2.2.2. Procedure
The psychometric test procedure (Fig. 1), lasting about 30 min, was
adapted from Cepulic et al. (2018) and conducted individually before the
EEG experiment. After the overall test instruction, six practice trials
with correctness feedback were provided. The tasks were designed for low
versus high difficulty levels; either 25 or 40 s were available to
memorize a matrix of either four or 15 target faces, respectively. All
target faces in a given matrix were either all Asian or all Caucasian.
Each of these four conditions was repeated once with different faces.
The faces in these matrices served as target faces in the recognition
phase of the task, which was conducted after an intermediate mental
speed task aiming to hamper contributions of working memory to face
recognition performance.
Figure 1 .
Example of an easy condition in the face memory task with Asian faces.
After memorizing a matrix with four previously unfamiliar faces and an
intervening mental speed task, the memorized faces were presented one by
one, in random order, and intermixed with novel distractor faces,
requiring an old/new decision by pressing one of two buttons.