Tuesday, April 30

Vervets: Flavor & Social Transmission

This week is vervet week. I have declared it. Coming from me, this means a lot, since I've never been particularly interested in vervet monkeys. But, two articles have been released in science recently: both on vervets, both so intriguing that I have been compulsively rereading them.

The first of these comes from Andy Whiten of primate culture fame. He has done impressive work in the past, and this latest vervet paper is an extension of that, though perhaps not the intuitive extension. The authors presented their wild vervet subjects with two types of food, varying two attributes of each type. First, the food was either colored blue or pink. Second, the food either tasted good, or tasted terrible.

Taste aversion can be found in pretty much all mammals; a type of learning that most humans are familiar with. By taste aversion, I mean that when you taste something bad you learn very quickly not to eat it again. Often it only takes one exposure to learn this, which in the animal behavior world is very very fast. Not only will animals learn to avoid foods that taste digusting, but they will also learn to avoid foods that they think made them sick, even if they didn't eat anything that tasted bad.

There is a broad literature on taste aversion in rats (a literature I happen to know pretty well), and in rats you will find even stranger, related phenomena. Rats possess the ability to socially transmit taste preferences through their sense of smell. They will actually smell the breath of other rats, and later, they will show a preference for food that smells and tastes like the odors they smelled on the other rat.

It turns out that vervets can do basically the same thing. The authors of this paper have shown that while vervets quickly learn to avoid the color of food that they know tastes bad, they can learn socially through watching other vervets to ignore their earlier preferences. For example, if a male vervet learns that pink food tastes gross, and then the male disperses to another group where everyone learned a long time ago that blue food doesn't taste good, the newcomer male will watch and learn to eat blue food, in spite of his earlier memories.

Rats possess a unique neurochemical mechanism for learning this kind of stuff, and cannot learn taste preferences socially. Yet this is exactly what vervets do: watch other members of their own species and using that information, learn new preferences and extinguish old ones.

To see this in vervets is striking. If someone reported these results in chimpanzees, it would not be particularly surprising because chimps are extremely smart and adaptive. Vervets are not great apes, not lesser apes, they're just old world monkeys whose brains are smaller than many other old world monkeys, notably macaques and baboons. If we see this kind of behavior in vervets, it really does suggest that this cognitive ability is fundamental in all old world monkeys.

Moreover, the authors refer to this type of learning as "cultural learning". I am not sure if I fully agree with this; the line between cultural and social learning is not clear. However, I would certainly say that this type of learning is at least an evolutionary antecedent to cultural learning.
van de Waal, E., Borgeaud, C., & Whiten, A. (2013). Potent Social Learning and Conformity Shape a Wild Primate's Foraging Decisions Science, 340 (6131), 483-485 DOI: 10.1126/science.1232769


  1. Excellent, so I can make the kids eat their vegetables by dispersing them to other families that eat vegetables... right?

    Very cool, in any case! :)

  2. Even better: start making the food they like taste terrible, so they have nothing left to eat but the vegetables.