When it comes to primate patience, bigger apes are willing to wait much longer for a better deal than smaller monkeys. Using data collected over a span of 10 years, University of Nebraska-Lincoln psychologist Jeffrey R. Stevens tested 13 species of primates to see who would wait longest for more grapes.
The biggest primates -- gorillas, bonobos and chimpanzees -- held out much longer than lemurs or marmosets. Chimps, for example, would wait for about two minutes for the promise of more fruit. Tiny cotton-top tamarins, which weigh about a pound, would wait all of 8 seconds before munching on the two grapes.
Stevens believes metabolic rates influence which animals are more patient. Small mammals, in general, burn through calories more quickly than larger ones. There's added pressure on these animals to eat now, instead of waiting for a bigger reward in the future. "You need fuel and you need it at a certain rate," Stevens states. "The faster you need it, the shorter time you will wait."
He thinks that factors like metabolic rate might influence human decision-making, too. Natural selection, as he points out, "applies to humans as well as to other animals."