Coordinated and individual responding in pairs of rats under variable interval schedules

The coordination of responses in pairs of rats was investigated by parametrically manipulating the duration of variable-interval (VI) schedule mean inter-reinforcer intervals (IRIs). Two conditions required coordination for a group of three pairs of rats (VI 5 s, 10 s, 20 s, 40 s, 80 s, 120 s, 160 s, 60 s, and 243 s) and individual responding for another group of three pairs of rats (VI 5, 10 s, 20 s, 40 s and 80 s). An inverted U-shaped function related responding measures and reinforcement rates: Overall response rates, coordinated episode rates and percentage of coordination increased with increasing reinforcement rates, and decreased at the highest rates of reinforcement in both groups. Rats exposed to VI schedules that required coordination generally showed higher rates and higher percentages of coordinated responses when compared to rats that responded under the individual schedules. Local rates of coordinated episodes showed that coordination occurred at a steady rate across the VI IRIs for the Coordination Group. The results extend previous research on the patterns of coordinated responses maintained by intermittent schedules of reinforcement.