Rigidity is an inability to change mental or behavioural sets when required. This resistance to change can be behavioural, cognitive or attitudinal. Rigidity requires two processes: set formation, where sets are learned patterns formed through repetition; and set perseveration, or continuation of the learned pattern. Rigidity may display itself as an inability to change beliefs or performance, or an inability to appreciate another person’s point of view or emotions.

Rigidity may be measured by assessing perseveration on the Wisconsin Card Sorting Task (WCST). Participants are asked to match cards and are given feedback as to whether their choices are correct based on undisclosed category rules. Perseverative errors occur when a study participant continues matching cards according to a previous rule, despite having been given negative feedback. The Test of Behavioural Rigidity (TBR) requires participants to copy a paragraph containing random upper and lower-case letters and then copy the same paragraph replacing the lower-case letters with capitals and vice versa. Participants are also asked to think of synonyms and anonyms for words, and alternate between the two.

What is the evidence for rigidity?

Moderate to high quality evidence finds a medium to large effect of more rigidity in people with schizophrenia than in controls, with largest effects found in studies of unmedicated patients, and in studies using the WCST.

Moderate to low quality evidence finds medium-sized associations between increased rigidity and greater symptom severity.

March 2022

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