Gyula Demeter

Shifting
The shifting component of the executive system is responsible for coordinating the
change between relevant and irrelevant sets. The task that is most often used to study the set-
shifting abilities of OCD patients is the Wisconsin Card Sorting Task (WCST, Berg, 1948;
Heaton, 1981). WCST is a complex task and depending on the structural equation modeling
analyses used it mainly reflects the shifting component of the executive system (Miyake et al.,
2000).
In the standard computer version of the task, four stimulus cards with symbols differing
in colour, shape, and number appear on the top of the screen and the subjects had to match a
target card which appeared on the middle of the screen with one of the four stimulus cards.
After each placement, the subject is informed via a message on the screen whether the
response is correct or incorrect. Participants are instructed to sort the target cards into piles
under the reference cards according to one sorting principle. The subject has to get as many
cards right as possible. After 10 consecutive correct matches with the first criterion (colour)
the sorting principle is changed without warning to a second one (form), then to a third one
(number) and the subject has to find the correct sorting strategy using the received feed-backs
on the screen. The subject must be able to reject the old rule and to switch to the discovered
new one. The procedure is repeated twice or until all of the 128 matching cards were used.
The indices considered for the test evaluation are as follows: Trails administered, Total
correct, Perseverative responses, Perseverative errors, Nonperseverative errors, Conceptual
level responses, Categories completed, Trails to complete first category, Failure to maintain
set and Learning to learn.
Some studies have described set-shifting deficits in OCD using the WCST (Boone,
Ananth, & Philipott, 1991; Hymas et al., 1991; Okasha et al., 2000; Roh et al., 2005;
Mukhopadhyay et al., 2010), but others have not (Zielinski et al., 1991; Abbruzzese, Ferri, &
Scarone, 1995a, 1995b, 1997; Moritz, Fricke, Wagner, & Hand, 2001). Roh et al. (2005) in a
more recent study have found that OCD patients commit more perseverative responses and
errors on this task. Because this task was one of our main assessment tool for the shifting
component of the executive system in our research (Study 1) we present at the end of this
section a detailed overview of the studies using WCST from the literature (see Table 1 for
details).
The results obtained on the Object Alternation Task (OAT, Freedman, 1990), Delayed
Alternation Task (DAT, Freedman and Oscar-Berman, 1986) (Abbruzzese et al., 1995a;
Gross-Isseroff et al., 1996; Abbruzzese et al., 1997; Moritz et al., 2001; Spitznagel and Suhr,
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