Dartmouth team than did Dartmouth viewers. One Dartmouth alumnus did not see any infractions committed by the Dartmouth side and erroneously assumed he had been sent only part of the film, sending word requesting the rest. Selective perception is also an issue for advertisers, as consumers may engage with some ads and not others based on their pre-existing beliefs about the brand. Seymour Smith, a prominent advertising researcher, found evidence for selective perception in advertising research in the early 1960s, and he defined it to be "a procedure by which people let in, or screen out, advertising material they have an opportunity to see or hear. They do so because of their attitudes, beliefs, usage preferences and habits, conditioning, etc." People who like, buy, or are considering buying a brand are more likely to notice advertising than are those who are neutral toward the brand. This fact has repercussions within the field of advertising research because any post-advertising analysis that examines the differences in attitudes or buying behavior among those aware versus those unaware of advertising is flawed unless pre-existing differences are controlled for. Advertising research methods that utilize a longitudinal design are arguably better equipped to control for selective perception. Selective perceptions are of two types: Low level – Perceptual vigilance High level – Perceptual defense See also Confirmation bias List of cognitive biases Selective attention Selective retention Cognitive dissonance Selection bias References Cognitive biases