If the title seems a bit odd, the results of the study most definitely were, and surprised almost everyone involved. The task itself was based on the behavior of wrasse fish—species that live near reefs, and are known as “cleaner” fish. They obtain their food by removing parasites, dead tissue, and scales from larger fish. They sometimes also consume healthy tissue and mucus, but they don’t that too often, so as not to lose their clients. They generally service the same fish over and over, but occasionally ignore their steady clientele to service fish that are not common residents but swim by the reef randomly—an ephemeral source of food. Supposedly, it is worth their time to do so, as their regular clientele will still be around and thus remain a steady source.
So, the experiment was set up as follows: subjects are given two alternatives, A and B, with identical reward provided for each; however, if they choose A, they also receive the reward associated with B, whereas if they choose B, the reward for A is removed. Thus, choosing A gives them two rewards, whereas choosing B gives them only one. The idea is to give them a situation like the reef: if they choose their standard clientele, they get a single reward; if they choose the ephemeral clientele, they can still go back to their steady clientele and get double payday.
Fish Pick The Right Dish
The fish were graded on how quickly they learned to choose A over B—in this case, a black dish versus a white one in a laboratory setting. Some of the fish solved the problem in about 30 trials, thought the majority needed 50. The experimenters also examined how quickly the fish learned to reverse their learning to choose B—a standard way of testing flexible understanding. The average needed for reversal was about 80 trials.
The striking aspect of the study was that the researchers also tested apes and capuchin monkeys. None of the monkeys and only two of seven apes solved the original task at all, but those needed well over the fishes’ 50 trials, and only one primate could do the reversal in under 100 trials. Only after the researchers tried some very different initial conditions could the apes and monkeys perform more like the fish (Salzwiczek et al., 2012).
Parrots Succeed Where Monkeys & Apes Fail
We came across this paper because a referee of one of our journal manuscripts thought it was relevant for the study being reviewed. We didn’t see the connection to that line of research at all, but thought it would be a fun experiment to try. So we tested African grey Griffin in our lab, as well as Pepper and Franco—two Greys owned by a couple who used to work in our lab and who understood all the procedural issues that would be necessary to replicate the study in their home.
It turns out that African grey parrots outperform apes and even most of the fish, succeeding on the task in fewer than 30 trials and in the reversal of the conditions in fewer than 50 trials (Pepperberg & Hartsfield, 2014). The issue is really interesting, because in most aspects of behavior (long lives, extended childhood, extensive foraging, dominance hierarchies, large complex brains, advanced cognitive processing, etc.), parrots are much more like apes than fish. So why are the parrots so good?
Some researchers (e.g., Zentall & Case, 2018) argue that optimal performance on this task depends on reducing impulsive choice, as well as the impossibility of grabbing two things at once—something the apes often tried to do, but an action that is impossible for the parrots and fish. This explanation does make some sense, given that research I described last month that demonstrated parrots are quite good at a delayed gratification task!
Pepperberg, I. M., & Hartsfield, L. A. (2014). Can grey parrots (Psittacus erithacus) succeed on a “complex” foraging task failed by nonhuman primates (Pan troglodytes, Pongo abelii, Sapajus apella) but solved by wrasse fish (Labroides dimidiatus)? — J. Comp. Psychol. 128:298–306.
Salwiczek, L. H., Prétôt, L., Demarta, L., Proctor, D., Essler, J., Pinto, A. I., Wismer, S., Stoinski, T., Brosnan, S. F., & Bshary, R. (2012). Adult cleaner wrasse outperform capuchin monkeys, chimpanzees, and orang-utans in a complex foraging task derived from cleaner-client reef fish cooperation. PLoS One, 7, e49068. doi:10.1371/journal.pone.0049068
Zentall, T.R., & Case, J. (2018). The ephemeral-rewards task: Optimal performance depends on reducing impulsive choice. Curr. Dir. Psych. Sci. 27:103-109.