A 21-year-old's mental age is typically considered to be around their chronological age (21) for average intelligence, but it varies greatly, with cognitive maturity often reaching adult levels before 18, though emotional maturity can lag into the 20s, and some skills peak much later. Modern IQ tests compare adults to other adults, not by calculating a specific mental age from a score, as the concept is complex, but a score of 100 is average.
Let's say the individual being tested is 23 years old. The psychologist would first take the individual's IQ score and divide it by the standard of 100 for a result of 1.2. Then the psychologist would multiply the answer by the person's chronological age of 20 to get a mental age of 24.
Some mental skills are sharpest at different ages, with many not peaking until age 40 or later. Short-term memory is strongest at age 25, stays steady until 35, and then starts to decline. Emotional understanding peaks during middle age, while vocabulary and crystallized intelligence peak in the 60s and 70s.
While neuroscience has revealed that the human brain doesn't fully mature until approximately age 25, our legal system continues to treat 18-year-olds as fully formed adults.
According to recent findings, the human brain does not reach full maturity until at least the mid-20s. (See J. Giedd in References.) The specific changes that follow young adulthood are not yet well studied, but it is known that they involve increased myelination and continued adding and pruning of neurons.
Thus, when people use the term age of majority, they are generally referring to when a young person reaches the age where one is considered to be an adult. Depending upon your state law, this usually happens at some point between 18 and 21.
Research Results. It has been shown that scores on IQ tests actually decrease with age. This chart shows how scores on Wechsler IQ tests peak between 25 and 29 years old, then decline throughout the rest of adulthood, with a decline becoming more steep after the age of 70.
The 20-40 age group is broadly called Young Adults, encompassing the "20-somethings" (vicenarians) and "30-somethings" (tricenarians), often aligning with the Millennial generation, though specific labels vary by context (e.g., social science, marketing, or demographic research).
As humans our peak fitness potential is usually around the age of 20. This is true for both men and women. From there, fitness typically declines between 5%-20% per decade in healthy individuals between the ages of 20 and 65.
Snoop Dogg has publicly stated he has an IQ of 147, a score that falls into the "highly gifted" or "genius" category, much to his own surprise given his self-described average school performance (straight Cs). While this self-reported score suggests exceptional intellect, IQ tests measure specific cognitive abilities, and success in life and business (like Snoop Dogg's multifaceted career as a rapper, entrepreneur, and media personality) reflects a broader range of intelligence and skills.
Careers in the medical field, computer programing, university research positions, and engineering are among the ones with the highest requirements to be smart and have a high IQ.
IQ scores between 90 and 109 indicate a normal IQ range or average intelligence. Individual adults usually score somewhere between the 70-130 range, with 100 being the theoretical average.
Overall mental functioning peaked between ages 55 and 60, before beginning to decline from around 65. That decline became more pronounced after age 75, suggesting that later-life reductions in functioning can accelerate once they begin.
Intelligence-related symptoms
The “age 25” marker comes from general trends in brain development, not a single definitive study. Even psychologist Larry Steinberg, often cited in these discussions, frames 25 as more of a ballpark than a deadline. In reality, some brains keep changing well into the 30s, while others plateau earlier.
Gen Z: Gen Z is the newest generation, born between 1997 and 2012. They are currently between 13 and 28 years old (nearly 69 million in the U.S.)
The young adult phase is typically defined as lasting from around the age of 18 to 25. The brain also finishes its development during this period, transitioning into full adulthood. The United States Census Bureau, for instance, defines young adults as those between the ages of 18 and 34.
Instead of viewing midlife as a loss, turning 40 can be seen as a period of growth and renewal. Aging can enhance emotional resilience and well-being. Midlife often brings a desire to strengthen social ties and give back. Lifelong learning and pursuing personal interests keep life dynamic and engaging.
No, an IQ of 97 is not considered dumb; it falls squarely in the average range (90-109), indicating typical cognitive abilities, though some tests might place it slightly below the exact midpoint of 100. An IQ score of 97 means you performed better than 42% of people, and due to the test's margin of error, your score could be anywhere from the high 80s to the mid-100s, still within normal intelligence.
Brain Development, IX: Human Brain Growth
Although total brain volume is about 95% of its adult size by the age of 5 years, various subcomponents of the brain do undergo age-related changes. In general, white matter—an indication of myelination—increases with age, while gray matter decreases with age.
A 72 IQ is considered Borderline Intellectual Functioning (BIF), falling just above the threshold for intellectual disability (usually around 70), placing it in the lower end of the spectrum (70-79) and indicating slower learning and potential needs for support in daily living, though it's not low enough for an official intellectual disability diagnosis by itself, notes Quora user. It's in the bottom few percentiles of the population, requiring more time to grasp complex concepts but not necessarily severe impairment.
Late adolescence (ages 19-24)
Their upbringing and cultural traditions may become values as they move into adulthood. Those in late adolescence may often experience "firsts," such as getting their first car, enrolling in university, or having their first serious relationship.
In various cultures, the 21st birthday is associated with significant privileges, such as voting and legally consuming alcohol. It is more than just a birthday; it's an event that reflects the 21-year journey towards maturity and independence.
A person becomes a teenager when they become 13 years old. It ends when they become 20 years old. Teenagers who are between 13 and 17 years old are usually considered legally children and teenagers.