The persistent belief that VIQ-PIQ splits suggest lateralized brain damage

Area of Science:

• Neuropsychology
• Clinical Psychology

Background:

• A common assumption in neuropsychology is that the Verbal IQ-Performance IQ (VIQ-PIQ) difference reliably indicates lateralized brain damage.
• This belief persists despite limited empirical validation in specific lesion populations.

Purpose of the Study:

• To investigate the diagnostic predictive validity of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) VIQ-PIQ difference scores for identifying lateralized brain damage.
• To assess the utility of the VIQ-PIQ split in patients with confirmed left or right hemisphere lesions.

Main Methods:

• Bayesian analyses were employed to evaluate the predictive accuracy of VIQ-PIQ differences.
• Patient samples comprised individuals with confirmed, cleanly lateralized right (n=23) or left (n=26) hemisphere lesions.
• Statistical measures including sensitivity, specificity, and positive predictive value were calculated.

Main Results:

• While patients exhibited average VIQ-PIQ differences in the expected direction, these differences lacked diagnostic power.
• The VIQ-PIQ split demonstrated no diagnostic predictive validity in non-aphasic patients with left hemisphere lesions.
• The VIQ-PIQ split showed only very limited diagnostic predictive validity in patients with right hemisphere lesions.

Conclusions:

• The VIQ-PIQ split is not a reliable indicator of lateralized brain damage, particularly in non-aphasic individuals with left hemisphere lesions.
• The diagnostic utility of the VIQ-PIQ split is severely limited even in cases of right hemisphere lesions.
• Clinical and neuropsychological reliance on the VIQ-PIQ split for inferring lateralized brain damage should be reconsidered.