You are having dinner with your former college roommate, who is a neurosurgeon. You are an account planner at an advertising agency, and you do a lot of ad testing. You're trying to get him to help you with some neurological tests to determine the effectiveness of some of your clients' ads, especially those that attempt to evoke strong emotional responses. He asks you, "If advertising is done to sell a product, why don't you just measure sales to determine the effectiveness of an ad?" You try to explain to him that it is not that simple, and you tell him about all the types of research you conduct at various stages of a campaign. Which of the following is a reason that advertisers use other measures in addition to sales as a measure of advertising effectiveness?