Effects of selective and divided attention arise from either serial or parallel processing depending on the task

Thesis (Ph.D.)--University of Washington, 2021Visual attention involves selecting relevant information for further processing. In selective attention, a single stimulus is selected while distractors are filtered out. In divided attention, multiple stimuli are selected. Both types of visual attention have been described by two competing theories: selective perception or selective decision. Selective perception can be described as a process in which attention enhances perceptual encoding. Selective decision can be described as a process in which attention influences decision making. Within these two broad theories, there are specific models. This dissertation focuses on distinguishing serial models of attention, in which only a single stimulus is processed at a time, and parallel models of attention, in which multiple stimuli are processed at the same time. The first two experiments of this dissertation asked whether selective attention is accounted for by a serial or a parallel process. In the first experiment, selective attention to Gabor patches was measured using the partially valid cueing paradigm where a cue indicated the location where a stimulus was most likely to appear. Results of this experiment indicate that selective attention for simple stimuli, such as Gabor patches, is consistent with selective decision and a model that assumes parallel processing for perception. In the second experiment, selective attention to masked words was measured using partially valid cueing. For this more complex stimulus, selective attention was consistent with an all-or-none serial model for perception. The final experiment asked whether divided attention to moving stimuli is accounted for by the all-or-none serial model or fixed-capacity parallel model . Divided attention was measured using the multiple object tracking paradigm. Results of this experiment were not consistent with either model, but elaborations of either model can account for the results. Together, the results of this dissertation indicate that the mechanisms underlying selective and divided attention depend on the stimulus being attended