According to the threat-capture hypothesis, fear-related stimuli have a high attentional priority. As a result, irrelevant-but-salient stimuli interfere more with a visual search task when they are perceived as threatening. We investigated the neural basis for behavioral interference in conditions that promote attentional suppression of distracting stimuli (i.e., easy search with fixed target/distractor roles). In Experiment 1, participants discriminated the shape of a neutral target (a flower), which competed for selection with a threat-related (spider) or neutral (leaf) distractor. In line with prior results, we observed larger interference from spider than leaf distractors. At an electrophysiological level, we found that participants actively suppressed both distractors as evidenced by the presence of a posterior positivity between 200-300 ms, the PD. Critically, the PD was delayed with spider compared to leaf distractors. Further, in the spider distractor condition, the offset of the PD component correlated with response time to complete the search task when the spider was present. Experiment 2 was a control experiment where we confirmed that the results depended on the execution of the peripheral search task. When participants performed a localization task on the fixation cross, the decisive results from Experiment 1 were not replicated despite equal peripheral stimulation. Our results indicate that the behavioral delay incurred by threatening stimuli is accompanied by a delay of suppressive mechanisms. In contrast, we found no evidence for initial capture followed by suppression that may be predicted by hypervigilance-avoidance theory. Disgust 17.1 (5.4) 9.2 (5.2) 41.6 (6.8) Reaction Times and Accuracy. A one-way (distractor type: no distractor, spider distractor, leaf distractor), repeated-measures ANOVA revealed that RTs were shorter on distractor-absent than distractor-present trials (618, 640, and 633 ms for no distractor, spider distractor, and leaf distractor, respectively), F(2, 34) = 15.26, p < .001, ηp 2 = 0.473. Critically, a paired t-test revealed that RTs were longer with the spider than with the leaf distractor (640 vs. 633 ms), t(17) = 2.32, p = .03, Cohen's d = 0.55. Additionally, accuracy was lower in the distractor-present conditions (0.96, 0.95, 0.94 for no distractor, spider distractor, leaf distractor, respectively), F(2, 34) = 3.49, p = .042, ηp 2 = 0.171. However, there was no significant difference between spider and leaf distractors, t(17) = 1.22, p = 0.23. Electrophysiological results Global N2pc/PD Amplitudes (230-330 ms). The difference waves obtained by subtracting ipsi-from contralateral activity are shown in Figure 2A. The same ANOVA as above was conducted on mean difference amplitudes. A significant effect of distractor type was revealed, F(1.24, 21.10) = 49.15, p < .001, ηp 2 = .74. The voltage difference was negative to targets (-1.29 µV), consistent with an N2pc, but it was positive to spider (2.16 µV) and leaf (2.11 µV) distractors, consistent with a PD. There was no signi...
According to the threat-capture hypothesis, fear-related stimuli have a high attentional priority. As a result, irrelevant-but-salient stimuli interfere more with a visual search task when they are perceived as threatening. We investigated the neural basis for behavioral interference in conditions that promote attentional suppression of distracting stimuli (i.e., easy search with fixed target/distractor roles). In Experiment 1, participants discriminated the shape of a neutral target (a flower), which competed for selection with a threat-related (spider) or neutral (leaf) distractor. In line with prior results, we observed larger interference from spider than leaf distractors. At an electrophysiological level, we found that participants actively suppressed both distractors as evidenced by the presence of a posterior positivity between 200-300 ms, the PD. Critically, the PD was delayed with spider compared to leaf distractors. Further, in the spider distractor condition, the offset of the PD component correlated with response time to complete the search task when the spider was present. Experiment 2 was a control experiment where we confirmed that the results depended on the execution of the peripheral search task. When participants performed a localization task on the fixation cross, the decisive results from Experiment 1 were not replicated despite equal peripheral stimulation. Our results indicate that the behavioral delay incurred by threatening stimuli is accompanied by a delay of suppressive mechanisms. In contrast, we found no evidence for initial capture followed by suppression that may be predicted by hypervigilance-avoidance theory.
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