Mechanism of Distractor Processing in Dynamic Inattentional Blindness: Is there Distractor Inhibition?

Abstract

Multiple object tracking (MOT) is a paradigm to study visual dynamic information processing. Studies with probe-dot detection task found that there was effective inhibition of the non-targets during the tracking process (Pylyshyn, 2006; Pylyshyn, Haladjian, King, Reilly, 2008; Flombaum, Scholl, Pylyshyn, 2008). Some other studies (Most et al., 2001; Most et al., 2005) also found that visual object was often neglected in dynamic information processing, which was called inattentional blindness (IB). Thus, it was proposed that similar processing mechanism underlying the inhibition of the non-targets was involved in the MOT and IB tasks. Some previous researches (Most et al., 2005; Koivisto Revonsuo, 2008) on dynamic IB did not find the inhibition of the distractors (non-targets and unexpected object). However, in their IB studies, they supposed that only the non-targets that were similar to the targets received inhibition, those that were distinguishable from the targets did not receive inhibition. Thus, maybe their research could not demonstrate whether there was distractor inhibition in dynamic IB task. Three experiments were designed in present study to examine selective distractor inhibition in dynamic IB task by controlling the color of the items. In experiment 1, the targets and non-targets were both white circles. If the results demonstrated that detection rate of unexpected black object was higher than that of unexpected white object, then the effect of inhibition was proved, but maybe the salient color feature caused higher detection performance of unexpected black object. In experiment 2, some of the non-targets were set to white circles, and others were black circles. And if participants’ performance on the detection of unexpected black object was better than that of unexpected white object, it suggested that participants had selectively inhibited the processing of the distractors. In experiment 3(a), all the non-targets were set to black circles to get rid of the salience of the color feature. If the results showed that the detection rate of unexpected white object was higher, it would validated the conclusion got from experiment 2, that was, distractor inhibition played an important role while finishing the targets tracking and counting task. And we added another experiment 3(b), in which the color of the items was totally opposite to that of the items in experiment 3(a), to further confirm the research hypotheses. The independent variable in the three experiments was the color of unexpected object (white or black), and there were two dependent variables: participants’ detection rate of the unexpected object on the critical trial and the error rate with which participants counted the number of bounces while the targets moving. Results of three experiments showed that participants’ detection rate of unexpected object was higher when the color of the unexpected object was different from the non-targets. The results suggested that we can use the idea of selective distractor inhibition to explain the dynamic IB phenomenon. Participants inhibited the processing of the distractors. As when there were different non-targets, distractors of different color received different level of inhibition; that was, distractors easy to differentiate from the targets in color received much less inhibition.