Hadyn D. Ellis

Capgras delusion: a window on face recognition

Capgras delusion is the belief that significant others have been replaced by impostors, robots or aliens. Although it usually occurs within a psychiatric illness, it can also be the result of brain injury or other obviously organic disorder. In contrast to patients with prosopagnosia, who cannot consciously recognize previously familiar faces but display autonomic or covert recognition (measured by skin conductance responses), people with Capgras delusion do not show differential autonomic activity to familiar compared with unknown faces. This challenges traditional models of the way faces are identified and presents some epistemological questions concerning identity. New data also indicate that, contrary to previous evidence, covert recognition can be fractionated into autonomic and behavioural/cognitive types, which is consistent with a recently proposed modification of the modal face recognition model.

Asperger Syndrome: Tests of Right Hemisphere Functioning and Interhemispheric Communication

The primary aim of this investigation was to assess to what extent Rourkes (1989, 1995) nonverbal learning disabilities syndrome (NLD) model resembles the pattern of assets and deficits seen in people with Asperger syndrome (AS). NLD can be characterized by a cluster of deficits primarily affecting nonverbal aspects of functioning, in the presence of proficiency in single word reading and a superior verbal memory. The neurological underpinnings of this syndrome may be dysfunction of white matter affecting right hemisphere functioning and interhemispheric communication. To explore this hypothesis, eight participants with AS (ages 10 to 41 years) were assessed in the following areas: the pragmatics of language and communication, verbal and visual memory, visual-spatial abilities, and bimanual motor skills. Results confirmed the close similarity in the neuropsychologic profiles of NLD and AS.

The Effect of Feature Displacement on the Perception of Well-Known Faces

The effect of feature displacement within two well-known faces (Terry Wogan and Cyril Smith) was examined. Image processing equipment was used to produce stimuli in which the features of an original facial image were displaced to form a number of modified images. This technique was first reported by Haig, in a recognition study in which the effect of feature displacement within unfamiliar faces was investigated. In the present experiment a perceptual judgement task was carried out in which subjects were presented with a number of modified faces and asked to judge how dissimilar these were with respect to an original image. A multidimensional scaling analysis of the comparative judgements of the subjects revealed a two-dimensional solution involving displacement of the eyes and mouth. A clear division between up/down and inward/outward displacement within these features (particularly the eyes) was observed. A similar pattern of results was found for both well-known faces. This result indicates that subjects were responding to changes in the facial configuration produced by the different types of feature displacement (horizontal or vertical), as opposed to movement of the features per se. Finally, the results also indicate that the displacement of inner features (mouth, eyes, nose) was more noticeable than displacement of the outer facial features (eg hairline).

Re-evaluating age-of-acquisition effects: are they simply cumulative-frequency effects?

The time it takes to read or produce a word is influenced by the words age of acquisition (AoA) and its frequency (e.g. Quarterly Journal of Experimental Psychology 12 (1973) 85). Lewis (Cognition 71 (1999) B23) suggested that a parsimonious explanation would be that it is the total number of times a word has been encountered that predicts reaction times. Such a cumulative-frequency hypothesis, however, has always been rejected because the statistical effects of AoA and frequency are additive. Here, it is demonstrated mathematically that the cumulative-frequency hypothesis actually predicts such results when applied to curvilinear learning. Further, the data from four influential studies (two of which claim support for independent effects of AoA and frequency) are re-analyzed to reveal that, in fact, they are consistent with a cumulative-frequency hypothesis. The conclusion drawn is that there is no evidence with which to refute the most parsimonious of explanations, i.e. cumulative frequency can account for both frequency and AoA effects.

Asperger syndrome: a simple matter of white matter?

Asperger syndrome, one of the Pervasive Developmental Disorders, is formally diagnosed on the basis of a cluster of cognitive, social and motor signs. It is also associated with poor visuo-spatial skills, good verbal performance, gauche social behaviour and clumsiness. Many of the difficulties evident in those with Asperger syndrome are closely associated with right-hemisphere dysfunction. In this respect they also resemble signs used to diagnose what has been labelled Nonverbal Learning Disorder. Here, these are treated as being the same or closely-related disorders with a possible common underlying aetiology; that is, a neurodevelopmental abnormality affecting white matter. This review examines the ability of this approach to account for a wide range of characteristics of the Asperger syndrome, and contrasts this with a theory-of-mind approach, which, although able to account for the primary features of Asperger syndrome, is less successful at explaining some of its secondary features.

