Putative behavioral history effects and aggression maintained by escape from therapists

Differentially higher rates of aggression in treatment sessions occurred in the presence of two staff members who had previously worked with the parti cipant at another facility. Adding an edible reinforcer for compliance and the absence of aggression in,sessions conducted by these two staff members decreased aggression to rates similar to those obtained with less familiar therapists. Results suggest that embedding positive reinforcement within a demand context may reduce the aversiveness of therapists correlated with a history of demand situations.