Aggression in Children Makes Sense—Sometimes

The Wall Street Journal:

Walk into any preschool classroom and you’ll see that some 4-year-olds are always getting into fights—while others seldom do, no matter the provocation. Even siblings can differ dramatically—remember Cain and Abel. Is it nature or nurture that causes these deep differences in aggression?

The new techniques of genomics—mapping an organism’s DNA and analyzing how it works—initially led people to think that we might find a gene for undesirable individual traits like aggression. But from an evolutionary point of view, the very idea that a gene can explain traits that vary so dramatically is paradoxical: If aggression is advantageous, why didn’t the gene for aggression spread more widely? If it’s harmful, why would the gene have survived at all?

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A study published last month in the journal Developmental Psychology, by Beate Hygen and colleagues from the Norway University of Science and Technology and Jay Belsky of U.C. Davis, found that the story was even more complicated. They analyzed the genes of hundreds of Norwegian 4-year-olds. They also got teachers to rate how aggressive the children were and parents to record whether the children had experienced stressful life events.

Read the whole story: The Wall Street Journal