Abstract
Feature-based attention has been shown to produce faster reaction times but not to improve accuracy for cues presented at fixation. However, shape-based attention is likely a higher level process and may be more susceptible to central cueing effects. In a 6AFC task, observers identified target numbers among letter distractors across time ranges spanning involuntary and voluntary attention. Two independent types of accuracy measures are investigated: the standard location judgment used in most published research which in this task is not subject to response bias, and an identification judgment. In addition, a multinomial model has been developed as a means of measuring and subtracting out response bias to the cued shape (number). The multinomial model allows investigation into how response processes (perceptual or decisional) such as response bias vary between cueing conditions (valid vs invalid), across attention systems, and between and within subjects over the course of the experiment. A non-informative (17% valid) numeric pre-cue was presented at the central fixation location followed by a circular array of 100% contrast alphanumeric characters (1° x 1°) presented at 7.5° eccentricity. The array contains one target number and 5 distractor letters and is followed by masking letters. Cue to mask onset time was varied from 110 to 350ms. Involuntary attention was examined for trials with less than the length of time required to voluntarily shift attention via an eye movement (~200ms). Intervals longer than this are believed to include involvement of voluntary attention. Across all subjects, involuntary and voluntary capturing of attention via a non-predictive central cue improved response accuracy for identifying the target location and identity. The level of abstraction in shape-based cueing may account for this difference from feature-based attention.
Meeting abstract presented at VSS 2013