J.H. De Swart

The effects of Nicotinic Acid and Xanthinol Nicotinate on human memory in different categories of age

The treatment effect of nicotinic acid and xanthinol nicotinate on human memory was compared with placebo in 96 healthy subjects. Forty-three subjects were young (35–45 years), 30 subjects middle aged (55–65 years) and 23 subjects were old aged (75–85 years). Pre- and post-treatment scores were measured on a battery of memory tasks, covering sensory register, short-term memory and long-term memory. The treatment regime was 1 dragee t.i.d. for 8 weeks. The administration of xanthinol nicotinate (500 mg, containing 141.7 mg nicotinic acid), nicotinic acid (141.7 mg) and placebo (lactose) was double-blind. Pre-and post-treatment scores were analysed by means of a multivariate covariance technique, the pre-treatment score serving as covariate. Nicotinic acid treatment resulted in improvement of sensory register and short-term memory, while xanthinol nicotinate improved sensory register, short-term memory and long-term memory. In comparison with placebo, both active compounds yielded improvements of 10–40%, depending on type of task. Treatment effects of nicotinic acid were predominantly found in the young and middle-aged, whereas treatment effects of xanthinol nicotinate were predominantly found in the old. These results are interpreted by the supposed activity of nicotinic acid at the cell membrane, improving neuronal transmission, and of xanthinol nicotinate inside the cell, enhancing cell metabolism and oxygen supply in the brain.

Variation within categories.

Abstract Two aspects of variation within categories, relating to different models of categorization, were investigated — frequency of dimensional values and typicality differences within values. The influence of range of typicality experienced during learning and of informational value of feedback was also studied. Finally, differential forgetting of values was examined. In the experiment subjects learned to categorize faces, and then performed a classification test task and pairwise comparisons of faces. A variety of dependent variables was employed, including the galvanic skin response (GSR). Typicality and frequency of values appeared to influence categorization performance independent of each other. It was concluded that both prototype distance models and frequency models explain different aspects of variation within the same categories, and that models of classification should account for frequency of values in contrasting categories. Results showed furthermore (1) the influence of typicality range on the extension of a category; (2) no influence of specific feedback regarding representativeness of a face; (3) less decay with more important values; and (4) a positive relationship between uncertainty reduction and GSR.

Effects of contrasting category, conjoint frequency and typicality on categorization.

Two experiments were conducted to investigate whether (a) experience with a contrasting category, (b) conjoint frequency of dimensional values, (c) range of typicality of values, and (d) type of information administered during learning influenced subsequent test performance. Each experiment began with an observational category learning task, employing faces as stimuli. This was followed by a classification test task and by pairwise comparisons of faces. Influence of a contrasting category was studied in experiment 1 by varying frequency of values of the contrasting category, and in experiment 2 by either including or not including a contrasting category in the learning task. Results indicated that (a) categorization is influenced by experience with a contrasting category, (b) conjoint frequency enhances the importance of values to a category, (c) broad typicality range experience reduces typicality differences among exemplars of a category, whereas small range experience diminishes differences in a contrasting category, and (d) information on representativeness of exemplars does not facilitate subsequent test performance. The implications of the results for categorization models are discussed.

Physiological activity in an attribute learning task.

Abstract The relationship between the amount of information processing in an Attribute Learning task and autonomic activity, measured by skin conductance response (SCR), was investigated. The amount of information processing was manipulated by type of concept and feedback. Furthermore, the influence of practice and verbalization was studied. Three types of concepts were used: conjunction, exclusion and joint denial. The stimulus population consisted of four three-valued dimensions. The results showed that (1) SCR did not differ among concepts; (2) SCR varied with type of feedback, it being smallest at blanks and largest at infirming feedback; (3) SCR was related to the number of confirmations preceding infirmation; (4) subjects mainly used the strategy ‘reject hypothesis only after infirmation’; (5) subjects usually selected not-yet-tested hypotheses; (6) practice influenced performance; (7) verbalization did not result in more efficient use of information; however, the appropriateness of the experimental set-up to study this factor was questioned; (8) conjunction was easier to learn than the other concepts. The results were discussed in terms of uncertainty reduction, resulting from testing hypotheses in a concept learning task.

A comment on Marks and Clarkson's explanation of conservatism

Abstract Marks and Clarksons explanation of conservatism (1972) was criticized. It was suggested that De Swart (1972a, b) offers an equally good or better explanation.

Typicality, physiological activity and concept identification.

The extent to which instances are good or poor examples of their categories (typicality) was varied in a concept identification (CI) task. Typicality was first established for the kind of artificial material traditionally used in CI tasks (experiment 1). This material was employed in a CI task (experiment 2) with a variety of dependent variables, including the galvanic skin response (GSR). To test the generality of the results, more realistic stimuli were employed (experiments 3 and 4). The results showed that typicality influenced performance on the CI task, that the GSR is primarily related to uncertainty reduction, that the findings with arbitrary materials are replicated with more meaningful materials, and that the multi-hypothesis sampling theory of Levine is supported by the findings.

Wilhelm Wundt and the cognitive shift

Abstract This paper compares Wundtian and cognitive psychology with respect to immediate and mediate experience, non-functionalism, and the status of the experiment. It is pointed out that the perspective of immediate experience, which can also be found in early American functionalism, has disappeared in the wake of behaviorism. Next cognitive psychology, which to some extent represents a correction of behaviorism, is compared with Wundts system. It is concluded that in spite of certain similarities the Wundtian and the cognitive perspective are irreconcilably opposed.

The reply of Marks and Clarkson reconsidered

Abstract In answering De Swarts comment on Marks and Clarksons (1973) explanation of conservatism, one of Marks and Clarksons conclusions was that De Swarts data supported the division rule. It is demonstrated that this conclusion is not warranted by De Swarts data.