By Enozia Vakil
In fact, it also claims that the Westerners may have lost 14 IQ points since the Victorian Era.
Co-author of the study Dr Jan te Nijenhuis says that the reason behind this decline in the IQ levels in humans may be strongly linked to the connection between IQ levels and fertility in women. There is a strong negative association of fertility and IQ levels of an individual, and women who have fewer children have demonstrated high intelligence.
“The reduction in human intelligence (if there is any reduction) would have begun at the time that genetic selection became more relaxed,” Dr. Gerald Crabtree, professor of pathology and developmental biology at Stanford University, told The Huffington Post in an email. “I projected this occurred as our ancestors began to live in more supportive high density societies (cities) and had access to a steady supply of food. Both of these might have resulted from the invention of agriculture, which occurred about 5,000 to 12,000 years ago.”
Dr te Nijenhuis and his colleagues carefully monitored the results obtained from 14 different studies conducted from 1884 to 2004, including a study by Sir Francis Galton, an English anthropologist and the cousin of Charles Darwin. Each of these studies focused on the subject’s visual reaction times—how fast they managed to press a button in response to an appropriate stimulus.
This was done mostly because the reaction time is a clear indication of the individual’s mental processing speed, which is strongly linked to the intelligence.
This visual reaction time was around 194 milliseconds on an average for the humans in the late 19th century, while in the year 2004, it has increased to a startling 275 milliseconds. Though the machine gauging time during the older days were much less sophisticated than those today, Dr te Nijenhuis claims that the old data can be directly compared to the modern data.
While another research suggests that there is an apparent rise in the I.Q. levels since the 1940s, Dr Nijenhuis claims that other factors such as proper nutrition, good education and hygiene may mask the true decline in intelligence.
This study was published in the journal Intelligence.