Typically-developing human children point. Pointing can mean that I want to make sure (for example) that you notice the baby rabbit outside, or I want to tell you that you dropped your fluffy scarf on the floor. The simple act of pointing can mean that I have a “theory of mind”—in this case, I believe that you are not experiencing the same perceptions I am. It is a way of establishing joint attention for better communication.
So far, there’s been little evidence that chimpanzees or gorillas point in a way that reveals theory of mind. But another primate species, bonobos, might have the ability, according to a new study. It’s an example of a repeated-measures design and a small N design.
The study found that bonobos would (helpfully) point at a hidden grape if their human researcher couldn’t see it..
Here’s how the work was summarized by NPR’s Science section:
The study involved three male bonobos, all living at an education nonprofit called the Ape Initiative. During each experimental trial, [researcher] Townrow sat across from one bonobo, who was in an enclosure, but looking through an opening covered by mesh.
The bonobo watched as a helper placed a treat, such as a grape, under one of three blue cups that were lined up in a row.
"We established a co-operative context to this task because if I knew where the treat or the food item was hidden, I would reveal it and then the bonobo would be able to receive that as a reward," he explains.
Sometimes, Townrow could see what was happening when the treat got placed under a cup. Other times, his view was obscured by a barrier, so he didn't know where it was.
No matter what he had or had not seen, Townrow would briefly scan the cups, saying, "Hmmm…where's the grape?" and then wait for ten seconds.
It turned out that when Townrow had enjoyed an unobscured view of the treat being hidden, the bonobos usually sat still and waited [during the 10 second gap].
But when his eyes had been behind the barrier, which blocked his view and made it so he couldn't see which cup had been picked as the hiding place, the bonobos tended to point their fingers through the mesh and tap towards the right cup.
Make a mental image of the scene, with a bonobo on one side, a researcher on the other (sometimes hidden by a partition), and a third human handling the three cups, and hiding the grapes, in the middle.
- This is a small-N experiment, and these types of designs almost always use within-groups independent variables (IVs). What is the IV in this study and what are its levels?
- What is the dependent variable (DV) in this study?
- What makes this a within-groups design?
- Is this study closer to a repeated measures or concurrent measures design, and why?
- Why was it important for the researcher, in both occluded and unoccluded conditions, to pause for 10 seconds and say “hmmm…where’s the grape?” Mention one of the four big validities in your answer.
Selected answers:
- The IV was what the experimenter could see: There were apparently two levels: either the experimenter behind the mesh could see the three cups on a particular trial, or his view was occluded.
- The DV was whether the bonobo pointed to the cup where the treat was hidden (or not).
- It is a within-groups design because the bonobo participants were exposed to both levels of the IV (some trials had vision occluded and some trials had un-occluded vision)
- It is a repeated- measures design because the IV was within-groups and the DV (pointing or not) was measured repeatedly across several trials.
- It was important for internal validity—they needed to be sure that the two conditions were the same in all respects except for whether the vision was occluded or not.
The empirical study appears in the Proceedings of the National Academy of Sciences.