The article by Timothy A. Salthouse explores the timing of age-related cognitive decline, a topic that has been a subject of much debate. Cross-sectional studies consistently show that cognitive performance declines with age, even in young to middle-aged adults (18-60 years). However, longitudinal studies often show stable or even improved cognitive performance with age, leading to discrepancies in the age at which decline begins. Salthouse suggests that these discrepancies are largely due to retest effects, where prior test experience can improve performance over time. The study examines three methods to estimate retest effects and finds that they are generally positive and larger than cross-sectional age differences. The results indicate that age-related cognitive decline begins relatively early in adulthood, around the 20s and 30s, but may not be detectable in longitudinal studies until retest effects are considered. The findings highlight the importance of controlling for retest effects in longitudinal studies to accurately assess age-related cognitive changes.The article by Timothy A. Salthouse explores the timing of age-related cognitive decline, a topic that has been a subject of much debate. Cross-sectional studies consistently show that cognitive performance declines with age, even in young to middle-aged adults (18-60 years). However, longitudinal studies often show stable or even improved cognitive performance with age, leading to discrepancies in the age at which decline begins. Salthouse suggests that these discrepancies are largely due to retest effects, where prior test experience can improve performance over time. The study examines three methods to estimate retest effects and finds that they are generally positive and larger than cross-sectional age differences. The results indicate that age-related cognitive decline begins relatively early in adulthood, around the 20s and 30s, but may not be detectable in longitudinal studies until retest effects are considered. The findings highlight the importance of controlling for retest effects in longitudinal studies to accurately assess age-related cognitive changes.