Abstract
In a series of seven experiments this study examined the effect of similarity — among targets, among distractors, and across targets and distractors — on visual target detection in the redundant target design (RTD). A pair of stimuli can be same in (at least) three ways: physically (AA), nominally (Aa) or semantically (AE). The issue of similarity of the pertinent stimuli has drawn considerable attention in studies of same-different judgment (SDJ) and visual search, but has been neglected in studies of RTD. In particular, nominal sameness has not been addressed within RTD. The mission of this work was to redress this situation.
Target-distractor similarity: Performance deteriorated to a comparable extent when the distractor went by the name of the target, or when it resembled the physical appearance of the target. Observers likely processed the nominal attributes of the stimuli, although it was gratuitous to the task at hand. Target-target similarity: Detection of double-targets was faster when the two targets in the display were identical than when they were physically distinct. Distractor-distractor similarity: Rejection of distractor pairs was fastest when the stimuli were physical replicas, again, demonstrating superiority for physical sameness.
The analysis was augmented by the mathematical tools offered by Systems Factorial Technology. Two rival modes of processing, serial and parallel, accounted for selected portions of the data. I adapted for the RTD a hybrid model with two processors — a fast parallel processor, and a slower serial processor — that has been suggested in studies of visual search and SDJ.
Collectively, the results show that similarity, notably common names, must be taken into consideration in studies of RTD. Performance is fastest with physical sameness. However, nominal sameness, hitherto unexamined in RTD, affected performance to a great extent. People activate the names of the stimuli and these names affect their detection.
This research is supported in part by a strategic training grant - communication and social interaction in healthy aging, and a group grant on sensory and cognitive aging, both funded by CIHR.