On the bimodality of the distribution of electrodermal orienting responses in schizophrenic patients.

Data are presented from four of the author's studies on the electrodermal orienting responss which fail to confirm the findings of Gruzelier and Venables of a markedly bimodal distribution of ORs in schizophrenic populations. A review of the findings of other earlier studies, none of which confirm the bimodal hypothesis although some used patients taking phenothiazines, shows that differential effects of drugs, although probably an important factor, by itself cannot account entirely for the discrepancies in results. It is hypothesized that due to changes in hospital discharge policies, the groups of patients tested by Gruzelier and Venables, compared to those tested in earlier studies, were more heavily weighted with patients whose symptoms were resistant to phenothiazines. These patients may either have come from the extremes of the responsivity distribution or have atypical reactions to neuroleptic drugs.