Global feature-based suppression without local target competition

Feature-based attention (FBA) enables the prioritization of behaviorally relevant stimulus features across the visual field by enhancing processing of attended and suppressing unattended information. While global amplification of attended features is well established, it remains unclear whether suppression of unattended features reflects a global mechanism or depends on local spatial competition with attended stimuli. Here, we tested whether suppression of unattended colors requires direct local competition with the attended color. Participants performed a feature-based attentional shifting task while viewing centrally task-relevant and peripherally task-irrelevant, frequency-tagged random-dot kinematograms. By systematically varying the combination of attended and unattended colors in the periphery, we isolated the conditions under which suppression emerges. Steady-state visual evoked potentials were used to track neural modulations in early sensory processing. As expected, cueing a particular color led to robust global amplification of the attended color. Critically, unattended colors were suppressed globally irrespective of whether they were presented together with the attended color. These findings demonstrate that suppression of unattended features does not require direct competition with the attended feature. FBA operates via global allocation of attentional resources that enhances attended features while suppressing non-attended features, consistent with accounts combining feature-similarity gain and biased competition.