Had I been a participant in your survey on animal-rights activism (Nature 470, 452–453; 2011), I would have replied that animal extremism once had a negative effect on me — but in an unexpected way.

I worked for many years as a primate researcher studying animal models of abnormal development. Two years after the publication of Peter Singer's Animal Liberation (New York Review/Random House; 1975), my lab was attacked and its rhesus monkeys released. The monkeys were all recaptured and none was seriously injured. I felt intimidated, insulted and furious at what I saw as anti-science stupidity.

My anger was such that I did not give a thought to the possibility that the perpetrators might have been infected with deadly herpes B virus from the monkeys. I failed to alert the emergency departments in the area about this lethal possibility.

For years, my fury blocked the self-reflection that is expected of any scientist who harms vulnerable animals for presumed human benefit. I dismissed even reasonable ethical questions directed at me and my work. Eventually, however, I took up a fellowship at the Kennedy Institute of Ethics at Georgetown University in Washington DC, and at the National Institutes of Health Clinical Center, where I studied bioethics on the moral standing of animals. My intellect and sense of compassionate responsibility broadened; research ethics became my life's focus.

Healthy debate about animal research and the ethical and scientific issues involved must be encouraged, even in the face of hostility. We must also remember that it is unreasonable and inaccurate to label everyone who opposes animal experiments as 'extremists'.