Examining the Flynn Effect in the General Social Survey Vocabulary test using item response theory

Most studies of the Flynn Effect (FE) use classical test theory (CTT)-derived scores, such as summed raw scores. In doing so, they cannot test competing hypotheses about FE, such as it is caused by a real change in cognitive ability versus it is a change in the tests that measure cognitive ability. An alternative to CTT-derived scores is to use latent variable scores, such as those from item response theory (IRT). This study examined the FE on the Vocabulary test in the General Social Survey using IRT. The results indicate that while there has been a decrease–increase trend since the 1970s, the IRT-based scores never differed from the 1970s comparison point more than would be expected from random fluctuation. In contrast, while the CTT-derived summed scores showed the same decrease–increase pattern, all comparisons among the time points and the 1980s group were outside a 95% confidence interval. Multiple reasons for these results are discussed, with the conclusion being there is a need for more multiple-time point studies of the FE using IRT.