Primate researchers need to explore alternative methods

In the U.S. alone, we experiment on more than 70,000 primates each year. We study primates because this kind of animal research has led to some remarkable improvements in human health. By studying monkeys about a century ago, scientists discovered a vaccine for polio. More recently, scientists found an effective treatment for HIV.  

The bipartisan federal spending bill enacted in December mandates government agencies conducting biomedical research to encourage their primate researchers to explore alternative methods. I have been an animal researcher for over 30 years. I believe this mandate is good for science. 

Biomedical research is in crisis: despite over 50 years of animal experiments, scientists haven’t discovered a single new category of drugs for the treatment of psychiatric illness. Part of the problem is that drugs that work for laboratory animals often don’t work for humans. 

Our biggest scientific obstacle is self-imposed ignorance. In nature, primates climb, jump, swing, and navigate areas more expansive than 600 football fields yet we confine them to steel cages no bigger than closets. We never ask whether this practice makes sense. 

A case in point is a new exposé of ongoing invasive brain research on primates at the National Institute of Mental Health. In these experiments, purportedly designed to study human anxiety, monkeys receive toxic injections to damage brain regions that control their behavioral responses to perceived threats. 

These monkeys are then confined inside metal cages barely larger than their bodies and presented with threatening objects, like rubber snakes and “hairy rubber spiders.” These experiments use exceptionally naïve, brain-damaged, animals that bear no resemblance to freely-moving monkeys, never mind humans.

For our experiments to work properly, our lab animals must be healthy but we ignore the possibility that our caged animals are bored and frustrated. They live inside small, contrived environments that deny them ongoing challenges they can overcome. Caged animals cannot dodge the rain, endure hunger, or feel the satisfaction of finding food. The temperature inside their cages never changes. Their conditions are not healthy. 

We also ignore how our justification for science contrasts with the logic we use to practice it. Many of us study brain circuits to understand psychological challenges, such as fear, anxiety, reward, and anticipation. Yet we disregard the possibility that captivity inside small cages causes any kind of psychological damage — even to our “healthy controls” — or how this damage affects other aspects of health, like cancer resistance and wound repair. 

We also ignore our scientific findings. For instance, we know that the brain is malleable to the environment. Mice living inside a larger cage with a few added objects are much more resistant to features of depression, anxiety, addiction, schizophrenia, Alzheimer’s disease than mice living inside standard-issue cages. If scientists are paid to challenge our assumptions, how can we ignore the evidence that animal cages affect the relevance of our research? 

Some scientists argue that we need animal cages to control the variables. That’s a myth. Animal research faces an ongoing reproducibility crisis because we don’t control the variables.  

The problem lies elsewhere. Scientists typically study small stuff, like molecules, rather than entire animals. We’re trained to dismiss evidence that animals harbor psychological experiences. And if, sometime in our careers, we begin to suspect that studies of caged animals lack relevance to freer humans, what can we do? The institutional pressure to haul in large amounts of grant money means we can’t afford to be skeptical.  

But if primate researchers can’t even be skeptical about the effects of caging, then the rest of us can no longer afford primate research. Plenty of great alternatives are in development. Ironically, some of the least well-funded liberal arts institutions often conduct the most forward-thinking research. Some researchers are using wireless technologies to study wild animals. 

Others are studying animals housed inside enclosed “naturalistic” environments, where they contend with the ongoing challenges natural for their species, akin to what they might get outside. Many universities and corporations are developing in vitro organ systems grown from human tissues. 

To be clear, a mandate to curb primate research should not be misconstrued as a failure of science. It’s a mandate driven by ethical concerns, which is always good, but it’s also grounded in solid science, a testament to what we’ve learned from animal research. But scientists aren’t trained to entertain what we can’t plot on a graph. Ironically, we need to lean on legislators for the bigger picture. Their mandate should give us hope. 

Garet Lahvis, Ph.D. is a former associate professor of Behavioral Neuroscience at Oregon Health & Science University. His laboratory discovered empathy and social reward in mice.