FRIDAY, June 10, 2005 (HealthDay News) -- When you see five similar objects in a group, the word "five" serves as a language hook to visually pull the objects together in your mind. But can nonlinguistic animals similarly recognize groups of objects as sharing common qualities?
A new study in monkeys suggests they can.
In the study, researchers at Duke University found that rhesus monkeys were able to match the number of voices they heard on an audiotape to the number of faces they expected to see, suggesting they can understand and anticipate number groupings without the aid of language.
Recordings of natural "coo" sounds made by unfamiliar monkeys were played to the primates. The recordings included either two or three monkeys making the sounds. At the same time, the rhesus monkeys were shown video images of either two or three monkeys.
In the vast majority of cases, the rhesus monkeys looked at the videos that matched the number of recorded monkeys they were hearing.
The results are consistent with previous research findings that both animals and human infants tend to focus on visual images that match the sounds they're hearing.
"The results we obtained provide evidence that monkeys spontaneously detect a correspondence in number between two different sensory modalities [hearing and vision], and this tells us that language is not necessary to represent number abstractly," researcher Elizabeth Brannon, of Duke University's Center for Cognitive Neuroscience and the department of psychological and brain sciences, said in a prepared statement.
"When we humans apply the word 'three' to sounds or visual images, we're using language to link these different sets from different modalities. And the question has been whether an animal without that kind of language-based representation can still notice or represent these commonalities," Brannon said.
She and her colleagues plan to use the same kind of experiment to test whether human infants, before they develop language, have the same cross-modal numerical ability as the monkeys.
The study appears in the June 7 issues of Current Biology.
More information
The U.S. National Institute on Deafness and Other Communication Disorders outlines infant speech and language development.
