Abstract
The flanker task requires selective attention to identify target objects among task-irrelevant distractors, or flankers. When the target and flankers are associated with different responses (incongruent), participants are reliably slower than when flankers are not associated with a response (neutral). This interference effect suggests that incongruent flankers impair target processing. In comparison, when the target and flankers are associated with the same response (congruent), participants can be faster than on neutral trials, suggesting enhanced target processing; however, this facilitation effect is usually small when present. To better understand facilitation and interference effects, we used mouse-tracking to record real-time response dynamics. In three experiments, participants were presented with five colored discs and instructed to respond by moving the mouse cursor to one of two response locations based on the color of the central target object (yellow or blue). Each experiment included congruent, neutral, and incongruent conditions. We also included close-congruent and close-incongruent conditions where flanker colors were 15° (Exp2) and 30° (Exp3) away in color space from the task-relevant colors. We found (1) interference for both mouse curvature and RT in all experiments, (2) facilitation for curvature in all experiments, but only in Exp1 and Exp3 for RT, and (3) a significant effect of similarity: Congruent-close trials showed significant facilitation for curvature at 15° (Exp2) but not at 30° separation (Exp3). For 30° separation on incongruent trials (Exp3), we also found interference, indicating that the magnitude of interference is larger than facilitation. Together, our results showed (1) facilitation can be reliably measured with a mouse-tracking method that is more sensitive to response selection dynamics, and (2) interference is more robust than facilitation: Interference persisted even when the flankers were 30° away from the incongruent color while facilitation was not observed at this separation.