Consumers are not just influenced by the words they hear or read, but also by the images that create context. As with verbal messages, graphic messages vary in their appeal—and their ability to drive specific actions. For example, the Lybrel image of a woman who looks like she's dancing in a flowing dress is most effective at convincing women to speak to their doctors at their next appointment. The YAZ image of a woman in a fighter's stance is most effective in motivating post-childbearing women to visit a Web site.

These images are quite different. Lybrel's graphic communicates grace and freedom (the woman looks almost as though she is about to take flight). YAZ's graphic, by contrast, suggests power and strength (the woman is poised to punch). Yet each of these photos is effective in driving a specific action. In order to select the right picture, it is critical to know who your target audience members are, as well as the action you want them to take.

In addition, it's important to remember that some images won't work well with any group, and can dilute the power of your message. For example, the Yasmin photo of a young woman passively resting her head on her boyfriend's shoulder was the least motivating, across the board. It is important to have a research tool that allows you to test the full range of possible graphic and message combinations, both to identify those that work, and to eliminate those that won't do your brand justice in the market.

Clearly, different messages and graphics appeal to different audiences. So how do you find the best combination of images, spokespeople, and messages for DTC campaigns?

First, test a large number of message and image combinations. To make sure your best ideas don't end up on the cutting room floor, be sure you choose a research methodology that allows space for a wide range of options—even the most bold. Taking all message and graphic options into consideration, it's possible to end up with 100 or more alternatives—and every one of those needs to be assessed to ensure the best results.

Second, consider the target audience. Think about whom the ad is seeking to motivate. Those with moderate or severe conditions? Current users, or those disengaged from the healthcare system? People on treatment, or those not yet diagnosed? Different audiences respond to different approaches.

Third, consider the actions the audience should take as a result of seeing the ad. The ad that will send a viewer to the doctor may be different than one that would convince him or her to call an 800 number or to visit a branded Web site. (Keep in mind that different actions are connected in driving brand performance. For example, a Web site visit can increase intent to contact a physician by as much as 50 percent. In fact, Web site visits are among the most common actions that DTC ads drive—and are strongly correlated with both new and total prescriptions.)

Fourth, test messages in bundles—just like viewers see them in the real world. It's a combination of all the elements that determines how well an ad will work. Looking at ad elements in isolation won't give you a true picture of how consumers will respond.

In the end, the key to an effective DTC ad is one in which all the elements work together. If the message doesn't resonate, the ad won't do its job. The key to effective advertising is selecting the right message to share and the right graphic context in which to share it.

David Kweskin is senior vice president at TNS. He can be reached at david.kweskin@tns-global.com