This study was designed to investigate the relationship between the amount of information processing in concept learning (CL) and autonomic physiological activity as measured by skin conductance response (SCR). Heart rate (HR) was also measured. Two conceptual rules were used: a conjunctive and an inclusive disjunctive concept. The results indicated that the SCR rose with increasing amount of information processing at the feedback during CL. Furthermore, it was shown that SCR increased with increasing difficulty of the conceptual rule. HR appeared not to vary with amount of information processing, nor with type of concept. In the conjunctive series, however, there was a significant difference between HR at stimulus presentation and HR at feedback.

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The relationship between the amplitude of P300, the mean amplitude of the Slow Wave, and uncertainty reduction after (dis)confirmation of hypotheses was studied in a Concept-Identification task. The subjects had to categorize stimuli according to a conceptual mIe (joint denial or exclusion) and to rate the confidence that their classification was correct. Three types of feedback were distinguished: confirming (subject's categorization was correct), disconfirming (subject's categorization was incorrect), and non-informative feedback. The EEG was averaged separately according to the three types of feedback and the two confidence ratings (low, high).The data showed the predicted interaction between type of feedback and confidence level. A larger P300 amplitude tumed up after confirming feedback when the subject was less confident, than when he was more confident. The reverse was found after disconfirming feedback. The P300 amplitude after non-informative feedback was not influenced by confidence. The mean amplitude of the Slow Wave showed approximately the same interaction pattem.The results were interpreted in terms of changes in the probability of hypotheses which subjects use to categorize stimuli in a Concept-Identification task.

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'i'he relationship between the amount of information processing in an Attribute: Learning task and autonomic activity, measured by skin conductance responrc (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 stimuius population consisted of four three-valued dimensions. The results ishowed 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 confiimations preceding infumation; (4) subjects mainiy used the strategy 'reject hypothesis only after infumation'; (5) subjects usually selected not-yet-tested hypotheses; (6) practice influenced performance; (7) verbalization did not resolt in more efficient use of information; however, the appropriateness of the experimental setup to stud,, this factor was questioned; (8) conjunction was easier to ie.srn than the other concepts. The results were discussed in terms of uncertainty reduction, restthing dart testing hypotheses in a concept learning task.

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.

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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.