Delayed disengagement from irrelevant fixation items: Is it generally functional?

In a circular visual search paradigm, the disengagement of attention is automatically delayed when a fixated but irrelevant center item shares features of the target item. Additionally, if mismatching letters are presented on these items, response times (RTs) are slowed further, while matching letters evoke faster responses (Wright, Boot, & Brockmole, 2015a). This is interpreted as a functional reason of the delayed disengagement effect in terms of deeper processing of the fixation item. The purpose of the present study was the generalization of these findings to unfamiliar symbols and to linear instead of circular layouts. Experiments 1 and 2 replicated the functional delayed disengagement effect with letters and symbols. In Experiment 3, the search layout was changed from circular to linear and only saccades from left to right had to be performed. We did not find supportive data for the proposed functional nature of the effect. In Experiments 4 and 5, we tested whether the unidirectional saccade decision, a potential blurring by adjacent items, or a lack of statistical power was the cause of the diminished effects in Experiment 3. With increased sample sizes, the delayed disengagement effect as well as its functional underpinning were now observed consistently. Taken together, our results support prior assumptions that delayed disengagement effects are functionally rooted in a deeper processing of the fixation items. They also generalize to unfamiliar symbols and linear display layouts.