Interstimulus Interference Effect with Stroop-Type Stimuli
The interstimulus interference in reacting to Stroop-type stimuli was investigated. Two aspects of the interstimulus organisation were analysed: the serial structure of the items in the test sheets and the spatial structure of the items on different test sheet types. More difficult serial structures were expected in cases where the correct colour-naming response to an incongruous combination was the suppressed word-naming response of either the previous or the next incongruous stimulus. Variation in the spatial organisation of the items was aimed at causing different opportunities for perceiving several adjacent items at once. As a third factor the study included not a characteristic of the test material, but a related cognitive style variable—the field dependence/independence, measured by a version of the Gottschaldt embedded figures. Every test condition (printed words in incongruous colours) was matched with a control condition (patches of colour) in a double-mirror design. A factorial design of 2 × 3 × 3 was applied and the data were processed with the aid of a three-way ANOVA. The results confirmed the importance of the interstimulus organisation of multiple Stroop-type stimuli. It is inferred that the extent to which perceptual and, in particular, selective-attention processes affect Stroop colour naming performance might be only a fraction of the whole interstimulus and intrastimulus interference effect.