J.J. Adam et al. (1998) provided evidence for an "age-related deficit in preparing 2 fingers on 2 hands, but not on 1 hand" (p. 870). Instead of having an anatomical basis, the deficit could result from the effortful processing required for individuals to select cued subsets of responses that do not coincide with left and right subgroups. The deficit also could involve either the ultimate benefit that can be attained or the time required to attain that benefit. The authors report 3 experiments (Ns = 40, 48, and 32 participants, respectively) in which they tested those distinctions by using an overlapped hand placement (participants alternated the index and middle fingers of the hands), a normal hand placement, and longer precuing intervals than were used in previous studies. The older adults were able to achieve the full precuing benefit shown by younger adults but required longer to achieve the maximal benefit for most pairs of responses. The deficit did not depend on whether the responses were from different hands, suggesting that it lies primarily in the effortful processing required for those subsets of cued responses that are not selected easily.

Pigeons pecked left versus right keys contingent upon the color presented at 1 of those locations. Spatial-response latencies were shorter when the color appeared at the same location as the required response than at the opposite location. This Simon effect occurred when the stimulus on the alternative key was constant, varied from trial to trial, or changed when the color cue appeared and when the reinforcement probability for correct responses was the same on corresponding as on noncorresponding trials. Humans performing the same task by touching the keys also showed the Simon effect. These findings demonstrate that for pigeons, too, a relevant symbolic cue activates a spatial code that produces faster responses at the location corresponding with the activated code.

The Simon effect, better performance when irrelevant stimulus location corresponds with the response location than when it does not, typically is larger for older than younger adults. However, Simon and Pouraghabagher [Simon, R. J., & Pouraghabagher, A. R. (1978). The effect of aging on the stages of processing in a choice reaction time task. Journal of Gerontology, 33, 553-561] found no age difference using an accessory-stimulus Simon task in which the relevant dimension was the color of a visual stimulus and the irrelevant dimension the location of a tone. Experiment 1 confirmed that older adults show a larger Simon effect than younger adults for the visual Simon task and that this age-related deficit is reduced or eliminated for the auditory-accessory task. Experiment 2 provided evidence suggesting that a small part of the age-related deficit in the visual Simon task is due to having to code the location of the relevant stimulus, but Experiment 3 showed that the majority of the deficit is due to the relevant and irrelevant information being conveyed by the same stimulus. Reaction-time distribution analyses show similar functions for younger and older adults, suggesting that the time course of activation is similar for both age groups.

If compatible and incompatible mappings of left-right stimuli to left-right keypresses are mixed such that participants must maintain both task sets, the typical stimulus-response compatibility (SRC) effect is eliminated. Four experiments examined whether the SRC effect is influenced similarly by inclusion of trials on which stimulus location is irrelevant. The SRC effect for the location-relevant trials, as eliminated in Experiments I and 3 when those trials shared left-right codes with the location-irrelevant trials. The SRC effect was not eliminated in Experiments 2 and 4. in which the location-relevant stimuli varied along the left-right dimension but the location-irrelevant stimuli were presented in the centre of the screen or in top-bottom locations. The Simon effect for the location-irrelevant trials in Experiments I and 3 as positive when the location-relevant mapping,vas compatible and reversed when it was incompatible, The results are generally consistent with alternative-routes model, according to which a direct response-selection route is suppressed hen compatible trials are mixed with location-irrelevant trials. Repetition analyses suggest that this suppression does not Gary on a trial-to-trial basis.

Many design guidelines encourage maintaining stimulus-response compatibility whenever possible. Payne found that naïve judgments for different stimulus-response (S-R) mappings were not very accurate, and suggested that designers may not be able to predict whether a particular display-control configuration will lead to better performance than another. Three experiments were conducted to determine whether naïve judgments for two-choice tasks in which stimuli and responses involve left-right spatial information are sensitive to (a) the influence of S-R mode relations and (b) pure versus mixed presentation of compatible and incompatible mappings. Initial performance judgments for these conditions were not very accurate, nor were those for four-choice tasks of the type studied by Payne, but subjects' estimates of performance improved with relatively little experience using the different S-R configurations.

The vast amount of information available through the Web has made it difficult to retrieve information relevant to a specific task. To help ensure that users' interactions with a system are successful, preparation of content and its presentation to users must take into account (a) what information needs to be extracted, (b) the way in which this information should be stored and organized, (c) the methods for retrieving the information, and (d) how the information should be displayed. The goal of this article is to discuss the generic problems facing content preparation and evaluate the current methods available to help remedy them, as well as identify areas in which more research is needed. The material presented in this article was a result of the collective efforts of the participants of a special "white paper" session that was part of the 9th International Conference on Human-Computer Interaction (HCI International 2001).

