Thermosensitivity and instrumental conditioning in newborn rats

Infant rats (20 minutes to 8 days old) display reliable locomotor responses to some thermal stimuli. They can be trained to escape from a cold (10–13°), surface to a warm (28–30°) one or to a warm (30–35°) air stream. Using this method, we found a significant (p<0.01) decrease in the mean latency of a locomotor escape response during a 10 trial session (intertrial interval=20 sec) in 4-to-8-day old Wistar rats. In the same situation, more than 60% of the rats of this age span reached a criterion of five consecutive correct responses in a spatial discrimination test during a 25 trial session (inter-trial interval=40 sec).