Ask somebody who's not from the United States to describe Americans, and almost invariably you'll get a description of someone who's outgoing and upbeat. No challenge is too great for us, no obstacle too high. In fact, to the outsider, our overwhelmingly sunny view of life sometimes seems a bit naive, our boundless enthusiasm rather childlike.

American optimism carries over into our economy, which is one reason why we've always been a nation of inventors and tinkerers, of innovators and experimenters and why we're the most productive economy in the world.

Optimism also explains why we save so little and spend so much. As long as such things have been measured and compared, Americans have had the lowest rate of saving and the highest rate of personal spending of any major economy, and over the last decade, we've saved less and less and spent more and more. Our willingness to go deep into debt and keep spending is intimately related to our optimism and our deepest assumptions about future peace, stability and progress.

But a week ago today, that optimism was shaken in a way it has never been shaken before. There have been terrible events in our nation's history, to be sure: presidents assassinated, leaders killed, battles lost. But the terror we experienced last week, the mass murder we witnessed with our own eyes on television, the grieving and the fear it has provoked is something new. We remain optimistic, of course. Our national character hasn't been reversed, but it seems unlikely we'll ever be entirely the same.

There's a lot of pondering going on in economic circles about consumer confidence over the next weeks or months, as if consumer confidence were a kind of barometric gauge that moves up or down around a normal level. Most analysts assume consumer confidence has dropped, both in light of last week's horror and also an economy already weakened before the attack.

The question analysts are trying to answer is when consumer confidence will be restored, when Americans will go back to our normal ways of spending a lot and saving little or nothing. No one knows the answer, of course, but it's possible that the gauge itself may have been altered somewhat by what happened a week ago today, and that what had been our normal level of confidence about future peace, stability and progress is no longer exactly what it used to be.