The correct answer is decline.
The Seattle Longitudinal Study (from 1956- 2004) is a longitudinal research study that investigated how age differences and the process of aging affects cognitive abilities. The Seattle Longitudinal Study investigated five primary mental abilities- 1) numerical ability, 2) verbal meaning 3) spatial orientation 4) word fluency and 5) inductive reasoning- and how these abilities change and are affected by age. The findings of this study indicated that the five cognitive abilities decline around age 60.