Predicting the Flynn Effect through word abstractness : Results from the National Intelligence Tests support Flynn's explanation

• The Concepts subtest of the National Intelligence Tests is analogous to Similarities of the Stanford-Binet Tests.
• The Abstractness of words in the Concepts subtest of the NIT correlates with the item presentation order (r =. 609).
• The Flynn Effect is more evident in the Concepts subtest than it is in the other NIT subtests.
• If word familiarity is controlled, then word abstractness can predict the results of the Concepts.

The current study investigates the Flynn Effect (FE) and its relation to abstract thinking ability. We compare two cohorts of Estonian students (1933/36, n = 888; 2006, n = 912) using the Concepts (Logical Selection) subtest of the Estonian adaptation of the National Intelligence Tests (NIT). The item presentation order of the subtest correlates with the abstractness of the words used in the items (r = .609) of the subtest. The different test results (right, wrong and missing answers) were analysed in order to make an estimate of the FE magnitude. The FE for abstract thinking ability of those samples was 1.06 Hedges' g (adjusted for guessing). The magnitude of the FE is dependent upon the degree of difficulty of the items (an item's difficulty is estimated by determining its abstractness and its familiarity to students). The more difficult part of the subtest (the second half) showed a FE = 1.80 whereas the easier part (the first half) of the subtest showed a FE = .72. Word abstractness was a strong predictor of all the testing results in both cohorts (Beta = .700). The familiarity of words used in the test items has no correlation with the test results if word abstractness is controlled in both cohorts. Our findings support Flynn's explanation that the FE is primarily an indicator of the rise in abstract thinking ability.