Automatic without autonomic responses to familiar faces : Differential components of covert face recognition in a case of Capgras delusion

Introduction. This study was designed to elucidate the relationship between different types of covert face recognition. Some patients with prosopagnosia (i.e., the profound inability to recognise previously familiar faces) nonetheless evince autonomic face recognition (elevated skin-conductance levels to familiar faces) or behavioural indices of covert recognition (i.e., priming; interference effects; matching effects; face-name learning). One prosopagnosic patient revealed both autonomic and behavioural covert face recognition-which suggests they may arise from some common basis. Method. To test this claim a patient with the Capgras delusion (i.e., holding the belief that others have been replaced by impostors, etc.) was tested on each type of covert face recognition and her results compared with agematched controls. We know that the Capgras delusion is characterised by good overt or conscious face recognition coupled with the absence of autonomic discrimination between familiar and unfamiliar faces. The question addressed here was whether, compared with age- and gender-matched controls, the patient, B.P., would show neither autonomic nor behavioural covert face recognition. Results. The answer was that, although she showed no autonomic discrimination, her performance on a priming task and a test of face/name interference were normal. The controls, as expected, revealed covert face recognition on both the autonomic and behavioural measures. Conclusions. The results imply in B.P. a clear dissociation between autonomic and behavioural measures of covert face recognition. The theoretical implications of these results are discussed.

Are anomalous perceptual experiences necessary for delusions

Several theories of delusions suggest that anomalous perceptual experience is necessary for delusion formation. This study evaluated levels of anomalous perceptual experience in a large group of nonclinical participants from the general population (N = 337), a group of psychotic inpatients (N = 20), and 2 groups of hallucinating (N = 24) and nonhallucinating (N = 24) deluded patients. The aims of the study were to evaluate the hypothesis that pathological levels of anomalous perceptual experience were necessarily associated with delusions. Using the Cardiff Anomalous Perceptions Scale, the main finding was that as a group, nonhallucinating deluded patients were not significantly different from nonclinical participants on any of the anomalous perceptual experience indices. We conclude that anomalous perceptual experience, as measured by the Cardiff Anomalous Perceptions Scale, is not necessary for the presence of delusions.

‘Internet Delusions’: A Case Series and Theoretical Integration

Background: Delusions involving the internet have been reported as examples of the influence of cultural innovations on delusion formation, although there has been some debate as to whether such innovations simply affect surface content, or whether they have more substantial clinical or psychopathological implications. Sampling and Methods: Four cases of patients with delusions involving the internet were identified following a general request to local consultant psychiatrists for referrals. Results: The internet had a specific effect on aetiology in one case, and knowledge of the internet seemed to constrain the type of delusion formed in two others. The presence of an internet-related delusion in the final case was used to frame a successful clinical intervention based on the ‘collaborative empiricism’ method, using cognitive behavioural therapy and collaborative use of the internet to resolve the delusional belief. Conclusions: Cultural technical innovations may have specific influences on the form, origin and content of delusional beliefs. For some patients the presence of internet-themed delusions may be a good prognostic indicator since, given the rich sources of information available, they may be well suited to treatment with cognitive behavioural therapy.

Satiation in name and face recognition

Massive repetition of a word can lead to a loss of meaning (i.e., semantic satiation). Satiation is a general property of neurons and so it would be expected that semantic satiation would be found for stimuli other than words. Three experiments examined the occurrence of satiation for the repetition of names, the visualization of faces, and the repetition of faces. Reaction times to a decision based on a repeated name or face were longer following 30 repetitions than following 3 repetitions, indicating that satiation had occurred. Mere visualization over the same time interval, however, did not elicit satiation effects.

Exploring a neural-network account of age-of-acquisition effects using repetition priming of faces.

The question of whether age-of-acquisition (AoA), frequency, and repetition priming effects occur at a common stage or at different stages of processing is addressed. Two single-stage accounts (i.e., cumulative frequency and a neural-network simulation) are considered in regard to their predictions concerning the interactions between AoA and frequency with aging and priming effects. A repetition-priming face-classification task was conducted on both older and younger participants to test these predictions. Consistent with the predictions of the neural-network simulation, AoA had an effect on reaction times that could not be explained by cumulative frequency alone. Also, as predicted by the simulation, the size of the priming effect was determined by the cumulative frequency of the item. It is discussed how this evidence is supportive of the notion that AoA, frequency, and priming all have effects at a common and single stage during face processing.