Two experiments examined adult age differences in the effects of perceptual grouping on attentional performance. In a search task, 48 young, middle-aged, and elderly subjects sorted cards based on the orientation of a target figure. The interfering effects of irrelevant information which did or did not contrast with the target in orientation were examined. The position of targets varied from one card to the next. Elderly, but not young or middle-aged subjects were slowed by the presence of contrasting irrelevant information. All three age groups were slowed by the presence of similar irrelevant information, but the elderly were slowed more than the young adults. A similar procedure was used in a second experiment, but the position of targets within each deck did not vary from one card to the next. No age group was slowed by the presence of contrasting irrelevant information, and only the elderly were slowed by the presence of similar irrelevant information. The importance of perceptual grouping in accounting for adult age-differences in attentional processes was discussed.

Mere observation of 30 presentations of a colored form results in slower reaction time responses to the familiarized stimulus than to a comparable novel stimulus. Prior research suggest that this result is due to two subsidiary effects of repetition: alertness decrement and encoding facilitation. Four experiments were conducted to compare the effects of stimulus repetition on colors and words. The two-factor theory of repetition was found to hold for words as well as for colors; for words, in contrast to colors, encoding facilitation was found to be stronger than alertness decrement.

2 experiments were carried out to clarify the process by which children encode briefly presented spatial positions. The task in both experiments was judging whether a test dot occupied the same position on a card as any 1 of a number of dots which had been presented tachistoscopically. Subjects were first, third, and fifth graders. In the first experiment, performance improved with grade level for stimulus arrays composed of more than 1 dot. The finding contrasts with an earlier report of only minimal developmental change in position encoding, but the procedures of the earlier study appear to have permitted a confounding of position and configural encoding. In the second experiment, position encoding was found to improve with increasing pattern goodness at all age levels. The finding attests to a powerful influence of pattern information on the perceptual system and further suggests that position information is encoded within configural information.

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First and fifth graders sorted cards into 2 piles based on the orientation of a T figure. Cards did or did not contain irrelevant information: irrelevant information did or did not contrast in line slope with the target. The position of targets varied within arrays from 1 card to the next. Children at both grade levels sorted more slowly in the presence of contrasting irrelevant information relative to no irrelevant information, but younger children were slowed more that older ones when sorting in the presence of similar irrelevant information relative to contrasting irrelevant information. A second card-sorting experiment examined similar effects in a filtering task in which target position was constant from card to card. Effects were minimal for fifth graders, wheras first graders were slower in the presence of contrasting irrelevant information relative to no irrelevant information, and slower in the presence of similar as compared with contrasting irrelevant information. Processing differences underlying these results are discussed.

First and fifth graders sorted cards into 2 piles based on the orientation of a T figure. Cards did or did not contain irrelevant information: irrelevant information did or did not contrast in line slope with the target. The position of targets varied within arrays from 1 card to the next. Children at both grade levels sorted more slowly in the presence of contrasting irrelevant information relative to no irrelevant information, but younger children were slowed more that older ones when sorting in the presence of similar irrelevant information relative to contrasting irrelevant information. A second card-sorting experiment examined similar effects in a filtering task in which target position was constant from card to card. Effects were minimal for fifth graders, wheras first graders were slower in the presence of contrasting irrelevant information relative to no irrelevant information, and slower in the presence of similar as compared with contrasting irrelevant information. Processing differences underlying these results are discussed.

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