Seven experiments are described here, all of which are concerned with attentional responses showing decrease in strength over repeated trials. More specifically, this paper considers the developmental course of habituation to visual inputs in the opening years of life. Experiments I through IV varied both the nature of the visual signal and the number of repeated presentations while Experiment V varied the interatrial interval. The results suggest that, in general, response decrement occurs to a repeated signal. This response decrement follows a lawful developmental pattern within the first three years of life with the youngest infants showing significantly less decrement than older infants, and this response decrement-age relationship follows an almost perfect ordering by age. Finally, within limits, this pattern was not affected by increasing the number of repeated trials or by changing the stimulus characteristics within the class of nonmeaningful, content-lacking stimuli. Response decrement under these conditions was believed to represent a learning phenomenon rather than some fatigue model. Experiments VI and VII were designed to demonstrate that response decrement was predictive of, and correlated to, other learning phenomena. A neuronal model-acquisition learning paradigm suggested by Kokolov (1963) was thought most appropriate in accounting for the results of the present set of experiments. Alternative hypotheses were suggested and discussed. These were shown not to be as consistent with the data or as parsimonious as a model acquisition hypothesis. Finally, data both from two new experiments and from experiments previously reported demonstrated that response decrement is correlated with the predictive of other learning tasks and individual difference variables associated with perceptual-cognitive capacity. Thus, it must be concluded that response decrement to a redundant visual signal is a measure of perceptual-cognitive capacity and follows a developmental pattern suggesting that model acquisition can be used as a measure of developmental organization. (JGL)
