What is cued by faces in the face-based context-specific proportion congruent manipulation?

In a typical context-specific proportion congruent manipulation, participants are presented with Stroop stimuli in one of two contexts. In one context, stimuli are mostly incongruent. In the other context, stimuli are mostly congruent. Despite task-wide instructions to ignore the word and to name the color in which the word appears, the size of the congruency effect varies as a function of context. Specifically, the size of the congruency effect is reduced for the mostly incongruent relative to the mostly congruent context. The purpose of the current series of experiments is to explore the mechanisms underlying this context-specific proportion congruent (CSPC) effect when faces are used as the context. Existing manipulations have reported a face-based CSPC effect, however the results of these studies are confounded with contingency learning biases leaving an open question as to what processes faces serve to cue. In the four experiments reported here both inducer (contingency-biased) and diagnostic (contingency-unbiased) stimuli were included in a face-based context level manipulation. Across four experiments, a face-based CSPC effect is observed for inducer but not diagnostic stimuli, suggesting that this effect is driven by participants learning context + stimulus associations.