Prosopagnosia, Phonagnosia, and other Disorders of Person Perception
Just like any other aspect of cognitive functioning, our “social brain” and its machinery – which enables us to recognize identity, emotional expression, and other signals from a face or a voice – may be severely compromised by brain lesions following stroke or traumatic injury. However, standard neuropsychological tests typically do not include tests on face perception, and human intraspection about one´s own ability to recognize faces or voices is known to be very unreliable, such that many patients may not spontaneously report such difficulties. This may have contributed to the fact that clinically relevant neuropsychological disorders in face perception (in their most extreme form, acquired prosopagnosia – the inability to recognize well-known people by their faces) have long been held to be extremely rare. Our own work in this area includes the study of groups of patients with unilateral posterior brain lesions and the functional impairments seen in patients with lesions of the right hemisphere [2, 3, 7, 8]. We and others argued strongly that prosopagnosia is not a unitary condition, but can be the consequence of a breakdown at various functional and neuroanatomical levels of face processing [1, 9, 10]. In addition, we performed several detailed case studies of patients with dense prosopagnosia [4, 5], showing that such impairments can exist even when other aspects of visual object recognition are preserved to a surprising extent. Using sophisticated experimental techniques, “covert recognition” of unrecognized faces can be demonstrated in many of these patients, and we have extensively studied this important aspect of intact processing [4, 9]. Systematic studies with larger groups of unselected patients from a neurological rehabilitation clinic  also led us to conclude that clinically relevant disorders in the perception of faces, voices, or names are more frequent than previously assumed. More recently, there has been a strong raise in interest in a group of people who show very poor face recognition in the absence of any known neurological disorder. This condition, termed “developmental” or “congenital” prosopagnosia, is now thought to be genetically mediated. We emphasize that all these cases require careful functional diagnosis similar to what has become state-of-the-art in acquired prosopagnosia, as there is no a priori reason to believe that congenital prosopagnosia is a unitary condition any more than acquired prosopagnosia is. Very recently, a case has been reported with selective developmental deficits in voice recognition [12-14]. More systematic research on participants with developmental disorders in person recognition  will further increase our understanding of the human system for face and person perception.
 Schweinberger, S.R. (1992). Funktionelle und neuroanatomische Aspekte der Prosopagnosie. Zeitschrift für Neuropsychologie, 3, 106-119.
 Schweinberger, S.R., Buse, C., Freeman, R.B., Jr., Schönle, P.W., & Sommer, W. (1992). Memory search for faces and digits in patients with unilateral brain lesions.Journal of Clinical and Experimental Neuropsychology, 14, 839-856.
 Schweinberger, S.R. (1995). Personal name recognition and associative priming in patients with unilateral brain damage. Brain and Cognition, 28, 23-35.
 Schweinberger, S.R., Klos, T., & Sommer, W. (1995). Covert face recognition in prosopagnosia: A dissociable function? Cortex, 31, 521-536.
 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, 289-296.
 Neuner, F., & Schweinberger, S.R. (2000). Neuropsychological impairments in the recognition of faces, names, and voices. Brain and Cognition, 44, 342-366.
 Schweinberger, S.R., Klos, T., & Sommer, W. (2002). Face and Word Recognition in Patients with Left and Right Hemispheric Lesions: Evidence from Reaction Times and ERPs. Zeitschrift für Neuropsychologie, 13, 67-81.
 Schweinberger, S.R., Landgrebe, A., Mohr, B., & Kaufmann, J.M. (2002). Personal names and the human right hemisphere: An illusory link? Brain & Language, 80, 111-120.
 Schweinberger, S.R., & Burton, A.M. (2003). Covert recognition and the neural system for face processing. Cortex, 39, 9-30.
 Schweinberger, S.R. (2007). Agnosien. In: S. Gauggel & T. Herrmann (Hrsg.):Handbuch der Psychologie. Band 8: Handbuch der Neuro- und Biopsychologie. Göttingen: Hogrefe.
 Dobel, C., Bölte, J., Aicher, M., & Schweinberger, S.R. (2007). Prosopagnosia without apparent cause: Overview and diagnosis of six cases. Cortex, 43, 718-733.
 Garrido, L., Eisner, F., McGettigan, C. Stewart, L., Sauter, D., Hanley, R., Schweinberger, S., & Duchaine, B. (2008). A case of developmental phonagnosia.Meeting of the Experimental Psychology Society, London, 3-4 January, 2008.
