Previous studies show that the pecking rate of naive 3-day-old chicks increases after ingestion of food and decreases after ingestion of sand, but these changes have not been specific to the stimulus that was ingested. In the present experiments with a total of 450 Burmese Red Junglefowl chicks, Exps I and II showed that neither 1 nor 4 10-min simultaneous-choice tests were sufficient for discrimination to be shown between food and sand. Exp III showed that many hours of experience with food or sand were sufficient for discrimination if Ss were tested for 10 min with only 1 stimulus at a time. Similar results were found in Exp IV in which Ss had only 10 min of experience with food or sand. Pecking rates to food and sand were the same during the 1st 2 min of the test and only later diverged. These results imply that the discrimination is based on feedback that develops 2-3 min after ingestion but develops only if chicks have had previous experience with food or sand. (15 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)