In light of new data from a longitudinal study, we might have a better understanding of why human intelligence is increasing: each subsequent generation, so far, has enjoyed a higher standard of living than the one preceding it – better nutrition and medical care, education and job opportunities.
Researchers from the University of Aberdeen and Scottish health board NHS Grampian studied 751 people born in Aberdeen, divided into two groups — one born in 1921 and the other in 1936 — known as the Aberdeen Birth Cohort. They were all tested at age 11 and then again up to five times between 1998 and 2011.
When the two groups were tested at age 11, the researchers found an IQ disparity of 3.7 points between the two generations, but after age 62, the difference jumped to 16.5 points — more than three times what was anticipated. Study leader Dr. Robert Staff described the intelligence gains of the 1936 group as “surprisingly large,” and says that he expects average intelligence gains to rise further.
“One especially interesting aspect of the study is that the IQ difference between the cohorts grew by a very large amount over the course of 50 years,” educational psychologist and intelligence researcher Jonathan Plucker said in an email to The Huffington Post. “This provides further evidence that one’s intelligence –- at least the aspects that can be examined using tests –- is not fixed at an early age and can be quite malleable over the course of our lifespans.”
The study, published in the journal Intelligence, isn’t the first to suggest that global IQ is on the rise. In a phenomenon known as the “Flynn effect” (named after psychologist and human intelligence researcher James R. Flynn), IQ has been shown to raise by 3-4 points each decade.
“These IQ gains are probably not unique to Aberdeen, with similar environmental changes being experienced across the UK,” Staff said in a statement.
“The results fit with numerous other studies documenting the Flynn Effect,” said Plucker. “The Aberdeen results suggest that causes of the Effect, as Flynn originally surmised, are largely environmental in nature: As our living standards -– involving nutrition, education, safety, and many other factors -– steadily improved over the past 100 years, our ability to solve cognitive problems likewise increased.”