Warneken and Rosati first tested sixteen chimpanzees on whether they would choose to delay and receive a larger portion of food that was either raw or cooked or if they would choose an immediate but smaller portion of food. The chimps chose to wait (and thus consume a larger quantity) 60% and 84.4% of the time for the raw and cooked food respectively, showing that the chimps are more willing to suffer the delay to consume a cooked item than a raw item. This finding isn't surprising, as any zookeeper can tell you apes prefer many cooked foods to raw ones. It gets much better though.
The next experiment tested whether or not the chimpanzees understood cooking. Subjects chose between a container that "cooked" the item and bowl that did not cook the item. Raw food was placed in both the container and the bowl, the experimenter shook both of them, but only the container resulted in cooked food. The chimps chose the container with cooked food over 87% of the time. The next test was to determine whether chimps would immediately consume a piece of available food or place it in either the cooking device or the bowl (that didn't cook the item). Thirteen out of twenty-one chimps chose the cooking device at least one time. Chimps that chose a device chose the cooking device more than 80% of the time. The next experiment gave the chimps carrots, which they had not seen in the context of the cooking devices, and the chimps chose to cook the carrots more often than not. When given non-edible items, the chimps didn't try to cook those. All of these experiments point to chimps having the ability to comprehend cooking on a very basic level. They're not cooking everything and they're choosing to cook items that make sense.
|Photo credit: Neil McIntosh|
This study is impressive because the sample size is quite robust for a primate cognition study. (Usually you get sample sizes that are smaller because zoos don't have the ability to house so many animals). Because this study was done with semi-free-ranging chimps at a rehabilitation center, the sample size is larger. We're not talking about one ape that knows some sign language, although that's amazing too. We're talking about roughly thirteen individual chimps that are now probably wondering where that magical container went that cooked all of their food.
Links potentially of interest:
BBC Horizon Video-Did cooking make us human?
How human are chimps?
Felix Warneken, Alexandra G. Rosati. Cognitive capacities for cooking in chimpanzees. Proceedings of the Royal Society B., June 2015 DOI: 10.1098/rspb.2015.0229