Twenty-two long-stay severely ill male schizophrenic patients were employed in a hospital workshop for 16 weeks. They all lived in one villa where the standard of social treatment was high. The two workshop supervisors were a male and a female staff nurse. The sex of the supervisor did not influence the results. The conditions of supervision were varied experimentally. There was a sharp increase in output (on a simple sleeve folding task) whenever social incentives were introduced, and a sharp fall whenever passive conditions of supervision were resumed. The 10 patients with the highest initial output, together with 1 other (ranked 13 on initial output), accounted for over 90% of the output under passive conditions, and for all the improvement due to practice. However, they contributed only 40% of the improvement due to additional social incentives. The remaining patients, therefore, functioned at a very low level relative to the initially high scorers and showed no practice effect, but 7 of them responded very markedly to encouragement. Time-sampling of workshop behaviour showed that the increase in working activity, under active conditions of supervision, was accompanied by a significant decrease in various abnormalities of behaviour (immobility, mannerisms and restlessness). Ward behaviour was unaffected.Abstract Teaser