As well as features of respective if-then plans (e.g., the precision, viability, and instrumentality of the plan components), two other factors are important in determining the strength of implementation intention effects. The first concerns the presence of a self-regulatory problem. When there are few barriers to goal achievement, then favorable goal intentions and self-efficacy can suffice in promoting performance, and implementation intention formation might be superfluous (e.g., Gollwitzer & Brandstätter, 1997, Studies 1 & 2; Sheeran & Orbell, 1999, Study 1). However, when goal striving is difficult, or when people have chronic difficulties in striving to obtain their goals (e.g., schizophrenic patients, opiate addicts, patients with a frontal lobe injury; see Brandstätter et al., 2001; Lengfelder & Gollwitzer, 2001) then it is especially worthwhile to engage in if-then planning (Gollwitzer & Sheeran, 2006).
Strength of Goal Intentions
A second determinant of the strength of implementation intention effects is the state of the respective goal intention. When people have no intention of pursuing a health goal then they are unlikely to form an implementation intention that spells out adequately when, where, and how the goal will be pursued, even when asked to do (Sheeran, Milne, Webb, & Gollwitzer, 2005). Sheeran, Webb, and Gollwitzer (2005) showed that strong effects of implementation intentions were obtained predominantly when the underlying goal intention was strong and activated (see also Seehausen Bayer, & Gollwitzer, 1994, cited in Gollwitzer, 1996). Similarly, Koestner, Lekes, Powers, and Chicoine (2002) showed that if-then plans benefited the completion of personal projects more when those projects were consistent with personal interests and values than when projects were motivated by external reasons such as social pressure. Because implementation intentions are formed for the purpose of enhancing the translation of goal intentions into action, it is important to ensure that strong positive goal intentions exist among one’s target sample. If goal intentions are unfavorable, then studies may need to start out with a motivational intervention to promote the requisite goal intentions before having participants form implementation intentions that are designed to strengthen intention-behavior consistency (Oettingen, Barry, Guttenberg, & Gollwitzer, 2007).