Jessica Cantlon and Elizabeth Brannon described their findings with macaque monkeys in an article published online the week of Oct. 31, 2005, in the Early Edition of the Proceedings of the National Academies of Science. Cantlon is a graduate student and Brannon is an assistant professor in the Department of Psychological and Brain Sciences, as well as a member of the Center for Cognitive Neuroscience. Their work was supported by the National Institute for Child Health and Development, The National Science Foundation and a John Merck Scholars Award.
In their experiments, the researchers sought to test whether monkeys show a phenomenon known as "semantic congruity" when making numerical comparisons.
"When adult humans compare any two things, such as the size of two animals, and they're asked 'which is smaller, an ant or a rat?' one might think it's the same kind of question as 'which is larger, an ant or a rat?'" said Brannon. "But humans are faster at saying an ant is smaller than saying a rat is larger. By contrast, if the two animals are large, such as a cow or an elephant, they're quicker at saying the elephant is larger than saying the cow is smaller. This 'semantic congruity' holds for all kinds of comparisons, including numbers and distances.
"It would seem that this is entirely a linguistic effect, totally dependent on language," said Brannon. "But we sought to understand whether monkeys showed this semantic effect, even though they don't have language."
In their experiments, Cantlon and Brannon presented monkeys with two arrays of randomized numbers of dots displayed on a computer touch screen at randomized positions. Ho
Contact: Dennis Meredith