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Chimpanzees Enjoy Solving Puzzles Just as Much as Humans

If chimps could read, they'd probably enjoy crosswords.
The study apparatus, via the Zoological Society of London

Here's another study to add to the growing pile of evidence that differences between chimpanzees and humans, while not non-existent, are slight enough that we ought to be reconsidering their place in the world.

The latest research, conducted by the Zoological Society of London at the Whipsnade Zoo, finds that chimps "are motivated to solve a puzzle when there is no food reward," and "get the same feeling of satisfaction [as humans] from completing tricky puzzles."


Obviously no crosswords or Sudoku was involved, rather researchers set up a puzzle made up of ordinary plumbing pipes networked together, through which chimps could move dice, or Brazil nuts, with sticks in order to push them out the exit. The dice fell into a closed chamber, whereas the nuts fell out for the chimps to eat.

No matter whether it was dice they were moving or Brazil nuts, "the chimps were keen to complete the puzzle regardless of whether they received a food reward," ZSL researcher Fay Clark said in a release.

It's from here that Clark draws the conclusion that chimps must be getting the same feeling of satisfaction at completing a difficult puzzle as do humans.

A chimpanzee completing a puzzle faster than a human, in a separate study from 2009.

Importantly, the study, published in the American Journal of Primatology, was conducted with an entire adult family grouping of chimps, none of whom were trained how to use the contraption. In other words, the chimps were solving the puzzle on their own volition, in as an ordinary environment as can be with animals in captivity.

One of the Whipsnade chimpanzees strolls about its enclosure.

That chimps enjoy solving puzzles is only the latest finding to suggest the primates are cognizant, emotional creatures. In Guinea, chimps have been observed attempting to deactivate snares set by bushmeat hunters for other animals, sometimes successfully, sometimes not. To do so they employ a variety of techniques but are always careful to avoid touching the wire loop of the snare, which they apparently know is the dangerous part that could trap them.

As for reaction to the death of a comrade, scientists at a Scottish safari park have noted some chimp behavior that is quite striking. In one instance, a 50 year old female chimp was dying. In the lead up to her death, which apparently was obviously coming, her friends and family became lethargic and groomed her through her final moments. After she died, her daughter stayed nearby, even though ordinarily mother and daughter never slept in the same vicinity.

Reacting to his discovery that chimps can mentally measure the relative volumes of liquids as they pour, doing very well at it at that, Dr Michael Beran writes in Animal Cognition:

"These kind of capabilities, like many others that we continue find in non-human animals, require rethinking our positions on animal intelligence. The results also support the position that there is psychological as well as biological continuity across species, at least for many cognitive and intellectual abilities."

It seems clearer than ever that chimps are similar mentally to ourselves, which begs the question: Are we justified in keeping them pent up in captivity, however puzzle-filled their habitats may be? Doing so in the past may have allowed us to discover many amazing things about our closest relatives in the animal kingdom, furthering scientific knowledge and building appreciation of these animals. But the knowledge we've gained increasingly shows that we are keeping intelligent creatures locked away.

It's pretty clear that the chimps themselves don't care for it. Whipsnade Zoo dealt with a rather high-profile chimp escape in 2007, in which a pair tunneled their way out of the zoo, and one ended up shot dead. Thankfully, there's momentum towards cutting back on the use of experimental chimps, which on top of ethical questions, are costly to keep. The NIH has already announced plans to retire 401 of its 451 chimps to a sanctuary, which is a big step towards keeping the smart primates out of the lab.