Eager inhibition, lagging enhancement: The time course of selective attention

Foreknowledge of target features biases attention toward those features even before search begins, indicating proactive activation of the target template. However, whether foreknowledge of distractor features leads to proactive inhibition remains debated, raising questions about whether target and distractor templates operate through similar mechanisms. The current study investigated this by presenting multiple task-irrelevant singleton probes before search display onset, combined with EEG. The probes either matched the color of the target, the distractor or had a neutral color. If a feature-specific template is activated proactively, we expect to see a reliable probe N2pc-modulation: With target template enhancement, probes matching the target color should elicit a more pronounced N2pc than neutral probes, whereas a distractor template inhibition should lead to an opposite pattern. In line with this prediction, results showed that the target-colored probes produced a more pronounced N2pc, with the largest amplitude for the last probe in the sequence, suggesting an increasing template activation from probe 1 to 4. Distractor-colored probes elicited a less pronounced N2pc than neutral probes at the first probe, suggesting an inhibited template activation at the start of the preparation. Both ERP and decoding results time-locked to search display onset showed that foreknowledge of the target color facilitated target selection, reaching its peak after 200 ms. Foreknowledge of the distractor color allowed active distractor inhibition within the first 200 ms and then vanished quickly. Taken together, separate temporal profiles during preparation and search support distinct mechanisms for target selection and distractor rejection in visual search.