Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

After enduring a brutal 500-point drop to end last week, investors can expect a positive start to the stock market today: The Dow Jones Industrial Average (DJINDICES:^DJI) gained 62 points, or 0.4%, in premarket trading this morning.

World markets continued their declines in overnight trading, but investors may focus on the flood of corporate profit reports instead. We are about one-quarter of the way through earnings season, and profits are up 6.4% overall, which is slightly better than the 6.2% rise that analysts are expecting. Apple is set to report its results after the closing bell today. In the meantime, news is breaking this morning on a few stocks that could see heavy trading in today's session, including Caterpillar (NYSE:CAT), Vodafone (NASDAQ:VOD), and Roper Industries (NYSE:ROP).

Caterpillar this morning booked a 48% rise in fourth-quarter profit, to $1.54 a share. Revenue fell by 10%, to $14.4 billion, on continued weakness in the mining business. Still, that sales performance was better than analysts expected: Wall Street had looked for a 15% drop in revenue. The heavy machinery manufacturer also made some solid progress at paring down its inventory levels, which could set the stage for improving results in the quarters ahead. The company expects this year's sales to be roughly even with 2013's result, at about $56 billion. The stock is up 6.5% in premarket trading.

AT&T (NYSE:T) isn't interested in buying Vodafone. The telecom giant said this morning that rumors about a potential acquisition or merger are wrong, and that AT&T "does not intend to make an offer for Vodafone." The U.K-based communication company's shares rose 27% in the last six months as speculation over a deal has grown. But Vodafone's stock is giving up some of those gains this morning, down 4.8% in premarket trading.

Finally, Roper today reported fourth-quarter earnings of $1.65 a share on revenue of $890 million. Both figures were slightly higher than analysts anticipated. However, the company gave an earnings outlook for 2014 that was a bit below expectations. Roper sees profits coming in at about $6.15 per share this year, as opposed to the $6.28 that analysts forecast. Roper's stock is unchanged in premarket trading.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.