Context affects implicit learning of spatial bias depending on task relevance

Recent studies on the probability cueing effect have shown that a spatial bias emerges toward a location where a target frequently appears. In the present study, we explored whether such spatial bias can be flexibly shifted when the target-frequent location changes depending on the given context. In four consecutive experiments, participants performed a visual search task within two distinct contexts that predicted the visual quadrant that was more likely to contain a target. We found that spatial attention was equally biased toward two target-frequent quadrants, regardless of context (context-independent spatial bias), when the context information was not mandatory for accurate visual search. Conversely, when the context became critical for the visual search task, the spatial bias shifted significantly more to the target-frequent quadrant predicted by the given context (context-specific spatial bias). These results show that the task relevance of context determines whether probabilistic knowledge can be learned flexibly in a context-specific manner.