NASHVILLE, Tenn. — As anxiety on Wall Street led banks and other investors to hoard cash last week, a different kind of market fear gripped cities across the Southeast.

A hurricane-related disruption in gasoline supplies prompted jittery drivers from Atlanta to Nashville to top off their fuel tanks more than usual, causing sporadic shortages and temporary shutdowns of stations. These closures only magnified the problem, of course, leading to more shortages, which sent local prices skyrocketing.

"It's a wonder people didn't go out and empty all of the grocery store shelves, too," said Larry Lamb, of Nashville. "All you need to do when something like this happens is just calm down."

Perhaps — in hindsight — that is the sensible thing to do.

But economists and other experts say individuals — not just Americans — are hard-wired to respond quickly when they are scared, and in a way that is not always in their own, or their neighbors', best interests.

Dennis Jacobe, chief economist for Gallup Inc., said an emotional response is quite normal when expectations — such as gas being available or the safety of a money-market fund — suddenly are called into question.

"When those basic assumptions of your daily life are violated, it sends you a shock and you do get emotional, irrational reactions," Jacobe said. "That means panic."

Lars Perner, an assistant professor of clinical marketing at the University of Southern California, said the combination of worries about the economy and gasoline supplies may have exacerbated motorists' reactions.

"Once you get into that kind of negative thinking, you often have a vicious cycle going on," Perner said. "You get into sort of a protective instinct that comes out — and you go and fill up."

This protective instinct is what drove pension funds, corporations and other institutional investors to make large-scale withdrawals from U.S. money-market mutual funds earlier this month, jeopardizing the nearly $3.4 trillion industry — until the government stepped in to prop it up.

That run was prompted after Reserve Primary Fund, the nation's oldest money-market fund, suffered a setback that had occurred just once before in the industry's nearly four-decades-long history: Its underlying assets fell to 97 cents for each investor dollar put in, a phenomenon the industry calls "breaking the buck."