Non-genetic transmission of information: Candidate cognitive processes and the evolution of culture.

The evolution of dual-inheritance systems, specifically the evolution of human culture, are considered as evolutionary events of profound significance. In this paper I adopt the view commonly held amongst biologists in recent years that human cultural change can be fruitfully understood as cultural evolution. Such an approach does not deny the possibility of understanding cultural change from other viewpoints. It does, however, have the advantage of having to be couched in explicitly psychological terms. Using the replicator-interactor theory of Dawkins and Hull I explore what cognitive mechanisms might be identified as having the properties of a replicator, and how reconstructions of human evolution may help in identifying such mechanisms.

Further experimental analysis of the social learning and transmission of foraging information amongst Norway rats.

Adult male Norway rats were tested to see if their foraging efficiency could be improved by social learning and to investigate whether foraging information could be socially transmitted along a chain of animals. In Experiment 1, 'observers' were placed in one of four conditions, distinguished by the nature of their experience during an observation phase, in which they either observed: (1) a trained conspecific unearthing buried carrot; (2) a trained conspecific digging; (3) carrot pieces only; or (4) an empty enclosure (the control group). When tested 24 h later it was found that subjects in group 1 alone exhibited a significantly elevated foraging ability relative to the control group, being more active, and unearthing more carrot pieces in total. The results show that perception of a trained demonstrator conspecific successfully foraging for food is necessary for social learning of foraging information to occur, probably by a local enhancement mechanism. In Experiment 2, chains of transmission were established by allowing each observer to act 24 h later as the demonstrator for the next observer. In one of two transmission groups subjects were given an extra period of individual foraging experience in the test enclosure, with no demonstrator present. Enhanced levels of foraging efficiency were maintained across eight transmission episodes for both transmission groups relative to a no-transmission control. Subjects in the group with the additional experience unearthed significantly more buried food than subjects in the other transmission group. The experiments extend our standard transmission group was upheld. The superior performance of demonstrators in this group, as reflected in their higher level of carrot digging, suggests that the extra period of experience did indeed enhance their ability to act as effective demonstrators. The elevated performance of subjects in this group is attributed to a combination of social and individual learning. This finding suggests that the stability of social transmission may, under some circumstances, be bolstered by individual reinforcement of socially learned and enhanced patterns of behaviour. It also lends support to the hypothesis, proposed to account for the findings of our earlier study, that motivational factors such as fatigue, may detract from subjects' performance as demonstrators when this demonstration follows closely after the additional period of individual experience, but that a 24 h period is sufficient to allow such motivational factors to decay. If individual experience can buttress socially learned traits then this interaction may act so as to prolong the period of time that a socially transmitted trait remains in a population. It is conceivable that an additional period of foraging longer than 10 min may further enhance subjects' subsequent performance as demonstrators. The complex relationship between individual and social learning has received little attention. It is not clear how, if at all, social learning is different from other forms of learning (Plotkin, 1988), apart from the obvious requirement that another animal somehow be involved in the social learning process. Boyd and Richerson (1985) argue that social and individual learning are, at least in humans, alternative ways of acquiring a particular behavioural variant. Most recent studies of animal social learning, on the other hand, tend to emphasize the stimulus enhancing role of the demonstrator animal (Galef, 1988a), thereby suggesting that social learning is a sub-category of individual learning. This study shows that individual learning can reinforce the acquisition and expression of socially acquired behavioural variants.

The role of social experience in the development of sexual competence in Rattus norvegicus.

To clarify the hitherto ambiguous role of pubertal social experience in determining adult sexual competence in male Rattus norvegicus , the quality of the subjects' social interactions was manipulated. In Experiment 1, subjects were raised from weaning onwards in male-only groups, in groups with limited periods of social deprivation at various ages, or in total isolation. Only the latter showed a significant degree of sexual impairment. In Experiment 2, subjects were raised in mixed-sex groups, in total physical (but not visual or olfactory) isolation from a surrounding mixed-sex group, or in physical isolation except for one hour's social contact per day with a peer. All of these subjects were sexually competent as adults. It thus appears that, in the laboratory rat, social deprivation must consist of total physical and visual and/or olfactory isolation in order to produce a significant degree of sexual impairment.

Learning in surgical and functional hemidecorticate rats: a preliminary study of compensation.

A case is made for the conjoint use of surgical and functional hemidecorticate preparations in the investigation of compensation. Direct comparison of the effects of surgical and functional hemidecortication in rats in an active runway avoidance learning situation is reported. Trials to successively higher avoidance criteria, total avoidance responses, longest runs of consecutive avoidance responses, response latencies and running times are compared. None of these measures reveal differences between the two types of hemidecorticate preparation, although compared with a normal group both hemidecorticate groups show a deficit. The implications of this finding in terms of the compensation issue are discussed.

Ontogeny of spontaneous locomotor activity in rabbit, rat, and guinea pig.

Postnatal locomotor activity was investigated in rabbit, rat, and guinea pig. A peak was found in this behavior at 5 days of age in the rabbit and, in confirmation of earlier studies, at 15-20 days in the rat. Neonatal guinea pigs showed no variation in activity levels due to age. The guinea pig is born at an advanced stage of neural maturation in comparison with the rat, and the rabbit is born at an intermediate stage. This difference accounts for the observed variations in postnatal activity profiles if it is assumed that the behavioral peak coincides with the transition from a stage of primarily mesencephalic arousal system maturation to a stage of primarily diencephalic and telencephalic inhibitory system maturation.

Backward conditioning in the rabbit (Oryctolagus cuniculus).

Backward conditioning of the nictitating membrane response of rabbits was studied. The prior exposure to unconditional stimulus-conditional stimulus (US-CS) pairings retarded subsequent forward conditioning. Control procedures eliminated latent inhibition and forward safety-signal effects as accounting for the data. The relevance of this report to other recent studies of backward conditioning is discussed.