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Shifting set refers to the process of updating or "shifting" cognitive strategies in response to changes in the environment. For example, in some neuropsychological tests, patients are first asked to perform according to some rule (e.g., given a choice between a red and a yellow object, always choose the red object). Next, patients are asked to switch to a new rule (e.g., always choose the larger object, regardless of color). Successful performance requires the ability to abandon an old strategy and start responding according to a new rule.

Patients with damage to the frontal lobes are often impaired at tasks which require shifting set. They may have difficulty abandoning the old rule -- continuing to pick the red object even though they know their choice is wrong -- and they may also have difficulty learning a new rule to replace the old one.

Patients with Parkinson's disease may also have trouble shifting set. This is because Parkinson's disease destroys neurons in the substantia nigra, a brain region that normally helps regulate function in the frontal lobes; as the neurons in the substantia nigra die, the frontal lobes may become somewhat dysfunctional.