Mackinnon, AndrewChristensen, Helen2015-12-081040-3590http://hdl.handle.net/1885/33331Intellectual ability is assessed with the Spot-the-Word (STW) test (A. Baddeley, H. Emslie, & I. Nimmo Smith, 1993) by asking respondents to identify a word in a word-nonword item pair. Results in moderate-sized samples suggest this ability is resistant to decline due to dementia. The authors used a 3-parameter item response theory model to investigate the measurement properties of the STW in a large community-dwelling sample (n = 2,480) 60 to 64 years of age. A number of poorly performing items were identified. Substantial guessing was present; however, the number of words correctly identified was found to be an accurate index of ability. Performance was moderately related to a number of tests of cognitive performance and was effectively unrelated to visual acuity and to physical or mental health status. The STW is a promising test of ability that, in the future, may be refined by the deletion or replacement of poorly functioning items.Keywords: accuracy; adult; article; cognition; dementia; female; human; intelligence test; major clinical study; male; measurement; mental health; Spot the Word Test; theoretical model; visual acuity; Aging; Australia; Cognition; Cognition Disorders; Cohort Studies dementia; guessing; item and test information; item response theory; premorbid intelligence200710.1037/1040-3590.19.4.4592015-12-08