Twenty-four young (M = 28 years) and 24 old (M = 70 years) adults completed a lexical decision task in which they saw two strings of letters on each trial and were asked to respond "yes" only if both strings were words. For both ages, decisions were faster when the words were associated than when they were not. This pattern emerged for both ages, regardless of whether the associated pairs were category-member or descriptive-property associates. The same participants were also presented with a list of words to free recall. There was a decline with age both in the number of words recalled and in the degree of categorical clustering, particularly of low frequency category exemplars. Viewed from the perspective of two-process semantic activation models, these results place constraints on processing-deficit theories, and are consistent with the hypothesis that effortful processes change with aging, whereas automatic processes do not.

We investigated visual texture segregation, using a task for which reaction time to locate a discrepant quadrant in an array of 36 elements was the dependent measure. Two dimensions of segregation were used: line orientation (horizontal vs. vertical, horizontal vs. left diagonal, and left vs. right diagonal) and hue (9 vs. 7 Munsell color steps). Levels on these two dimensions were varied singly to produce control arrays, in orthogonal combination to measure possible interference effects, and in redundant combination to measure possible facilitation effects. Segregation for control arrays was much more difficult when the two diagonal lines produced regions of texture than when arrays used lines involving one or two main axes, and 7-step hue-difference arrays were more difficult to segregate than 9-step arrays, as expected. Orientation and hue were equally effective in producing fast texture segregation when used with optimal levels. The pattern of interference and facilitation for orthogonal and redundant combinations depended on the particular pair of line orientations used to produce texture: With horizontal and vertical lines, there was symmetric interference of each dimension on the other, as well as a redundancy gain. With horizontal and left diagonal lines, there was asymmetric interference of hue variation on orientation segregation, and no redundancy gain. With the two diagonals, there were symmetric interference and strong redundancy gains. These results clarify why different line orientations provide different effectiveness in texture segregation, and suggest that both interstimulus confusability (as with the two diagonals) and intrastimulus stability (as with horizontal and vertical lines) properties determine the ability of a dimension to interfere with, or to be interfered with by, another dimension in texture segregation.

The effects of interstimulus and stimulus-specific factors on central (vs. peripheral) oblique effects were examined using classification, focusing, discrimination, and sequential same-different tasks. Classification results showed that grouping the vertical with the horizontal line and the two diagonal lines with each other facilitated performance. Discrimination results revealed that the two diagonal lines were more confusable with each other than were the members of any other stimulus pair. Focusing results indicated that the vertical and horizontal lines served as better focusing stimuli. A set of sequential same-different tasks, each using only two alternative stimuli, allowed for the examination of stimulus-specific factors in focusing; the effects of similarity relations between all stimuli in the total set were greatly reduced by the constrained context. The two diagonal lines were the most difficult to compare and proved to be the worst foci in these tasks as well. In conclusion, there are two factors operating in the central oblique effect: greater confusability between the two diagonal lines and more favorable stimulus-specific properties of vertical and horizontal lines.

In two experiments, the accuracy with which subjects detected a conjunction of features was examined as a function of the spacing between items and the goodness of the axis along which they were located. In each array, two items were arranged along a vertical, a horizontal, or a diagonal axis. Based on the well-established oblique effect, the vertical and horizontal axes were considered to be good global patterns and the diagonals were considered to be poor. In Experiment I, the two items in an array could be two horizontal lines, two vertical lines, a vertical and a horizontal line, or a plus sign with one of the single lines. In Experiment 2, a positiveand a negative-diagonal line were used as the individual features, and an "X" was used as the conjunction. The results from Experiment 1 indicated that global goodness influenced only the rate of illusory conjunctions, and not of feature errors. lllusory conjunctions of vertical and horizontal line segments were more likely to occur in vertical and horizontal arrangements. The results from Experiment 2 revealed a reversal of the effect of global goodness on the rate of illusory conjunctions: Illusory conjunctions of negative-and positive-diagonal line segments were more likely to occur in diagonal arrangements. The results of both experiments taken together showed the existence of an important and new factor that influences the likelihood that features of shape will be conjoined: the ease with which line segments conjoin when they are translated along their extent toward each other. In both experiments, greater spacing between items produced more feature-identification errors and fewer feature-integration errors than did less spacing.

The hypothesis that automatic processes do not change during aging was investigated using Warren's (1972) modification of the Stroop procedure. The subjects were 14 adults in each of three age groups: young (20 to 39), middle (40 to 59), and old (60 to 79). On each trial, subjects held three category members in memory while they named the ink color in which a base item was printed. For all three age groups, color naming latencies were longer when the base item was from the same category as the memory list items. According to network theories of long-term memory, these findings suggest that, throughout adulthood, holding words in working memory results in activation of the memory nodes corresponding to the words themselves, and also in activation spreading to semantically related nodes. The results are consistent with the hypothesis that acquired automatic processes do not deteriorate with aging.