Studies about effects of aging on the estimation of short temporal intervals are not conclusive. The aim of the present research was to evaluate age-related differences in the reproduction of a short interval (10 s) using a computerized method. The sample comprised thirteen young adults (M = 26.15 years) and twelve elderly adults (M= 79.1 years). Three parameters of time estimation were measured: estimated time, absolute error, and standard deviation. Results showed that time estimates performed by elderly participants were shorter than those of younger ones, although there were no significant differences between the two age groups in the percentage of absolute errors or standard deviations. These findings could be explained by changes in the rate of the internal clock or to an interaction between more general changes in cognitive processes.

Individual differences in the behavioral responses to a novel environment have been proposed as a research tool to predict responsiveness to other behavioral tasks, response to certain events and individual vulnerability to nicotine addiction. In rats and mice, novelty seeking (defined as enhanced specific exploration of novel situations) is a complex behavior confirmed by a large body of neurochemical, endocrinological and behavioral data. We review the main standardized procedures employed to measure the novelty seeking trait in rodents and the ontogeny of this behavior throughout the life-span taking into account that novelty seeking can be permanently modified as a consequence of particular early experiences, maternal care, and environmental enrichment. Studies in animal models suggest that individual differences in the sensitivity to nicotine depend on different variables such as basal locomotor activity of the experimental subjects, their response to novel environments (open-field, hole-board) and level of impulsivity. It is concluded that these basic findings contribute to a better understanding of smoking behavior and to the establishment of improved pharmacological treatments if individual differences are borne in mind.

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During agonistic encounters the two sub-groups of mice (SL and LL) may display differential sensitivity in drug-induced changes on aggressiveness, since bupropion increased attack only in mice with "long attack latency" in the pre-screening test. In the plus-maze, this drug does not seem to have specific actions on anxiety and in the hole-board a high dose had similar effects to those induced by anxiogenic drugs.