The Categorical Attentional Control In The Stroop Task

The conflict control could be regarded as the attentional control by nature, which is one of the most important human intelligence. In previous researches, two main strategies have been found in conflict control:enhancement of the target and suppression of the distracter. The suppression mechanism has got evidence from both behavioral researches and neuroimaging researches, however, there was only neuroimaging evidence for enhancement mechanism. Additionally, it is still unclear how attentional control influences stimulus processing.The purposes of the present research were twofold:to provide the first complete piece of behavioral evidence for enhancement and suppression mechanisms, and to investigate the influential scope of conflict control.We investigated this issue in three Stroop task experiments utilizing a pretest-training-posttest design. Subjects were given extensive training on the Stroop task using typical incongruent Stroop trials. The rates of color naming and word reading, which reflect the efficiency of stimulus processing, were assessed in pretest and posttest. The stimuli and tasks used in pre-and posttest were same, therefore, the difference in rates between posttests and pretests could reflect the influence of attentional control, acquired during the training phase, on stimulus processing, In order to value suppression mechanism and enhancement mechanisms separately, each experiment was divided into two sub-experiments. In Experiment 1, members of color category were used in the training phase. Specifically, in Exp.1A, suppression mechanism was investigated with reading tasks in pre-and posttest, and the test stimuli were white color words which were the same as the training words; in Exp. 1B, enhancement mechanism was investigated with color naming task in pre-and posttest, and the test stimuli were colored XXX strings whose colors were the same as the trained colors. In Experiment 2, members of color category were used, but not in the training phase. Similar to Experiment 1. suppression mechanism was examined in Exp.2A and enhancement mechanism was examined in Exp.2B. To be more exact, test stimuli in Exp.2A were untrained color words which were printed in white, and test stimuli in Exp.2B were XXX strings which were printed in untrained colors. In Experiment 3 test stimuli were neither in the color category nor were they used in the training. Enhancement and suppression mechanisms were explored in Exp.3A at the same time, with test stimuli being white neutral words and task being word reading task. Enhancement of the neutral color (i.e., white), or suppression of the neutral words, or both could delay the word reading in posttest. Exp.3B further excluded an alternative explanation for the results of Exp.3 A.The results consistently showed that the suppression of word reading and the enhancement of color naming were developed in the training phases (Exp.1 and Exp.2). More importantly, both suppression and enhancement affected the members of color category regardless of whether they were trained or not (Exp. 1 and Exp.2), and would not affect the members out of color category (Exp.3). The present findings suggest that the influence of attentional control on stimulus processing is category specific. We discuss the implications of the present results in terms of existing research on the locus of attentional control in Stroop tasks.