New research from the Yale School of Medicine is providing unprecedented insight into what makes humans smarter than other animals. The study has linked the dopamine system in humans to higher intelligence.

The researchers showed that humans have abundant dopamine in the brain that guides in thinking and planning. Dopamine is a chemical that plays a central role in reward-motivated behavior.

The research team established that the progression of the dopamine system in humans is much different than of other species.

For the study, the researchers compared the brains of five macaque monkeys, five chimpanzees and six humans. After analyzing 247 samples of brain tissue, they found substantial differences in dopamine levels.

The inconsistencies were not apparent in some regions of the brain, but differences were very noticeable in the neocortex and the striatum.

The team found that two enzymes which aid in the production of dopamine were more active in the human brain than in the brains of the other species. The scientists also discovered that three times as many neurons in the human striatum were producing dopamine compared to the ape striatum.

“That caught our attention,” said study co-author Dr. Andre Miguel Sousa.

In addition to reward processing, dopamine plays a role in regulating the brain’s executive functions such as memory, attention, and reasoning.

The findings of the study, which are published in the journal Science, challenge previous assumptions about the human brain, such as the idea that the neocortex is the only region involved in intelligence.

The researchers hope the investigation will lead to a better understanding of the brain, as well as help to explain the causes of brain disorders.

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By Chrissy Sexton, Earth.com Staff Writer