Modulations of Response Activation Contribute to Block-Wide Control: Evidence From Proportion Congruency Effects in the Prime-Probe Task

Distractor-related congruency effects are smaller in blocks of mostly incongruent (vs. mostly congruent) trials. It remains unclear, though, how control processes produce this proportion congruency effect (PCE). The attentional shift account posits that experiencing conflict more frequently in mostly incongruent (vs. mostly congruent) blocks biases control processes to shift attention away from the distractor. The response modulation account posits that, if participants identify the distractor before the target, control processes use the distractor’s identity to prepare a congruent response in mostly congruent blocks and/or an incongruent response in mostly incongruent blocks. We conducted four experiments (N = 192) to investigate whether a modulation of response activation contributes to the PCE in the prime-probe task. We observed a larger PCE when the prime/distractor appeared 166 ms before (vs. simultaneously with) the probe/target (Experiment 1) and a PCE without an overall congruency effect at a longer, 933-ms stimulus onset asynchrony (SOA; Experiment 2). Critically, the latter PCE was associated with a negative congruency effect in mostly incongruent blocks, consistent with a modulation of response activation but not a shift of attention. Finally, in a modified prime-probe task, wherein participants respond to each stimulus before the next one appears (1,133 ms SOA), we observed analogous PCEs and negative congruency effects (Experiment 3) and a PCE-like effect in response force just before the probe appeared (Experiment 4). These findings indicate an independent contribution of control processes that modulate response activation to the PCE at long prime-probe SOAs, which extends beyond minimizing distraction from irrelevant stimuli.