Anosognosia for aphasia: impact of statistical biases and aphasia severity

Anosognosia for aphasia is a condition in which patients may show reduced awareness of their language deficits. Statistical biases that may arise when people with very mild or very severe aphasia are included in group studies have raised concerns about the validity of self-report measures. Given these concerns, the interplay of cognitive biases such as the Dunning-Kruger effect (DKE) should be considered when evaluating awareness of language deficits.

A sample of 66 individuals with a unilateral left-hemisphere brain lesion completed a standardized aphasia assessment (the Aachen Aphasia Test; AAT) and an awareness measure (the Visual Analogue Test Assessing Anosognosia for Language Impairment; VATA-L) to evaluate the frequency and extent of anosognosia and overestimation of language difficulties, and to evaluate the possible impact of statistical biases.

The results showed a significant percentage (37.9%) of patients with pathological or borderline distorted awareness, with a tendency to underestimate (25.8%) rather than overestimate (6.1%) language deficits. No association was found between aphasia severity and awareness levels in our sample, even when individuals with very mild or very severe aphasia were accounted for.

Findings suggest that unawareness for language difficulties cannot be solely attributed to statistical biases, and that aphasic individuals with a unilateral left-hemisphere brain lesion may not be fully aware of their language difficulties.