The influences of intrinsic motivation on execution of social behaviour within the theory of planned behaviour

The present study examined the utility of two forms of measurement of intrinsic motivation in increasing the predictive validity of the theory of planned behaviour. Self-report questionnaires were administered to school pupils (n1⁄4 174), University students (n1⁄4 129) and adults (n1⁄4 157). The data were analysed using confirmatory factor analysis and regression analysis. Confirmatory analysis supported discriminant validity between Forms A and B measures of intrinsic motivation. In addition, hierarchical regression analysis demonstrated that Form B measure of intrinsic motivation increased effectiveness of the theory of planned behaviour in predicting intentions and social behaviour. Further, the regression analysis showed that age and past behaviour did not reduce the effects observed for intrinsic motivation. It is recommended that intrinsic motivation could increase the predictive utility of the theory of planned behaviour. Copyright # 2006 John Wiley & Sons, Ltd. The theory of planned behaviour provides a useful framework for predicting and explaining social behaviour (Ajzen, 1991). According to this theory, behaviour can be best predicted from a person‘s intention, which is an indicator of how hard people are willing to try, and how much effort people plan to exert toward performance of behaviour (Ajzen, 1991). Intention is in turn a function of attitudes (positive or negative evaluation of performing the behaviour), subjective norm (perceived influences that significant others may exert on the execution of behaviour) and perceived behavioural control (the extent to which people believe that they can control performance of social behaviour). For Ajzen (1991), perceived behavioural control can also predict behaviour directly when behaviour is not under complete volitional control and when perceptions of control are realistic. The theory of planned behaviour also deals with antecedents of attitudes, subjective norms and perceptions of control. The theory proposes that attitudes arise out of a combination (multiplicative function) of beliefs that the behaviour will lead to certain consequences (behavioural beliefs) and Received 24 March 2004 Copyright # 2006 John Wiley & Sons, Ltd. Accepted 23 February 2005 *Correspondence to: Nikos L. D. Chatzisarantis, School of Health and Exercise Sciences, University of Exeter, Heavitree Road, Exeter, EX1 2LU, UK. E-mail: [email protected] evaluations of these consequences. This relationship between behavioural beliefs and evaluations is known as the expectancy value model and is grounded in subjective expected utility theory (Ajzen, 1991). Subjective norms and perceptions of control are also proposed to have similar origins. Subjective norms are determined by a combination of normative expectations of others (normative beliefs) and a motivation to comply with those others. Perceptions of control are determined by beliefs about the presence of factors that may facilitate or impede performance of behaviour (control beliefs) and a perceived power of these facilitative and/or constraining factors (Ajzen, 1991). Meta-analytic reviews of previous research have found that attitudes, subjective norms and perceptions of control are good predictors of intentions, and that intentions and perceptions of control predict behaviour (Hagger, Chatzisarantis, & Biddle, 2002). Nevertheless, as Ajzen (1991), and more recently Hagger et al. (2002a) noted, additional predictors should be included in the theory if it is shown that they explain a significant portion of variance in intentions or behaviour after the theory’s original components have been taken into account. The Theory of Planned Behaviour and Intrinsic Motivation The present study considers the role of intrinsic motivation in the theory of planned behaviour. Based on self determination theory (Deci & Ryan, 1980), Hagger, Chatzisarantis, and Biddle (2002b) argued that the expectancy value model, proposed by the theory of planned behaviour, may not be sufficient for predicting and explaining human behaviour because human judgment and behaviour are not always a function of the computational rules suggested by the expectancy value model. Intrinsic motivation for example is a spontaneous form of motivation that arises from the fundamental needs for relatedness, competence and autonomy, and refers to: ‘the doing of an activity for its inherent satisfactions rather than for some separable consequences’ (Ryan & Deci, 2000, p. 56). As is apparent from this definition of intrinsic motivation, the performance of social behaviours is not always a function of expected outcomes that are operationally separable from the activity, and that people may engage in social behaviour for its own sake and for the interest and pleasure that are experienced during performance of the activity. Nevertheless, Chatzisarantis, Hagger, Biddle, and Karageorghis (2002) and Hagger et al. (2002b) did not find direct effects of intrinsic motivation on intentions and behaviour. This may be due to measurement issues. Specifically, Chatzisarantis and Hagger et al. (2002) and Hagger et al. (2002b) used the behavioural regulation for physical activity questionnaire (Mullan, Markland, & Ingledew, 1997) to assess the motives of enjoyment and interest as indicators of intrinsic motivation (e.g. I exercise because I enjoy physical activity). We use the term Form A to describe this measure of intrinsic motivation. It could be said that direct measures of enjoyment are not satisfactory indicators of intrinsic motivation. This is because the measure could elicit responses made on the basis of outcome expectancies. As Deci, Koestner, and Ryan (1999) suggested, such measures will encompass both intrinsic and extrinsic components of motivation. Unfortunately, the behavioural regulation questionnaire used by Chatzisarantis and Hagger et al. (2002) and Hagger et al. (2002b) does not prevent people from using outcome expectancies as a basis for answering questions about intrinsic motivation. For example, people may report that physical activity is enjoyable because they expect to obtain positive outcomes, which is an expression of an expectation to obtain an outcome that is separable from the activity itself, i.e. it is not intrinsic to the activity. In response to such concerns, the current study used a form of measurement of intrinsic motivation (Form B) that attempted to remove the influences of outcome expectancies from appraisals of intrinsic motivation. As recommended by Deci et al. (1999), Form B required participants to indicate their intrinsic motivation with respect to a hypothetical scenario describing a situation in which they had 230 Nikos L. D. Chatzisarantis et al. Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Soc. Psychol. 36, 229–237 (2006) achieved all salient behavioural outcomes. It was expected that the hypothetical scenario describing successful attainment of behavioural outcomes would prevent people from appraising intrinsic motivation on the basis of outcome expectancies; thus, providing more accurate estimates of intrinsic motivation. The present study tested three hypotheses. In accordance with the view that only the Form B measure of intrinsic motivation prevents people from using outcome expectancies as a basis for answering questions about intrinsic motivation, it was hypothesized that Forms A and B would elicit a distinct pattern of responses to queries of intrinsic motivation, and therefore that Forms A and B would display discriminant validity (H1). The second aim of the present study was to examine the influences of intrinsic motivation on intentions and behaviour within the theory of planned behaviour. Based on self determination theory (Deci & Ryan, 1980), it was hypothesised that only the Form B measure of intrinsic motivation would contribute to the prediction of intentions and of social behaviour over and above the components of the theory of planned behaviour (H2). In addition, we examined moderating effects of both measures of intrinsic motivation (Forms A and B) on the relationships between variables in the theory of planned behaviour and physical activity. Whilst we explored all possible moderating effects of intrinsic motivation, we expected moderation only for the effect of the Form B measure of intrinsic motivation on the intention–behaviour relationship. Deci and Ryan (1980) proposed that performance of intrinsically motivated behaviour depends more on environmental cues relevant to initiation of intrinsically motivated activity than on explicit judgments about behaviour and intentions. Therefore, when behaviour is intrinsically motivated, the effect of intentions on behaviour should diminish because attention to intended action decreases (H3). Finally, we included measures of past behaviour in order to rule out the alternative hypothesis that the Form B measure of intrinsic motivation is simply a proxy measure of past behaviour.