SCIENCE
Notebook

Monday, February 20, 2006

Need an Answer? Sleep on It.

When decisions involve a lot of complex factors, thinking deeply about them can produce worse outcomes than decisions made simply after "sleeping on it," according to research published last week in Science.

Volunteers asked to make judgments about the quality of different cars based on four criteria were more likely to choose the best car if they did think deeply about it, compared with those who did not put much effort into thinking about the decision.

But volunteers provided with 12 criteria about the cars fared worse when they thought deeply about their decision, compared with volunteers who were given the same information, were deliberately distracted by other things, and then were asked to make a judgment call.

Ap Dijksterhuis and colleagues at the University of Amsterdam said over-thinking complex decisions seems to produce dissatisfaction with the final answer, compared with simple gut responses. They hypothesized that the reason people do not make good decisions by thinking deeply in complex situations is because multiple evaluations of an issue can produce inconsistent conclusions. Additionally, people really can take into account only a limited number of things and, when presented with too much information, they focus on the wrong things.

"We tend to inflate the importance of some attributes at the expense of others, leading to worse choices," the scientists wrote. They later added that it "should benefit the individual to think consciously about simple matters and to delegate thinking about more complex matters to the unconscious."

-- Shankar Vedantam

Indians Depleted Wildlife, Too

Like the Europeans who came later, the first Americans apparently had a propensity for killing and eating any animal they could lay their hands on without giving a lot of thought to the future, judging by the bones they left behind at one notable site.

"The general public probably buys into the 'Pocahontas version' that Native Americans were inherently different and more in tune with nature," said University of Utah archaeologist Jack Broughton. "The evidence says otherwise."

After studying thousands of animal bones found in a garbage heap on the shores of San Francisco Bay, Broughton concluded that Native Americans living in an area where Emeryville is now located hunted several species to local extinction from 600 B.C. to A.D. 1300.

The lowest strata from the Emeryville Shell Mound showed many bones from large geese and cormorants, but the number and size of the birds dwindled over time: "About 1,500 years ago, there's a big crash in cormorants, and by the end of the sequence, all you get is the odd adult that wanders into the area," Broughton said.

Broughton, writing in Ornithological Monographs, said his most recent study of bird consumption showed the same pattern as his earlier studies of mammals and fish.

He said the lowest strata had the largest number of big animals, but number and size both decreased over time: "Longevity decreased due to harvest pressure."

Broughton acknowledged that European settlers speak of a "land of plenty," but they were latecomers, he said. Wildlife probably had rebounded after European diseases thinned the Native American population starting in the 1500s.

-- Guy Gugliotta

Stomach Hormone Boosts Brain

A hormone produced by the stomach can boost the number of connections between neurons in a part of the brain involved in forming new memories, providing new evidence for the close connection between the brain and the gut.

The recently discovered hormone, ghrelin, is released into the bloodstream by the stomach when it is empty and travels to the brain, where it stimulates appetite. But the hormone's function in other parts of the brain has been unknown.

In new experiments, Tamas Horvath of Yale Medical School and colleagues found that mice genetically engineered to lack the gene necessary to produce ghrelin have 25 percent fewer connections in a part of the brain known as the hippocampus, which is involved in forming new memories.

When normal mice are injected with extra ghrelin, they form extra connections in that part of the brain. Moreover, tests show that the animals have enhanced ability to learn and remember, the researchers reported in a paper published online yesterday by the journal Nature Neuroscience.

More research is needed to explore why the hormone has that effect, the researchers said. The findings suggest the hormone might be useful for treating learning and memory problems, such as those caused by aging and brain ailments such as Alzheimer's disease, they said.

-- Rob Stein