It has often been asserted that working-memory limitations are a major factor contributing to problem difficulty; for example, Johnson-Laird's (1983) mental-models theory appeals to workingmemory limitations to explain the difficulty of syllogistic reasoning. However, few studies have directly explored working memory in problem solving in general or syllogistic reasoning in particular. This paper reports two studies. In the first, working-memory load was varied by presenting syllogistic tasks either verbally or visually (so that the premises were continuously available for inspection). A significant effect of memory load was obtained. In the second study, premises were presented visually for a subject-determined time. Dual-task methods were used to assess the role of working-memory components, as identified in Baddeley's (1986) model. Syllogistic performance was disrupted by concurrent random-number generation but not by concurrent articulatory suppression or by concurrent tapping in a preset pattern. Furthermore, the concurrent syllogism task interfered with random generation and to a lesser extent with articulatory suppression, but not with tapping. We conclude that while the central-executive component of working memory played a major role in the syllogistic-task performance reported here, the articulatory loop had a lesser role, and the visuospatial scratch pad was not involved.

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P. C. Wason's paper “On the Failure to Eliminate Hypotheses in a Conceptual Task” is criticized on the grounds that the task set is in important respects untypical of problem solving situations in general. It is suggested that few or no subjects are “Eliminators” in Wason's sense and that although many are “Enumerators” in his sense, enumerative behaviour is a function of the situation. An experiment is reported in which it appears that modification to the situation can sharply reduce the incidence of enumerative behaviour and increase the subject's chance of success at an early stage. The frequency with which hypotheses are directly eliminated is shown to be very low in all groups.

Six groups of subjects with known BCOIW on reported controllability end vividness of imagery were tested on five cognitive teaks. A high 'controllability of visual imagery' group performed two divergent thinkine; tasks better than a low 'controllability' group. Self-rated use of imagery we8 positively associated [with performance on the divergent thinking taaka and negatively associated with performance on a Gestalt-type problem task. No relationships were found between reported imagery and performance on two concept tasks, one of which ww purely visual.

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