Continuous Performance Task

A Continuous Performance Task/Test, or CPT, is a neuropsychological test which measures a person's sustained and selective attention and impulsivity. Sustained attention is the ability to maintain a consistent focus on some continuous activity or stimuli, and is associated with impulsivity. Selective attention is the ability to focus on relevant stimuli and ignore competing stimuli. This skill is associated with distractibility.^[1]

There are a variety of CPTs, the more commonly used being the Integrated Visual and Auditory CPT (IVA+Plus), Test of Variables of Attention (T.O.V.A.) and the Conners' CPT-II. These attention tests are often used as part of a battery of tests to understand a person's 'executive functioning' or their capacity to sort and manage information. They may also be used specifically to support or to help rule out a diagnosis of Attention Deficit Disorder

Test Administration

Although the tests may vary in terms of length and type of stimulus used, the basic nature of the tests remains the same. Clients are presented with a repetitive, "boring" task and must maintain their focus over a period of time in order to respond to targets or inhibit response to foils. Tests may use numbers, symbols, or even sounds, but the basic task has the same concept.

In the IVA+Plus CPT, clients are told that they will see or hear the numbers "1" or "2" and that they are to click the mouse when presented with a visual or auditory "1" and inhibit clicking when presented with a "2". The task is made more challenging by the shifting of modalities between the visual and auditory stimuli. In the five "high demand" sections of the test, the targets are presented frequently. This creates a continuous response set so when the test-taker is suddenly presented with a foil, he or she may find it difficult to "put on the brakes." Thus, the high demand sections pull for "errors of commission", or impulsivity. The five "low demand" sections of the test pull for "errors of omission" or inattentiveness; targets are presented infrequently, and the inattentive test-taker is likely to lose focus and drift off, thus missing the target when it appears. Data are provided for over-all attentional functioning and response control, as well as separate visual and auditory attention and response control.^[2]

The T.O.V.A. is similar but is administered on a separate device rather than a computer screen. Separate tests are administered for visual vs. auditory modes. In the visual version, the T.O.V.A. uses geometric shapes so that reading levels do not play a part in the scoring. The T.O.V.A. has two sections, similar to the high and low demand sections discussed above for the IVA. The first section is a "low brain stimulation task" where the targets are infrequently presented. The boring nature of this task pulls for "errors of omission" when the person is distracted and not responding to the target. The second half of this test is a "high brain stimulation task" in which targets are frequently presented. This task pulls for "errors of commission" since a person may expect to see a target and impulsively respond.^[3]

In the Conners' CPT-II clients are told to click the space bar when they are presented with any letter except the letter "X". The person must refrain from clicking if they see the letter "X" presented. ^[1]

Another CPT, the Immediate and Delayed Memory Task is a computer administered test that involves the rapid presentation of 5-digit number. Successful identification of consecutive matching 5-digit numbers are interpreted as representing attentional capacity. However, this task also includes "catch" trials in which consecutive stimuli match on 4 out of 5 digits, responses to which are interpreted as impulsive. The use of these catch stimuli results in a higher base rate of commission errors, which may be necessary for testing impulsivity in higher functioning or adult populations.^[4]

Test Scoring

While scoring varies from test to test, there are four main scores that are used.

Correct Detection This indicates the number of times the client responded to the target stimulus. Higher rates of correct detections indicate better attentional capacity.

Reaction times This measures the amount of time between the presentation of the stimulus and the client's response.

Omission errors This indicates the number of times the target was presented, but the client did not respond/click the mouse. High omission rates indicate that the subject is either not paying attention (distractibility) to stimuli or has a sluggish response.

Commission errors This score indicates the number of times the client responded but no target was presented. A fast reaction time and high commission error rate points to difficulties with impulsivity. A slow reaction time with high commission and omission errors, indicates inattention in general.

A client's scores are compared with the normative scores for the age, group and gender of the person being tested.^[1]

References

1. ^ ^{a b c} Conners, C.K. & MHS Staff. (Eds.) (2000) Conners’ Continuous Performance Test II: Computer Program for Windows Technical Guide and Software Manual. North Tonawanda, NY: Multi-Health Systems.
2. ^ "IVA+Plus - Visual and Auditory Attention Testing". BrainTrain, Inc.. http://www.braintrain.com/professionals/adhdtesting/ivaplus_pro.htm. Retrieved 2011-02-18. 
3. ^ "Introducing the Test of Variables of Attention (T.O.V.A.)". The Tova Company. http://www.tovatest.com/. Retrieved 2008-03-22. 
4. ^ Dougherty, D. M., Marsh, D. M., and Mathias, C. W. (2002). Immediate and Delayed Memory Tasks: A computerized measure of memory, attention, and impulsivity. Behavior Research Methods, Instruments, and Computers, 34, 391-398.