Color as a gate to verification: Super-additive costs in oculomotor disengagement

Visual search theories distinguish between attentional capture and disengagement, yet how multiple feature dimensions combine to delay disengagement remains unclear. This study investigated whether shared features (color, shape, object category) produce additive or super-additive costs in oculomotor disengagement. Forty-three participants performed a delayed-disengagement task where a central fixated stimulus shared zero to three features with a peripheral target. Saccadic latency (SL) served as the index of disengagement cost. Results showed that SL increased nonlinearly with the number of shared features, following a quadratic trend. A component decomposition revealed that this acceleration was driven primarily by color: Color overlap produced large main effects, whereas shape and object-category overlap produced costs primarily when combined with color. Our findings suggest that disengagement is not a simple summation of feature similarities. Instead, color may act as a high-priority gate: A color match may open a capacity-limited verification stage in which each additional shared feature disproportionately prolongs inspection. We interpret these findings in terms of a candidate hierarchical gating account, in which high-salience features such as color may govern entry into verification.