Capgras Delusion Ellis & Lewis 2001 Roy Cox, 0008877 & Erik Withoud, 0008346
What is the Capgras Delusion? • Belief that some people have been replaced by doubles, impostors, aliens etc. • Usually occurs in psychiatric setting, but also occurs after neurological damage. • Can also occur for some familiar objects.
Prosopagnosia vs. Capgras Capgras delusion is opposite of prosopagnosia in some respects: • Prosopagnosics are unable to overtly (consciously) recognize faces, but often show covert (subconscious) responses (e.g. SCR) • Sufferers from Capgras delusion do recognize faces overtly, but show no covert responses.
Prosopagnosia vs. Capgras (2) Capgras delusion mirrors prosopagnosia
Skin conductance response (SCR) The SCR method involves recording the changes in the electrical conductivity of a person’s skin. It is used for identifying autonomic responses to stimuli.
SCR in Capgras delusion • Capgras patients show no differential SCR to familiar faces, although they have normal SCR for repeated tones.
Covert face recognition A Capgras delusion-patient was given both SCR and behavioral/cognitive tests. As expected the patient showed no autonomic covert recognition. The scores for the behavioral/cognitive test, however, were perfectly normal. This indicates a dissociation between these recognition types.
Two types of covert face recognition • Autonomic covert recognition (SCR and event-related potentials) • Behavioral/cognitive types (e.g. face-name priming)
Breen’s model (2) According to Breen et al. face recognition consists of: • core face recognition stage • parallel identification (A) and affective-response stages (B) Model accounts for both prosopagnosia and Capgras delusion.
Possible implications It seems that person recognition is not purely dependent on recognizing features of the face, but it also depends on an affective labeling. This might be extrapolated to other areas than face recognition: everything we have encountered before has an emotional meaning which helps us to recognize it.
Questions? Not too many and/or difficult.