Measuring Stroop interference in the absence of response generation using the attentional blink
36.4043, Sunday, 17-May, 2:45 pm - 6:45 pm, Pavilion
Gregory Wade1, Brad Wyble1; 1Department of Psychology Penn State University
Stimulus-stimulus compatibility effects, such as Stroop interference, have been studied for many years as differences in reaction times when stimuli have varying levels of compatibility. However, it is not known whether such interference can be observed in the absence of a response, which would definitively answer questions about whether such interference can exist in a purely perceptual task. To answer this question we measured the difference in the attentional blink of a neutral word caused by a preceding word that was a congruent, incongruent or neutral Stroop stimulus. During the experiment, a fixation cross was presented at the beginning of each trial that was followed by the first target (T1) which was a congruent, neutral or incongruent word presented for 80 msec. On half of the trials, a mask was presented immediately after T1 for 80 msec. The second target (T2) was a neutral word that appeared at one of several latencies following T1 and was always masked. Participants reported the color of both words and always ignored the words themselves. Analyzing accuracy of the T2 on trials when the T1 was accurately reported, we observed a main effect of T1 congruence and an interaction between T1 congruence and inter-target lag. This revealed that the attentional blink was deeper for incongruent T1s. Surprisingly, omitting the first target mask did not reduce the effect of congruence. These results provide the clearest evidence yet that incompatible stimulus attributes reduce the speed of processing during stimulus identification, even in the complete absence of the need to generate a speeded motor response. These results also strongly support computational models in which the identification or encoding of a stimulus can be slowed by the presence of stimulus-stimulus conflict (Kornblum, Stevens, Whipple and Requin 1999; Wyble, Sharma, and Bowman 2008).