'Pseudoextinction': Asymmetries in simultaneous attentional selection
We report robust visual field asymmetries associated with selectingsimultaneous targets. One letter embedded in a rapid serial visual presentation(RSVP) of letters was encircled by a white ring, cueing it as the target to report. In some conditions, 2 RSVP streams were presented concurrently, and targets appearedsimultaneously in both. When only 1 stream was cued, performance was similarregardless of whether it was in the left or right visual field. Cueing 2 streams barelyaffected performance in the left stream, but performance in the right stream sufferedmarkedly. We term this phenomenon pseudoextinction, by analogy to pseudoneglectwhereby observers bisect lines to the left of center. Such attentional asymmetries areoften believed to originate from a processing imbalance between the 2 cerebralhemispheres. But pseudoextinction also occurred with vertically arrayed streams, withhigher efficacy in the superior than in the inferior stream. Mixture modeling of errorsindicated that pseudoextinction did not affect the temporal precision or latency ofselection episodes; rather, only the efficacy of selection suffered. These findings leadus to suggest that pseudoextinction arises because perceptual traces are activatedsimultaneously in a visual buffer but must be tokenized serially. Observers succeed inselecting simultaneous targets because trace activation occurs in parallel. However,observers often fail to report both targets because tokenization proceeds serially:While 1 target is being tokenized, the other’s trace may decay below the activationlevel necessary for tokenization.