What happens when you pay two monkeys unequally? This is what happens, as narrated by primatologist Frans de Waal. This is an excerpt from the TED Talk: “Frans de Waal: Moral behavior in animals.”
Effects of Inequity: Demonstrated by two monkeys eating cucumbers and grapes
It’s not just monkeys. All social animals (or perhaps just higher mammals) likely have a sense of fairness. I once did an experiment with two dogs (they were the pets of a friend). I got some dog treats and alternated having each dog do a simple trick (sit, shake, lie down, etc.). After one of the dogs did a trick, I’d give it a treat but no praise. After the other dog did a trick, I’d give it praise but no treat. After about 6-8 tricks, the dog that received no treats got up and left the room, while the dog that received all the treats was perfectly willing to continue.
Grumpy – is it possible that the no-treat dog left the room simply because the task wasn’t being rewarded, rather than because the other dog DID receive a treat? In other words, did you do the control version first (neither dog gets a treat)?
A negative control group is a control group that is not exposed to the experimental treatment or to any other treatment that is expected to have an effect. A positive control group is a control group that is not exposed to the experimental treatment but that is exposed to some other treatment that is known to produce the expected effect. These sorts of controls are particularly useful for validating the experimental procedure. For example, imagine that you wanted to know if some lettuce carried bacteria. You set up an experiment in which you wipe lettuce leaves with a swab, wipe the swab on a bacterial growth plate, incubate the plate, and see what grows on the plate. As a negative control, you might just wipe a sterile swab on the growth plate. You would not expect to see any bacterial growth on this plate, and if you do, it is an indication that your swabs, plates, or incubator are contaminated with bacteria that could interfere with the results of the experiment. As a positive control, you might swab an existing colony of bacteria and wipe it on the growth plate. In this case, you would expect to see bacterial growth on the plate, and if you do not, it is an indication that something in your experimental set-up is preventing the growth of bacteria. Perhaps the growth plates contain an antibiotic or the incubator is set to too high a temperature. If either the positive or negative control does not produce the expected result, it indicates that the investigator should reconsider his or her experimental procedure.
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