A time course analysis of Stroop interference and facilitation: comparing normal individuals and individuals with schizophrenia.

Using randomized stimulus onset asynchrony (SOAs), the authors traced the time course of Stroop interference and facilitation in normal participants and participants with schizophrenia. Unlike earlier findings using blocked SOAs, singular peaks in interference, facilitation, or both occurred at particular SOAs. The peaks of normal participants and participants with schizophrenia differed. Findings are congruent with a model of Stroop performance that posits individual differences in processing speeds of target and nontarget stimulus dimensions, coupled with critical points in response selection. Participants with schizophrenia also showed more overall interference than normal control participants. A second experiment that added a temporal gap between the distractor word and target color obliterated Stroop effects only for individuals with schizophrenia. These findings provide a new empirical basis for models of Stroop effects. They are also consistent with hypotheses about the importance of the prefrontal cortex for working memory and prefrontal dysfunction in schizophrenia.

Stroop theory, memory, and prefrontal cortical functioning: reply to Cohen et al. (1997)

In this article, the authors respond to J. D. Cohen, K. O. Dunbar, D. M. Barch and T. S. Braver's (1997) comment on their target article. The present article (a) takes issue with the characterization given by Cohen et al. of the authors' approach as a classical speed-of-processing account of Stroop effects, (b) discusses the value and relevance of other theoretical concepts, such as traditional accounts of working memory and parallel distributed processing (PDP) approaches to Stroop effects, (c) further examines the possibility that the differences the authors observed in Experiment 2 between normal participants' performance and that of participants with schizophrenia may have been due to distractor stimulus degradation, particularly for participants with schizophrenia, and (d) argues for the relevance of the prefrontal cortex, as well as other brain areas, in accounting for their results. The authors conclude with a final theoretical question.

Adult age differences in memory for routes: effects of instruction and spatial diagram.

Free-recall and multiple-choice measures of memory for landmarks, sequential order, turns, and route configurations were obtained from younger and older adults after they viewed slides of 2 overlapping routes. Instructions focused attention on either the contents of the slides or on the course of the path; a control condition provided no orientational instructions. Half the subjects viewed maplike diagrams of the joint spatial configuration. Age interacted with instruction only for multiple-choice tests of landmark memory. Age interacted with diagram for each of the other 3 route memory components, although the generality of this interaction across instruction condition depended on whether free-recall or multiple-choice tests were used. The results suggest that route memory may involve both scene and layout representation, which may be differentially sensitive to age and presentational variables.

Continued inhibitory capacity throughout adulthood: conceptual negative priming in younger and older adults.

Two negative priming experiments in older and younger adults are reported. Participants in Experiment 1, involving both positive and negative priming conditions, showed both types of priming. There were no significant differences between age groups. If anything, older participants showed more negative priming. In Experiment 2, involving only negative priming conditions, similar results were obtained. Our findings rule out possible effects of experimental conditions that episodic retrieval theorists have suggested might account for negative priming in older adults. Although our results may be consistent with an explanation of negative priming in older adults by an expansively specified theory of episodic retrieval, they are at least as consistent with the view that inhibitory processes are intact in older adults. In light of these findings, conflicting empirical results and alternative views of negative priming in older adults are examined.

Age and gender differences in the effectiveness of map-like learning aids in memory for routes.

Young (ages 25-40 yrs) and older (ages 60-75 yrs) adults viewed a series of slides depicting a route through a neighborhood and were tested on their ability to remember the route. Subjects either received no learning aid, a sketch of the route labeled as a "map," or the same aid labeled a "diagram." Aids either did or did not include route landmarks. Relative to younger men, older men's performance was significantly poorer only when they had no learning aid. In contrast, age differences for women were obtained only when the aid had been labeled a "map." The presence of landmarks eliminated age-related decrements in scene memory for men but increased them for women. In addition, results were consistent with the hypothesis that memory for large-scale environments is composed of "layout" (i.e., configural) and "scene" components.

Semantic relations as graded concepts.

This experiment tests the hypothesis that semantic relations are graded concepts. It also tests the predictions of relation element theory and of Klix's (1986) theory of semantic relations regarding possible predictors of graded structure for semantic relations. Results support the hypothesis that semantic relations have graded structures, and indicate that differences among relations in gradedness reflect the families of semantic relations described by Chaffin & Herrmann (1984). In addition, Klix's distinction between property relations and event relations appears to be useful in explaining differences among relations in graded structure.

On the relationship between category intensions and extensions in children.

We contrasted four theories of natural language category acquisition by investigating the relation between category intensions and extensions in children (kindergarteners, second graders, fifth graders) and in college students. Everyone was asked to define a category term, to make category membership judgments of possible exemplars, and to judge whether the possible exemplars possessed features generated by them and by previous adult subjects. Adult judges were also asked to judge whether the possible exemplars possessed the features generated by the subjects. Children's intensions and extensions were very consistent. In addition, children's extensions were reliably smaller than adults', and the features which children generated were more specific than those generated by adults. None of the existing theories discussed can explain this pattern of results. An exemplar-based model is proposed to do so.

Problem solving by reference to rules or previous episodes: the effects of organized training, analogical models, and subsequent complexity of experience.

Subjects learned a microcomputer drawing package under different conditions of training organization and practice complexity. Training instructions were presented in either a random or an organized order, and with or without an analogical model of the software package. Practice trial varied in visual and logical complexity. Performance on paper-and-pencil and problem-solving tests was better following the model than following the no-model condition when practice trials were logically complex; the reverse was true when they were logically simple. Performance on the test of problem solving was also better following organized training than following randomly ordered training when practice trials were visually complex; the reverse was true following visually simple practice. We propose that the subjects performed the tasks by engaging in either episode-based or rule-based processing, and that performance was optimized when the processing used at encoding and retrieval was the same. The acquisition of skill in solving real problems is explained as procedural compilation.

The effects of analogical training models and age on problem-solving in a new domain.

Young and middle-aged adults learned a microcomputer drawing package either with or without an analogical model of the package. Following training, problem-solving flexibility was assessed. Although no age differences were obtained following no-model training, middle-aged subjects performed worse than young subjects following model-based training. These results support the hypothesis that model-based training encourages elaboration and abstraction processes, and that older adults are less likely or less able to engage in such processing.

Age effects on analogy-based memory for text.

We examined age influences on analogy-based learning, in particular, analogy-based text memory. Adults (20-72 years) read pairs of passages describing analogous topics. We manipulated encoding complexity for the first passage and superficial topic similarity between passages, and assessed second-passage memory. Across all age groups, memory was better in the superficially similar topic condition only when encoding complexity had been simple. More critically, performance was better for similar topics only for the youngest adults. Younger adults performed worse than older adults in the dissimilar condition. Thus, only older adults identified and used the parallels between passages spontaneously.