Neuroscientific research on monkeys is ethically troubling—but vital

THE HUMAN brain may be the most complex object on Earth. It contains 85bn nerve cells and trillions of interconnections. As these cells process information, people experience consciousness and thought. The brain is made even more mysterious by the fact it is scrutable only when alive. To truly understand brains means examining them while they are functioning inside the body.

Few humans in their right mind would volunteer to plug today’s instruments and sensors into their living brains. Doing so often involves having someone drill into your skull, with the risk of infection or brain damage. And so neuroscientists seeking to understand human brains turn to humanity’s nearest animal relatives, primates.

This is controversial. Monkeys’ usefulness as a model for human neurology also raises the stakes of conducting experiments upon them: the better their brains serve as analogues for human ones, the more it follows that they probably suffer analogously, too. Animal-rights activists rightly point out that monkeys cannot consent to such treatment. It is unlikely they would acquiesce were they able to do so.

The controversy has had an uneven impact round the world. In Europe and America, under pressure from animal-rights groups, the amount of neuroscience research carried out on monkeys is flat or declining. Both places...