Prior Entry for Feature-based Attention: Are Objects of the Attended Color Perceived Earlier?

Prior entry refers to the hypothesis of attended objects being perceived prior to unattended objects. In the current study, we employed the paradigms of temporal order judgment (TOJ) and simultaneity judgment (SJ) to investigate prior-entry effects for objects of the attended feature (color). Stimuli comprised two differently oriented bars equidistant from fixation, presented either simultaneously or successively, with a variable stimulus-onset asynchrony between them. Color feature cues preceded the stimuli with variable cue lead-time. To reduce the confounding effect of response bias, we employed an orthogonal judgment method in the TOJ task: observers reported the temporal order based on the orientation, rather than the color of the stimuli. Using the TOJ paradigm, significant prior-entry effect based on attending to the color feature was/ was not observed when observers performed/did not perform an attentional task on the color cue. A similar trend of effect was observed with the SJ paradigm, but the effect was not statistically significant. One possibility is that there are separate mechanisms subserving TOJ and SJ tasks, and the mechanism underlying the TOJ task is more likely to reveal prior-entry effect.