EXPRESS: Two minds don't boost together: Target detection enhances the recognition of self-relevant, but not other-relevant, items.

In the Attentional Boost Effect (ABE) participants recognize stimuli paired with targets to which they responded during the encoding phase better than stimuli paired with distractors that they ignored. Based on previous evidence indicating that the simulation of a motor action can enhance the incidental encoding of study words (the Joint Memory Effect: JME), we asked whether the ABE could be likewise triggered by simply observing the responses provided by a co-actor in a joint-action condition. In Experiment 1, pairs of participants studied words paired with self-relevant squares (to which they were to respond), other-relevant squares (to which the co-actor responded) and non-task-relevant squares (to which neither of them responded). Experiment 2 used a variation of this paradigm aimed at reducing the possibility that participants disengaged their attention from the encoding of other-relevant words, in which turns were dictated by the colors of the words (rather than by the colors of the squares). Experiments 1 and 2 used recognition memory, the standard assessment of the ABE. Experiment 3 examined the generalizability of the results to a final test of free recall. In all experiments, the results converged in showing that the ABE was significant for self-relevant trials (participants recognized self-relevant words better than non-task-relevant words), but not for other-relevant trials (participants recognized other-relevant and non-task-relevant words equally well). The findings are discussed in terms of revised version of the dual-task interaction account of the ABE, and the social-epistemic account of the JME.