Tuesday, November 27, 2007

WJ III Pair Cancellation test as measure of vigilance (sustained attention)

As a result of my recent "harvesting" of various unpublished CHC/WJ III-related thesis/dissertations, my interest in the WJ III Pair Cancellation (PC) test has been rekindled. Since the WJ III was first published I've maintained that the Pair Cancellation test was a good measure of sustained attention or vigilance, an aspect of executive functioning. Unfortunately, we (the WJ III authors) did not report much in the way of special validity studies to support of this interpretation.

[Conflict of interest note - I am a coauthor of the WJ III]

The purpose of this post is to share my recent thinking re: the WJ III PC test. My bottom line conclusion - I still believe that the WJ III Pair Cancellation test is an under appreciated test in the WJ III battery. Because Pair Cancellation's administration is not required to obtain any of the primary cognitive clusters (General Intellectual Ability; CHC factor clusters) it is a test that is often ignored (not administered). I think practitioners need to pay closer attention to the potential of this test, particularly when issues of vigilance, ADHD and executive functions are prominent in a referral for assessment. On what basis do I make this recommendation?

First, lets start with a description of the task. In the WJ III Pair Cancellation task a subject is presented with rows that contain repeating pictures of a dog and a ball (in no particular sequence) and must circle all instances of when the “ball is followed by the dog”. The test has a three-minute time limit. Thus, a subject must locate and mark a repeated pattern of pictures while simultaneously controlling for interference of potentially distracting information (i.e., demonstate good inhibition).

Second, lets consider the CHC basics for Pair Cancellation. As per my most recent CHC classification of all WJ III tests, Pair Cancellation (based on the published CFA analysis in the WJ III Technical Manual) is clearly a speeded test (Gs). Original logical narrow ability content analysis suggested a classification as a measure of P (perceputal speed) and/or AC (sustained attention/concentration). Using Ackerman and colleagues recent fine-grained analysis of perceptual speed measures (which suggests that perceptual speed may be an intermediate stratum ability between narrow and broad abilities defined by four narrow sub-abilities), the Pair Cancellation test might better be consider a measure of "complex perceptual speed" (Pc), which is the "ability to perform visual pattern recognition tasks that impose additional cognitive demands such as spatial visualization, estimating and interpolating, and heightened memory span loads."

Third, in a study of 39 subjects (21 with ADHD; 18 controls) Poock (2005) reported that the Pair Cancellation test, along with the Concept Formation and Auditory Working Memory tests, reliably differentiated ADHD and non-ADHD subjects.

Fourth, there is a rich base of neuropsychological literature that has demonstrated that various "cancellation tasks" are good measures of sustained attention or vigilance. Borrowing from Brawn's (2007) review of the literature:

  • Cancellation Tasks (CTs) are the immediate antecedents to CPT's [continuous performance tests]. Indeed, some researchers refer to CTs as "paper-and-pencil" CPTs (e.g., Barkley, 1998). They assess "...visual selectivity at a fast speed on a repetitive motor response task" (Lezak, 1995, p. 548), by requiring that a subject rapidly scan printed rows of digits, letters, symbols, or pictures in order to mark pre-specified targets interspersed throughout the symbols, or pictures in order to mark pre-specified targets interspersed throught the array.
  • Cancellation Tasks have been demonstrated to be sensitive to response slowing and inattentiveness as a fundtion of diffuse cerebral damage or acute brain conditions, and, like CPTs, they are classified as basic vigilance tests (Lezak, 1995). However, of the two, CPTs may be the purer measure of vigilance. Cancellation tasks require the subject to use a pencil, as well as to quickly and accurately scan rows of printed stimuli; thus, performance relies substantially on motor processing, visual-motor integration, and subject driven visual scanning (Lezak, 1995; Wechsler, 1997b; Woodcock et al., 2001).

Interested readers may wish to check out the recent "meta-search" I completed (and posted) re: the cancellation task assessment paradigm.

Finally, in a previously reported "Carroll analysis" of the complete WJ III battery, Pair Cancellation was found to the strongest loading test on the broad "cognitive" processing speed (Gsc) factor [this analysis also produced a broad "achievement" processing speed factor-Gsa]. In my opinion, this is consistent with the Ackerman-based classification of Pair Cancellation as a measure of complex perceptual speed (Pc).

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Swimming for ME said...

This was very helpful information that I will use in a report I am writing. As I gave the Pair Cancellation task to a student this week, the very fact that you highlighted "dawned" on me .. that in fact it is a paper and pencil version of a CPT task. It nicely supports my conclusion, based on other data and interview and observation, that this student does indeed have attentional deficits consistent with ADHD.

Kevin McGrew said...

You are welcome. Thank you for the clinical confirmation.