Interpretation of symptoms: Fact or fiction?

Psychotic patients frequently display bizarre behaviour patterns, usually considered to be symptomatic of the psychiatric disturbance. The present study is an illustration of how such symptoms can be measured in terms of frequency of occurrence. A bizarre symptom (compulsive broom-carrying) was developed, and maintained, by making reinforcement contingent on its occurrence. The reinforcement consisted of cigarettes or tokens which could be exchanged for cigarettes. The severity of the symptom, in terms of amount of time during which it was displayed, was shown to be a function of the temporal intervals between rewards. When reinforcement was withdrawn, the bizarre behaviour pattern disappeared.