Diferential appetitive contextual conditioning: Time of exposition to the non-reinforced context and intersession interval

Abstract

Two experiments examined the trial-spacing effects in appetitive contextual conditioning in rats using a discrimination procedure. Exposition time to the appetitive context (5 min) and rein-forcement intervals (10 reinforcers delivered according to a variable time 30-5 schedule) were kept constant. Exposition time to the negative (non reinforced) context was varied between groups: 5 minutes ("massed trials", group 5) versus 15 minutes ("spaced trials", group 15). Subjects received one positive and one negative session per day. When the intersession interval was short (60 s) group 15 showed more anticipatory ambulation in the positive context than group 5 (Experiment 1). With a longer intersession interval (95 min) both groups showed equal anticipatory ambulation in the positive context (Experiment 2). These results are discussed in terms of current models that propose contextual conditioning as the underlying mechanism of trialspacing effects.