Behavioral and Electrophysiological Evidence for Intertrial Priming of Pop-out in Touch.

In mixed-features search tasks, the target-defining feature changes unpredictably across trials. Responses are faster when the same feature is repeated across successive trials. This effect, known as intertrial priming of pop-out (PoP), suggests that the selection of a perceptually salient singleton target is modulated by the properties of the preceding search array. To investigate whether PoP can be observed in touch, we developed a mixed-features search task in which a singleton target was presented simultaneously with three homogeneous distractors to the index and middle fingers of the left and right hands. The target-defining vibrotactile frequency varied across trials (either a high-frequency target among low-frequency distractors or vice versa) so that on half of the trials, the singleton frequency was repeated on successive trials, while on the other half, it was alternated. To investigate the presence and the mechanisms underlying PoP in touch, behavioral and ERPs were recorded. Specifically, the N140cc component was used as a marker of spatial selective attention in touch. In line with visual search studies, improved performance for both RTs and accuracy was observed when the singleton target feature was repeated across trials than when it was alternated. Importantly, the N140cc component showed larger amplitudes on repetition compared with change trials, demonstrating that the attentional selection of a tactile target was modulated by PoP. Results demonstrate for the first time that PoP effects emerge also during the search for a tactile target.