1. Rats were undernourished in early life by feeding their mothers a restricted quantity of a good-quality diet during pregnancy and lactation. All offspring were fed ad lib. from weaning. Behavioural tests were done using adult males.
2. Thresholds of aversion to electric shock were determined in a rectangular box, one side of which was designated ‘live’ and the other ‘safe’ (o V side) for any particular shock level. Three 15 min sessions were given at each of five shock levels. Previously undernourished rats had a lower aversion threshold than controls. They spent more time than controls on the o V side at two intermediate levels of shock.
3. Other male rats were subjected to six graded series of brief, unavoidable shocks. Previously undernourished rats responded to a greater total number of shocks than controls.
4. These results support the hypothesis that previously undernourished rats have a lowered threshold of arousal.