Tied to expectations: Predicting features speeds processing even under adverse circumstances

When participants predict the upcoming stimulus in a randomized choice reaction task, a match between prediction and stimulus increases processing speed at a level similar to that observed in cueing studies with highly valid cues. This might be taken to suggest that people cannot help but fully use their self-generated, verbalized predictions for preparing task processing. Thus, we tested how flexibly participants can control formation and implementation of predictions. In Experiment 1, we varied validity and response-relevance of predictions. We observed that prediction effects on RT can be boosted by increasing validity, but prevail under adverse circumstances. This was not the case in a control group who read rather than predicted the feature words, suggesting that the effect was specific to predictions as such. Experiment 2 provided further evidence for limited control of participants over implementing and forming predictions. Participants were provided with practice on stimuli occurring with varying frequency, but neither learned to strategically choose predictions to maximize the number of match trials, nor did they reduce the amount of prediction-based preparation when predicting an infrequent stimulus. As sequential aftereffects of prediction match did not vary with validity, they were identified as an independent effect of verbalizing a response-relevant stimulus feature. The results are consistent with the view that the predicted stimulus feature is represented in the focus of attention in working memory and that the amount of implementation can be subject to weighting.