 An additional cognitive process that might be of interest when evaluating HBOT is short-term memory. A common behavioral measure of short-term memory is a delayed matching-to-sample DMTS procedure. In such procedures, a sample stimulus is presented and then removed and a delay occurs between the removal of the sample stimulus and the presentation of two or more comparison stimuli. The participant earns reinforcement for choosing the correct comparison stimulus. The delay between the removal of the sample stimulus and the presentation of the comparison stimuli can vary from zero to any conceivable duration, but typically does not exceed 60 seconds. 