The category test (CT) is a neuropsychological evaluation of the examinee’s abstract thinking by looking into how quickly he can learn to sort various objects into their respective classifications. This was developed by Ward Halstead in 1943 and over the years, other versions have been published. Generally, this assessment involves the presentation of pictures of various shapes where the examinee has to choose the concept which is exhibited by a certain image. Feedback is given every after decision to let the examinee know if he is right or wrong. This way, he can realize the underlying concept by analyzing the pattern of the correct images. The frequency of errors identifies the learning progress.