Low dopamine levels in the brain may be linked to aggression, says a new study.
The small study showed that during periods of competition, those with low levels of the neurotransmitter stopped focusing on their goals and acted out aggressively.
Dopamine is commonly linked to feelings of pleasure, gratification and motivation.
"The results of this study were astonishingly opposite of what was previously hypothesized," said Ingo Vernaleken, lead author and scientist at Aachen University in Germany, according to Science Daily.
"Subjects with more functional dopaminergic reward-systems were not more aggressive in competitive situations and could concentrate even more on the game. Subjects with lower dopaminergic capacity were more likely to be distracted by the cheating behavior."
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The study looked at 18 people in their 20s who played a computer game in which they could win money.
The participants were told that opponents in the other room were able to cheat and steal their winnings, reported HealthDay.
Positron emission tomography (PET) scans were used to watch the dopamine levels of the players as they competed.
As the game was played and the players perceived they were being cheated, reported Science Daily, those with lower dopamine levels became more frustrated and aggressive.
The research was presented at the Society of Nuclear Medicine's annual meeting and has not yet been published in a peer-reviewed journal.