The Spot-the-Word test: a robust estimate of verbal intelligence based on lexical decision.

The development of a test aimed at estimating premorbid intelligence is described. The test, Spot-the-Word, involves presenting the subject with pairs of items comprising one word and one non-word, and requiring the subject to identify the word. Data show that performance correlates highly with verbal intelligence as estimated by Mill Hill Vocabulary score and by performance on the National Adult Reading Test (NART). Performance does not decline with age, in contrast to an associated test of verbal recognition memory. A second study attempted to test the effect of intellectual deterioration due to age on Spot-the-Word performance. Elderly subjects who had high vocabulary scores scored well on the Spot-the-Word regardless of whether fluid intelligence as measured by the AH4 test was well preserved, or was low, implying intellectual deterioration. A final study collected normative data on a sample of 224 subjects stratified by age and socio-economic status, with each subject performing two parallel forms of the test, A and B, together with the NART. Correlation between the two forms was .884, while correlation with NART was .831 for Form A and .859 for Form B, suggesting adequate reliability and validity. It is concluded that the test provides a potentially useful additional method of estimating premorbid intelligence.