PERCEPTUAL GROUPING DUE TO PITCH AND AMPLITUDE IN HALLUCINATING SCHIZOPHRENICS

17 subjects with a diagnosis of schizophrenia and hallucinations in th eir case history were compared with 16 subjects of a reference group r egarding the appearance of a perception of streaming in a presentation of pitch alternating tones. One scale going up and down was used as p art of a stimulus and the same scale going down and up as the other pa rt (as distracter). The amplitude of the distracter was varied in orde r to make the perceptual regrouping (streaming) evident, which normall y occurs when the amplitude approaches the same level in the two stimu li. Sixteen presentations were made. The subjects of the reference gro up began to hear the streaming after the sixth presentation and all of them heard it at the eighth. At the eleventh presentation some ceased to perceive any streaming and none heard it after the fourteenth pres entation. In the schizophrenic group none showed a normal pattern. Ove rall, less than half of the schizophrenic probands heard a streaming w hen subjects in the reference group did. Amongst those who did, a few heard it early and kept hearing it to the end. Others started to hear it late and kept hearing it to the end, while a few heard it on and of f. The remarkable aberrant grouping strategies among the schizophrenic s are discussed in relation to current ideas on perceptual disturbance s of the illness.