The Silver Spring monkeys were 17 wild-born macaque monkeys from the Philippines who were kept in the Institute for Behavioral Research in Silver Spring, Maryland. From 1981 until 1991, they became what one writer called the most famous lab animals in history, as a result of a battle between primate researchers, animal advocates, politicians, and the courts over whether to use them in research or release them to a sanctuary. Within the scientific community, the monkeys became known for their use in experiments into neuroplasticity—the ability of the adult primate brain to reorganize itself.Doidge, Norman. The Brain That Changes Itself. Viking Penguin, 2007, p. 136: Doidge calls them the most famous lab animals in history. Blum, Deborah. The Monkey Wars. Oxford University Press, 1995, p. 106.
The monkeys had been used as research subjects by Edward Taub, a behavioral neuroscientist, who had cut afferent ganglia that supplied sensation to the brain from their arms, then used arm slings to restrain either the good or deafferented arm to train them to use the limbs they could not feel.Doidge 2007, p. 141-2. In May 1981, Alex Pacheco of the animal-rights group People for the Ethical Treatment of Animals (PETA) began working undercover in the lab, and alerted police to what PETA viewed as unacceptable living conditions for the monkeys.Pacheco, Alex and Francione, Anna. "The Silver Spring Monkeys" in Singer, Peter. In Defense of Animals. Basil Blackwell, 1985, pp. 135–147. Also see Boffey, Philip M. "Animals in the lab: Protests accelerate, but use is dropping", The New York Times, October 27, 1981. The National Institutes of Health initially said that Taub's laboratory was "grossly unsanitary" and suspended his funding, a decision that was later reversed; see Dajer, T. "Monkeying with the Brain", Discover, January 1992, pp. 70–71. In what was the first police raid in the U.S. against an animal researcher, police entered the Institute and removed the monkeys, charging Taub with 17 counts of animal cruelty and failing to provide adequate veterinary care. He was convicted on six counts; five were overturned during a second trial, and the final conviction was overturned on appeal in 1983, when the court ruled that Maryland's animal cruelty legislation did not apply to federally funded laboratories.
The ensuing battle over the monkeys' custody saw celebrities and politicians campaign for the monkeys' release, an amendment in 1985 to the Animal Welfare Act, the transformation of PETA from a group of friends into a national movement, the creation of the first North American Animal Liberation Front cell, and the first animal research case to reach the United States Supreme Court.Carlson 1991. Schwartz, Jeffrey and Begley, Sharon. The Mind and the Brain: Neuroplasticity and the Power of Mental Force. HarperCollins, 2002, p. 161. Newkirk, Ingrid. Free the Animals. Lantern Books, 2000, p. xv, says the case triggered the formation of the first North American ALF cell. In July 1991, PETA's application to the Supreme Court for custody was rejected. Days later, the last two monkeys were killed after veterinarians determined they were suffering and should be euthanized.
During the subsequent dissection of the monkeys, it was discovered that significant cortical remapping had occurred, suggesting that being forced to use limbs with no sensory input had triggered changes in their brains' organization.Leary, Warren E. "Renewal of Brain Is Found in Disputed Monkey Tests", The New York Times, June 28, 1991. This evidence of the brain's plasticity helped overturn the widely held view that the adult brain cannot reorganize itself in response to its environment.Schwartz and Begley 2002, pp. 160, 162.
Background
Edward Taub Edward Taub (born 1931) is a behavioral neuroscientist currently based at the University of Alabama at Birmingham. He became interested in behaviorism while studying philosophy at Columbia University and went on to study under Fred Keller and Wiliam N. Schoenfeld, the experimental psychologists. He took a job as a research assistant in a neurology lab to gain more understanding of the nervous system and became involved in deafferentation experiments with monkeys.
An afferent nerve is a sensory nerve that conveys impulses from the skin and other sensory organs to the spine and the brain. Deafferentation is a surgical procedure in which the spinal cord is opened up and the sensory nerves cut so that these impulses do not reach the brain. A monkey whose limbs have been deafferented will not feel them, or even be able to sense where they are in space. At his trial in 1981, Taub told the court that deafferented monkeys are notoriously difficult to look after, because they regard their deafferented limbs as foreign objects, mutilating them and trying to chew them off.Schwartz and Begley 2002, p. 149. Taub continued working with deafferented monkeys at New York University, where he obtained his Ph.D. in 1970. Engaged in what he saw at first as pure research, he conducted several kinds of deafferentation experiments. These included deafferenting monkeys' entire bodies, deafferenting monkeys at birth, and deafferenting fetuses before returning them to the uterus.
When Taub began his research in the neurology lab, the prevalent view was that monkeys would not be able to use limbs they could not feel. Norman Doidge writes that Taub wondered whether the reason the monkeys abandoned use of the deafferented limbs was simply that they were still able to use their good ones. He tested his idea by deafferenting one arm of a monkey and restraining the good arm in a sling. The monkey subsequently used its deafferented arm to feed and move itself around. He reasoned that, if a monkey refused to use a deafferented arm because it could rely on its good arm, then deafferenting both arms would force the monkey to use them, a finding that seemed paradoxical, but which his experiments confirmed. He even deafferented the entire spinal cord, so that the monkey received no sensory input from any of its limbs, but it still used them. Doidge writes that Taub had an epiphany, guessing that the reason the monkeys would not use their deafferented limbs was simply because they had learned not to, an idea he called "learned non-use".Doidge 2007, pp. 139, 141.
