Marco Poli

Social status in mice: behavioral, endocrine and immune changes are context dependent.

The aim of the present study was to investigate the effect of social status on the endocrine, immune and behavior response of male mice. We found that in mice reared in a group of siblings since weaning, no difference exists between dominants and subordinates in basal corticosterone level, in behavior in the open-field test (OFT) and in a series of immune parameters. These results suggest that living with siblings is not a stressful condition for either dominant or subordinate mice. Therefore, group-housed siblings can be regarded as a valid control group in social stress studies. When mice were subjected to chronic psychosocial stress for 21 days, four types of social outcome occurred: residents becoming dominants, intruders becoming subordinates, residents becoming subordinates and intruders becoming dominants. Interestingly, the behavioral profile in the OFT revealed a status-dependent effect, with resident dominants (RD) and intruder dominants (InD) showing the highest locomotor and exploratory activity, whereas the corticosterone level was higher than control for all four categories. In addition, a context-dependent effect emerged at the immune level: resident subordinates (RS) had a reduced splenocyte proliferation and IL-4 and IL-10 production. Mice in all the other three social ranks showed no immune alterations. Therefore, the loss of an individuals social rank position seems a promising field of study to investigate the psychological impact of stressful events.

Early mother-infant interaction during breast- and bottle-feeding.

Abstract Thirty-two primiparous mothers with their neonates, 20 breast-fed and 12 bottle-fed, were videotaped during feeding longitudinally (at 3, 10 days, 1 and 3 months) in order to investigate whether patterns of mother-infant interaction observed during breast- and bottle-feeding differ also for behavior not directly related to sucking. Infant state, sucking behavior, mother behavior and mother-infant interaction were analyzed by both sequential and non sequential analysis. Results suggest that the method of feedings affects mother-infant interaction observed during and just after feeding also for some behavior not directly related to sucking. The percentage of mutual touch, tactile stimulation and mothers gaze to infant was significantly more elevated during breast-feeding. Independently of the feeding mode, significant sequential dependencies between infant state of alertness and auditory stimulation, and auditory stimulation and mutual gaze were found.

Methodology of motor skill and laterality: new test of hand preference in Macaca nemestrina.

Ten female pig-tailed macaques (Macaca nemestrina) were tested for hand preference and hand skill (i.e., speed of performance and error rate). The experimental task was naturalistic, calling for adaptive manual skills and fine manipulation: the monkeys had to remove small food rewards embedded in a vertical array, and precision opposition of thumb and forefinger was needed to extract each pellet. Each monkey was tested 10 times on 10 different days. The results indicated individual hand preference rather than population-level handedness; however, a tendency toward right predominance was found. The results on hand skill showed a relation between error rate and hand preference, as the preferred hand made fewer errors. A different and unexpected finding was obtained when skill was evaluated in terms of speed of performance: in adult subjects the left hand was quicker than the right. Therefore, different kinds of skill showed different patterns in relation to hand preference.

Social learning in the golden hamster (Mesocricetus auratus).

This study investigates whether golden hamster (Mesocricetus auratus) pups can acquire a new behavior by interacting with an experienced adult conspecific. The behavior consisted of using teeth and forepaws to retrieve a piece of food dangling from a small chain. Instrumental learning techniques were used to train the demonstrators. Four groups of pups were exposed to different kinds of social experience. In the first group, the pups interacted with their skilled mother; in the second group, they did the same with their inexperienced mother; in the third group, they interacted with inexperienced littermates; and in the fourth group, the pups were tested individually. At the end of an acquisition period, the pups were tested individually to assess their performance. The results demonstrate that interacting with a skilled mother has a remarkable effect on the acquisition of a new feeding behavior by hamster pups.

Species-Specific Differences in Learning

From the beginnings of his written history, man has shown a deep interest in understanding “animal intelligence” and in trying to make sense of the many instances of apparently “intelligent” behaviors exhibited by many animals; quite obviously the species he was more interested in were usually either the domestic ones or those, such as the apes and the monkeys, appallingly similar to himself. Although formal philosophical theories on this topic can be dated back at least to Aristotle, the most influential developments of ideas on the subject are much more recent.