, W. (1995). Covert face recognition in prosopagnosia - A dissociable function? Cortex, 31(3), 517-529] and additionally studied voice recognition. Confirming the persistence of deficits, M.T. exhibited substantial impairments in famous face recognition and memory for learned faces, but preserved face matching and object recognition skills. Critically, he showed substantially impaired voice recognition skills. These findings are congruent with the ideas that (i) prosopagnosia after right anterior temporal lesions can persist over long periods > 20 years, and that (ii) such lesions can be associated with both facial and vocal deficits in person recognition.

The Twenty Item Prosopagnosia Index (PI20) provides meaningful evidence of face recognition impairment

The Twenty Item Prosopagnosia Index (PI20) is a self-report questionnaire used for quantifying prosopagnosic traits. This scale is intended to help researchers identify cases of developmental prosopagnosia by providing standardized self-report evidence to complement diagnostic evidence obtained from objective computer-based tasks. In order to respond appropriately to items, prosopagnosics must have some insight that their face recognition is well below average, while non-prosopagnosics need to understand that their relative face recognition ability falls within the typical range. There has been considerable debate about whether participants have the necessary insight into their face recognition abilities to respond appropriately. In the present study, we sought to determine whether the PI20 provides meaningful evidence of face recognition impairment. In keeping with the intended use of the instrument, we used PI20 scores to identify two groups: high-PI20 scorers (those with self-reported face recognition difficulties) and low-PI20 scorers (those with no self-reported face recognition difficulties). We found that participant groups distinguished on the basis of PI20 scores clearly differed in terms of their mean performance on objective measures of face recognition ability. We also found that high-PI20 scorers were more likely to achieve levels of face recognition accuracy associated with developmental prosopagnosia.

Musicianship Influences Language Effect on Musical Pitch Perception

Given its practical implications, the effect of musicianship on language learning has been vastly researched. Interestingly, growing evidence also suggests that language experience can facilitate music perception. However, the precise nature of this facilitation is not fully understood. To address this research gap, I investigated the interactive effect of language and musicianship on musical pitch and rhythmic perception. Cantonese and English listeners, each divided into musician and non-musician groups, completed the Musical Ear Test and the Raven’s 2 Progressive Matrices. Essentially, an interactive effect of language and musicianship was found on musical pitch but not rhythmic perception. Consistent with previous studies, Cantonese language experience appeared to facilitate musical pitch perception. However, this facilitatory effect was only present among the non-musicians. Among the musicians, Cantonese language experience did not offer any perceptual advantage. The above findings reflect that musicianship influences the effect of language on musical pitch perception. Together with the previous findings, the new findings offer two theoretical implications for the OPERA hypothesis—bi-directionality and mechanisms through which language experience and musicianship interact in different domains.