Reducing and restoring stimulus-response compatibility effects by decreasing the discriminability of location words

Abstract

In two experiments, we compared level of activation and temporal overlap accounts of compatibility effects in the Simon task by reducing the discriminability of spatial and non-spatial features of a target location word. Participants made keypress responses to the non-spatial or spatial feature of centrally presented location words. The discriminability of the spatial feature of the word (Experiment 1), or of both the spatial and non-spatial feature (Experiment 2), was manipulated. When the spatial feature of the word was task-irrelevant, lowering the discriminability of this feature reduced the compatibility effect. The compatibility effect was restored when the discriminability of both the task-relevant and task-irrelevant features were reduced together. Results provide further evidence for the temporal overlap account of compatibility effects. Furthermore, compatibility effects when the spatial information was task-relevant and those when the spatial information was task-irrelevant were moderately correlated with each other, suggesting a common underlying mechanism in both versions.

Figure 1

Response time (RT) and percent error (PE) with standard errors for compatible and incompatible trials in the Simon task in Experiments 1 and 2. The discriminability of the spatial information (word legibility) was either high or low.

Figure 2

Scatterplot with regression lines for Z-scores of compatibility effects in the high-discrimination conditions of the SRC and Simon tasks in Experiment 1 (open circles, solid line) and Experiment 2 (filled circles, dotted line).

Figure 3

Compatibility effects at each response time quartile for high (filled circles) and low (open circles) stimulus discriminability conditions in the Simon task in Experiments 1 and 2. Exp 1 = task-irrelevant feature discriminability manipulated, Exp 2 = task-irrelevant and task-relevant discriminability manipulated.