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Continuous Performance Test – AX version
This is an experiment of conditional target-nontarget discrimination ability, sustained attention, and the ability to sustain effort in a cognitively demanding situation. This experiment is an A-X CPT. In this test, the subject will be instructed to respond with a right mouse press whenever the stimulus is an X that was preceded by an A. The left mouse button is pressed for all other stimuli, including an A, an X that was not preceded by an A, and any other letter. Stimuli are selected according to the structure and randomization algorithm set out in this document.
20% of the stimuli are targets (A-X). Stimuli are presented for 200 msec each. The inter-trial interval varies across trials and may be 1.5, 2.0 or 2.5 seconds (this includes the duration of the stimulus), so the average ITI is 2.0 seconds. This is randomized across 150 trials. Practice trials are given and the subject is trained in the correct performance of the test before formal testing is initiated.

Experiment Sequence
• Welcome screen
• Demonstration of letters on screen
• Practice Trials – 40 trials of which 20% targets (4 correct responses to
target stimuli needed to proceed)
• Trials – 150 trials of which 20% targets
• End

Response Mode
Right and left mouse buttons;
Left button = frequent (non-target) stimulus;
Right button = rare (target) stimulus.
Responses occurring during the first 200ms of each trial are recorded as a response to the previous stimulus if there has been no response recorded to the last stimulus. If there was, an invalid response is recorded.

Summary Variables
% Correct Detections (the proportion of correct Xs that were hit, ie, those that followed an A and were responded to correctly)
% False Alarms (the proportion of all Xs that were hit when they should not have been because they were not preceded by an A)
% Correct non-target detections (the proportion of non-targets responded to correctly)
Mean Reaction Time Correct Detections
SD Reaction Time Correct Detections
Mean Reaction Time False Alarms
SD Reaction Time Correct Detections
Mean Reaction Time Correct non-target detections
SD Reaction Time Correct non-target detections

Related References
Harvey, P.D., Moriarty, P.J., Serper, M.R., Schnur, E., Lieber, D. (2000)Practice-related improvement in information processing with novel antipsychotic treatment. Schizophrenia Research 46, 139-148

Oades, R.D. (2000) Differential measures of ‘sustained attention’ in
children with attention-deficit/hyperactivity or tic disorders: relations tomonamine metabolism. Psychiatry Research 93, 165-178

O’Brien, J.D., Halperin, J.M., Newcorn, J.H., Sharma, V., Wolf, L., &
Morganstein, A. (1992) Psychometric differentiation of conduct disorder and attention deficit disorder with hyperactivity. Developmental and Behavioral Pediatrics 13:4, 274-277

Servan-Schreiber, D., & Cohen, J.D. (1992) A neural network model of catecholamine modulation of behavior. Psychiatric Annals 22:3, 125-130

Van Leeuwen, T.H., Steinhausen, H.-Ch., Overtoom, C.C.E., Pascual-Marqui, R.D., van’t Klooster, B., Rothenberger, A., Sergeant, J.A., & Brandeis, D. (1998) The continuous performance test revisited with neuroelectric mapping: impaired orienting in children with attentional deficits. Behavioural Brain Research 94 97-110

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