An important paper published in Psychological Science: “When Does Cognitive Functioning Peak? The Asynchronous Rise and Fall of Different Cognitive Abilities Across the Life Span” Here is the abstract (emphasis added):
“Understanding how and when cognitive change occurs over the life span is a prerequisite for understanding normal and abnormal development and aging. Most studies of cognitive change are constrained, however, in their ability to detect subtle, but theoretically informative life-span changes, as they rely on either comparing broad age groups or sparse sampling across the age range. Here, we present convergent evidence from 48,537 online participants and a comprehensive analysis of normative data from standardized IQ and memory tests. Our results reveal considerable heterogeneity in when cognitive abilities peak: Some abilities peak and begin to decline around high school graduation; some abilities plateau in early adulthood, beginning to decline in subjects’ 30s; and still others do not peak until subjects reach their 40s or later. These findings motivate a nuanced theory of maturation and age-related decline, in which multiple, dissociable factors differentially affect different domains of cognition.”
Definitely look at Figure 1 in the pdf.