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How are Developments in Neurobiology Changing our View of Children? 8 Prefrontal Association Cortex Promotes Life-long Growth

Dialogue between Noboru Kobayashi and Toshiyuki Sawaguchi

8 Prefrontal Association Cortex Promotes Life-long Growth

Sawaguchi: Two reasons have been given for the development of the prefrontal association cortex. The first reason, from an evolutionary perspective, is to pass on one's genes. The second reason is that the group as a whole improves through the functioning of the prefrontal association cortex. The prefrontal association cortex doesn't function just on an individual level. It evolved so that people can expand their capabilities and be active in society and also make a contribution to the society.

The basis for this idea is that people still have the ability to grow even after their own children reach the reproductive age of about twenty. The ability called crystal intelligence is the ability to solve social-related problems. This is the ability that politicians, corporate managers, and others develop and it keeps growing even after the age of forty. We know that this is also a function of the prefrontal association cortex.

We end up attributing everything to the prefrontal association cortex, but it allows us to use our abilities to benefit society even after we have reached adulthood. I think this is due to genetic or evolutional program that we have. In other words, if we live life seriously, we end up trying to do something for the good of society. This is a sign that the brain has been full developed in the right way.

When we are children, humankind is not one of our concerns. Up to the age of twenty, we only think in an abstract way. We get married and are busy raising our children. Other living things reach the end of their life spans when their offspring reach reproductive age. If they continued to live, they would use up precious resources so they die to avoid creating hardship for their children.

In this sense, the life span of the homo sapient is meant to be about 40 or 50, but some people live to 100. This indicates that we are programmed to use our abilities to benefit society, including our own children.

From a biological perspective, I was always puzzled that adults and the elderly worked to improve society. I thought it was rather puzzling. This made me think that there might be an ability that grows in humans as we get older and that this might be an ability that we use for the benefit of society.

We have found that two areas of the brain continue to grow even after we reach adulthood. One area is the prefrontal association cortex which is in charge of crystal intelligence and continues to grow after we mature. We discovered this when we learned that the neurons of prefrontal association cortex of an elderly monkey increases. The hippocampus stores experiential knowledge and it makes sense that the ability associated with it would increase as we grow older.


Pediatrician and Director, CRN
Born in Tokyo in 1927. Doctor of Medicine, Faculty of Medicine, The University of Tokyo, 1954. Books include Human Science, Kodomo wa mirai de aru (Children are Our Future), Kodomogaku, Sodatsu sodateru fureai no kosodate (Reciprocal Development Through Child-raising).

Toshiyuki SAWAGUCHI, Ph.D.
Professor of Neurobiology, Hokkaido University School of Medicine
Born in Tokyo in 1959. Majored in biology, Faculty of Science, Hokkaido University. Doctor of Science, Kyoto University. Specializes in cognitive neuroscience and primatology. Research interests include mechanisms within the brain related to thought and self and evolution of the brain and cognitive function. Publications include Wagamama na no (The Selfish Brain), Watakushi wa no no doko ni iru no ka? (Where is the Self in the Brain?), and Yoji kyoiku to no (Early Childhood Education and the Brain).
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