http://www.signonsandiego.com/news/science/20080930-0732-financial-psychology-.html

Experts Say Herd Mentality Rules in Financial Crisis
from the San Diego Union-Tribune (Registration Required)
WASHINGTON (Reuters)—Herd mentality rules during a financial crisis
because people are wired to follow the crowd when times are uncertain,
experts say.
Brain and behavior studies clearly show that when information is
scarce and threats seem imminent, people often stop listening to their
own logic and look to see what others are doing.
"People are afraid, and the reason they are afraid is there is
tremendous uncertainty right now in the markets," Gregory Berns, a
neuroeconomist at Emory University in Atlanta who studies the biology
of economic behavior, said in a telephone interview. Berns puts people
in magnetic resonance imaging or MRI scanners while he tests their
responses to various scenarios, and studies patterns of their brain
activation.