Estimation of Premorbid Intelligence in Adult Populations

Estimation of premorbid intelligence seeks to reconstruct an individual’s peak cognitive functioning prior to the onset of neurological, psychiatric or developmental conditions. This assessment underpins the accurate identification of cognitive decline in contexts such as dementia, brain injury and stroke, by providing a baseline against which current performance can be measured. Dominant approaches exploit the relative preservation of crystallised knowledge—particularly vocabulary and irregular word reading—to infer prior intellectual ability. Instruments including the National Adult Reading Test and its international variants are supplemented by demographic regression models that adjust for age, education and socio-economic background. Recent efforts have addressed challenges posed by semantic deterioration in neurodegenerative disorders, which may compromise reading-based estimates, and have pioneered shorter hierarchical scales and refined statistical methods to mitigate floor and ceiling effects. Robust premorbid estimation informs diagnostic clarity, prognostic modelling and tailored rehabilitation, offering global relevance for clinicians and researchers seeking to differentiate true cognitive change from individual variability.

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Estimation of Premorbid Intelligence in Adult Populations publication trend

The graph below shows the total number of articles in estimation of premorbid intelligence in adult populations across all publications each year (not limited to Nature Index journals).

Technical terms

Premorbid intelligence: An estimate of an individual’s maximal cognitive ability prior to disease onset or injury.

Irregular word reading task: A test requiring pronunciation of words with non-standard orthography-phonology relationships, used to infer crystallised intelligence.

Floor and ceiling effects: Limitations in a test’s sensitivity when individuals score at the extreme lower or upper bounds of the scale.

Crystallised knowledge: Accumulated verbal and factual information that tends to remain stable despite neurological insult.

References

1. Irregular word reading as a marker of semantic decline in Alzheimer’s disease: implications for premorbid intellectual ability measurement. Alzheimer's Research & Therapy (2024).
2. Estimating premorbid intelligence in people living with dementia: a systematic review. International Psychogeriatrics (2021).
3. From “Aisle” to “Labile”: A Hierarchical National Adult Reading Test Scale Revealed by Mokken Scaling. Psychological Assessment (2015).
4. The prediction limits of the National Adult Reading Test and its abbreviated and international variants. Journal of the International Neuropsychological Society (2024).