Ironically, the more bad news there is, the less likely people may be to give.

"Hearing about too many disasters makes some people not give at all, when they would have if it had been just one disaster," says Michal Ann Strahilevitz, who teaches marketing at Golden Gate University and specializes in the factors at play in charitable giving.

Compared with disasters like the Asian tsunami and Hurricane Katrina, those in China and Myanmar have generated just a trickle of aid. As of Friday, Americans had given about $12.1 million to charities for Myanmar, according to the Center on Philanthropy at Indiana University. The group said on Monday that it was too soon to count contributions to China.

A number of factors may be at play in the slow American response, including a lack of sympathy for the repressive governments involved, doubts about whether aid will get through, and an inclination to save pennies because of shaky economic times at home.

But Americans may have also been influenced by the quick succession of monumental catastrophes in two distant lands. At least 130,000 people are dead or missing in the Myanmar cyclone, and more than 34,000 in China's earthquake.

"For the vast number of Americans, if they just gave to some disaster far away and then another disaster happens, in their mind that's clumped as 'faraway disaster,'" Strahilevitz says. "So they will feel, 'I just gave to a faraway disaster.'"

This problem came up after the 2004 Asian tsunami, an event that brought an avalanche of $1.92 billion in charity from the United States, according to the Giving USA Foundation. Hurricane Katrina eight months later generated even more, $5.3 billion.

But then fatigue seemed to set in. The earthquake in Pakistan that killed nearly 80,000 people generated just $150 million from Americans. And the Guatemala mudslide shortly thereafter that killed at least 800 was virtually forgotten.

If one disaster can be galvanizing, several in a row can be paralyzing.

"It's too much pain, too much tragedy for someone to process, and so we tend to pull ourselves away from it and either close off from it out of psychological defense, or it overwhelms us," says Cynthia Edwards, a professor of psychology at Meredith College in Raleigh, N.C.

A string of tragedies can also make potential donors feel nervous about their own safety, making them less likely to give. That could be especially troubling now for Americans, many of whom are worried about their jobs and rising food and gas prices.

It's too soon to judge the effects of the economic downturn on giving, says Del Martin, chair of the Giving USA Foundation, although early figures show that donations rose in 2007. In general, people tend to give to causes closer to home. In 2006, Americans gave more than $295 billion to charity, but less than 4 percent of that went overseas.

One thing that may make people give to foreign causes is their personal connection to a region, either by knowing someone there or hearing an individual's story, Strahilevitz says. That's something that's difficult when unpopular governments are involved, or media access is restricted, as in Myanmar.

Lurma Rackley, spokeswoman for CARE USA, is heartened that Americans are giving to Myanmar at all, considering the lack of images from the disaster. "There's always concern that the tragedy is going to be forgotten," Rackley says.

CARE USA, World Vision and Mercy Corps all say giving for Myanmar is on pace to match the amount given after the Pakistan earthquake, although the Myanmar death toll appears to be far bigger. That's partly because of concerns about whether aid will reach the intended recipients, with reports that Myanmar's military government may be confiscating the aid or diverting it away from those most in need.

That's part of why Dave Morris, 34, has yet to open his checkbook - he's not sure he could really help.

Morris aims to give 10 percent of his income to causes such as public radio, the Red Cross and breast cancer. But the engineer from Ypsilanti, Mich., hasn't given to the relief efforts in Myanmar and China, in part because the world's problems seem impossibly large.

"If you thought about at this very second the number of people who were suffering and dying, I could dedicate all my resources to that and yet it would be a drop in the bucket," he says.

Still, experts in the field are optimistic that Americans may still come through for victims of these disasters. The Giving USA Foundation says companies are pledging relief funds for China, perhaps because so many do business there.

"I think we may also see a surge of donations for the China relief effort because of people's frustrations with the Myanmar government's resistance to the aid effort there," says Gerard Jacobs, director of the Disaster Mental Health Institute at University of South Dakota.

Jacobs was in Bangkok working with the Asian Disaster Preparedness Center when the cyclone struck Myanmar, and he got word of the earthquake while in a meeting about helping governments in the region to respond to victims' psychological needs.

"People may feel a sense of relief that the China earthquake presents a situation where the public can genuinely make a difference," he says.