At what age range does intellect plateau after peaking at age 30?

The age at which intellect is believed to plateau after reaching its peak varies among different studies, but many cognitive psychologists and neuropsychologists suggest that intellectual abilities, particularly fluid intelligence—which encompasses reasoning, problem-solving, and the ability to learn new information—tend to peak around the age of 30. After this peak, certain aspects of intelligence may begin to stabilize or show less pronounced growth.

The rationale behind the choice that identifies the age range of 50-60 as the point where intellectual performance plateaus is supported by observations that cognitive decline may not be as noticeable until later in life; meanwhile, one might still maintain or even grow in certain types of knowledge, particularly crystallized intelligence, which includes accumulated knowledge, vocabulary, and experiences. Therefore, the 50-60 age range is significant in that it allows for the opportunity to observe stable cognitive functioning in many individuals before any decline becomes more evident.

The other age ranges either precede or follow the 50-60 age bracket. The years 40-50 could be considered too early, as many individuals are still experiencing cognitive development and growth during this period. Meanwhile, the ranges of 60-70 and 70-80 generally encompass a time when cognitive decline might become more noticeable,