Understanding Indirect Speech in Frontotemporal Dementia and Alzheimer's Disease Dementia: Validation of the Hinting Task - Dutch Version (HT-NL).

Objective: Impairments in social interaction are common symptoms of dementia and necessitate the use of validated neuropsychological instruments to measure social cognition. We aim to investigate the Hinting Task - Dutch version (HT-NL), which measures the ability to infer intentions behind indirect speech to assess Theory of Mind, in dementia.

Method: Sixty-six patients with dementia, of whom 22 had behavioral variant frontotemporal dementia (bvFTD), 21 had primary progressive aphasia, and 23 had Alzheimer's disease (AD), and 99 healthy control participants were included. We examined the HT-NL's psychometric properties, including internal consistency, between-group differences using analyses of covariance with Bonferroni-adjusted post hoc comparisons, discriminative ability and concurrent validity using the area under the receiver operating characteristic curve (AUC), and construct validity using Spearman rank correlations with other cognitive tests.

Results: Internal consistency was acceptable (Cronbach's α = 0.74). All patient groups scored lower on the HT-NL than the control group. Patients with bvFTD scored lower than patients with AD dementia. The HT-NL showed excellent discriminative ability (AUC = 0.83), comparable to a test of emotion recognition (ΔAUC = 0.03, p = .67). The HT-NL correlated significantly with a test for emotion recognition (r = .45), and with measures of memory and language (r = [.31, .40]), but not with measures of information processing speed, executive functioning, or working memory (r = [.00, .17]). Preliminary normative data are provided.

Conclusions: The HT-NL is a psychometrically sound and valid instrument and is useful for identifying Theory of Mind impairments in patients with dementia.