Schizotypy and pseudoneglect: A critical update on theories of hemispheric asymmetries

Abstract

Introduction. Positive schizotypy has been associated with a leftward spatial bias (pseudoneglect) in different tasks and populations. We tested whether this relationship (1) can be observed for two different hemispatial tasks in the same participants, and (2) is specific to positive schizotypy.

Methods. Forty right-handed men performed a conventional line bisection task and a whole-body movement task. In the latter task, participants were presented with illuminated target locations on the floor, and had to visit the remembered locations (equal number in right and left hemispace) after a short time interval. We assessed side preferences in both tasks. Positive schizotypy, negative schizotypy, and cognitive disorganisation were assessed with a validated self-report questionnaire.

Results. Irrespective of schizotypy, pseudoneglect was observed in both tasks. We found a rightward bisection and walking bias as a function of positive schizotypy, and also as a function of cognitive disorganisation for walking initiation.

Discussion. This unexpected finding resulted in a review of hemispheric asymmetry for function in schizotypy, and in the discussion of potential variables that might account for the present discrepancy. We suggest that different schizotypy questionnaires and their presentation mode might be a potential contributor to the opposite findings in the literature.

Acknowledgements

This research was supported by the British Academy (#SG-39550), the Biotechnology and Biological Sciences Research Council (7/518013), and the Medical Research Council (G0401132). The authors thank Iain Gilchrist and Bruce Hood.

Notes

¹Note that in the subsequent manuscript, SBR is always understood as a positive relationship between hemispatial biases to one side and increasing schizotypy scores.

²In the instruction for the O-LIFE questionnaire (as provided by the authors, but not in the original publications), it is stated that the questionnaire contains items that may relate to one's thoughts, feelings, experiences, and preferences.

³In the instruction for the Chapman questionnaires (as provided by Dr Thomas R. Kwapil (version from 17 May 2002), but not included in the original publications), it is stated “Please answer each item true or false. Please do not skip any items. It is important that you answer every item, even if you are not quite certain which is the best answer. An occasional item may refer to experiences that you have had only when taking drugs. Unless you have had the experience at other times (when not under the influence of drugs), mark it as if you have not had that experience. Some items may sound like others, but all of them are slightly different. Answer each item individually, and don't worry about how you answered a somewhat similar previous item.”