Stimulus dimensions or stimulus aspects

Summary The questionableness of geometric models of stimulus similarity has led to the development of an alternative approach by Tversky which makes no dimensional or metric assumptions. Rather, stimuli are described as sets of qualitative stimulus aspects and stimulus similarity as a function of common and non-common aspects. According to Restle's model of stimulus similarity, however, the perception of stimuli of a categorial nature can be organized along dimensions because stimulus aspects form dimensions under certain conditions. The present study supports the empirical validity of this assumption. Further it is suggested that contrary to the present opinion quantitative stimulus characteristics are probably not perceived as dimensions in the sense of the geometric models but only dimensions as described in the Restle model.     

Interaction of genetics and separation in canine hyperkinesis and in differential responses to amphetamine

A model of childhood hyperkinesis, using the Telomian-beagle hybrid dog, is described, demonstrating the interactions of genetics and separation in the development of this syndrome and in the favorable responses of some of these dogs to amphetamine. This work represents the collaboration of three laboratories, utilizing chiefly methods of inhibitory training. Inducing separation distress enhanced the resistance to inhibitory training and the favorable responses to amphetamine.     

Discriminative infant smiling to orientations of talking faces of mother and stranger.

Thirty-two infants aged 14 and 20 weeks were presented with a live face in each of eight conditions, which consisted of all combinations of (a) a 0° or 90° orientation; (b) familiar face (the infant's mother) or distinctively unfamiliar face; and (c) talking or silent context. The previous findings that younger infants smile longer at 0° than at 90° faces and that this differential responsiveness to orientation wanes with increasing age were replicated; the hypothesis that older infants would smile longest at their mothers' talking faces in the 0° orientation was confirmed. In addition, infants of both ages smiled more at their mothers than at the stranger, although this effect interacted with orientation and sex of the infant.     

Crucial role of the postnatal maternal environment in the expression of prenatal stress effects in the male rats

Methodological and conceptual problems common in prenatal stress experiments were analyzed, and an experiment incorporating solutions to those problems were designed and executed. Rats were prenatally stressed or served as controls and then were cross-fostered within or between treatment groups. In adulthood, one male from each litter was tested over 20 trials in an open-field box and then tested over 20 successive discrimination reversals in a T-maze. A T-factor analysis was performed on each of the two sets of observations, and factors scores were subjected to elevational analyses. Major hypotheses generated from the results are the following: (a) Male rats subjected to prenatal stress acquire emotional reactivity levels in adulthood that are either elevated or reduced depending on the postnatal maternal environment. (b) Male rats subjected to prenatal stress acquire reversal learning sets in adulthood with a rapidity that parallels and indeed is produced by the pattern of emotional reactivity reflected in the above a and as mediated by cognitive processes. (c) T-factor analysis of trials is required in order to avoid construct validity problems as well as internal validity problems, both brought about by the confounding of trial variables, and in addition, it may generate valuable hypotheses giving further meaning to the dependent variables under observation.