Prior work has established that measuring intents can influence the likelihood of behavior. Laboratory and field experiments extend past work and show that intentions are unique memorial structures that, once accessible, have profound influences on information processing and behavior. The results consistently demonstrate that measurement influences behavior and that measuring intent has a stronger influence on behavior than measuring attitudes. In addition, the laboratory experiment shows that measuring intents influences the accessibility and extremity of related yet previously unmeasured attitudes. However, measuring attitudes did not influence previously unmeasured intents. The research furthers our understanding of measurement effects and their impact on cognitive structure and behavior, and has implications for survey methodology and public policy. In addition, the research highlights the need for additional research on how intentions are represented in memory. ᭧ 2001 John Wiley & Sons, Inc.We have to remember that what we observe is not nature itself but nature exposed to our method of questioning. (Heisenberg, 1958, p. 58) Survey instruments are not passive vehicles for collecting information. Research indicates that the mere act of measurement influences the things being measured (e.g., Greenwald, Carnot, Beach, & Young, 1987;Gregory, Cialdini, & Carpenter, 1982; Morwitz, Johnson, & 812 CHAPMAN Schmittlein, 1993;Sherman, 1980). Historically, in the social sciences, a variety of terms have been used to label the effect of measurement on the things being measured, including measurement reactivity (Campbell & Stanley, 1966;Carlsmith, Ellsworth, & Aronson, 1976), the selferasing nature of errors in prediction (Sherman, 1980), context effects (e.g., Schwarz & Sudman, 1992), self-generated validity (Feldman & Lynch, 1988), and more recently, specific to the measurement of intent, mere measurement effects (Fitzsimons & Morwitz, 1996;Morwitz, Johnson, & Schmittlein, 1993). A common thread among these terms is simply that the process of questioning someone about their attitudes, beliefs, or intentions changes their cognitive structure and behavioral actions. As Feldman and Lynch (1988, p. 422) have stated, ". . . measurement changes the phenomena under study, producing the thought processes predicted by the theory being tested and quite possibly influencing behavior."If the measurement instrument itself were acting on memory and behavior, this would call into question much of our research, particularly predictive models of behavior such as the Theory of Reasoned Action (TRA). In fact, researchers testing the TRA appear to be concerned about self-generated validity effects, yet few have acted on this concern. Bonfield (1974, p. 383, footnote 1) issued one of the earliest, although footnoted, warnings, "A potential problem with respect to this and previous research testing Dulany's theory is reactivity." Similarly, Ajzen (1985, p. 21) acknowledged that, "It is interesting to note that the very act...