Grateful orangs

One of the studies I've been following here is trying to find out if orangutans will display gratitude. The experiment requires training the orangs to trade one wood peg for one grape in order to establish a standard value - peg = grape. To do this, Katrin, the experimenter, scatters about 15 pegs on the floor of the ape cage before they enter. Once the subject arrives in the test cage, she sits at a Plexiglas window with two clear containers - one empty and one filled with 10 grapes. Katrin then requests pegs by holding out her hand. The orangs give them to her by sticking them through a hole in the window with their mouths. For each, peg they receive a grape until there are no more left. Then Katrin waits a minute to see if they try to trade more - by the end of training they should not because there are no more grapes to be had.

The orangs willingly exchange anything for food creating some interesting stories. At one point, Bimbo, the big dude, was being filmed by a TV crew who wanted to get a close-up. I'm not sure how they positioned the camera but Bimbo managed to grab it and get it into his cage. From there he broke it apart and traded the pieces for food.

The goal for the Gratitude study is to create an expectation of a fair exchange and to make clear that once the 10 grapes are gone, there is no point trying to trade more pegs. Once this pre-condition is established, the test phase will start with a normal one to one exchange, but then Katrin will give the subject 10 grapes for just one peg - an act of generosity. With no more grapes to acquire, the question is whether the ape will continue to give pegs as a sign of gratitude. There is more to this experiment in order to control the results to help interpret the behavior, but that is the basic idea. Interestingly, human children in a similar design showed no sign of gratitude. They accepted the windfall gain as if it were normal. A new version is under development.

From my perspective, these studies open the door to exploring fair exchange and a sense of value across species. For children, this is a developmental question; for apes, exchange is not a natural act, but the ability to learn this behavior quickly indicates the capacity for a "market sense."