Alex Pacheco Alex Pacheco (born 1958) was a graduate student at George Washington University when he volunteered in May 1981 to work as a research assistant in Taub's lab. The Washington Post writes that he was raised in Mexico, the son of a doctor, and wanted to become a priest. He took a tour of a slaughterhouse in the 1970s and said it changed his life; he read Peter Singer's Animal Liberation (1975), stopped eating meat, and became an animal rights activist. He worked on an anti-whaling ship for the Sea Shepherd Conservation Society, joined the Hunt Saboteurs Association in England, and when he returned to the United States to study political science at George Washington, he teamed up with Ingrid Newkirk, a local poundmaster, to form People for the Ethical Treatment of Animals in March 1980. The point of taking the research position in Taub's lab was to gain firsthand experience of what happens in animal research laboratories, so he looked through a list of government-funded labs and chose the one nearest his home in Takoma Park. Taub offered him an unpaid position and put him to work with a student, Georgette Yakalis.
The monkeys Inside the Institute for Behavioral Research, Taub was conducting deafferentation experiments on 16 male crab-eating macaques (Macaca fascicularis), and one female rhesus macaque (Macaca mulatta), each about tall, all born wild in the Philippines. Each monkey lived alone in a wire cage measuring , with no bedding, no food bowl, and no environmental enrichment, the cages kept in a windowless room measuring square.Guillermo, Kathy Snow. Monkey Business. National Press Books, 1993, pp. 13–14, 20. Also see Pacheco, Alex and Francione, Anna. "The Silver Spring Monkeys" in Singer, Peter. In Defense of Animals. New York: Basil Blackwell, 1985, pp. 135–147. Pacheco writes that 12 of the 17 monkeys had had one or both arms deafferented, while according to the Laboratory Primate Newsletter 10 had undergone deafferentation, the seven others acting as the control group.Clarke, A.S. 'Silver Spring' Monkeys at the San Diego Zoo, Laboratory Primate Newsletter, Volume 27, No. 3, July 1988.
The researchers had named the monkeys Chester, Paul, Billy, Hard Times, Domitian, Nero, Titus, Big Boy, Augustus, Allen, Montaigne, Sisyphus, Charlie, Brooks, Hayden, Adidas, and Sarah. Sarah, the lone female, was a control subject, which meant she had been left intact. She had been purchased from a dealer, Litton Laboratories, when she was one day old, and had lived since then, for eight years, in the institute.Carlson, Peter. "The Strange Case of the Silver Spring Monkeys", The Washington Post magazine, February 24, 1991. Paul was the eldest. He had had one arm deafferented. He had chewed off all the fingers on that hand and pulled the skin and flesh off the palm, exposing the bone. Billy had undergone surgery to deafferent both arms and used his feet to pick up food pellets.
Police raid and charges Pacheco's description of the laboratory Pacheco wrote that he found the monkeys living in filthy conditions. He found frozen monkey corpses in a refrigerator, and others floating in formaldehyde. He alleged that, in the surgery room, human and monkey records were scattered everywhere, including under the operating table, while soiled clothes, old shoes, rat droppings, and urine covered the floor, with cockroaches in the drawers, on the floor, and around the scrub sink. He said the wires of the cages were caked in filth, with feces piled in the bottom of the cages, and urine and rust on every surface, with the 17 monkeys picking at scraps of food that had fallen through the wire floor of the cages into the waste tray below. He alleged that the cages had not been cleaned for months, that there were no dishes to keep the food away from the feces, and that there was nothing for the monkeys to sit on but the cages' wire bottoms. He wrote that 12 of the monkeys had deafferented limbs, with 39 of their fingers deformed or missing. He described them as neurotic, attacking their deafferented limbs as though they were foreign objects:
Informal inspections and raid Pacheco decided to document the conditions in the lab. He told Taub he wanted to work at night and took photographs that showed the monkeys' living conditions. He showed them in July to animal rights activists, including Cleveland Amory, who gave him money for a better camera and some walkie-talkies, so that a look-out outside could alert him if visitors arrived unexpectedly. He also asked Peter Hamilton of the Vancouver-based Lifeforce Foundation to assist with the investigation. In August, Pacheco began inviting veterinarians and scientists into the lab to witness the conditions. According to The Washington Post, Geza Teleki, a primatologist at George Washington University, wrote that he had never seen a lab so poorly maintained, and psychologist Donald Barnes, a former primate researcher, wrote that it was a "miserable and unhealthful environment for the primates" and a health hazard for humans. One local veterinarian, Richard Weitzman, agreed that the lab was very dirty, but said the monkeys seemed well fed and "in pretty good health".