People cannot know what they want in all possible situations. Rather, they must construct specific preferences from more basic values. In making these inferences, people must seek cues in a world that might be indifferent, helpful, or manipulative. The better they understand the factors shaping their inferences, the better their chance of learning what they want. An analogous challenge faces researchers, decision analysts, counselors, and others seeking to elicit people's values. It also faces those (advertisers, politicians, pundits, etc.) hoping to manipulate those factors and get people to convince themselves that they want a particular product, candidate, ideology, or lifestyle.

Identifying the factors shaping behavior is psychology's central challenge. To study theoretically relevant factors, researchers must control irrelevant ones. Over time, those nuisance factors often prove important in their own right. McGuire (1969) has depicted the history of psychology in terms of turning “artifacts into main effects.” Table 35.1 assembles parts of this history in terms of the four essential elements of any behavior: the organism whose preferences matter, the stimulus intended for evaluation, the response mode for expressing preferences, and potentially distracting contextual elements.

In the 25 years since Table 35.1 was created, the attention paid to its various topics has varied, reflecting researchers' sensitivity to them as artifacts and interest in them as main effects. For example, affective influences on preferences are better understood now, partly due to advances in psychophysiology (Slovic, Finucane, Peters, & MacGregor, 2002).