Women of high intelligence have fewer children on average than less-intelligent women, said study co-author Jan te Nijenhuis, a University of Amsterdam professor.
Dr. te Nijenhuis and colleagues . . . analyzed the results of 14 intelligence studies conducted between 1884 to 2004, including one by Sir Francis Galton, an English anthropologist and a cousin of Charles Darwin. Each study gauged participants’ so-called visual reaction times — how long it took them to press a button in response to seeing a stimulus. Reaction time reflects a person’s mental processing speed, and so is considered an indication of general intelligence.
In the late 19th Century, visual reaction times averaged around 194 milliseconds, the analysis showed. In 2004 that time had grown to 275 milliseconds.
U.S. IQ scores rose by three points from the 1930s to the 1980s in what’s known as the Flynn Effect, notes the Daily Mail. Scores also rose in Japan and Europe. Improved education, nutrition and living conditions explain the rise, says James Flynn of the University of Otago, after whom the effect is named.
Some believe the Flynn effect has masked a decline in the genetic basis for intelligence, so that while more people have been reaching their full potential, that potential itself has been declining.
Richard Lynn, a psychologist at the University of Ulster, believes average IQs around the world declined by one point from 1950 to 2000 and could fall another 1.3 points by 2050.
British 14-year-olds’ IQ scores declined by more than two points from 1980 to 2008, Flynn found. The drop was six points for teens in the upper half of the intelligence scale. “Youth culture is more visually orientated around computer games than they are in terms of reading and holding conversations.”
The movie Idiocracy starts with an explanation for declining intelligence in a society that’s lost natural predators.