Ingestive responses of human newborns to salty, sour, and bitter stimuli.

Human newborns (1-4 days old) were offered two fluids differing in taste for 3 min each. The volumes ingested were measured. Infants offered water and bitter or sour solutions did not ingest them differentially, which corroborated earlier observations with weaker solutions. A sucrose solution was used to raise baseline ingestion above that of water. Infants offered the sucrose solution with and without urea, citric acid, or sodium chloride consumed less of it when citric acid was added. They were indiffferent to the addition of urea or sodium chloride. The failure to observe intakes lower than that of water suggests that newborns maximally inhibit their ingestion of water. The effects of sex, age, birth weight, and individual consistency on intake were assessed.