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 respond faster (conserving time). The latter of these predictions was supported by the present experiments with free-feeding rats for which portion size (pellet size or duration of feeder presentation) and portion price within meals were varied. Response rate was a function of the unit price (responses/g) of food: Rats responded faster when portions were smaller or when prices were higher. Meal size and frequency were relatively unaffected by unit price, but were influenced by the price of meal initiation. The results are discussed in relation to the economic differences between traditional operant and free-feeding paradigms and to both traditional and more recent formulations of the law of effect.

Studies in both humans and animals suggest a positive relationship between the intake of ethanol and intake of fat, which may contribute to alcohol abuse. This relationship may be mediated, in part, by hypothalamic orexigenic peptides such as orexin (OX), which stimulate both consumption of ethanol and fat, and circulating triglycerides (TG), which stimulate these peptides and promote consummatory behavior. The present study investigated this vicious cycle between ethanol and fat, to further characterize its relation to TG and to test the effects of lowering TG levels. In Experiment 1, the behavioral relationship between fat intake and ethanol was confirmed. Adult male Sprague-Dawley rats, chronically injected with ethanol (1 g/kg i.p.) and tested in terms of their preference for a high-fat compared to low-fat diet, showed a significant increase in their fat preference, compared to rats injected with saline, in measures of 2 h and 24 h intake. Experiment 2 tested the relationship of circulating TG in this positive association between ethanol and fat, in rats chronically consuming 9% ethanol vs. water and given acute meal tests (25 kcal) of a high-fat vs. low-fat diet. Levels of TG were elevated in response to both chronic drinking of ethanol vs. water and acute eating of a high-fat vs. low-fat meal. Most importantly, ethanol and a high-fat diet showed an interaction effect, whereby their combination produced a considerably larger increase in TG levels (+172%) compared to ethanol with a low-fat diet (+111%). In Experiment 3, a direct manipulation of TG levels was found to affect ethanol intake. After administration of gemfibrozil (50 mg/kg i.g.) compared to vehicle, TG levels were lowered by 37%, and ethanol intake was significantly reduced. In Experiment 4, the TG-lowering drug gemfibrozil also caused a significant reduction in the expression of the orexigenic peptide OX, in the perifornical lateral hypothalamus. These results support the existence of a vicious cycle between ethanol and fat whereby each nutrient stimulates intake of the other. Within this vicious cycle, ethanol and fat act synergistically to increase TG levels, which in turn stimulate peptides that promote further consumption, and these phenomena are reversed by gemfibrozil, which lowers TG levels.

Effects of social stimuli on behavioral and physiological responses were examined in infant rhesus monkeys at 4 and 9 months of age. Infants and mothers were removed from the social group and housed as dyads. Following this period, infants were removed and separated under four counterbalanced conditions: (a) totally isolated--placed in a holding cage for 24 hr; (b) mother present, no contact--housed in a single cage in view of their mother, no contact; (c) mother present, contact--similar to above, with mother in proximity to the infant; and (d) peer present--separated but in proximity to a peer. In the first experiment, the infants rarely vocalized when totally isolated but showed high rates of vocalization in the presence of the mother, both with and without contact. In the mother-present conditions, they failed to show a plasma cortisol response. In contrast, totally isolated infants showed a significant elevation in plasma cortisol. At 9 months of age, these infants were separated for 3 days under two different conditions: mother present and totally isolated. Once again, the infants that were totally isolated showed little vocalization but significant elevations in plasma cortisol. In contrast, infants separated in the presence of their mothers showed high vocalization rates but no cortisol response. The concepts of protest and despair are discussed as they relate to behavioral and physiological differences observed following different separation paradigms.

These data show that galanin injected in the third ventricle increases EtOH consumption and that the effect can occur during both the light and the dark periods of the diurnal cycle in the presence of food and water. This suggests that galanin may play a role in augmenting voluntary alcohol intake and perhaps the development of alcohol dependence.

ABSTRACT. We have documented several sexually dimorphic patterns of behavior that develop during the first year of life in infant Japanese macaques and their mothers. Mothers treated their infants differently by sex--mothers of males broke contact with them and retrieved them more frequently than did mothers of females. And mothers of male infants moved more frequently than did mothers of female infants. Male infants played more, played in larger groups, and mounted more frequently; female infants groomed and spent more time close to other monkeys in larger social groups than did males. Female infants were also punished by other group members more frequently than were male infants. We conclude that male and female Japanese macaque infants receive differential treatment early in life by both their own mothers and other animals, and males and females in turn treat their mothers and other animals differently. There appears to be a reciprocal relationship between the behavior of infants, mothers and other social partners that contributes to the development of sexually dimorphic patterns of behavior.