Abstract: Memory for time by animals appears to undergo a systematic shortening. This so-called choose-short effect can be seen in a conditional temporal discrimination when a delay is inserted between the sample and comparison stimuli. We have proposed that this temporal shortening may result from a procedural artifact in which the delay appears similar to the intertrial interval and thus, produces an inadvertent ambiguity or 'instructional failure'. When this ambiguity is avoided by distinguishing the intertrial interval from the delay, as well as the samples from the delay, the temporal shortening effect and other asymmetries often disappear. By avoiding artifacts that can lead to a misinterpretation of results, we may understand better how animals represent time. An alternative procedure for studying temporal discriminations is with the psychophysical bisection procedure in which following conditional discrimination training, intermediate durations are presented and the point of subjective equality is determined. Research using the bisection procedure has shown that pigeons represent temporal durations not only as their absolute value but also relative to durations from which they must be discriminated. Using this procedure, we have also found that time passes subjectively slower when animals are required to respond to the to-be-timed stimulus.

Abstract: The influence of age, dominance rank, kinship and aggressiveness over affiliative relationships and sexual behaviours were analysed in a herd of Sorraia horses, Equus caballus, kept under extensive management. Subjects were 10 adult mares 5-18 years old that had known each other since birth, and a stallion introduced into the group for breeding for the first time. Kinship coefficient and dominance rank were the most important factors affecting affiliative relationships. Bonds were reciprocal and stronger among mares with higher kinship. Mares spent more time in proximity to close-ranking and lower-ranking females. Mares with stronger affiliative relationships or higher relatedness were not less aggressive towards each other. Affiliative relationships between the stallion and the mares were not reciprocal: lower-ranking mares formed stronger bonds with the stallion but he preferred the less genetically related mares for proximity. However, the stallion was involved in sexual behaviours more frequently with the mares that were more genetically related to him. These results suggest that kinship beyond close relatives may affect affiliative relationships both among familiar and among unfamiliar horses. However, the influence of kinship does not imply that horses possess a kin recognition system and alternative explanations are discussed.

Abstract: Measurement of social status is an important component of many behavioural studies. A variety of techniques have been developed and adopted, but while there have been some analyses of index properties using simulated data, the rationale for selecting a method remains poorly documented. As a first step in exploring the implications of index choice, we compared the characteristics of eight popular indices by applying each to the same data set from interactions between male fowl Gallus gallus, the system in which social hierarchies were first described. Data from eight social groups, observed over four successive breeding seasons, were analysed to determine whether different indices produced consistent dominance scores. These scores were then used in tests of the relation between social status and crowing to explore whether index choice affected the results obtained. We also examined the pattern of dominance index use over the last decade to infer whether this has likely been influenced by tradition, or by taxa of study animal. Overall agreement among methods was good when groups of birds had perfectly linear hierarchies, but results diverged when social structure was more complex, with either intransitive triads or reversals. While all regression analyses revealed a positive relationship between dominance and vocal behaviour, there were substantial differences in the amount of variance accounted for, even though the original data were identical in every case. Index selection can hence perturb estimates of the importance of dominance, relative to other factors. We also found that several methods have been adopted only by particular research teams, while the use of others has been taxonomically constrained, patterns implying that indices have not always been chosen solely upon their merits. Taken together, our results read as a cautionary tale. We suggest that selection of a dominance index requires careful consideration both of algorithm properties and of the factors affecting social status in the system of interest.

Abstract: Nonreinforced preexposure to a conditioned stimulus impairs subsequent conditioning with that stimulus. The goal of these studies was to assess the extent to which acquisition performance could be predicted from preexposure performance using a correlational approach. For both preexposure and autoshaping, four measures of performance were computed, including overall average lever pressing, lever pressing in the initial session, percentage change in lever pressing, and slopes. These measures were correlated in a large sample of rats trained in an autoshaping situation. None of the three measures of autoshaping performance was consistently predicted by any of the three measures of preexposure performance. These results are consistent with the view that latent inhibition is not reducible to long-term habituation.