all Primate Cognitive Neuroscience Laboratory stories

Monkey see, monkey infer

70652986 — Mon, 26 Mar 2007 06:26:58 -0400

Monkeys keep turning out to be smarter than people think they are. Researchers have shown that they can count to four and are aware of differences between languages like Dutch and Japanese, even though they don't known what is being said. Now, Harvard psychologists find that monkeys can draw correct conclusions about novel situations. For example, shown a white towel that turns blue, a blue knife, and a glass of blue paint, they can figure out that the paint, not the knife, is responsible for the change in color.

"Our studies reveal a striking continuity between humans and monkeys in their capacity to draw causal inferences without the help of familiarity with the events or situation," says Marc Hauser, a Harvard professor of psychology. "This ability highlights the richness of the monkey mind in terms of its understanding of the material world."

Hauser has been working with a colony of free-ranging rhesus monkeys on an island off Puerto Rico for many years. He and Bailey Spaulding, formerly a student of his, tested individual adult males and females of the colony on their ability to figure out cause and effect in unfamiliar situations.

In their experiments, they used a glass of water and a knife along with a whole apple and an apple cut in half. The knife can halve the apple, but the water can't. Do the monkeys grasp this?

In one set of tests the monkeys saw a glass of water and two whole apples. Then they viewed a knife being lowered and the apple cut in half. These are two perfectly plausible situations. Next, they saw the glass of water and two halves of an apple. Following this, a knife was lowered, and two apple halves seemingly became a whole apple.

To a human, even an infant who had never seen such things before, the last two apparent happenings would never really happen. Can monkeys infer the same outcomes? Evidently, the answer is "yes." They looked longer when a glass of water appeared to cut the apple than when a knife seemed to do the same. The longer look signaled disbelief.

Monkeys unable to master grammar crucial to human language

70652986 — Mon, 26 Mar 2007 05:34:40 -0400

Grammar is essentially a system of rules for taking a finite set of discrete elements and combining them into a limitless range of novel expressions. For humans, grammar cobbles together words to create sentences. There is no evidence that animals have a similar system to produce sequences of calls with more expressive meaning. Together with W. Tecumseh Fitch of the University of St. Andrews, Marc D. Hauser, professor of psychology and Harvard College Professor, exposed cotton-top tamarins to two novel grammars based on patterns of meaningless syllables. Following this initial exposure, the tamarins heard a series of recordings, some of them violating the rules of Hauser and Fitch's grammars. When the animals perceived such inconsistencies, they tended to glance toward the speaker piping out the sounds, a behavior often used as an indicator of novelty detection in studies involving both animals and infants. Based on the percentage of the time the tamarins looked to the speakers, Hauser and Fitch determined that the animals were able to perceive violations of the simpler grammar but did not take note of infractions involving the more complex grammar. Their study was reported in the journal Science.

Researchers debate origin of language

70652986 — Mon, 26 Mar 2007 05:26:25 -0400

Birds sing, chimps grunt, and whales whistle, but those sounds fall far short of expressing the richness of their experiences. Their lack of language goes to the question of why humans have it but no other animals do. That question in turn leads to two major theories of the origin of language. One is the idea that language arises from bird song, dolphin whistles, monkey hoots, and other precursors that extend back through hundreds of millions of years of evolution. The other theory maintains that language is a uniquely human adaptation, or series of adaptations, with no precursors among other species. Marc Hauser, a Harvard professor of psychology, and his colleagues have come up with a third idea.

Monkeys distinguish different languages

70652986 — Mon, 26 Mar 2007 05:08:26 -0400

Researcher Marc Hauser and his colleagues tested the reactions of both cotton-top tamarin monkeys and French infants to the different sounds of Dutch and Japanese languages. Both monkeys and babies listened to speakers of one language until they became bored. When the speakers switched to a new language, babies instantly showed a shift in attention by increasing the rate at which they sucked on pacifiers. The monkeys quickly looked in the direction of the speakers. It's not just the change in sound that attracts their attention. When the sentences are played backward, neither responds.