The subsequent measurement of these two meanings of intention is easily observable among some of the most popular physical activity theories. For example, stage theories use a binary algorithm to assess intention (27). A similar dichotomization of intention (intend/do not intend) and behavior (success/failure) is present in the physical activity action control framework (32,33,43). By contrast, the theory of planned behavior, variants of social cognitive theory, protection motivation theory, and the health action process approach use a fixed statement (e.g., "I intend to exercise X times per week") and response options that allow respondents to grade the intensity of their agreement (e.g., strongly disagree to strongly agree) (9). Clearly, both meanings of intention are measured differently and with frequent application in the physical activity domain.
The Relation of Intention With Behavior and Social Cognitive Constructs
The definition of intention in a theory is as important to structure as measurement. Courneya (10) provided an early test of the predictive capability of intention direction (dichotomous) and intensity (continuous) and showed that intensity had a significantly larger association (r = 0.71 to 0.51) than direction (r = 0.66 to 0.43) in several tests. Thus, the two types of intentions are not functionally equivalent predictors of physical activity behavior.
The mediation of social cognitive variables through intention also differs by direction and intensity, as hypothesized (Fig. 2). This is evident both directly in comparisons within the same data set and indirectly through meta-analyses of different theoretical approaches. For example, in a study from our laboratory, 298 undergraduate students completed measures of the theory of planned behavior and a self-reported follow-up of moderate and vigorous intensity physical activity 2 wk later. When a measure of the direction of intention was used, intention failed to account for the relation between behavior and affective attitude, instrumental attitude, subjective norm, and perceived behavioral control (30). By contrast, when a measure of the intensity of determination was used, instrumental attitude and subjective norm did not have a direct relation with behavior, whereas affective attitude and perceived behavioral control did show significant direct effects (31). A similar finding was identified for a random sample of 1192 Canadian adults who completed social cognitive measures of the transtheoretical model and self-reported moderate to vigorous physical activity 6 months later. When a measure of the direction of intention was used, intention failed to account for the relation between behavior and self-efficacy, pros, and cons; only the cognitive processes of change did not have a direct relation with physical activity (38). By contrast, only self-efficacy explained physical activity independent of intention when a measure of intensity was used (37).
Evidence that measures of direction and intensity of intention are not functionally equivalent also has been shown in proxy constructs, such as parental support behavior for child physical activity. For example, in a random sample of Canadian mothers (N = 1253) of children aged 5 to 12 years, intention to support child physical activity, measured as intensity, mediated the relation between support behavior 6 months later and theory of planned behavior constructs of instrumental attitude and affective attitude but not perceived behavioral control (40). However, when intention was measured as a direction, only instrumental attitude had evidence of mediation (39).
Similar results for how the two concepts of intention relate to physical activity and social cognition are evident in meta-analyses and reviews. In assessments of the theory of planned behavior, which uses the intention concept of intensity, perceived behavioral control/self-efficacy has had either mixed support (17) or no support (23,47) for a direct effect on behavior after controlling for intention and these reviews do not indicate support for direct effects of attitudes or subjective norm (17). By contrast, review of the transtheoretical model, which uses a direction measure of intention (contemplation vs behavioral stages), supports direct relations with physical activity between self-efficacy and pros and cons (conceptually similar to attitudes) after controlling for intention (46). Similarly, a review of the action control framework, which uses a measure of intention correspondent with direction, also found that instrumental attitude and subjective norm did not have direct overall effects on physical activity after accounting for intention, but affective attitude and perceived behavioral control did have direct effects (33).
In summary, the cumulative results support our hypothesis that there are meaningful empirical differences between the two concepts of intention. Intention, when positioned as a concept of intensity to enact physical activity, is a better predictor of behavior and a more robust mediator between behavior and social cognitive constructs than the concept of intention when positioned as a decision to perform regular physical activity.
Application to Physical Activity Theory Testing and Intervention Design
These two meanings of intention can have very different implications for theory. Our recommendation is for researchers to state the type of intention concept conceptualized and measured in the health behavior model with the rationale for its use. Table 3 and Figure 3 outline some of the matches of intention by popular or emerging physical activity behavior models, yet the list is not meant to be definitive or exhaustive. For example, if intention is conceived as intensity of commitment, it stands to reason that the construct represents the final and definitive culmination of deliberate motivation upon behavior (1,20). In the previous section, we provided evidence for this assumption, as the intensity concept of intention was a superior mediator of social cognitive constructs compared with the direction concept of intention. Thus, intention, when defined as the intensity of commitment, can involve tests of dual process models (11) or volitional behavior sequence models (16) because the intention construct is a summary concept for all conscious motivation. For example, the action phase model (20) suggests that planning is a postintentional construct and makes the conceptualization very clear that postintentional is equivalent to postmotivational.
By contrast, if intention is conceived as mere direction, this would not necessarily indicate the final and definitive motivational variable. Instead, it may be an indicator of a process in physical activity decision-making and subsequent enactment (29). In these cases, motivational factors, volitional factors, or automatic factors may still contribute to the enactment of the intention, and thus postintentional does not equate to postmotivational. Our previous section showed evidence for this approach because perceived behavioral control and affective attitude were relatively consistent predictors of physical activity independent of the direction concept of intention, but instrumental attitude and subjective norm often were mediated by intention. The definition of intention as a decisional direction allows for the examination of pre- and postdecisional constructs in the process of health behavior change and the interaction between direction, volition, and motivation.
