“…Previous research by Gallup et al (1977) had used much longer periods of exposure, for example, nearly 2 weeks, before TI testing. However, accompanying this extended period were profound growth deficiencies and, insofar as deprivation attenuates TI (Kaufman & Rovee-Collier, 1978, but see , interpretations of their results are equivocal (Magladery, Rovee-Collier, & Collier, 1979). Given that 5-HT synthesis is acutely sensitive to alterations in precursor supply (Fernstrom, 1986), we hoped to preferentially affect 5-HT levels while minimizing effects on growth by giving chicks only a brief exposure to the tryptophan-deficient diet.…”