The sensory filter in schizophrenia: a study of habituation, arousal, and the dopamine hypothesis.

The possible failure of a notional sensory filter in schizophrenia was studied by means of habituation of the orienting response. Non-paranoid schizophrenics failed to habituate, but paranoids habituated normally. Paranoids, however, showed a different impairment: they responded to a dishabituating tone as if the novel stimulus were somewhat familiar. The failure of habituation in non-paranoids could not be explained in terms of arousal when the index was the rate of skin conductance fluctuation. Neurotic controls showed considerably higher levels than either group of schizophrenics. Non-paranoid schizophrenics had lost the normal inverse relationship between habituation and level of arousal as manifested in the rate of spontaneous skin conductance fluctuation.