Associative memory test

Upon completing the associative learning phase, participants performed the post-learning scans. Then, a surprise memory test was given. In each trial, participants were presented with an A face that appeared at the top of the screen (either famous or novel) and three B faces that appeared at the bottom of the screen, one of which had been paired with the A face during the learning session. All three faces were intralist within the pair type (i.e., if an A face was famous, the two distractors were B faces that appeared with other famous faces). The allocation of the distractors was pseudorandomized such that a triad of the same B faces could not appear twice throughout the test. One-third of the B faces appeared as targets in their first presentation, one-third appeared as targets in their second presentation, and one-third appeared as targets in their third presentation. Within each condition (PK/n-PK), the location of the target was equally divided between the three possible locations, and each B face appeared once as a target and twice as a distractor.

In each trial, participants were asked to choose the B face that had appeared with the A face during the learning session. After a face was chosen, the other two faces disappeared, and participants were asked to make a three-level confidence judgment (sure, probably, or maybe, corresponding to high, medium, or low confidence that the faces appeared together, respectively). Both stages of each trial were self-paced, but each stage was limited to 10 s. A 500-ms fixation cross appeared between trials. The order of the trials was randomized such that no more than two trials of either the PK or the n-PK condition appeared consecutively. Within each condition, trials were randomized, and B faces were allocated as distractors such that no face would appear in two consecutive trials, either as target or as distractor.