Experiments are reported which address the nature of the working memory system. Articulatory suppression (continuous recital of the digits 1 to 4) disrupted concurrent performance of a verbal reasoning task, but had no effect upon performance of a spatial reasoning task. In contrast, spatial suppression (continuous sequential tapping) produced reliable interference only with spatial reasoning. These findings are taken as consistent with Baddeley's argument for two slave systems in working memory: the articulatory loop and the more controversial visuo-spatial scratch-pad.
The effects of target-background similarity and background uniformity were investigated in two experiments in which subjects reported the presence or absence of an achromatic target item in arrays containing irrelevant chromatic items. In Experiment I, both "present" and "absent" decision times were an increasing function of the similarity of a predefined target item to the background, and were shortened when the interitem similarity of the background set was increased. In Experiment 2, the effects of target-background similarity on the "present" decision were replicated when subjects were not informed on each trial as to which member of the target set might appear in the array, and the "absent" decision was faster when each row of the array comprised background items of a single color than when these items were allocated randomly to array locations. The results are interpreted in terms of the role of preattentive grouping operations.
Studies have shown that anxiety can positively or negatively affect performance with respect to focusing of attention or distractibility, subjective workload and effort (Humphreys and Revelle, 1984). The inhalation of carbon dioxide (CO(2)) is associated with physiological and psychological effects of anxiety (Bailey et al., 2005) but its effects on performance have rarely been reported. The studies reported here looked at the effects of CO(2) inhalation on physiological and subjective measures and performance on two tasks. Eight healthy male participants completed a tracking task with a reaction time component, and 12 healthy participants (six male) completed a complex target identification task. Tasks were performed during 20-min inhalations of 7.5% CO(2)/21% O(2)/71.5% N(2) mixture or medical air. Continuous heart rate and blood pressure measures were taken, in addition to subjective measures of mood and workload. In comparison with air, CO(2) increased heart rate and blood pressure, increased subjective scores of panic, anxiety, fear, and tension, and reduced subjective scores of relaxation and happiness. Attention was focussed when inhaling CO(2) during the simple task, and central demand was greater when inhaling CO(2) during the complex task. Therefore, inhalation of 7.5% CO(2) produces effects on task performance which are consistent with anxiety.
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