Objective: The Six Elements Task (SET; Shallice and Burgess, 1991; Burgess et al., 1996) measures examinees’ ability to plan and organize their behaviour, form strategies for novel problem solving, and self-monitor. The task has adequate specificity (Wilson et al., 1996), but questionable sensitivity to mild impairments in executive function (Jelicic, et al., 2001). The SET is vulnerable to practice effects. There is a limited range in possible scores, and ceiling effects are observed. This dissertation sought to evaluate the validity and clinical utility of a modification of the SET by increasing the difficulty of the test, and expanding the range of possible scores in order to make it more suitable for serial assessments.
Participants and Methods: The sample included 26 individuals with mixed acquired brain injury, and 26 healthy matched controls (20 – 65 years). Participants completed a battery of neuropsychological tests on two occasions eight weeks apart. To control for confounding variables in executive function test performance, measures of memory, working memory, intelligence, substance abuse, pain, mood and personality were included. Self and informant reports of executive dysfunction were also completed. The two groups’ performances on the various measures were compared, and the external validity of the 12ET was examined. In addition, normative data and information for reliable change calculations were tabulated.
Results: The ABI group exhibited very mild executive function deficits on established measures. The matched control group attempted more tasks on the 12ET, but the difference was non significant. Neither group tended to break the rule of the task. The 12ET showed convergent validity with significant correlations with measures of cognitive flexibility (Trailmaking B and Ruff Figural Fluency), and a measure of planning (Tower of London). The 12ET and published measures were also significantly correlated with intelligence in the brain-injured group. The 12ET did not show divergent validity with a test of visual scanning speed (Trailmaking A). No demographic variables were found to be significant predictors of 12ET performance at Time 2 over and above performance at Time 1, and both participant groups obtained the same benefit from practice. The 12ET did not suffer from ceiling effects on the second administration, and the test-retest reliability of the 12ET variables ranged from low (r = .22 for Rule Breaks in the brain-injured group) to high (r = .78 for Number of Tasks Attempted in the control group).
Conclusions: Despite their (often severe) brain injuries, this sample of brain injured participants did not demonstrate executive impairments on many published tests and their scores were not significantly different from the control group’s scores. Therefore, it was not possible to determine if the 12ET was a more sensitive measure of mild executive deficits than the SET. However, the increase in range did reduce the tendency for participants to perform at ceiling levels. The 12ET showed a number of significant correlations with other executive measures, particularly for the brain-injured group, though these correlations may have been moderated by general intelligence. Two variables of the 12ET, deviation from the optimal amount of time per task and Number of Tasks Completed, showed promise as measures of reliable change in this sample over an 8-week interval.
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/256 |
| Date | 29 November 2007 |
| Creators | Sira, Claire Surinder |
| Contributors | Mateer, Catherine |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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