Babies by bar-press: Maternal behavior in the rat

Pregnant rats were trained to press a bar for food rewards: Postpartum these Ss were tested when each bar-press delivered a rat pup (S’s own or foster) into the food cup. Ss repetitively bar-pressed, snatched up the pup as it tumbled down the chute and retrieved the pup into the adjacent nest box. Ss lived with 6 nursing pups but bar-pressed for hundreds: E removed all but 6 pups from the nest box after S had accumulated about 20. Maximal performance was 684 responses in a 3-h period. This technique is currently being used to study weaning and hormonal factors involved in the rat’s maternal motivation.