How inflexible is the attentional bias towards recently selected locations?

Attention is strongly biased towards the location where a previous target was recently found. This priming-of-location (PoL) effect is thought to reflect a primitive mechanism by which selecting an object automatically and proactively enhances the attentional priority at its location. This account predicts that PoL should be unaffected by changes in task context. However, in most previous PoL studies the task context remained constant. Here, we tested this prediction using a probe paradigm. We manipulated task context by interleaving search trials where participants searched for a shape target among nontargets (2/3 of trials), search-probe trials where they reported letters briefly superimposed on the search display after a short delay (1/6), and probe trials where only the letters appeared (1/6). In Experiments 1 and 2, we found that a letter was more likely to be reported when it appeared at the previous target location than elsewhere. Crucially, this bias was similar when task context repeated (search→search-probe sequences) and when it changed (search→probe sequences). However, in these experiments participants expected a search task on most trials. Therefore, when the context changed, the expected context did not. In Experiment 3, we reversed the task probabilities (probe task on 2/3 of the trials) and in Experiment 4, we used an AABB design, such that the upcoming task was known with 100%-certainty. The bias to report the letter from the previous target location was reduced as the task-change expectation increased. Interestingly, in probe->search sequences, RTs in the search task were faster when the target appeared at the location of a previously reported letter than elsewhere, in all experiments - but this effect was not modulated by task-change expectations. Overall, our findings indicate that selecting an object proactively enhances the attentional priority at its location but expectations about the tasks' context reduce this bias.