Comparing Stroop-like and Simon Effects on Perceptual Features

Stroop-like and Simon tasks produce two sources of interference in human information processing. Despite being logically similar, it is still debated whether the conflicts ensuing from the two tasks are resolved by the same or different mechanisms. In the present study, we compare two accounts of the Stroop-like effect. According to the Perceptual Account, the Stroop-like effect is due to Stimulus-Stimulus congruence. According to the Decisional Account, the Stroop-like effect results from the same mechanisms that produce the Simon effect, that is, Stimulus-Response compatibility. In two experiments we produced Stroop-like and Simon effects by presenting left/right-located stimuli consisting of a colored square surrounded by a frame of the same color as the square or of a different color. Results showed that discriminating either the color of the square (Experiment 1) or that of the frame (Experiment 2) yielded additive Stroop-like and Simon effects. In addition, the patterns of temporal distributions of the two effects were different. These results support the Perceptual Account of the Stroop-like effect and the notion that the Stroop-like effect and the Simon effect occur at different processing stages and are attributable to different mechanisms

Living on the edge: strategic and instructed slowing in the stop signal task

The stop signal task is widely adopted to assess motor inhibition performance in both clinical and non-clinical populations. Several recent studies explored the influence of strategic approaches to the task. In particular, response slowing seems to be a strategic approach commonly adopted to perform the task. In the present study, we compared a standard version with a strategic version of the task, in which participants were explicitly instructed to slow down responses. Results showed that the instructed slowing did not affect the main inhibition measure, thus confirming the robustness of the stop signal index. On the other hand, it apparently changed the nature of the task, as shown by the lack of correlation between the standard and the strategic versions. In addition, we found a specific influence of individual characteristics on slowing strategies. In the standard version, adherence to task instructions was positively correlated with compliant traits of personality. Despite instructions to maximize response speed, non-compliant participants preferred to adopt a slowing strategy in the standard version of the task, up to a speed level similar to the strategic version, where slowing was required by task instructions. Understanding the role of individual approach to the task seems to be crucial to properly identify how participants cope with task instructions

The role of visual distractors in the simon effect

The Simon effect lies on the automatic generation of a stimulus spatial code, which, however, is not relevant for performing the task. Results typically show faster performance when stimulus and response locations correspond, rather than when they do not. Considering reaction time distributions, two types of Simon effect have been individuated, which are thought to depend on different mechanisms: visuomotor activation versus cognitive translation of spatial codes. The present study aimed to investigate whether the presence of a distractor, which affects the allocation of attentional resources and, thus, the time needed to generate the spatial code, changes the nature of the Simon effect. In four experiments, we manipulated the presence and the characteristics of the distractor. Findings extend previous evidence regarding the distinction between visuomotor activation and cognitive translation of spatial stimulus codes in a Simon task. They are discussed with reference to the attentional model of the Simon effect

Why are left-right spatial codes easier to form than above-below ones?

Previous studies have shown that spatial compatibility is stronger in the left-right than in the above-below dimension. This left-right dominance cannot be attributed to a better representation of the effectors in left-right than in above-below locational codes or to the fact that incompatible left-right stimulus-response pairings cross the body midline, whereas incompatible above-below ones do not. Nicoletti and Umilt\ue0 (1985) proposed that the left-right dominance should be attributed to the allocation of attention to the more difficult discrimination, which, in vision, is that concerning the left-right dimension. This attentional hypothesis was tested in the present study, in which we used the auditory modality. We reasoned that because in the auditory modality the above-below discriminations are more difficult than left-right ones, attention should be preferentially allocated to the former. Therefore, in audition an above-below dominance should replace the left-right dominance observed in vision. Experiments 1 and 2 showed a clear-cut compatibility effect in the auditory modality for both the left-right and above-below dimensions. Experiment 3 showed that spatial compatibility was still stronger for the left-right than for the above-below dimension. Since the left-right one proved to be the more discriminable dimension, this finding rules out the attentional hypothesis, at least in the version originally proposed

Neurophysiological markers of retrieval-induced forgetting in multiplication fact retrieval

Event-related potential (ERP) counterparts of practice effects in multiplication fact retrieval were examined. Participants performed a multiplication verification task after having practiced a specific problem set. Practice was either active (retrieval of solutions to multiplication problems) or passive (reexposure to the same operands plus the correct result). Behavioral data showed retrieval-induced facilitation for practiced items and retrieval-induced forgetting for related, unpracticed items, irrespective of practice type. ERPs revealed that, for the active practice group, forgetting was reflected in a reduced N100 component time-locked to result onset. Irrespective of practice type, forgetting was also reflected in a reduced result-locked P350 component, whereas facilitation was associated with an increased amplitude of the same component. These results suggest that beneficial and detrimental effects of practice may be mediated by partially distinct processes