Americans have pictured the stock market the exact same way for generations.

Men in blue jackets scamper across a trading room floor at the New York Stock Exchange, alternatively delighted or despondent, following rises and falls of geopolitical turmoil, the specter of regulation or, perhaps, the whims of other investors.

Most trading these days does not happen on the floor of the exchange. The majority are the result of selections made by algorithms, trades executed from one machine to another.

What these images of men on the trading floor convey is the mood of Wall Street, where the action affects everything from the fortunes of corporate executives to retirement savings of middle-class families with 401(k) accounts. And on days like Monday, when the Standard & Poor’s 500-stock index and the Dow Jones industrial average both experienced historic drops, pictures of anguished traders in news stories were reminders that what goes up inevitably comes back down (if only to go back up once again).