This study evaluated the hypothesis that an increase in set-level stimulus-response compatibility produces facilitation for congruent mappings and interference for incongruent mappings. The degree of set-level compatibility was manipulated by varying combinations of conceptual, perceptual, and structural similarity. Experiment 1 varied perceptual similarity, by combining two stimulus codes (spatial, verbal) with two response modalities (manual, vocal) for orthogonal spatial dimensions, which have structural similarity. The element-level mapping effect did not vary as a function of the code-modality relation, in contrast to findings obtained with parallel spatial dimensions, which also have conceptual similarity. Experiment 2 manipulated combinations of conceptual and perceptual similarity by combining vertical and horizontal stimulus and response orientations, using verbal or spatial stimuli and vocal responses. The element-level mapping effect was larger for parallel than orthogonal orientations, with congruent mappings showing facilitation and incongruent mappings showing interference. The largest effect was facilitation for parallel orientations with the verbal-vocal set, consistent with the view that perceptual similarity contributes to performance primarily when responding with the identity of the stimulus. Our results indicate that conceptual similarity, but not perceptual similarity, produces the facilitation/interference pattern suggestive of automatic activation of the corresponding response regardless of mapping.

Regardless of whether stimulus location is relevant or irrelevant to a task, responses are faster and more accurate when stimulus location and response location correspond than when they do not. Stimulus-response compatibility (SRC) effects of this nature are robust and typically considered to be automatic consequences of stimulus-response associations that are either hard-wired or acquired through years of experience. An exception to the robustness of SRC effects has been shown to occur when compatible and incompatible mappings are mixed. In the present paper, we review the literature on mixing compatible and incompatible mappings and show that mixing does not always reduce the SRC effect. We then present results from studies in which location-irrelevant (LI) trials are mixed with location-relevant (LR) trials. The SRC effect for LR trials of physical locations to keypresses is eliminated when stimulus color, rather than location, is relevant on half of the trials. However, the SRC effect for LR trials is unaffected by mixing when the location information is conveyed by arrows and amplified when it is conveyed by words. With vocal location responses, the SRC effects for all three stimulus types are enhanced by mixing. In addition, regardless of stimulus type and response modality, mixing intensifies the correspondence effect for trials on which location is irrelevant when the mapping for LR trials is compatible and eliminates or reverses the effect when the mapping is incompatible. These results show that SRC effects are not as hard-wired as previously depicted and are affected by the demands on subjects imposed by the task environment.

When stimulus and response sets vary along horizontal and vertical dimensions, the horizontal dimension is more dominant than the vertical one, an effect called right-left prevalence. Three accounts have been proposed that attribute the effect to a reduced ability to code vertical locations when horizontal codes are also present, the use of right-left effectors, or a difference in salience of the 2 dimensions. The accounts differ in terms of whether the ability to code and process the 2 dimensions is of limited capacity and whether the prevalence effect is a consequence of the effectors used for responding. The authors report 4 experiments that evaluated these issues. Results indicate that use of right-left effectors is important to the right-left prevalence effect because it increases the salience of the horizontal dimension. However, a top-bottom prevalence effect can be obtained if the vertical dimension is made more salient.

The Theory of Event Coding (TEC) presented in Hommel et al.'s target article provides a useful heuristic framework for stimulating research. Although the authors present TEC as providing a more integrated view of perception and action than classical information processing, TEC is restricted to the stage often called response selection and shares many features with existing theories.

Metacognition, a person's knowledge of her or his own cognitive processes, is a concept that can be applied to many areas of human-computer interaction. This article reviews the state of contemporary knowledge regarding metacognition and describes implications for the domain of human-computer interaction. A conceptual framework is presented that distinguishes monitoring and regulation processes of metacognition. One aspect of metacognition, self-evaluation of knowledge, was investigated for a word processing application as an illustration. An experiment was conducted to evaluate which of four methods of self-assessment of expertise was the best predictor of declarative knowledge (accuracy and completeness of descriptions on how to perform a task). In addition, the experiment examined whether classifying users based on self-reported estimates of expertise would produce differences in their declarative descriptions. Results showed that individuals' ratings of their overall knowledge were better predictors than were estimations of frequency of use, as would be expected from the literature on metacognitive monitoring. In addition, classifying; users based on their self-ratings of expertise showed differences in accuracy of declarative knowledge and strategy chosen to perform a task. Experts were more accurate in their descriptions of how to complete a task compared to novices and used more complex strategies to complete hard tasks.