Great apes make sophisticated decisions

Chimpanzees, orangutans, gorillas and bonobos make more sophisticated decisions than was previously thought. Great apes weigh their chances of success, based on what they know and the likelihood to succeed when guessing, according to a study of MPI researcher Daniel Haun, published on December 21 in the online journal PLoS ONE. The findings may provide insight into human decision-making as well.

The authors of the study, led by Daniel Haun of the Max Planck Institutes for Psycholinguistics (Nijmegen) and (Leipzig), investigated the behaviour of all four non-human great . The apes were presented with two banana pieces: a smaller one, which was always reliably in the same place, and a larger one, which was hidden under one of multiple cups, and therefore the riskier choice.

The researchers found that the apes' choices were regulated by their uncertainty and the probability of success for the risky choice, suggesting sophisticated decision-making. Apes chose the small piece more often when they where uncertain where the large piece was hidden. The lower their chances to guess correctly, the more often they chose the small piece.

Risky choices

The researchers also found that the apes went for the larger piece – and risked getting nothing at all – no less than 50% of the time. This risky decision-making increased to nearly 100% when the size difference between the two banana pieces was largest. While all four species demonstrated sophisticated decision making strategies, chimpanzees and orangutans were overall more likely to make relative to gorillas and bonobos. The precise reason for this discrepancy remains unknown.

Haun concludes: "Our study adds to the growing evidence that the mental life of the other great apes is much more sophisticated than is often assumed."

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Citation: Great apes make sophisticated decisions (2011, December 29) retrieved 25 May 2019 from
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User comments

Dec 29, 2011
Nothing "sophisticated" here--the visual system in much simpler animals does this kind of Bayes information processing. The real test is whether they can do it in the presence of distractions.

Dec 29, 2011
I read somewhere that in ancient times great apes were sometimes considered to be just another race of humans.

Dec 29, 2011
" Laziness is not evidence of a highly evolved mind but rather a mind that is not properly being employed because of a lack of proper motivation. "

~ Crapton

Yet, if you want to know the easiest way to do a hard job, you give the job to a lazy man.

Laziness is the father of invention.

Dec 29, 2011
This study is a throwback to the inane animal studies of the 19th century. I think humans choose the smallest portion of animal understanding every time, because the acknowledgement of the enormity of innate animal logic and intelligence is too threatening to the fragile human ego.

Dec 30, 2011
Laziness is just another way to say expend the minimum amount of energy to gain the minimum reward needed to achieve your goal.

In terms of survival (apparent) laziness has massive advantages as wasting energy can lead to starvation and death - do enough to survive and no more.

I fully agree with Telekinetics take on this type of experiment and the fragility of the human ego.

Dec 31, 2011
One day somebody does this with cats and dogs, later somebody else with mice, and then somebody with a snail. And each time the scientific community goes Ohh and Wow, while everybody else just yawn.

This truly is one area where scientists make only the tiniest of steps, almost grudginly. Oh, what we'd know today, if only...

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