AbstractPigeons reared from 2 pairs of healthy pigeons were fed on diets of either adequate (18%), medium (11%), or low (8%) protein for the first 30 days of life. The subjects were then placed on the 18% diet from 30 days of age until training and testing which was begun at 60 ± 3 days of age. Performance on a MULT FR30 FI60 was evaluated and the differences in the time necessary for the medium and low groups to stabilize were found to be statistically significant. Massed extinction trials to the FI were then begun followed by a schedule of MULT FR EXT. Differences between the adequate and inadequate protein groups were again found in both conditions. Other qualitative differences were found among the goups which suggested an analog of emotional lability and retardation