Analysis of warm-up effects during avoidance in the Mongolian gerbil

Mongolian gerbils were trained under unsignaled free-operant avoidance until performance stabilized. They showed slight warm-up effects, receiving approximately 40% of the total session shocks in the initial one-third of the session. Leverpressing was then studied during l-h extinction periods as a function of the duration of an avoidance period which immediately preceded it. Responding during extinction showed only a small increase as the duration of the avoidance period increased from I to 60 min. The majority of gerbils showed nonsignificant correlations between the number of extinction responses and avoidance time, avoidance responses, and shocks. The results appear to support an explanation of warm-up which emphasizes differences in activation/arousal between domesticated and nondomesticated animals.