Facial Recognition as a Distinct Psychological Phenomenon - Essay Example

1 The issue of face recognition and research Face perception and recognition has been the of a lot of recent psychological research. Central to the problem is the question : are faces recognized by us humans any differently than other objects There is recent scientific evidence that facial recognition occurs at a subconscious level, without the subject being aware of it. In particular there is emerging evidence that in 'prosopagnosia', a disorder where subjects are unable to identify 'faces, 'covert' recognition does occur although the complex process that leads to actual identification of the person by name is impaired. On the other hand there is some evidence too that expertise plays a role too - as facial recognition for species other than humans is demonstrated by professionals working with those areas ( dog breeders, judges, sheep farmers etc). In this paper we would examine the evidence for against the issue of whether facial recognition is a distinct psychological phenomenon. 2 A Critical Review of the Evidence that Facial Recognition Uses Distinct Cognitive processes from other types of Object Recognition Initial studies on facial recognition did not recognize that facial perception was a separate cognitive process. In one of the early reviews form the University of Aberdeen ( Ellis, 1975) it was concluded that facial perception was in no way different from that of any other complex geometrical object. They were however recognized as a distinct category in view of their unique social importance, the association of facial patterns with emotional states and the fact that faces were important in non-verbal communication. Gilbert and Bakan (1973) were among many others who started experiments with chimeric faces, where one half of a face was combined with its own mirror image to produce a composite image. It was soon apparent form their work and that of many others that our brains have an inherent bias to attribute the half of the face in our left visual field ( the right half of faces) in their perceptual judgment of the owner's identity, personal characteristics and other psychological attributes. In Gilbert and Balkan's study, participants chose left-left composite images as more representative of likeness, than even true right-left real images. This was a major shift to the realisation that facial recognition is a distinct cognitive process. The most popular current model for facial processing is that of Bruce and Young (1986) who proposed three stages in facial processing: firstly the structural encoding stage, the second stage of face recognition, and thirdly, the familiarity-decision stage. In the first stage, as the visual data of someone's face enters the striate visual cortex in our brains they are then processed as a recognizable 'face'. Thereafter, some of the basic features of the facial image like orientation, positional features and color, are re-created to form the 'mental' image of a face. In the second stage, the brain ties to identify unique and distinguishable features of the face, which makes it possible to identify it as 'belonging' to an individual, and selects features of a facial pattern which will make it possible to identify the 'broad distinguishing features'. In the third stage, the now familiar face is processed with all the specific details of episodes, semantic memory and emotional attributes that are necessary to definitely identify the person to whom the face belongs. The only other competing model is the interactive activation and network competition model (Burton, Bruce, & Johnston, 1990), which only describes an alternate sequence of events in facial recognition, but does not provide a comprehensive framework of how such information ties up together in a pattern of recognition. The Margaret Thatcher illusion is an important part of this process described by the British psychologist Peter Thompson on a photograph of Margaret Thatcher shortly after she became the Prime Minister of Britain. In this effect, the appearance of an inverted image of her face in which her eyes (with their eyebrows) and mouth were inverted appeared normal to observers. But when the same image was presented the right way up, the image appeared grotesquely hideous to the same viewers when the face was viewed as a whole so that only the eyes and mouth are inverted. The illusion of normality in the inverted image is called the 'differential inversion effect' and highlights the difficulties of recognizing configurational incongruities in inverted faces. Also called the Maggie effect or the Thatcher illusion, this demonstrates powerfully that facial recognition is different from recognition of other objects. These experiments illustrate the shift in our thinking about facial recognition, as evidence has mounted that facial recognition is achieved by discrete, neurological processes. 3 Cognitive neuropsychological research on facial processing Cognitive neuropsychological research into facial processing aims to delineate the precise neurological mechanisms by which facial processing occurs. One important clue about this subject comes from studies that demonstrate the speed with which facial recognition occurs. Electrophysiological studies involving Event-related potentials (ERPs) from various events can be compared to find out whether facial processing is faster than other modes of processing. Recordings form both humans and primates show that processing of 'faces' in the cortex can happen as fast as 100 milliseconds, compared to 200 milliseconds or double the amount of time for other types of processing. (Pegna and Khateb, 2004). Faster processing speeds have also been found for various emotional states which are detected from the face suggesting that there are entirely different pathways for facial cognitive processes as an 'automatic' phenomenon. Whether facial recognition can occur as an entirely subconscious process can be demonstrated well in the condition called prosopagnosia in which subjects lose the ability to 'recognize' faces selectively, while other forms of recognition of objects and visual stimuli are intact. Though usually the condition presents acutely as a result of injury to the fusiform gyrus, it can also present as a congenital disorder as found more recently. The study of prosopagnosia has been crucial to the process of developing theories of facial recognition. There are various differences in the way that this can present, suggesting that there are separate processes leading to facial recognition that can lead to specific impairments. For instance in some patients, facial recognition is intact, but reading emotions is affected, while in others, it is the other way around. In addition, it is recognized that there are several other visual defects associated with this condition, thought top be directly linked to the visual area damage. In addition, other recognition cues remain intact - Personal identity, Vocal recognition and Emotion detection thus adding evidence to the theory that facial recognition is an independent, subconscious phenomenon. Recent studies have shown that even in the absence of conscious recognition, adult subjects show 'covert' recognition, as demonstrated by changes in electrophysiological skin responses (Bauer, 1984). Essentially, subjects with