Visual discrimination of male and female faces by infant rhesus macaques.

Recent studies have revealed that human infants process female faces differently from male faces. To test whether a similar preference for female faces exists in other primates, we presented nursery-reared infant rhesus macaques with photographs of macaque faces and human faces. At <1 month old, infant macaques preferentially oriented towards female macaque faces when faces were presented upright.

Tufted capuchin monkeys (Cebus apella) spontaneously use visual but not acoustic information to find hidden food items.

Foraging choices in tufted capuchins monkeys are guided by perceptual, cognitive, and motivational factors, but little is known about how these factors might interact. The present study investigates how different types of sensory information affect capuchins' ability to locate hidden food. In two experiments, capuchins were presented with two cups, one baited and one empty.

The foraging ball as a quick and easy enrichment device for pigs (Sus scrofa).

Providing research pigs with enrichment objects can encourage species-typical behavior such as rooting and foraging. The authors gave pigs hard plastic 'foraging balls' that resembled enrichment devices commonly used for nonhuman primates. Holes were custom-drilled into the balls, and animal caretakers filled them with palatable food items such as jellybeans, unsalted peanuts, cereal, Beggin' Strips, primate biscuits and dog biscuits.

On loss aversion in capuchin monkeys.

Chen, Lakshminarayanan, and Santos (2006) claim to show in three choice experiments that monkeys react rationally to price and wealth shocks, but, when faced with gambles, display hallmark, human-like biases that include loss aversion. We present three experiments with monkeys and humans consistent with a reinterpretation of their data that attributes their results not to loss aversion, but to differences between choice alternatives in delay of reinforcement.

Essential value of cocaine and food in rats: tests of the exponential model of demand.

Rationale: To provide a prospective test of the predictive adequacy of the exponential model of demand (Hursh and Silberberg, Psych Rev 115(1):186-198, 2008).

Objectives: In Experiment 1, to measure the 'essential value' (the propensity to defend consumption with changes in price) of cocaine and food in a demand analysis (functional relation between price and consumption) by means of the exponential model; in Experiment 2, to test whether the model's systematic underestimation of cocaine consumption in Experiment 1 was due to weight loss; and in Experiment 3, to evaluate the effects of cocaine on the essential value of food.

Materials And Methods: In Experiment 1, demand curves for food and cocaine were determined by measuring consumption of these goods in a multiple schedule over a range of fixed ratios; in Experiment 2, a demand curve for only cocaine was determined; and in Experiment 3, demand for food was determined in the absence of cocaine.

Early maternal separation and sex differences in the aversive effects of amphetamine in adult rats.

Early life stress increases vulnerability to psychostimulant abuse, sometimes in a sex-dependent manner. These effects are presumably produced by modulation of neurobiological reward mechanisms; however, drug intake is also influenced by sensitivity to the drug's aversive properties, and little is known about the effects of early life stress on stimulant aversion. To assess this possibility, Sprague-Dawley rat litters experienced daily separation from the dam for 3 h (MS) or 15 min (H) on post-natal days 2-14; control litters (AFR) experienced twice-weekly routine animal facility care only.

Reduction of cocaine seeking by a food-based inhibitor in rats.

Environmental stimuli can exert a powerful influence over drug seeking and taking. For example, previous experiments found that combining multiple drug-related stimuli tripled drug seeking and doubled drug intake (L. V.

Mark tests for mirror self-recognition in capuchin monkeys (Cebus apella) trained to touch marks.

In Experiment 1, three capuchin monkeys (Cebus apella) were exposed to a mirror in their home cage for 3 days and then given food treats for touching orange marks located on the surface of an experimental chamber. Following training, a mirror was added to the chamber to see if the monkeys would use it to guide non-reinforced contacts with an orange mark on their foreheads that was only visible as a mirror reflection (mark test). Two monkeys touched the head-mark more often with the mirror present than absent, but no mark touches were emitted while looking at the mirror.

Separation stress, litter size, and the rewarding effects of low-dose morphine in the dams of maternally separated rats.

Potential differences in sensitivity to the rewarding effects of morphine as a function of litter separation stress were assessed in post-weaning rat dams. During the first two weeks postnatal, Sprague-Dawley rat litters were subjected to daily 15- or 180-min sessions of dam-pup separation while control litters only experienced twice-weekly animal facility care. One week after weaning, the dams (n=7 per group) underwent a fully unbiased conditioned place preference (CPP) procedure to 1 mg/kg subcutaneous morphine.