washingtonpost.com
Science Digest

Monday, July 20, 2009

Monkeys Recognize Grammar Principle

Researchers at Harvard University have evidence that monkeys can understand the difference between prefixes and suffixes, showing that animals may have more capacity to learn language than previously thought.

In a study released this month in Biology Letters journal, Ansgar D. Endress and his colleagues tested 14 cotton-top tamarins to see if they could learn the linguistic rule that adds "-ed" to create the past tense, as in transforming "kick" to "kicked."

The scientists used the nonsense syllable "shoy" as a base, then they added prefixes and suffixes such as "ba, pu, di, ki, lu, ro and mo" and played the monkeys recordings of humans saying these "words." One group became familiar with prefixes, such as "ba-shoy" and "mo-shoy," and the other group heard suffixes, such as "shoy-ba" and "shoy-mo."

On testing day, the researchers played a recording of words, half of which stuck to the monkey's familiarization pattern and half that violated it -- similar to saying "kicked" and "edkick." When the tamarin turned his head at least 60 degrees toward the speaker, the researchers counted this as a response. The human equivalent would be if someone said, "The girl edkick the ball," and the listener cocked his head as if to say, "What?" The tamarins responded 52 percent of the time after hearing a violation, compared with 37 percent for correct grammar.

"One of the big mysteries is why we speak and other animals don't," Endress said. He said he "would be surprised" if the ability to understand prefixes and suffixes were limited to humans and primates.

-- Rachel Saslow

Predicting Water Needs of Troops

Humans typically need to drink six to 12 cups of water or other noncaffeinated or nonalcoholic drinks a day to stay hydrated, but soldiers, especially those in Iraq and Afghanistan who wear body armor in very hot climates, can require three times as much. A study published in the online version of the Journal of Applied Physiology may help military planners determine how much water soldiers on a mission will need.

"It is important not to predict wrongly," said Samuel Cheuvront, a research physiologist and principal investigator at the U.S. Army Research Institute of Environmental Medicine. "Other than fuel, water is the most expensive thing to transport onto the battlefield."

The new research updates the former equation and in laboratory settings improves water-need predictions by 58 to 65 percent. The new equation takes into account a broader range of metabolic rates, clothing types, the use of body armor and a longer duration of work. It has yet to be tested in the field.

Cheuvront, an author of the study, said there are also public health applications. He said the Institute of Environmental Medicine will be using the new equation to update its dietary guidelines.

"But in terms of your average Joe who goes to the gym for 30 minutes and works out on the StairMaster? There are better ways to determine your water needs," Cheuvront said.

He suggested the best way for people who exercise an hour or less a day to determine how much water they lose -- and therefore how much they need to replace -- is to weigh themselves before and after their workout.

"For every pound that you lose, that means you've lost 16 fluid ounces," he said. The amount of fat lost in a short bout of exercise is minimal and will not alter the approximate measurement of sweat loss, according to Cheuvront.

Cheuvront also suggested paying attention to the color of your urine in the morning.

"If it is [the color of] apple juice or darker, then you aren't drinking enough. If it's lemonade or lighter, then you are meeting your fluid needs," he said.

-- Ibby Caputo

View all comments that have been posted about this article.

© 2009 The Washington Post Company