Attending is not enough: Responding to targets is needed for across-trial statistical learning.

Recent evidence shows that observers are able to learn across-trial regularities as indicated by faster responses to targets whose location was predicted by the target's location on the preceding trial. The present study investigated whether responding to both targets of the pair, as was the case in studies thus far, was needed for learning to occur. Participants searched for a shape singleton target and responded to the line inside. There were two across-trial predicting-predicted regularities regarding target locations: if the target appeared at one specific location on a given trial, it would appear at another specific location on the next trial. Unlike previous experiments, for one of these regularity pairs a response was only needed on either the first or the second target in the pair. Experiment 1 showed that across-trial learning only occurred when responding was required to both targets of a pair. If the response to one target of a pair had to be withheld, no learning occurred. Experiment 2 showed that the absence of learning cannot be attributed to carry-over inhibition resulting from not having to respond. After learning across-trial contingencies, learning remained in place even when the response to the first target of the pair had to be withheld. Our findings show that the execution of the (arbitrary) simple key-press response for both trials of the pair was needed for across-trial statistical learning to occur, whereas solely attending target locations did not result in any learning.