Contributed Session II: Neural correlates of serial processing during divided attention across multipart objects.

Abstract

Judgments of multiple simultaneously presented stimuli produce a variety of divided attention effects. For example, participants can detect colors in two locations as well as in one, but can recognize only one masked word at a time (White, Palmer, & Boynton, Psych Science 2018). Here, we ask whether judging objects with interchangeable parts, similar to letters in words, also produces performance deficits consistent with serial processing, and which brain areas subserve this process. In a probe recognition task, participants discriminated abstract objects made of Duplo™ parts. On each trial, two objects were presented, with either one or both objects cued as relevant (single- and dual-task conditions, respectively). The distractor probes were made of the same parts in a different order. The difference in performance between the single- and dual-task conditions was 17±1% (n=13), consistent with the prediction of a serial model and rejecting the fixed-capacity parallel model. This result suggests that there is a visual brain area where information can be processed about only one object at a time. Currently, we are using fMRI to examine activity in object-selective regions of the human lateral occipital cortex. To seek evidence of serial processing, we are assessing how stimulus-related modulation is mediated by selective attention; the area of interest should show a modulation for only the attended stimulus location.