Implementation Intentions
Peter M. Gollwitzer, and Paschal Sheeran

Most theories designed to understand and predict health behaviors–including protection motivation theory (PMT, Rogers, 1983 xClose
Rogers, R. W. (1983). Cognitive and physiological processes in fear appeals and attitude change: a revised theory of protection motivation. In B. L. Cacioppo & L. L. Petty (Eds.), Social psychophysiology: A sourcebook (pp. 153-176). London: Guildford.), the prototype/willingness model (PWM; Gibbons, Gerrard, & Lane, 2003 xClose
Gibbons F. X., Gerrard, M., & Lane, D. J. (2003). A social-reaction model of adolescent health risk. In J. J. Suls & K. A. Wallston (Eds.), Social psychological foundations of health and illness (pp. 107-136). Oxford, England: Blackwell.), the theory of planned behavior (TPB; Ajzen, 1991 xClose
Ajzen, I. (1991). The theory of planned behavior. Organizational Behavior and Human Decision Processes, 50, 179-211.), and social cognitive theory (Bandura, 1997 xClose
Bandura, A. (1997). Self-efficacy: The exercise of control. W. H. Freeman: New York.)—construe the formation of a goal intention as the key act of willing that promotes goal attainment. Goal intentions can be defined as the instructions that people give themselves to perform particular behaviors or to achieve certain desired outcomes (Triandis, 1980 xClose
Triandis, H. C. (1980). Values, attitudes, and interpersonal behavior. In H. Howe & M. Page (Eds.), Nebraska symposium on motivation (Vol. 27, pp. 195-259). Lincoln, NB: University of Nebraska Press.) and are measured by items of the form, "I intend to achieve X!" Goal intentions can vary in strength as they index a commitment to pursuing a goal or performing a behavior (Gollwitzer, 1990 xClose
Gollwitzer, P. M. (1990). Action phases and mindsets. In E. T. Higgins & J. R. M. Sorrentino (Eds.), The handbook of motivation and cognition (Vol. 2, pp. 53-92). New York: Guilford.; Webb & Sheeran, 2005 xClose
Webb, T. L., & Sheeran, P. (2005). Integrating concepts from goal theories to understand the achievement of personal goals. European Journal of Social Psychology, 35, 69-96.). For example, smokers may have weak intentions to quit smoking next week but strongly intend to quit ‘some day;’ a woman may intend to get a mammogram soon, and an overweight man might definitely intend to lose a certain amount of weight during the coming year.

Correlational surveys that measure participants’ goal intentions at one time-point and measure behavioral outcomes at a later time-point seem to support the predictive validity of goal intentions. For instance, a meta-analysis of 10 previous meta-analyses found that goal intentions accounted for 28% of the variance in behavior, on average, across 422 studies (Sheeran, 2002 xClose
Sheeran, P. (2002). Intention-behavior relations: A conceptual and empirical review. In W. Stroebe & M. Hewstone (Eds.), European Review of Social Psychology (Vol. 12., pp. 1-30). Chichester: Wiley.). Although R² = .28 is a large effect size (cf. Cohen, 1992 xClose
Cohen, J. (1992). A power primer. Psychological Bulletin, 112, 155-159.), a substantial proportion of the variance in behavior is not explained by goal intentions. The magnitude of the gap between intentions and action is illuminated by studies that decomposed this relationship in terms of a 2 (goal intention: to act vs. not to act) X 2 (goal attainment: acted vs. did not act) matrix (Orbell & Sheeran, 1998 xClose
Orbell, S., & Sheeran, P. (1998). "Inclined abstainers": A problem for predicting health-related behavior. British Journal of Social Psychology, 37, 151-165.). A review of health behavior matrices (e.g., condom use, exercise, cancer screening) found that people translated their ‘good’ intentions into action only 53% of the time (Sheeran, 2002 xClose
Sheeran, P. (2002). Intention-behavior relations: A conceptual and empirical review. In W. Stroebe & M. Hewstone (Eds.), European Review of Social Psychology (Vol. 12., pp. 1-30). Chichester: Wiley.). More seriously, evidence indicates that correlational studies overestimate the consistency between intentions and behavior. A meta-analysis of experimental studies that succeeding in changing goal intentions among treatment versus control conditions (Webb & Sheeran, 2006 xClose
Webb, T. L., & Sheeran, P. (2006). Does changing behavioral intentions engender behavior change? A meta-analysis of the experimental evidence. Psychological Bulletin, 132, 249-268.) found that the magnitude of the difference in subsequent behavior was only small-to-medium (R² = .03). In sum, accumulated evidence indicates that forming even strong goal intentions does not guarantee goal attainment.