Several studies have reported that, in addition to the minimum information required for a categorization task, redundant information is also acquired during category learning. However, it is possible that previous studies have failed to control for the difficulty of deriving categorization rules, weak category coherences, or the tendency to ascribe attributes to each category. This study conducts two experiments to eliminate these factors. The task in both experiments involved classifying rectangles into one of two easily identifiable categories based on the ratio of width to height. In the category-learning phase, one item in each category was given a unique and idiosyncratic color attribute (category-specific), which was not a definite cue for distinguishing the category. The results from the transfer test indicated that when an item was marked with the idiosyncratic color attribute of the other category (opposite-category-specific), the proportion of correct responses and participant confidence ratings were both low (Exp. 1) or just participant confidence ratings were low (Exp. 2). These results suggest that redundant attributes influence categorization, even when the categorization rule is easy to learn and category learning is perfect.

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The intention-superiority effect refers to the superior retention of information about intended but uncompleted tasks compared with the retention of information about tasks that are unintended. We conduct two experiments to examine this effect in a situation where the participants were presented with multiple plans. The first experiment attempts to replicate the effect with 24 participants. The results indicated that the time needed for a lexical decision tended to be shorter for items included within a script when the script was yet to be performed compared to when the script had already been carried out. In the second experiment, 24 participants performed actions from two scripts that were memorized in advance. Longer response times were observed for items from the second script, when the decision task was administered before performing the first script compared to when the decision task was administered after performing the first script (i.e., immediately before performing the second script). These results indicate that participants efficiently control activation levels related to both uncompleted and completed plans.

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The paper examines the merit of a small memory capacity on the detection and utilization of correlations within a multiple-variable environment that contained dummy variables. The participants were asked to predict a number (1 or 2) hidden within a figure with four features (color, shape, size, and number) on each trial. All features were binary variables, and only color was correlated with the hidden numbers. The results indicated that a small working-memory-capacity group performed better than a large working-memory-capacity group, which suggests that a smaller working memory capacity is advantageous for detecting and utilizing correlations. This implies an adaptive advantage of a smaller memory capacity.

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Context variability refers to the number of different contexts in which words appear. In the present study, the effect of context variability on recall and recognition performance is examined using two-kanji compound words as stimuli. The results of Experiment 1 indicate that both free recall and recognition performances were better for low context variability words than for high context variability words. Similarly, Experiment 2 indicates that the effect of context variability remained, despite having controlled for the frequencies of the stimuli kanji. It is also found that words containing low-frequency kanji have higher rates of recall accuracy. Experiment 3 examines the effect of context variability by manipulating the environmental conditions at presentation and recognition. The Remember/Know procedure is introduced to distinguish between responses based on recollection with those based on familiarity. The results of the three experiments suggest that the binding of item and context information plays an important role in forming accurate recollection judgments.

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Performance-based vehicle ignition-interlock devices (IID) have the potential to directly detect deficits in cognitive ability, a key factor in driving safety, and are expected to play a pivotal role in traffic safety. However, as the absence of a standard method for evaluating performance tests is an obstacle to their further development, this paper proposes a new evaluation method. Regression analysis is used to calculate a border point (BP), where an upper 95% confidential interval (CI) for performance would not exceed the mean performance at a blood alcohol concentration (BAC) of 0 mg/ml, and a critical point (CP), where an upper 95% CI for performance would not exceed the lower 95% CI for performance at 0 mg/ml BAC. Compared to conventional analyses, it is found that the new method exhibits superior features, such as direct comparability not only across tests but across experiments and accurate capability estimations from degraded data set. Thus, we argue that the new method of evaluating performance tests in terms of BP and CP points is suitable for use as a standard in future IID studies.

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