 Garrido, L., Eisner, F., McGettigan, C., Stewart, L., Sauter, D., Hanley, R., Schweinberger, S., & Duchaine, B. (2008) A case of developmental phonagnosia. 15th Annual Meeting of the Cognitive Neuroscience Society, San Francisco, 12-15 April, 2008.
 Garrido, L., Eisner, F., McGettigan, C., Stewart, L., Sauter, D., Hanley, J.R., Schweinberger, S.R., Warren, J., & Duchaine, B. (2009). Developmental phonagnosia: a selective deficit to vocal identity recognition. Neuropsychologia, 47, 123-131.
 Della Sala, S., & Schweinberger, S.R. (2013). Face blindness and person misidentification in non-scientific parlance. Cortex, 49(8), 2276-2280.
 Németh, K., Zimmer, M., Schweinberger, S.R., Vakli, P., & Kovács, G. (2014). The Background of Reduced Face Specificity of N170 in Congenital Prosopagnosia. PLoS One, 9(7), e101393.
DFG-Projekt Schw 511/6-1
Stimulus examples (Windows Media Player required)
So far, our research has uncovered the importance of the integration between visual and auditory information in the recognition of familiar speakers (Schweinberger, S.R., Robertson, D. & Kaufmann, J.M. (in press). Hearing facial identities. The Quarterly Journal of Experimental Psychology.)
Below are some examples of the types of stimuli we use to investigate the effects of audiovisual integration on speaker recognition in our ongoing research:
Corresponding Static: An example of a familiar voice, combined with the correct (corresponding) static face
Corresponding Dynamic: An example of a familiar voice, combined with the correct (corresponding) dynamic face
Noncorresponding Dynamic: An example of a familiar voice, combined with an incorrect (non-corresponding) dynamic face, edited so as to ensure precise temporal synchronisation.
Non-corresponding Dynamic (with delayed video clarity): An example of a familiar voice, combined with an incorrect (non-corresponding) dynamic face. The video was presented in black and white and the blurred face becomes clearer over time. This was done to investigate whether the voice can affect face recognition.
We investigated the effects that asynchronous audiovisual presentations had on voice recognition. Below are examples of those stimuli.
Corresponding Backwards: An example of a familiar voice, combined with the correct (corresponding) backwards-animated face.
Non-corresponding Backwards: An example of a familiar voice, combined with an incorrect (non-corresponding) backwards-animated face.
Manipulation of audiovisual synchrony:
Corresponding -600ms: An example of a familiar voice and face video, where the voice leads the facial motion by 600 milliseconds (voice begins 600ms before facial motion).
Corresponding Synchronous: An example of a familiar voice and face video, where the voice and facial motion are in synchrony.
Non-corresponding Synchronous: An example of an unfamiliar voice with a familiar face video, where the voice and facial motion are in synchrony.
Corresponding +200ms: An example of a familiar voice and face video, where the voice onset lags behind the facial motion by 200 milliseconds (voice begins 200ms after facial motion).
Corresponding +600ms: An example of a familiar voice and face video, where the voice onset lags behind the facial motion by 600 milliseconds (voice begins 600ms after facial motion).
Schweinberger, S.R., & Robertson, D.M.C. (in press). Audiovisual integration in familiar person recognition. Frontiers in Bioscience.
Experiment 1: Two example videos each for two personally familiar speakers, with either corresponding or noncorresponding auditory and visual speaker identities.
Experiment 2: Two example videos of auditory speakers that were combined with corresponding or noncorresponding visual identities, with the video clip playes backwards (time-reversed).
Corresponding A2V2 time reversed
Noncorresponding A1V2 time reversed
Experiment 3: Two example videos of visual speakers that were combined with corresponding or noncorresponding auditory voice identities. Note: Videos were linearly deblurred during the first 1000 ms of presentation.
Corresponding A2V2 deblur
Noncorresponding A1V2 deblur
The McGurk Effect
Furthermore, as has been well established in previous research, audiovisual integration is important in speech perception. Our own demonstration of the classic McGurk effect (McGurk and Macdonald, 1976) is displayed here.
This video is a combination of an auditory /aba/ and a visual /aga/, but what most adults (98%) perceive is /ada/. You should play the clip while looking at the face and listening to the voice. Try listening to the voice with your eyes closed to get an idea of the difference between what you hear auditorily and what you perceive audiovisually.
The McGurk effect works for full sentence stimuli as well. The first two parts of the video contain the auditory-only “Bichter und Benker bachten basselbe” followed by the visual-only “Gichter und Genker gachten gasselbe”. The third and final part of the video allows you to perceive the result of the integration of these two signals.