prosopagnosia unable to identify photos of a familiar faces still showed electro-dermal responses (GSR) to familiar names when the appropriate names cropped up from within a list of names read out to them. This test designed from a 'lie detector test' also known as the 'Guilty knowledge test' relies on changes in skin electrophysiological potential that results from sub-cortical awareness of recognition, and is considered objective evidence that facial recognition can occur at a subconscious level of perception, irrespective of us being aware or not. Patients with the 'Capgras syndrome' can also be considered another group of subjects that provide evidence that facial recognition is a distinct neuropsychological activity. This condition which can result either form brain disease or psychiatric disorder can lead patients to believe that friends or relatives have been replaced by impostors, who have similar faces but different identities. In this respect, developmental evidence from newborns is also important to consider when it comes to assessing neuropsychological evidence. From their birth infants prefer to look at faces; as several face/non-face discrimination experiments show that newborns preferentially track faces in their immature visual fields than non-face objects. (Johnson and Morton, 1991). They suggested that a primary sub cortical mechanism mediated by the superior colliculus in the brain mediates this tracking of moving face-like stimuli till one month of age, and they named it CONSPEC. This is soon replaced by a second mechanism called CONLEARN which takes effect from 6-8 weeks onwards which is associated with identification and recognition of faces definitively, as the cortical pathways mature and take over. This is another important phenomenon in support of the view that facial recognition has a distinct neurological basis. 4 The Evidence for a Framework of Dual Processing Pathways in the Visual System sub serving facial recognition Based on the above evidence Bauer (1984) hypothesized there are two distinct pathways when it comes to facial recognition : (1) An 'overt' ventral-visual limbic system which does not consciously detect faces, but lead to an 'emotional' recognition through the mediation of the limbic system. This has been verified by the event-related potentials (ERPs) from the skin as mentioned earlier, and is thought to be the primary mechanism which is affected in cases of prosopagnosia. (2) A 'covert' dorsal visual - limbic system which leads to an awareness of recognition of faces consciously, but does not lead to emptional affective responses. Patients with the Capgras syndrome are typically seen if this pathway is disordered. Further studies on the subject of covert and overt facial recognition were carried out by Renault (1989) who found shorter latency responses on brain signals of prosopagnostic patients who were presented with familiar faces compared to longer responses seen in unfamiliar ones, although they were totally unaware of any recognition at all. This provides powerful support to the concept of the dual processing pathways, operating through conscious and unconscious mechanisms. However in recent years, as data from other sources has emerged, it has become clearer that covert and overt systems of facial recognition as defined by earlier skin electrophysiological studies are part of one united facial recognition system that utilizes several pathways. This evidence has mainly emerged from combined radiological studies with the advent of the RRI and newer ways of neural modelling. It is now recognized that the same neural processes can generate more than one type of ERP - in case of facial recognition these have been referred to as N 250 and N400 reflecting the different average latencies in milliseconds and have been associated with the two pathways respectively. (Schweinberger 2003). Recent radiological studies (Schweinberger 2003) have also been helpful in finding that different parts of the brain are linked together in a complex manner. The fusiform gyrus of the occipital visual cortex is primarily concerned with the 'unchangeable' aspects of the face and thus mediates 'identity'. On the other hand, the superior temporal sulcus is thought to mediate the aspects of facial movements, and thus identifies emotions, eye gaze and mouth movements. Both these areas receive their input from the inferior occipital gyrus, and together form the three key areas of the brain mediating facial recognition. Other accessory areas might involve retrieval of a person's name or biographical data from the memory store and yet others his name. In this 'new' integrated view therefore an emotion pathway for recognition is therefore unnecessary. Upon looking at someone's face, several areas of the brain are immediately activated and simultaneously produce multiple responses. Syndromes like Capgras and prosopagnosia are just names given to two of the multiple patterns of deficits in facial recognition as a result of lesions in the pathways. 5 Conclusion Facial recognition has been the subject of a lot of research in recent years, as it is now generally accepted that in humans and other primates facial recognition is a distinct process compared to recognition of non-face objects. Since the eighties, most of the research on the subject focused on finding specific pathways for finding the different elements of recognition. In particular, emotional responses to facial recognition was thought to be a separate pathway that provokes sub-conscious feelings in adults and could be verified by skin responses from patients suffering form prosopagnosia, who could not consciously recognize faces. On the other hand patients with Capgras syndrome were thought to suffer from a deficit in the recognition and naming pathway, who could identify familiar faces but were deluded that they belonged to impostors. As an integrated view is now emerging with the advent of modern neuro-imaging it has become clearer that visual recognition might be one unified complex system involving many areas of the brain and multiple pathways. References Bauer,R. (1984). Automatic recognition of names and faces:A neuropsychological application of the guilty knowledge test. Neuropsychologia, 22, 457-469. Bruce, V., & Young, A. (1986). Understanding face recognition. British Journal of Psychology, 77, 305-327. Burton, A. M., Bruce, V., & Johnston, R. A. (1990). Understanding face recognition with an interactive activation model. British Journal of Psychology, 81, 361-380. Ellis H D. Recognizing faces. Brit. J. Psychol. 66:409-26, 1975. Gilbert, C., & Bakan, P. (1973). Visual asymmetry in perception of faces. Neuropsychologia, 11(3), 355-362. Johnson, M. H., Dziurawiec, S., Ellis, H.,&Morton, J. (1991). Newborns' preferential tracking of face-like stimuli and its subsequent decline. Cognition, 40, 1-19. Pegna, A. J., Khateb, A., Michel, C. M., & Landis, T. (2004). Visual recognition of faces, objects, and words using degraded stimuli: Where and when it occurs. Human Brain Mapping, 22, 300-311 Renault B, Signoret J et al ( 1989) Brain potentials reveal covert facial recognition in prosopagnosia. Neuropsychologia,Volume 27, Issue 7,1989, Pages 905-912 Schweinberger SR, Burton AM (2003) Covert Recognition and the Neural System for Face Processing. Cortex,Volume 39, Issue 1,2003, Pages 9-30 *** Read More