We inherit 40 percent of our lifetime intelligence while the environment we grow up in impacts the rest 60 percent, researchers say.

Scientists at University of Queensland, Australia studied a unique group of nearly 2000 unrelated people in Scotland who were tested for their intelligence, using the same test, at age 11 and again at age 65, 70 or 79 years.

Most people who began life with above average intelligence were above average when they were older, while others who had below average intelligence tended to stay below average, a website reported.

However, the researchers did notice that there were some whose intelligence improved and some whose got worse compared to others.

They also took genetic samples and quantified the role genes play in determining how much transformation there is in intelligence as we age.

"We estimate roughly a quarter to a third of that change is genetic," Professor Peter Visscher, lead author of the study said in a statement.

"Measuring detailed environmental factors over a person's entire life course is very difficult."

The study revealed that overall, environment contributes more than genes to determining intelligence, although, both play an important role.