W. Lawrence Hill

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A corollary of the law of effect predicts that the larger the reinforcement, the greater the rate of responding. However, an animal must eat more small portions than large portions to obtain the same daily intake, and one would predict, therefore, that when eating smaller portions an efficient animal would eat less (conserving time and energy) and/or(More)
Male ruffs (Philomachus pugnax), a lekking shorebird, can generally be divided into two morphs according to behavior and plumage coloration. Predominantly dark-colored, “independent” male ruffs defend small territories on a lek, whereas lighter colored “satellite” males are non-territorial and less site-faithful to a particular lek. The traits associated(More)
Fifty-five 6- to 7-month-old human infants were trained in an operant conditioning procedure, adapted from a procedure developed for 3-month-olds, in which kicks were reinforced by conjugate movement of a mobile. Retention was assessed in a simple forgetting paradigm (Expt. 1) or in a reactivation paradigm (Expt. 2) with either the training mobile or a(More)
The inverse relationship between serotonin and aggression was investigated in rats treated with aspartame, a sweetener thought to interfere with the synthesis of this neurotransmitter. Eleven adult, male Long-Evans rats received either aspartame (200-800 mg/kg, IP) or the vehicle prior to testing in a standard resident-intruder paradigm. Contrary to our(More)
The onset of circadian rhythms in many animals occurs during prenatal development. We conducted four experiments, using the domestic chick as a model, to assess when these rhythms can first be entrained and the type of light zeitgeber necessary. In Experiment 1, the presence of circadian rhythms was assessed using tonic immobility, an antipredator behavior,(More)
The manner in which rapidly growing chicks distribute their time among diurnal activities was measured in two studies in which the amount of available light was varied to match seasonal extremes. The effectiveness of the chick's time budgets was assessed in terms of the impact on growth. In Experiment 1, 24-hr patterns of feeding, drinking, nesting, and(More)
It is well known that androgens play a critical role in mediating the reproductive behavior of males. However, many laboratory experiments that examined the effects of testosterone in male songbirds typically limited their investigations to the early phase of breeding. We sought to determine the influence of testosterone on social behavior, pair bonding,(More)
We investigated the effects of para-chlorophenylalanine (PCPA), a serotonin (5-HT) antagonist, on social aggression and brain neurochemistry in young domestic chickens (Gallus domesticus). In Experiment 1, the effects of four different doses of PCPA (0, 100, 200, and 400 mg/kg) were examined for 3 days after injection. Immediately after PCPA injection,(More)
Tonic immobility (TI) and high-intensity vocalizations are two antipredator behaviors employed by domestic chicks (Gallus gallus) which vary in their function and the proximate mechanisms that govern them. In the present study, we sought to determine the influence of age (3 or 10 days old), diet (control or tryptophan-free), and time of testing (A.M. or(More)