Conners' Continuous Performance Test (CPT) The CPT requires tabbing on the space key when any character other than X shown on the screen. There were six sets in total, with 20 characters within each set. The Inter-Stimulus Intervals (ISIs) are 1, 2, and 4 seconds, and different ISIs varied between sets. Each character maintains on the screen for 250 ms. Correct hits, omission errors, commission errors, and reaction times will be collected as indices of response selection and capacity/focus. The d' value known as a discriminate factor is one of the indices for sustained attention.