Throughout the past four years, the bull market has repeatedly withstood challenges to its endurance, often coming back from substantial morning losses to finish higher on the day. Today, though, the market has followed the opposite trend: Early gains have given way to losses as investors anticipate potentially market-moving comments from various Federal Reserve officials and the Bank of Japan. With so much riding on global economic growth and so much policy action aimed at stoking greater business activity, investors won't be convinced that the economy can move forward on its own until they actually see it with their own two eyes. Until that happens, nervousness like we've seen today will persist. As of 1:30 p.m. EDT the nervousness was winning out, sending the Dow Jones Industrials (^DJI -0.12%) down 95 points, or 0.63%.

Yet when you look at the winners of today's session, you'll notice that they largely represent follow-through gains from the news of previous sessions. Merck (MRK 0.25%) is 2.4% higher, touching another multiyear high after gaining almost 4% yesterday on the heels of a positive announcement about its promising early-stage cancer treatment. What investors might be realizing is that yesterday's news on Merck isn't just about a single treatment, but rather an entire new class of treatments that stimulate the PD-1 protein within a patient's body in order to fight cancer. Immunotherapeutic techniques aren't brand new, but as Merck gains expertise in dealing with this particular treatment, it's also building a foundation to expand its overall presence in the immunotherapy niche, and that arguably has greater long-term value than any single treatment.

Intel (INTC -1.60%) has climbed about 2% today, adding to yesterday's 4% jump. Considering how important it is that Intel builds its presence in the mobile-device market, the introduction of Samsung's Galaxy Tab 3 tablet with an Intel-branded Atom Clover Trail+ dual-core processor marks a potential breakthrough for the company. That Intel has traded at such modest valuations owes to its seeming inability to make its presence felt in the mobile space. Although a single device doesn't create a trend, Intel's stock could see more big gains if the company can follow up on this win by getting its processors into other high-profile products.

Finally, AT&T (T 0.19%) has climbed 1.6%. Last night's news that the telecom giant is working with IBM to build more efficient mobile apps probably wasn't enough to move the stock, and AT&T still faces potential restrictions in an FCC auction of wireless spectrum scheduled for next year to ensure that smaller carriers are able to get a share of available spectrum. The more likely explanation for the gain is simply that the high-yielding stock got beaten down especially hard during last week's run-up in interest rates, and as the bond market has shown signs of stabilizing at least for now, a small bounce for AT&T stock seems warranted. In the long run, AT&T should be able to count on its reliable revenue stream from wireless customers well into the future.