Inside Pepperberg’s Lab: Parrots’ Cognitive Abilities Put To The Liquid Test

Piagetian Liquid Conservation: Parrots Match Older Children’s Expertise

Athena drinking grape juiceIf you’ve been reading this blog for awhile, you’ll know that my studies often involve comparing the abilities of my parrots to those of young children. Many of the tasks we use were originally created by the Swiss child developmental psychologist Jean Piaget. Piaget was fascinated by the ways in which children’s cognitive capacities changed as they interacted with, and learned more about, their world. One of his interests centered around how children learned that a specific amount of material, be it liquid or solid, would be unaffected by transformations of its shape. This concept was formally called “conservation” because the amount was conserved during the change.

Understanding conservation would seem to be fairly a straightforward proposition, but it isn’t grasped by children until they are at least 5 years old. In fact, most children do not acquire the concept until they are older, around 6. The problem for these children is understanding that changes in one dimension (e.g., height) can be compensated by changes in another (e.g., width).

How Children React To The Conservation Task

One part of the classic task involves liquids (Piaget & Inhelder, 1966/1969). Here, children are shown two glasses of juice, both having the exact same quantity, and asked which they’d prefer. The children mostly giggle and say something to the effect that it doesn’t matter, they are the same. Then the experimenter pours one glass of juice into a tall, thin transparent container and contents of the other glass into a short, fat one. The experimenter then again asks the children which they’d like. If the children are 5 years old or younger, they choose the tall, thin container. If asked why, they say that there’s more in that container. They don’t seem to understand that the quantities remain the same.

Older children, usually by around their sixth birthday, might make the same choice, but when asked why, they say something about one container being easier to handle, or more fun to use — because they understand that nothing has really changed. If, however, the older children do not see the experimenter transfer the juice, but just see the two filled differently shaped containers, they make the same mistake as the younger children. That result is expected, because those so-called “invisible transfer” trials show that if the children have no reason to think the amounts are the same, they can’t make the correct inference. The tall, thin one definitely looks like it has more, and the children choose based what they perceive is true.

Why Birds Need The Conservation Skill

My students and I were interested in whether our African grey parrots would understand conservation. In the wild, it would come in quite handy: Birds likely would need to know that a squished piece of fruit had the same nutritional value as one that hadn’t been deformed, or, when trying to decide where to get the most food, that it is the comparison of relative quantities of other creatures foraging in specific areas rather than of their apparent densities that is the appropriate criterion upon which a decision should be made as to whether to join or move on. But would bird that never actually had to forage still develop this understanding?

Testing Whether Birds Understand Conservation

We decided to test this on our Griffin, who was then 18 years old, and also on Athena, who at the time was only 6 months old. Would Griffin understand conservation? Would Athena develop this concept over time? We also tested two companion birds, Pepper and Franco, who belonged to the Hartsfields, who had worked in our lab; their birds had already taken part in a few experiments, but had had nowhere near the laboratory experience of Griffin. Using Pepper and Franco allowed to determine if having lots of lab experience was important: Would it make up for lack of interaction with the natural world, or did this concept develop through any sort of daily interactions?

We started with Griffin, to see how he would perform on the classic test. We used U.S. standard measuring spoons, showed him two half-teaspoons filled with juice, and then emptied them into a teaspoon and a tablespoon. One container was thus half full and the other was one-sixth full. We also gave him trials starting with a full teaspoon. We needed to determine if he could perform the task at all, particularly on his first trials — before he had significant experience in drinking from the containers and possibly learning that differently sized spoons provided an identical sense of satiation or even that emptying them took the same amount of time (another possible indication of equivalence). If an adult, laboratory-trained African grey succeeded, as did the older children, it would make sense to go forward, testing him on other variations and testing the other birds for comparison. We found that Griffin did succeed on all trials, choosing randomly — which showed he knew that there was no difference between the destination spoons.

We then had to make sure that he actually cared about getting more juice: Maybe his random choice meant he didn’t actually want more. We therefore gave him a choice between spoons containing more versus less juice. He always chose more, showing that he really did care about the quantities. When we tested Pepper and Franco on more versus less, they also always chose more. Athena, however, was another story. At 6 months of age, she was so excited by getting juice that she just grabbed at the spoons randomly. It wasn’t until she was about 10 months old that she started calming down and choosing rationally, and we could then start her tests.

How The Birds Performed In Conservation Tests

We decided to give Pepper, Franco, and Athena invisible transfers first, during which they would see only the result of the transfers, and similarly test Griffin, to see if they would all respond like the children. Pepper, Franco, and Athena did — they all chose the spoons that looked as though there was more juice. Griffin, however, couldn’t be fooled…after having experienced the visible transfers, he probably remembered the levels and again chose randomly.

The important tests for Pepper, Franco, and Athena now were to see if they would not be fooled when they saw the transfers from the original same-sized spoons to the differently sized destination spoons. They all succeeded, although Franco was occasionally distracted by seeing a full teaspoon in some trials. Nevertheless, all three birds were correct (as was Griffin earlier) at statistically significant levels. Even Athena, who was less than 2 years old when we completed the study, performed at a level equivalent to about a 6-year-old child! We did a few more tests to make sure that our results held under different conditions, and the birds succeeded on those as well. (See Pepperberg et al., 2017 if you want all the details). Thus, another study has shown the intelligence of our feathered friends!

Pepperberg, I. M., Gray, S. L., Lesser, J. S., & Hartsfield, L. A. (2017, August 31). Piagetian liquid

conservation in Grey Parrots (Psittacus erithacus). Journal of Comparative Psychology. Advance

online publication. http://dx.doi.org/10.1037/com0000085.

Piaget, J., & Inhelder, B. (1966/1969). The psychology of the child (H. Weaver, Trans.). London, England: Routledge and Kegan Paul. (Original work published 1966).

Irene Pepperberg, Ph.D.

About Irene Pepperberg, Ph.D.

Dr. Irene Pepperberg is an adjunct associate professor at the Dept. of Psychology, Brandeis University, Waltham, MA. She is also a lecturer and research associate at Harvard University, in Cambridge, MA.