In the mental speed task, taking 1-1.5 min, one of four different 2-choice decisions to visual stimuli presented at the center of the screen were required by means of button presses about whether or not (1) a letter out of eight possible letters (A Q Z T S P R W ) was an “A”, (2) a one-digit number out of eight was “3”, (3) a line-drawn face was smiling (out of smiling, neutral and sad expression), and (4) whether two symbols, letters or numbers shown side by side were identical.

In the recognition phase of the face memory task, single faces were presented that were to be classified as quickly and accurately as possible by choice-response button presses (without feedback) as to whether or not they had been present in the study matrix. In easy tasks, each of the four target faces was presented four times, randomly mixed with 16 unknown same-race distractor faces (32 trials per run). In difficult tasks, 15 target faces were mixed with 15 new same-race distractor faces (30 trials per run). The task order was fixed for all participants, as follows: (1) Asian, easy, Run 1, (2) Asian, easy, Run 2, (3) Asian, hard, Run 1, (4) Asian, hard, Run 2, (5) Caucasian, easy, Run 1, (6) Caucasian, easy, Run 2, (7) Caucasian, hard, Run 1, and (8) Caucasian, hard, Run 2. None of the faces shown in the matrices of the learning phases was used in any of the other matrices and none of the distractors in the recognition phase was used twice.