Top-down modulation of gaze capture: Feature similarity, optimal tuning, or tuning to relative features?

It is well-known that we can tune attention to specific features (e.g., colors). Originally, it was believed that attention would always be tuned to the exact feature value of the sought-after target (e.g., orange). However, subsequent studies showed that selection is often geared towards target-dissimilar items, which was variably attributed to (1) tuning attention to the relative target feature that distinguishes the target from other items in the surround (e.g., reddest item; relational tuning), (2) tuning attention to a shifted target feature that allows more optimal target selection (e.g., reddish orange; optimal tuning), or (3) broad attentional tuning and selection of the most salient item that is still similar to the target (combined similarity/saliency). The present study used a color search task and assessed gaze capture by differently coloured distractors to distinguish between the three accounts. The results of the first experiment showed that a very target-dissimilar distractor that matched the relative color of the target but was outside of the area of optimal tuning still captured very strongly. As shown by a control condition and a control experiment, bottom-up saliency modulated capture only weakly, ruling out a combined similarity-saliency account. With this, the results support the relational account that attention is tuned to the relative target feature (e.g., reddest), not an optimal feature value or the target feature.