The CST is a new neuropsychological test created to measure information processing speed, which is frequently impaired in patients with multiple sclerosis. The aim of the study is to validate the CST through the administration on a representative sample of healthy subjects of the Italian population. Each subject will be administered a standardized battery of neuropsychological tests (Digit Span Task and Brief Repeatable Battery of Neuropsychological Tests which includes Selective Reminding Test, Spatial Recall Test, Symbol Digit Modalities Test, Paced Auditory Serial Addition Test and Word List Generation), and the CST in order to verify its validity. After 15 days from the baseline, the CST will be re-administrated to all subjects to assess the reliability of the test.