By Victoria Gill
Science and nature reporter, BBC News
The monkeys displayed their ability to understand the concept of quantity
Old World monkeys have better numerical skills than previously thought, researchers have discovered.
In a basic numeracy test, long-tailed macaques were able to work out which of two plates contained more raisins.
Strangely, they only excelled in this test if they were not allowed to eat the raisins they were shown.
The scientists report in the journal Nature Communications that the animals have the ability to understand the concept of relative quantities.
The team of researchers from the German Primate Center in Goettingen initially tested the macaques by showing them two plates containing different numbers of raisins. When the animals spontaneously pointed to one of the plates, they were fed the raisins.
But in this test, the monkeys often got it wrong - choosing the smaller amount.
Lead researcher Vanessa Schmitt said that this was because, rather than thinking about quantities, the animals were thinking about how much they wanted to eat the raisins.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.