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Background. Incidental " ndings are items of visual search that are potentially of signi" cance, but were not the main object of the initial search. ! ey have been previously widely discussed in the " eld of radiology. However, the underlying perceptual mechanisms of such phenomenon are still unclear. Objective. ! e current study aims to examine incidental " ndings in di# erent paradigms of visual search in order to reveal their primary perceptual aspects. Design. Two behavioral visual search experiments were conducted. ! e mixed hybrid search task model was used in the " rst experiment, while the subsequent search miss e# ect was employed in the second experiment. ! e task was to " nd targets among distractors, according to given instructions. Stimuli material consisted of images of real-life objects that were randomly distributed across the screen for each trial. Results. Accuracy and reaction time of the participants were analyzed in both experiments. Similar e# ects were observed for both parameters. Speci" c targets in the " rst experiment and typical targets in the second experiment were found signi" cantly faster and more accurately in comparison to categorical and atypical targets. Moreover, this tendency did not depend on the order of target identi" cation. Hence, the prevalence of the targets was revealed to be the primary factor in the case of incidental " ndings. Conclusion. ! e study revealed the emergence of incidental " ndings in both experiments. Typical or speci" c targets were detected signi" cantly more accurately, compared to atypical or categorical targets. Subsequent search misses were not detected, suggesting that target prevalence could be a crucial factor that is speci" c for incidental " ndings.

Subsequent search misses refer to the decrease in accuracy of second target detection in dualtarget visual search. One of the theoretical explanations of SSM errors is similarity biasthe tendency to search for similar targets and to miss the dissimilar ones. The current study focuses on both perceptual and categorical similarity and their individual roles in SSM. Three experiments investigated the role of perceptual and categorical similarity in subsequent search misses, wherein perceptual and categorical similarity were manipulated separately, and task relevance was controlled. The role of both perceptual and categorical similarity was revealed, however, the categorical similarity had greater impact on second target detection.

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