Riordan, Katherine (2009) The Impact of Greater than Predicted WTAR Scores on Estimates of IQ. Honours thesis, University of Southern Queensland. (Unpublished)
Abstract
Estimates of premorbid cognitive abilities provide clinicians with a comparison against which to assess current levels of functioning. The Wechsler Test of Adult Reading (WTAR) was designed specifically to provide clinicians with estimates of premorbid function on the Wechsler Adult Intelligence Scale –Third Edition (WAIS-III) and Wechsler Memory Scale – Third Edition (WMS-III) and is founded on the knowledge that reading is relatively stable in the presence of neuropathology. However, in order to use the WTAR for predicting premorbid IQ, it is first necessary to assess the validity of the client’s obtained WTAR score. This is achieved by evaluating the discrepancy between the actual WTAR and a demographically predicted WTAR. Concerns have been raised in the WTAR Manual that premorbid estimates based on extremely low WTAR scores will result in an estimated low level of premorbid ability in the individual being assessed (the assumption being that an individual with poor reading skills will produce premorbid estimates that are not reflective of intellectual ability but impaired reading skills) thus, increasing the risk for an under detection of pathology if present. Consequently, the WTAR Manual recommends using caution for predicting premorbid abilities when the predicted WTAR is 15 points higher than the actual WTAR. Furthermore, for instances where the predicted WTAR is 20 points or more than actual WTAR, the manual recommends current WTAR scores not be used to estimate premorbid IQ. Currently no such rules are applied at the opposite end of the distribution: when the actual WTAR 15 points or greater than predicted WTAR. Such discrepancies may be reflective of an individual who presents as average in their abilities but who has a specific skill for reading. Thus there is a risk that estimates of premorbid ability using an inflated WTAR score will be set too high for that individual, resulting in the over detection of pathology. The purpose of this study is to examine the impact of greater than predicted WTAR scores on premorbid estimates of IQ. It was hypothesized that the WTAR-Demographic method for predicting WAIS-III IQ would over detect the presence of pathology when based on greater than predicted WTAR scores. Archival data was used to collate a clinical sample of 261 individuals who were administered the WTAR and the WAIS-III. Cases were divided into three categories based on the discrepancy score between actual and predicted WTAR; Low WTAR (-16 points or less), Within Range WTAR (-15 to + 15 points difference) and High WTAR (+16 points or greater). Results of this study found, Low WTAR did not under-detect pathology but was as effective in the detection of pathology as Within Range WTAR, while High WTAR over-detected the presence of pathology. These results bring into question the accuracy of the WTAR for predicting premorbid IQ within this sample and suggest that current manual warnings relevant to Low WTAR may be applied at the wrong end of the distribution. These findings are restricted to the forensic medicolegal milieu from which the data was drawn. Future research should examine the utility of the WTAR for predicting premorbid estimates in other assessment settings such as hospitals or educational sectors.
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| Item Type: | Thesis (Non-Research) (Honours) |
|---|---|
| Item Status: | Live Archive |
| Additional Information: | Current UniSQ staff and students can request access to this thesis. Please email research.repository@unisq.edu.au with a subject line of SEAR thesis request and provide: Name of the thesis requested and Your name and UniSQ email address |
| Faculty/School / Institute/Centre: | Historic - Faculty of Sciences - Department of Psychology (Up to 30 Jun 2013) |
| Supervisors: | Douglas, Lucille |
| Qualification: | Bachelor of Science (Honours) (Psychology) |
| Date Deposited: | 16 Mar 2026 01:42 |
| Last Modified: | 16 Mar 2026 01:42 |
| Fields of Research (2008): | 17 Psychology and Cognitive Sciences > 1799 Other Psychology and Cognitive Sciences > 179999 Psychology and Cognitive Sciences not elsewhere classified |
| Fields of Research (2020): | 52 PSYCHOLOGY > 5299 Other psychology > 529999 Other psychology not elsewhere classified |
| URI: | https://sear.unisq.edu.au/id/eprint/52699 |
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