What is general intelligence?
The word “intelligence” is vague, but every day, we make calculations and predictions, read from a range of sources, and use our brains for various things as we conduct our lives.
While there may be things that each person is better or worse at, in general, intelligent people produce better results than people who are less so when solving calculation problems, learning foreign languages, or taking tests for some sort of qualification.
This kind of “cleverness” is called “general intelligence” in the field of psychology. Now, at the start of the 21st century, how much do we know about general intelligence?
General intelligence and genes
The fact that children of smart parents frequently have good academic results seems to suggest a relationship of some kind between general intelligence and genes, but how strong could it be?
Studies on twins have shown that general intelligence is strongly affected by environmental factors while children are young, but as they approach their teens, genetic factors come to the fore and at least half of general intelligence can be explained by genetics. Moreover, in middle age, almost 70% of general intelligence can be explained by genetics.
Still, we do not yet clearly know which genes affect intelligence, but a trend has been observed where people who have a special type of the APOE gene, which relates to the onset of Alzheimer’s disease, have very slightly lower intelligence, and this trend grows stronger with age.
It is also thought that there is not a single gene that determines general intelligence, but rather, it may be determined by relationships between many genes.
Interestingly, it has been reported that people with more symmetrical bodies and faces (i.e., whose left and right sides look more similar) have higher general intelligence.
General intelligence and the brain
There is a term “egg-headed”, but anatomical studies report that it is true that the volume of the cerebrum is related to general intelligence, in that a larger volume is associated with higher general intelligence, and that the volume of the cerebral white matter fibers that communicate with the cerebrum, the thickness of the cerebral cortex, the thickness of the outer area of the prefrontal cortex, which is involved in working memory, and other areas are related to general intelligence.
General intelligence and life
Research has reported that being smart does not necessarily mean getting rich.
Investigations have shown that the correlations between general intelligence and academic history, job, and income are 0.46, 0.31 and 0.21 respectively, so while higher general intelligence tends to correlate with a better academic history, the correlation becomes a little weaker when it comes to the link to a good job, and the possibility of it leading to a higher income is weaker still.
However, another study reports that people with high general intelligence can make rational decisions when making choices in life and can calmly assess the conceivable risks and merits in various scenes, which can lead to higher income.
It is also reported that people with lower general intelligence when young have a higher risk of heart problems and psychological problems once they become adults, and they have also been shown to live shorter lives, which has been hypothesized as potentially relating to alcohol and tobacco use, and eating habits.
Being intelligent may not necessarily make you happy, but I wondered whether being smart has benefits in life, or whether the social systems from ancient times to today have attempted to reduce the influence of intelligence on life, although there may be some variation.
Reference URL: Intelligence
