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Is spatial uncertainty necessary for the context specific proportion congruency effect?

Bozkurt, Özge
Cognitive control is generally measured with the Stroop effect which is signified by slow responses in the incongruent (the word and color mismatch) items. The magnitude of the Stroop effect is modulated by experimental manipulations, for instance it is reduced by presenting items in mostly incongruent contexts as compared to mostly congruent contexts. The difference between the Stroop effects observed in these contexts is called the context specific proportion congruency (CSPC) effect. A large number of CSPC studies used the rather unconventional prime-probe version of the Stroop task. By its very nature, this version creates spatial uncertainty for the color dimension, since the word dimension is presented at the center of the screen, while the color dimension is presented at the bottom or top half of the screen. We speculated that this uncertainty might have contributed to the CSPC effect. For this reason, the current study aimed to examine the role of uncertainty on the CSPC effect. With two systematic manipulations, it was aimed to eliminate the uncertainty of the color dimension in one condition, and both the color and word dimension in the other. It was hypothesized that both manipulations would lead to the elimination of the CSPC effect. According to results, although the CSPC effect was not observed in the first condition, it was still observed in the second. These results partially support the hypothesis that uncertainty played a significant role in the CSPC effect. Findings were discussed under the scope of spatial attention and evidence accumulation perspectives.