Effects of Age and Processing Speed on Tilt Are Primarily Linear and Additive, Not Nonlinear and Multiplicative

Tilt refers to an ability pattern based on within subject differences in two distinct abilities (e.g., technical and academic), producing strength in one ability (technical) and weakness in another (academic). The current study was the first to examine nonlinear (quadratic) and interactive effects of age and processing speed on tilt in adolescence (13- to 17-years). According to magnification and investment theories, the effects of age and speed on tilt should accumulate over time, magnifying tilt levels and producing nonlinear and interactive effects. Effects of age and speed on tilt were estimated using test scores from the Armed Services Vocational Aptitude Battery in the National Longitudinal Survey of Youth ( N = 6969). Tilt was based on differences in technical and academic (math or verbal) scores, yielding tech tilt (technical > academic) and academic tilt (academic > technical). In general, quadratic and interactive effects of age and speed on tilt were negligible (explaining less than 1% of variance in tilt), whereas linear effects of age and speed on tilt were robust. Together, the results indicate that the effects of age and speed on tilt are primarily linear and additive (rather than nonlinear and multiplicative), with tilt levels changing at the same rate across all levels of age and speed. Exceptions to the overall pattern included quadratic effects of speed on academic tilt, indicating that faster speeds magnified academic tilt, and interaction effects of age and speed on math tilt, indicating that speed-tilt relations increased at older ages. These effects survived controls for g (general intelligence) and support magnification and speed theories, which assume that faster speeds accelerate the acquisition of specific abilities at older ages. No multiplicative effects were found for tech tilt, which is based on technical activities that are typically ignored in school, providing limited opportunities for development. Future research might examine quadratic and interactive effects of age and speed on tilt over the lifespan (20- to 80-years), when increases in g may inhibit the expression of specific abilities that produce tilt, producing accelerated declines in tilt.