Abstract
Subsequent search misses (SSM) effect is the decrease in accuracy of second target detection after finding the first target in visual search task. One of the SSM explanations considers that searchers are likely to become biased towards targets that share similar features with the initially found target. One study (Biggs et al., 2015) revealed the role of both perceptual and conceptual similarity in SSM errors. The main focus of the current study was to experimentally separate categorical and perceptual similarity in order to discover their individual contribution to SSM. Participants' task was to search for targets of vertical orientation among differently oriented distracters. Targets and distracters were uppercase and lowercase letters of Russian alphabet. On each trial, it could be one, two or no targets. In dual-target trials, targets could have both perceptual and categorical similarity, only perceptual similarity, only categorical similarity, or neither perceptual, nor categorical similarity. Perceptual similarity was manipulated by color (same or different), categorical similarity was manipulated by letter identity (targets could be the same letter - one was uppercase and another was lowercase, or different letters). Accuracy and reaction time were analyzed. Two-way rmANOVA tested the effects of perceptual and categorical similarity. Dual-target trials were also compared to matched single-target displays. Categorical similarity had a significant effect on second target detection: categorically similar second targets were found better as compared to categorically dissimilar ones. No main effect of perceptual similarity was found in the second target detection accuracy, except the case of categorically dissimilar targets. SSM effect was observed for perceptually, but not categorically similar targets and for dissimilar targets. For reaction time, categorical and perceptual similarity effects were significant. Overall, both categorical and perceptual similarity had the impact on SSM errors, and the effect of categorical similarity revealed its superiority over the perceptual similarity.