Healthy, highly-schizotypal individuals can tickle themselves – evidence for a continuum of psychosis.
There is growing evidence that schizophrenia patients fail to suppress sensations resulting from their own actions, and that this underlies their characteristic tendency to misattribute self-generated actions to external sources (e.g., passivity experiences). Evidence is provided by the classic study of Blakemore and colleagues (2000) who found that, in contrast to control participants, patients with schizophrenia rated self-generated tactile stimulation as being equally ticklish to experimenter-generated stimulation; i.e., schizophrenia patients could tickle themselves.
Schizotypy is a psychological construct that relates to the presence of psychotic-like experiences in the general population. This study aimed to investigate whether Blakemore’s (2000) finding that schizophrenia patients are able to tickle themselves was also apparent in non-clinical, highly schizotypal individuals. 83 first-year psychology students from UNSW participated in the study. Participants were classified as ‘High Schizotypy’ (n=42) or ‘Low Schizotypy’ (n=41) groups, based on their score on the Schizotypal Personality Questionnaire.
The experimental methods were identical to Blakemore et al., (2000). A simple mechanical device was used to deliver tactile stimulation to the palm of the hand. The device was operated either by the experimenter (externally-generated), or the participant themselves (self-generated). Participants were asked to rate the ticklishness of this tactile stimulation on a 10-point Likert scale.
The Group (High vs. Low Schizotypy) x Agency (Self vs. External) interaction was highly significant. Post-hoc analyses revealed that while the Low-Schizotypy group rated self-generated tactile stimulation as less ticklish than externally-generated stimulation, the High-Schizotypy group rated Self and External stimulation as equally ticklish. Conclusions: The results of this study suggest that non-clinical, highly-schizotypal individuals fail to suppress the sensory consequences of their own actions. These results replicate the findings of Blakemore et al., (2000) in patients with schizophrenia, and provide support for the notion of a continuum of psychosis.
