An effect of maleness

An article by Alla Katsnelson in Nature (28 April; doi:10.1038/nature.2014.15106; currently free) reports on new results from Jeffrey Mogil, a well-known pain researcher at McGill. Mogil and his team have shown that olfactory exposure to males (humans, rats, cats, dogs, guinea pigs) dampens pain responses in mice. In a paper published in Nature Methods (doi:10.1038/nmeth.2935), Mogil and his team report that even a T-shirt, or the scent of chemicals from a male armpit, had the same effect. The only exception was male cage-mates of the subjects. Women, on the other hand, had no effect on pain sensitivity.

Sensitivity to pain was decreased (by about 40%), it turned out, because male scent increased stress, as indicated by increased levels of cortiosterone.

That the presence of an experimenter could alter the responses of animals to pain was long suspected. Mogil says it is

“something that people have been whispering about at meetings for years […] But no one had bothered to look at this systematically.”

Two take-home results are indicated in the article:

“It’s the kind of result a lot of people wish wouldn’t happen,” says Douglas Wahlsten, an emeritus professor of psychology at the University of Alberta, Canada who has studied how animals react to experimenters. Such effects should be taken more seriously, Wahlsten says. “I think this paper will make people more aware.”

Animal researchers, says [Joseph] Garner, will have to embrace statistical methods that compensate for a greater range of variability. “We need to think about animals as more like human subjects,” he says, “than as controllable reagents.”

It’s worth noting that in an all-male lab a systematic biasing of results by the presence of males would not be noticed (the same would hold, of course, in an all-female lab).

Perhaps the same could be said of philosophical results.

Three other articles on pain and empathy I noticed while researching the above:

• Jeffrey Mogil. “Animal models of pain: progress and challenges.” Nature Reviews Neuroscience 10.4 (2009): 283–294. (doi:10.1038/nrn2606).
• Bartal, Inbal Ben-Ami, Jean Decety, and Peggy Mason. “Empathy and pro-social behavior in rats.” Science 334.6061 (2011): 1427–1430. Reported on in Nature by Virginia Gewin. (See also Mogil 2012.)
  From the abstract: “To test for empathically motivated pro-social behavior in rodents, we placed a free rat in an arena with a cagemate trapped in a restrainer. After several sessions, the free rat learned to intentionally and quickly open the restrainer and free the cagemate. […] They freed cagemates even when social contact was prevented. When liberating a cagemate was pitted against chocolate contained within a second restrainer, rats opened both restrainers and typically shared the chocolate.”
• Monya Baker. “Animal models: Inside the minds of mice and men”. Nature 475, 123–128 (07 July 2011) doi:10.1038/475123a. On the use of animals in the study of mental illness. Intriguing quote:
  As human genetic studies reveal gene variants with increasingly smaller impacts on disease, there is increasing demand for new behavioural tests to assess them. Results of assays are highly variable, and they may not measure the most meaningful symptoms, says Jeffrey Mogil, a neuroscientist at McGill University in Montreal, Canada. “We’ve made a lot of advances in making ever-fancier mice, but at the end of the day the question is, what’s your assay and what’s your measure and are they relevant?” he says. “The slow link in the chain, the messy link in the chain, has always been the behavioural assays.”