> Access to education is currently the most conclusive factor explaining disparities in intelligence, according to Ritchie. In a separate study that has not been released, he and his colleagues looked at existing research in an effort to demonstrate that staying in school longer directly equates to higher IQ scores.

> But more research is needed to better understand other environmental factors thought to be linked to intelligence. Robin Morris, a professor of psychology at Kings College in London who was not involved in Ritchie’s research, suggests that traditional measures of intelligence, such as the IQ test, might be outmoded in today’s fast-paced world of constant technological change.

> “In my view, we need to recognize that as time changes and people are exposed to different intellectual experiences, such as changes in the use of technology, for example social media, the way intelligence is expressed also changes. Educational methods need to adapt to such changes,” Morris said.

The first step is to run the same test. The second step is to work out why the results are different (if they are), which might include teaching styles, focus issues, malnutrition, or many other things.