Answer: The Wisconsin Card Sorting Task is a behavioral test for humans that evaluates cognitive flexibility.
Source: Wikipedia
In the Wisconsin Card Sorting Task (WCST), a subject is shown 4 different cards. The cards vary from every other card in number, shape, and color.
The subject is given a different card. They are tasked with matching this card to one of the 4 other cards on the table by either number, shape, or color. Behind the scenes, the experimenters have a specific criteria that they expect the individual to match. The subject is told whether or not they matched the card correctly or incorrectly based on the criteria. The next card is drawn, and the process repeats.
The criteria is kept the same until the subject accurately matches the card several times in a row. Then, the criteria is changed. The subject must now match the card to a different trait. Subjects with good cognitive flexibility will be able to adapt to the new criteria quickly. Patients with poor cognitive flexibility will perseverate, and match the card based on the wrong criteria multiple times despite being told they are incorrect.
Performance on the WCST is sensitive to frontal lobe damage. The frontal lobe is responsible for carrying out functions such as critical thinking, abstract reasoning, and goal directed behaviors. When the frontal lobe of a patient is damaged, they will likely perseverate in selecting a previous criteria of sorting, despite being incorrect.
A complete description of the WCST can be found here.