The teenage brain has not reached full development, and their choices can be different than what is expected by adults. Teens understand that others have differing viewpoints. But they often firmly believe their own perception is the most true or valid. This is normal, but can be hard for parents.
Studies have, in fact, shown that the adolescent brain is only about 80 percent developed, findings that Jensen says make it clear that teenagers are not just “young adults with fewer miles.”
In fact, there are characteristic developmental changes that almost all adolescents experience during their transition from childhood to adulthood. It is well established that the brain undergoes a “rewiring” process that is not complete until approximately 25 years of age.
17-Year-Old Language and Cognitive Milestones
But even though many 17-year-olds think they are adults, their brains still have not yet fully developed. So while they may have skills to regulate their impulses, they also may behave recklessly at times.
The rational part of a teen's brain isn't fully developed and won't be until age 25 or so. In fact, recent research has found that adult and teen brains work differently. Adults think with the prefrontal cortex, the brain's rational part.
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.
90 Percent of a Child's Brain Develops by Age 5
A newborn's brain is about a quarter of the size of the average adult brain. Incredibly, it doubles in size in the first year and keeps growing to about 80 percent of adult size by age three and 90 percent — nearly full grown — by age five.
Although the brain stops growing in size by early adolescence, the teen years are all about fine-tuning how the brain works. The brain finishes developing and maturing in the mid-to-late 20s. The part of the brain behind the forehead, called the prefrontal cortex, is one of the last parts to mature.
90% of Brain Growth Happens Before Kindergarten
It keeps growing to about 80% of adult size by age 3 and 90% – nearly full grown – by age 5. The brain is the command center of the human body.
Developmental Milestones
Most girls will be physically mature by now, and most will have completed puberty. Boys might still be maturing physically during this time. Your teen might have concerns about her body size, shape, or weight. Eating disorders also can be common, especially among girls.
Physical development. By age 15, most teens have entered puberty. Most girls are close to their adult height and have completed the phase of rapid growth that precedes the first menstrual period. Boys often continue to grow taller and gain weight.
Called glioblasts and neuroblasts, these cells divide and multiply to create the number of nerve cells a person will have for life—approximately 100 billion.
Your brain reaches its 'cognitive peak' - that is when it is most powerful - at age 35, according to a study, but it starts to decline by the time you are in your mid-40s.
For example, raw speed in processing information appears to peak around age 18 or 19, then immediately starts to decline. Meanwhile, short-term memory continues to improve until around age 25, when it levels off and then begins to drop around age 35.
It has been widely found that the volume of the brain and/or its weight declines with age at a rate of around 5% per decade after age 401 with the actual rate of decline possibly increasing with age particularly over age 70.
"At 14, most teens have the ability for complex thought and can express their thoughts and opinions verbally," says Florencia Segura, MD, FAAP, a pediatrician with Einstein Pediatrics in the Washington D.C. metro area.
Teenager's circadian rhythms – the cycle of sleep and wakefulness – typically begin two hours after adults. Neuroscientists say they are biologically predisposed to go to sleep around midnight and not feel fully awake and engaged until between 9am and 10am.
Development during this period will center on how children process language, literacy and creative arts. They will move from always viewing something in a concrete way (just the facts) to being able to look at things with an abstract approach (having multiple meanings).
The brain reaches 50% of adult size at age 1.
Also by age 16, teens can learn to process more complex problems and to develop and test theories. They are better able to handle a more demanding high school curriculum as their memory and organizational skills improve. These skills include time management, test preparation, and study skills.
Adolescence is a time of significant growth and development inside the teenage brain. The main change is that unused connections in the thinking and processing part of your child's brain (called the grey matter) are 'pruned' away. At the same time, other connections are strengthened.
An individual's IQ does not change with age. In other words: if you did an IQ test now and then another one in 10 years' time, your IQ score will probably be very similar. This is because IQ is always measured relative to other people your age.
Importantly, whereas cognitive capacity reached adult levels around age 16, psychosocial maturity reached adult levels beyond age 18, creating a “maturity gap” between cognitive and psychosocial development.
Thinking and Learning
Children in this age group might: Have more ability for complex thought. Be better able to express feelings through talking. Develop a stronger sense of right and wrong.
IQ peaks at around 20-years-old and later effort will not improve it much beyond this point, research finds. The complexity of people's jobs, higher education, socialising and reading all probably have little effect on peak cognitive ability.