More than 3 years after it hosted a workshop on the science and ethics of biomedical studies on monkeys, the National Institutes of Health (NIH) this week convened another workshop on nonhuman primate research. And much like the previous event, the meeting is drawing sharply divergent reactions from biomedical and animal advocacy groups.

“It was a very good look at the opportunities and challenges of doing this type of research,” says Alice Ra’anan, director of government relations and science policy at the American Physiological Society, a group that represents nearly 10,000 scientists, doctors, and veterinarians. It was “an excellent and robust discussion around fostering rigorous research in nonhuman primates,” adds Matthew Bailey, president of that National Association for Biomedical Research.

But Emily Trunnell, a research associate at People for the Ethical Treatment of Animals, an animal rights group, counters that the event was a wasted opportunity to talk about the ethics of using nonhuman primates in the first place. “It was just a bunch of scientists clamoring for more money and more monkeys.”

The workshop comes at a time when scientists are using a near-record number of rhesus macaques, marmosets, and other nonhuman primates in biomedical research. The animals, many researchers say, have become increasingly important in revealing how the human brain works and in developing treatments for infectious diseases. There’s been a particular surge in demand for marmosets , which are being genetically engineered to serve as models for autism, Parkinson’s, and other neurological disorders.

But it also comes at a time of increased scrutiny of monkey research. In the past 3 years, the Food and Drug Administration (FDA) has ended nicotine addiction studies on squirrel monkeys, scientists have increasingly struggled to transport nonhuman primates , and some members of Congress have called for stricter oversight of research with these animals. In addition, President Donald Trump signed language into law in December 2019 that requires NIH to explore alternatives to monkeys, FDA to draft a plan to reduce the number of monkeys it uses, and the Department of Veterans Affairs to reduce or eliminate its use of nonhuman primates within the next 5 years.

None of these moves—all pushed by animal advocacy groups—was on the agenda at this week’s workshop, held Tuesday and Wednesday on the NIH campus in Bethesda, Maryland. Nor was there a discussion of monkey retirement to sanctuaries , a growing issue in the biomedical community.

Instead, the meeting focused mainly on improving the rigor and reproducibility of monkey studies. “We want to make sure experiments are designed well to best address scientific concerns, and that all of the information allows other scientists to confirm and validate the results,” says Carrie Wolinetz, NIH’s associate director for science policy.

Keynote speaker Steve Hyman, director of the Stanley Center for Psychiatric Research at the Broad Institute, which conducts research on nonhuman primates, kicked off the workshop by stating that monkeys were “very important and valuable models”—a sentiment echoed throughout the meeting. Simon Barratt-Boyes, a primate researcher at the University of Pittsburg, said nonhuman primates have provided “fundamental advances” in our understanding and treatment of human infectious disease, and that they will be key to continuing to fight these diseases, including the current coronavirus outbreak . When it comes to this area of research, he said, mice can’t accurately replicate the physiology of humans.

Others called for more funding and facilities so that scientists could increase the number of monkeys they use. “We are going to need more primates in the short run,” said William Newsome, a neuroscientist at Stanford University. Because these animals are the best model for a number of types of research, he argued, “It may help us save thousands or millions of mice.”

Joseph Garner, a behavioral scientist at Stanford, pushed back. “There seems to be an assumption that primate models are better,” he said. “I don’t think that’s always true. I’m really scared that if we start mass producing genetically modified primates, we’re going to fall into the same traps we have with other animals.”

Garner was among a handful of participants who argued that improving the lives of research animals isn’t just good for their welfare, it’s good for the science as well. This could include providing the monkeys with larger cages and more naturalistic environments, others said at the meeting, and training nonhuman primates to volunteer for procedures like injections and blood draws. “Treating animals more like human patients is the future of lab animal science,” Garner said.

Other sessions focused on choosing the right monkey species for specific kinds of studies, better ways to share data so that unnecessary experiments aren’t conducted, and optimizing study design to collect the most accurate results. “We need to be very thoughtful and deliberate about the way we are answering these questions,” Wolinetz says. A study that isn’t designed well could end up using more animals than it needs, she says, or failing because it used too few animals. “Nonrigorous science is unethical.”

Still, Trunnell says there wasn’t nearly enough discussion of ethics at the workshop—something she blames, in part, on organizations like hers not being invited to participate. “People kept on saying that welfare was key to good science, but no one has stopped their research to make these vital changes,” she says. “If they truly cared about the data and the welfare of these animals, they would get these things done first.”

Asked whether there was a disconnect between Congress pushing for less monkey use and scientists arguing for more, Ra’anan agrees that there is. But she says there’s also a contradiction posed by Congress telling NIH that it needs to do more to address diabetes, the opioid epidemic, and other human health concerns, while at the same time telling it to stop using “the best research model you have” to study these things. “That’s a disconnect, too.”