These differences in theory also translate to applied differences in intervention design. If interventionists are interested in the formation versus enactment of decisions such as New Years physical activity resolutions, opting into weight loss programs, or volunteering for randomized controlled trials, then intention models that use the concept of direction seem suitable. These types of programs clearly involve uniformity of direction in intention, and the focus of intervention is on postdecisional variables but not necessarily postmotivational variables. For example, the multiprocess action control framework (29) suggests that instrumental outcome expectations of health and social benefit as well as basic capability to perform the behavior are largely predecisional aspects that contribute to the intention to be active but not the enactment of behavior. By contrast, the affective aspects associated with physical activity (enjoyment) and opportunities to be active (social and built environment) continue to be important to intervene upon during enactment of the activity along with self-regulation skills (plans, monitoring) and the formation of habit and identity. The transtheoretical model (27) has a more complicated algorithm of stages between intention and behavior that has some controversy but generally suggests that predecisional populations should have a focus more on the benefits of physical activity and cognitive processes of change, whereas postdecisional factors should focus on behavioral processes of change and reduction of barriers.
Intervention design using the intensity concept of intention seems suitable to apply across any population for physical activity intervention where motivation (intensity of determination) is variable, but may be particularly interesting when comparative concepts of volition and automatic processes are of interest. This concept is recommended for use when researchers wish to evaluate the relative contributions of motivation compared with automatic or implicit processes on behavior (11). Similarly, the intensity of intention concept seems of better use for examining the relative intervention contribution of motivational and volitional processes on physical activity behavior (4,42) than direction of (decisional) intention. Decisional intention may be of use to examine how automatic or volitional factors interplay with decision-making and behavioral enactment, but the concept is not meant to include the entirety of the motivational spectrum and thus would not represent an adequate conceptualization to understand the relative contributions of motivational, automatic, and volitional factors in intervention.
Recommendations for Moving Forward
Our analysis shows clear support that intention encompasses two conceptually and empirically distinct meanings in physical activity research. Thus, there is futility in moving forward by suggesting a singular meaning for intention — the concept is complex — and an attempt to define intention with a singular meaning is not commensurate with the history of this concept in research or in lay vocabulary. Furthermore, our overview of the conceptual and empirical application of intention to physical activity demonstrates that both meanings may have use in theory and underlie different measurement requirements. This suggests that continuing with the double-barreled meaning of intention is adding confounds to measurement, application, and testing of physical activity theory. Clarity of the concept is helpful, particularly as intention-based theories are being challenged for their utility in health behavior research. For example, an intention-behavior gap that represents the discordance between a decision to enact a behavior and the commitment to enact a behavior seems substantively different, yet both remain relevant and important in physical activity science.
We suggest that the two meanings should still retain the wording of intention, to tie the concepts to past history, yet both concepts require an additional word to clarify what meaning of intention is being put forward. We suggest decisional intention to represent the direction meaning of intention. This includes the presence or absence of self-instructions, an aim, or outcome plan. We suggest that intention strength be used to represent the commitment to enact behavior. This term dates to the original theorizing of Fishbein and Ajzen (13) and represents the magnitude of commitment, effort, and motivation one is willing to engage in to enact a behavior. We recommend that these terms be used whenever the intention concept is applied to physical activity theory testing to provide clarity from this point forward.
With these terms established, adequately powered psychometric testing of measures of decisional intention and intention strength would be helpful. For example, decisional intention can be measured with dichotomized measures, or open-scaled choice options (10), but this would not be appropriate to measure intention strength, because that concept represents a continuum of commitment. Furthermore, given the complicated meaning of the intention term, it would be useful to measure both of these constructs with items that make their conceptual distinction clear. It also would be prudent to use terms like “decision” or “aim” to avoid any confounding responses of decisional intention with intention strength. More consequential, we do not recommend the use of “intention” as an item key word for the measurement of intention strength. This is because it is not clear which meaning of the “intention” wording respondents are using when answering the item. For example, respondents could be answering that they strongly agree that they have made a decision to enact a behavior or that they strongly agree that they are determined to enact the behavior. In support of this recommendation, there is evidence to suggest that intention strength can be a superior predictor of behavior when measured with items that avoid the complexity of the intention term (35). We recommend the use of items that use other descriptions of intention strength (e.g., willingness to try hard, effort, commitment, resolve) to avoid the potential confound from participants who use the decisional intention definition when answering items meant to assess intention strength.
We believe the distinction of these two intention terms also will improve the validity of future theory testing and intervention. Population-based studies on people’s decisional intention and intention strength are needed to identify potential at-risk populations and to determine whether there are systematic differences as a function of sociodemographic factors such as age, sex, or education. Prospective and intervention studies are needed to establish if certain intervention strategies are more or less effective for manipulating decisional intention or intention strength and the magnitude that changes in decisional intention and intention strength affect physical activity change.
Intention-based models have been extremely important to physical activity theory and research by explaining health behavior and serving as a critical comparison for the relative value of volitional factors and nonconscious/implicit factors. In this article, we demonstrated that the intention concept is complicated by a double-barreled definition in both the lay- and researcher-driven literature. Intention can mean a decision taken toward performing a behavior and/or the commitment to enact a behavior. We showed that the two intention concepts are not equal predictors of physical activity and do not operate the same as mediators of social cognitive constructs. We provided examples for how the complexity of the intention concept may affect model development, measurement, and intervention design. Based on this evidence, we suggest that decisional intention be used to denote the direction meaning of intention and intention strength should be used to denote the intensity of commitment. We suggest that holding to these terms will improve measurement, theory testing, and intervention practices in physical activity research that uses intention-based models.
R.E.R. is supported by funds from the Canadian Cancer Society, the Social Sciences and Humanities Research Council of Canada, the Heart and Stroke Foundation of Canada, and the Canadian Institutes for Health Research. A.L.R. is supported by funds from the National Health and Medical Research Council of Australia.
No funding for this article. The authors report no conflicts of interest.
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theory of planned behavior; stages of change; mediation; motivation; action control; attitudes; intervention
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