Examination of the role of movement in brain-injured patients' processing of facial information
Bruce and Young's (1986) claims for the distinct processing routes involved in facial expression recognition, familiar face identity and unfamiliar face matching were examined in a group of brain-injured patients, using a common forced-choice procedure. Four patients were observed who showed specific dissociable impairments on one of the face processing tasks, whilst maintaining intact performance on the other two tasks. However, similar differences were observed in the performance of a group of normal subjects. Therefore, it was argued that if specific dissociable impairments are to provide support for the independence of each processing route, much larger unpairments are needed in the patient group. During our perception of facial information under everyday circumstances, we generally perceive dynamic faces. However, it was noted that the majority of face processing tasks, consisted of static stimuli (commonly photographs), making their task demands somewhat unnatural. It was considered important to examine the role of movement in the processing of facial information. Three agnosic patients' ability to process movement and facial expressions was assessed. One agnosic patient was able to successfully process movement and more importantly movement facilitated his impaired processing of static facial expressions. An extensive examination of this patient revealed that, dynamic information did not facilitate his processing of identity, for which he was severely impaired, but he was able to use movement in his processing of lip-read speech, as well as facial expressions. It was shown that movement is able to selectively feed into various face processing channels, with facilitative consequences upon recognition. Movement can provide both a supplementary source of information to static form and a pure movement pattern from which recognition can occur, in the absence of the underlying structural/configural information. There are several implications of these findings; firstly, greater emphasis needs to be placed upon the designs of future face processing tasks, specifically questioning the role of movement in the processing of facial information and secondly, this facilitative role of movement observed in this agnosic patient's processing of facial information, has important applications for the remediation of face processing deficits.