What triggers negative reactions?

Why do politicians want themselves photographed with babies? Why do sex and violence sell at the box office? Why do people pay more attention to bad news than good, even though they often say they want to hear more of the latter? Part of the answer may be that some information grabs people's unconscious attention without their being aware of it, says Stanford University psychologist Felicia Pratto, who studies automatic evaluation--unconscious mental categorization of people and objects as positive or negative, good or bad.

She and Oliver P. John of the University of California-Berkeley have discovered that this automatic processing is biased to pay more attention to negative stimuli than to positive ones. Negative words, for example, interfere more with conscious thinking than positive words do. Pratto calls the bias toward the negative "automatic vigilance" and believes it is an evolutionary adaptation of the species to protect individuals from immediate threats. Words that have to do with reproduction--such as babies and sex--are the only category of positively connoted nouns they have found that grab as much attention as negative nouns.

These unconscious judgments serve as an input to deliberate processing later, such as when a voter is trying to decide between candidates for public office. Her research found that this automatic evaluation goes on without the...