2.6.3. Wisconsin Card Sorting Test (WCST)
Cognitive flexibility was assessed using a computerized version of
WCST-64 (Kongs et al., 1993). Each trial required participants to sort
test cards according to one of three possible categories: number (1-4),
shape (triangle, circle, cross, star), or color (red, blue, yellow,
green). Every time participants made a choice, feedback was displayed on
the screen in the form of ”correct” or ”wrong”. Since the sorting rules
were not be instructed, participants needed to discover the rules
themselves through the feedback provided. Whenever participants
correctly sorted a series of ten cards, the rule changed. Each
participant completed 64 trials and finished 1 to 6 sorting sequences
depending on their performance. Although the WCST-64 provides several
measures as indicators of cognitive flexibility, the primary outcome of
interest within the present study was perseverative errors, which
indicate a continued application of a card sorting rule that is no
longer appropriate instead of shifting to the use of a new rule (Miyake
et al., 2000). Prior studies have noted that perseverative errors on the
WCST are the outcome most affected by acute stress, consistent with
earlier studies showing that perseverative errors point to a lack of
cognitive flexibility (Kalia et al., 2018; Nyhus & Barceló, 2009).