Abstract: PURPOSE: How do people allocate attention to upcoming distractors? Some studies have shown that individuals can proactively suppress the spatial locations or features of distractors (e.g., Gaspelin et al., 2015). On the contrary, some research has indicated that participants will allocate more attention to expected distractors under certain conditions, even when they have prior knowledge of what the distractors look like (Tsal & Makovski, 2006; Moher & Egeth, 2012). This is known as the attentional white bear (AWB) phenomenon. In recent years, several studies have found the AWB effect even when distractors and targets were presented at different times (Chen et al., 2023; Makovski, 2019). However, since the AWB effect was usually examined through probe tasks which had a certain probability in these studies (e.g., 25%), it is possible that the observed AWB effect resulted from enhanced attention to the possible dot probes rather than the distractors. To address this issue, this study aims to investigate whether there is an enhancement of attention prior to the presentation of irrelevant distractors when they are temporally separated from the target, especially when participants do not expect the probes at all.
METHODS: We conducted three experiments in this study. In Experiment 1, each participant was required to complete two blocks of memory trials (using change detection task). During the memory retention interval, an irrelevant distractor array was presented 800 ms after the memory array offset in the distractor-present block, but not in the distractor-absent block. Additionally, in a small proportion (10%) of trials, participants were asked to respond to a probe dot that was displayed at the expected distractor appearance time. By comparing participants' reaction times to the probe dots between the two blocks, the allocation of attention to the distractors could be inferred. In order to completely eliminate the confounding effects caused by the presence of the dot probe, in Experiment 2 we substituted the dot-probe task by a new surprise task. The experiment consisted of 48 trials, with the first 43 trials being memory trials same as Experiment 1. Participants were divided into two groups, one performing the memory task with distractors and the other without distractors. In the last five trials (surprise trials), an unexpected visual search task was presented at the time when distractors were supposed to appear, requiring participants to look for a stimulus different in size from the others. The impact of distractor presentation on attentional allocation could be examined by comparing the performance of the two groups of participants in the surprise trials. Experiment 3 employed a similar surprise task design to validate the results of Experiment 2, but replaced the surprise task with a detection task for memory items, in which participants were asked to recall the location of a color that had been presented in the memory array on that trial.
RESULTS: Experiment 1 revealed that participants responded significantly faster on the probe detection task in the distractor-present block (785 ms) than distractor-absent block (868 ms), t(28) = 3.222, P = 0.003, indicating a stronger allocation of attention before the presentation of expected distractors. This result replicated the presence of the AWB effect under a low probability of probe presence. In Experiment 2, participants in the distractor-present group had higher accuracy in the surprise trials (65.0%) compared to those in the distractor-absent group (30.0%), χ² (1) = 4.912, P = 0.027, which suggests that participants in the distractor-present group enhanced their attention prior to the distractors, leading to better performance in the surprise task. This result confirms the ABW effect even under conditions where the probes are totally irrelevant to the task. Experiment 3 exhibited the opposite pattern relative to Experiment 2, with a lower accuracy (5.88%) in the distractor-present group than that in the distractor-absent group (41.18%), χ² (1) = 5.885, P = 0.039. The result demonstrates that the distractor-present group allocated enhanced attention before the distractor display, resulting in interference in retrieving memory items. Therefore, Experiment 3 further supports the stable existence of the AWB effect.
CONCLUSIONS: By employing multiple experimental paradigms and conditions, this study demonstrated the stable existence of the AWB effect when irrelevant distractors were temporally separated from the target. When participants anticipate an upcoming distractor, they will allocate more attention to it, resulting in altered task performance at that moment even if they do not expect the task. These findings reveal how people prepare for irrelevant distractors, and provide new evidence for the AWB effect. The study also contributes to a deeper understanding of the underlying mechanisms governing attentional control over interfering information.

Key words: attentional white bear, selective attention, attentional enhancement, working memory task