[Spatial discrimination with thermal reinforcement in the young rat. (author's transl)]

Infant rats, because of their deficient thermoregulation, are very reactive to thermal stimuli. In our experiences, four to ten day old animals were trained a discriminative locomotor response between two places of a symmetrical device. A correct choice was reinforced by a 30-35 degree air stream during twenty seconds. One hundred and forty Wistar rats (male and female) were submitted to a twenty trial acquisition session (intertrial interval = 20 seconds). Those who reached a 70% correct criterion were trained to reverse their initial discrimination. Spontaneous alternation and "vicarious trial and errors" (VTE) were systematically observed. Percentages of correct responses in the two tests increased with age and reached a maximum in nine and ten day old rats. This increase was mainly due to a decrease of percentages of incorrect responses. Spontaneous alternation rate also progressed with age but did not reach adult level. VTE appeared in nine day old rats and were highly positively correlated with correct responses.