Empirical evidence for effects of moods (both naturally occurring and experimentally manipulated) on behavior is reviewed in terms of an integrative theory: the mood–behavior model (MBM). It is posited that moods can influence behavior via 2 processes: (a) by informational effects on behavior-related judgments and appraisals, which in turn will result in behavioral adjustments (i.e., the informational mood impact on behavior), and (b) by influencing behavioral preferences and interests in compliance with a hedonic motive (i.e., the directive mood impact on behavior). The strength of the informational mood impact depends on moods' effective informational weight for behavior-related judgments and on mood-primed associations. The strength of the directive mood impact is predicted to be jointly determined by 2 variables: the strength of a hedonic motive and the instrumentality of possible acts for affect regulation.

An experiment with 64 participants manipulated task difficulty and assessed cardiac reactivity in active coping over four levels of demand. Participants performed a memory task while preejection period, heart rate, and blood pressure were assessed. In accordance with the theoretical predictions of R. A. Wright's (1996) integration of motivational intensity theory (J. W. Brehm & E. A. Self, 1989) with Obrist's active coping approach (P. A. Obrist, 1981), preejection period and systolic blood pressure reactivity increased with task difficulty across the first three difficulty levels. On the fourth difficulty level-where success was impossible-reactivity of both preejection period and systolic blood pressure were low. These findings provide the first clear evidence for the notion of Wright's integrative model that energy mobilization in active coping is mediated by beta-adrenergic impact on the heart.

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In this article it is proposed that the principles of motivational intensity theory (Brehm & Self, 1989) apply to effort mobilization for challenges with consequences for performers’ self-esteem and self-definition (i.e., self-involvement). Accordingly, involvement of the self makes success important and thus justifies the mobilization of high resources. However, up to this level of maximally justified resources, actual effort is mobilized in correspondence to subjective task difficulty as long as success is possible. We report a series of experimental studies that have operationalized effort intensity as cardiovascular reactivity during task performance and used multiple manipulations of self-involvement (social evaluation, self-awareness, ego involvement, personal goals) and task difficulty. The empirical evidence clearly supports the idea that the principles of motivational intensity theory apply to performance conditions that have direct consequences for self-definition and self-esteem and challenges a number of other theoretical accounts.

This chapter deals with the psychological process that determines effort intensity in instrumental behavior. According to motivation intensity theory, effort should be proportional to experienced task difficulty as long as success is possible and justified and low when success is impossible or excessively difficult, given the available benefit. When task difficulty is unspecified or unknown, effort should be proportional to the importance of success. We report a program of experimental studies that have operationalized effort intensity as cardiovascular reactivity during task performance and used multiple manipulations of variables influencing subjective task difficulty (e.g., performance standards, ability, mood) and the amount of justified effort (e.g., material incentive, instrumentality, evaluation). The empirical evidence is in clear support of the principles of motivation intensity theory and challenges a number of other theoretical accounts. Directions for future research are discussed.