How Inflexible Is the Attentional Bias Toward Recently Selected Locations?

Attention is strongly biased toward the location where a previous target was recently found. This priming-of-location (PoL) effect is taken to indicate that 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. Here, we tested this prediction. In Experiments 1 and 2, we manipulated task context by interleaving search trials (2/3) where participants searched for a shape target, search-probe trials where they reported letters briefly superimposed on the search display after a short delay, and probe trials where only the to-be-reported letters appeared. We measured PoL on probe reports when the task context repeated (search -> search-probe sequences) and when it changed (search -> probe sequences). We found PoL to be insensitive to task changes, indicating that attention is proactively guided to previously selected locations by default, even in variable task environments. We then examined whether expectations about the upcoming task modulate PoL by inverting the task probabilities (2/3 probe trials and 1/3 search trials) in Experiment 3 and by informing participants with 100% validity as to what their next task would be, in Experiment 4. We found PoL to decline sharply as the expectation of a task change increased. We conclude that PoL is proactive but flexible. We discuss two possible mechanisms to explain these findings: proactive attenuation and proactive retrieval, both of which entail that priorities from previous selections are reduced as a by-product of participants' reconfiguring their task set.