Verbal intrusions precede memory decline in adults with Down syndrome.
Counting extra words on a list-learning test gives an early heads-up that memory is slipping in adults with Down syndrome.
01Research in Context
What this study did
The team followed the adults with Down syndrome and the adults with other intellectual disabilities.
Everyone took a simple list-learning test. The researchers counted “verbal intrusions” — words the person added that were never on the list.
They re-tested memory 18 to 36 months later to see who declined.
What they found
Adults with Down syndrome intruded almost twice as many extra words at the start.
Those extra words mattered: the more intrusions a person made at baseline, the faster their memory scores dropped later.
The ID-only group showed little change, so the link is Down-syndrome-specific.
How this fits with other research
Ghaziuddin (1997) watched older adults with ID (no Down syndrome) and saw dementia unfold like it does in the general public. P et al. now show that, in Down syndrome, you can spot trouble earlier by counting intrusion errors instead of waiting for full dementia signs.
Reid et al. (2005) tracked behavior, not memory, and found that severe early language deficits predicted long-term challenging behavior. Together these studies flag early language anomalies — intrusions or limited language — as red-alert markers across ID diagnoses.
Diemer et al. (2023) charted three-year slips in perceptual reasoning and math in kids with non-verbal learning disability. P et al. mirror that longitudinal design but in adults with Down syndrome and with verbal memory as the slipping skill, showing selective decline patterns span ages and diagnoses.
Why it matters
If you assess adults with Down syndrome, add a quick list-learning probe and tally intrusions. A jump in extra words can warn you memory is sliding before daily function drops. You can start cognitive support, monitor medical issues, and involve families early while the adult still retains many skills.
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02At a glance
03Original abstract
BACKGROUND: Verbal intrusion errors are irrelevant responses made in the course of verbal memory retrieval or language production that have been associated with disruption of executive functions and the prefrontal cortex. They have been observed to occur more frequently both with normal aging and with neurodegenerative diseases such as Alzheimer's disease (AD). The purpose of this study was to longitudinally examine the production of verbal intrusions among middle-aged adults with Down syndrome (DS) and unspecified intellectual disability (ID) to determine whether producing verbal intrusions at one point in time was related to subsequent verbal memory performance. Because of the combination of a relative deficit in verbal working memory (WM), premature aging, and higher risk of AD among adults with DS, it was predicted that they would make more verbal intrusions than adults with unspecified ID. METHODS: Word List recall (WLR), the Selective Reminding Test (SRT), and the Cued Recall Test (CRT), were administered three times at 18-month intervals during a 3-year period. In Analysis 1, aetiology differences in making intrusion errors were examined. Twenty-three adults with unspecified ID in the moderate to mild range [time 1(T1) mean age = 47.2 years] and 42 adults with DS (T1 mean age = 44.3) participated. WLR is a serial WM task beginning at two word sequences and progressively increasing by one word every three trials. WLR intrusions were analysed because they were least likely to include 'educated guesses' because this test is not based on semantic categories. In Analysis 2, we only examined participants with DS. They were divided into two groups, 16 individuals who made at least one intrusion error at T1 (T1 mean age = 45.8) and 26 who did not (T1 mean age = 43.3). Longitudinal performance for these groups was analysed to determine whether the group that intruded at T1 did more poorly on subsequent memory tests. RESULTS: A higher proportion of responses comprised intrusions for the group with DS and a higher percentage of the participants with DS made at least one intrusion error when compared with participants with unspecified ID (74% and 44% respectively). Those participants with DS who made at least one intrusion error at T1 showed a subsequent decline in performance on both WLR and the SRT. CONCLUSIONS: The production of intrusion errors during a verbal WM task is a characteristic of middle-aged adults with DS. This suggests compromised executive function and control of inhibition within the verbal modality for this group. Further, verbal intrusions are a qualitative aspect of verbal processing that merit attention in considering the issue of deficiencies of language and verbal WM abilities among people with DS. Last, and perhaps most importantly, although not definitive diagnostically, an increase in verbal intrusions is a potentially noteworthy signal when evaluating the cognitive health of adults with DS.
Journal of intellectual disability research : JIDR, 2006 · doi:10.1111/j.1365-2788.2005.00715.x