A journalist from the Washington Post has reported on a study showing that two ape species (chimpanzees and bonobos) appear to recognize old friends and family members.
You might be asking, how can researchers know what apes remember, when they can't speak? In this case, they did it via a concurrent measures design. Researchers at the Edinburgh Zoo worked with 26 apes who lived in ape sanctuaries in Japan, Scotland, and Belgium. They showed each ape two pictures:
Using a straw with fruit juice to keep their heads still and an infrared camera to track their eye movement, the team showed the animals a pair of side-to-side images for three seconds. The apes were not restrained during the experiment
“It’s an elegant, quite simple way to encourage them to keep their heads still,” said Laura Lewis, a postdoctoral fellow at the University of California at Berkeley and lead author of the study.
One image was of an ape they had previously lived with. The other was of a complete stranger.
On average, the bonobos and chimps that saw both images looked at their old groupmates for about a quarter of a second longer than the stranger.
This study illustrates a common ethical approach to animal research on higher apes. The method is typical of research with primates, in that no individual was coerced into participating. Instead, over time, apes in the sanctuaries learn they can sometimes get special treats (in this case, juice) by going to a certain section of their living compound and working with the researchers. Therefore, chimps and bonobos are only in the study if they volunteer.
a) I already mentioned that this study design was concurrent measures. Use that information to help you identify the study's IV and DV:
Variable name | What are the variable's possible levels? | Is this manipulated or measured? | Is this an IV or a DV? | For the IV: Is it manipulated as within-groups or between -groups? |
b) Sketch a graph of the study's results, as described in the last paragraph above. In the original article, the authors created a new DV called "looking bias" which was the difference between how long apes looked at former groupmates minus how long they looked at strangers. Try using that on your y-axis.
c) Later in the story, the journalist drops another level of the independent variable. Read it, and decide, now what are the three levels of the IV?
And bonobos and chimps looked longer at old groupmates with whom they had groomed and had positive relationships in the past — longer, that is, at friends than foes, though whether the animals are capable of friendship has been up for debate.
“It’s sometimes called the f-word in primatology,” Lewis said. “But it does seem … a lot of us are in agreement now that you could characterize these long-lasting, positive relationships as friendships.”
d) How might you sketch the result that "bonobos and chimps looked longer at old groupmates with whom they had groomed and had positive relationships"?
You can compare your figure sketches to those in the empirical journal article, which appears in PNAS. https://doi.org/10.1073/pnas.2304903120