Presenting two incongruent color words on a single trial does not alter Stroop interference.

Two experiments showed that having two incongruent words present on a single Stroop trial (e.g., both red and green in blue, say "blue") did not alter interference relative to having only one incongruent word. This was true whether the two incongruent words were presented successively at several stimulus onset asynchronies (Experiment 1) or simultaneously in adjacent positions (Experiment 2). We argue that the first word captures attention and "locks out" others, preventing additional interference.