Abstract.Two experiments investigated the way that beforehand preparation influences general task execution in reaction-time matching tasks. Response times (RTs) and error rates were measured for switching and nonswitching conditions in a color-and shape-matching task. The task blocks could repeat (task repetition) or alternate (task switch), and the preparation interval (PI) was manipulated within-subjects (Experiment 1) and between-subjects (Experiment 2). The study illustrated a comparable general task performance after a long PI for both experiments, within and between PI manipulations. After a short PI, however, the general task performance increased significantly for the between-subjects manipulation of the PI. Furthermore, both experiments demonstrated an analogous preparation effect for both task switching and task repetitions. Next, a consistent switch cost throughout the whole run of trials and a within-run slowing effect were observed in both experiments. Altogether, the present study implies that the effects of the advance preparation go beyond the first trials and confirms different points of the activation approach (Altmann, 2002) to task switching.

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In the present study, the affective impact of earcons on stimulus classification is investigated. We show, using a picture-categorization task, that the affective connotation of earcons in major and minor mode (representing positive and negative valence, respectively) can be congruent or incongruent with response valence. Twenty participants classified pictures of animals and instruments in 256 trials, using positive and negative Yes or No responses. Together with the pictures, either a chord in major mode or minor mode was played. The affective valence of the chords either did or did not match the valence of responses. Response-time latencies show congruency effects of the matching and non matching sound and response valences, indicating that it is important to carefully investigate human-computer interfaces for potential affective congruency effects, as these can either facilitate or inhibit user performance.

Affective computing, a human-factors effort to investigate the merits of emotions while people are working with human-computer interfaces, is gaining momentum. Measures to quantify affect (or its influences) range from EEG, to measurements of autonomic nervous system responses (e.g., heart rate, blood pressure), to less objective self-reports. Here we claim that simple response-time measurements may be a viable alternative to measure (indirectly) the effects of affect on performance by providing a review of experimental paradigms and associated models of human information processing. In particular, we focus on stimulus-response compatibility paradigms that have provided important insights for human-factors research, for instance regarding the important role of the spatial layout of interface design on the efficiency of human task performance, to show that these paradigms can also be applied to investigate the role of affect in human-computer interaction.

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