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theory of planned behaviour and health behaviour. (1)

  1. 1. THEORY OF PLANNED BEHAVIOUR AND HEALTH BEHAVIOUR1-. General backgroundTPB is an extension of the earlier TRA. Both models imply that people´s attitudes are formedafter careful consideration of available information.The TRA origins are in Fishbein´s work on the psychological processes by which attitudes causebehaviour and in an analysis of the failure to predict behaviour from individual’s attitudes. TheTRA used an expectancy-value framework to explain the relationship between beliefs andattitudes, and interposed a new variable, behavioural intention, between attitudes andbehaviourThe principle of compatibility: (Ajzen 1988). This principle holds that each attitude andbehaviour has the four elements of action, target, context and time, and states thatcorrespondence between attitudes and behaviour will be greatest when both are measured atthe same degree of specificity with respect to each element. Hence, any behaviour consists of: (a) An action (or behaviour) (b) Performed on or toward a target or object (c) In a particular context (d) At a specified time or occasion.Attitudes and behaviour will be most strongly related when both are assessed at the samelevel of specificity with regard to these four elements. Thus, general attitudes should predictgeneral classes of behaviours and specific attitudes should predict specific behaviours.2-. Description of the modelThe TRA suggests that the proximal determinant (or cause) of volitional behaviour is one´sbehavioural intention to engage in that behaviour. Behavioural intention represents a person´smotivation in the sense of her or his conscious plan, decision or self-instruction to exert effortto perform the target behaviour. Attitudes towards a specific behaviour impact onperformance of the behaviour via intentions. Thus in the TRA the issue of how theunobservable attitude is transformed into observable action is clarified by interposing anotherpsychological event: the formation of an intention between the attitude and the behaviour.However, the theory is less clear about the factors that lead attitudes to be translated intointentions. One possibility is that it is the anticipated opportunity to perform the behaviourthat promotes the formation of an intention. The TRA includes a second determinant ofintention: subjective norm represents the perceived social pressure from others to perform thetarget behaviour. The TRA restricts itself to the prediction of volitional behaviours.The TPB was developed to broaden the applicability of the TRA beyond purely volitionalbehaviours by incorporating explicit consideration of perceptions of control over performanceof the behaviour as an additional predictor of behaviour. Considerations of perceptions ofcontrol, or perceived behavioural control (PBC), are important because they extend theapplicability of the theory beyond easily performed, volitional behaviours to those complexgoals and behaviours which are dependent upon performance of a complex series of otherbehaviours. It is this lack of actual control which attenuates the power of intentions to predict
  2. 2. behaviour. However, given the myriad of problems defining and measuring actual control, PBChave tended to be employed. This inclusion of PBC in the TPB provides information about thepotential constraints on action as perceived by the actor, and explains why intentions do noalways predict behaviour. TPB describes behaviour as:B = w₁BI + w₂PBC (1)Where B is behaviour, BI is behavioural intention, PBC is perceived behavioural control, and w₁and w₂ are regression weights.The link between intention and behaviour reflects the fact that people tend to engage inbehaviours they intend to perform. However, the link between PBC and behaviour is morecomplex, PBC is held to exert both direct and interactive (with behavioural intentions) effectson behaviour. This is based on the following rationale: that however strongly held, theimplementation of an intention into action is at least partially determined by personal andenvironmental barriers. Therefore, in situations where prediction of behaviour from intentionis likely to be hindered by the level of actual control (i.e. volitional), PBC should (a) facilitatethe implementation of behavioural intentions into action and (b) predict behaviour directly.PBC will predict behaviour directly to the extent that the measure matches actual control.Determinants of intentionIn the TRA, attitudes are one predictor of behavioural intention. Ajzen define an attitude as “alearned disposition to respond in a consistently favourable or unfavourable manner withrespect to a given object”. Applying the principle of compatibility, the relevant attitudes arethose toward performance of the behaviour, assessed at a similar level of specificity to thatused in the assessment of behaviour.The TRA also specifies subjective norm as the other determinant of intentions, they consist of aperson´s beliefs about whether significant others think he/she should engage in the behaviour.Subjective norms are assumed to assess the social pressures individuals feel to perform or notperform a particular behaviour from salient referents.The TPB incorporates a third predictor of intentions, PBC, which is the individual´s perceptionof the extent to with performance of the behaviour, is easy or difficult.BI = w₃A + w₄SN + w₅PBC (2)The equation indicates that intentions are a function of one´s evaluation of personallyengaging in the behaviour, one´s perception that significant others think you should or shouldnot perform the behaviour, and perceptions of one´s control over performance of thebehaviour. Without the PBC component, equation 2 represents the TRA. It is worth notingthat, unlike other variables, PBC has links with both intentions and behaviour component inthe TPB. The PBC-intention link represents the fact that, in general, individuals are moredisposed (i.e. intend) to engage in positively valued behaviour that are believed to beachievable.
  3. 3. Research indicates that there may be individual differences in the weights placed on thedifferent components, with some individuals tending to base their intentions on attitudes andothers on norms across behaviours. In addition, in situations where (for example) attitudes arestrong, or where normative influences are powerful, PBC may be less predictive of intentions.Determinants of attitudesAn attitude is a function of salient behavioural beliefs, which represent perceivedconsequences or other attributes of the behaviour. Following expectancy-valueconceptualizations, consequences are composed of the multiplicative combination of theperceived likelihood that performance of the behaviour will lead to a particular outcome andthe evaluation of that outcome.A= (3)bi is the behavioural belief that performing the behaviour leads to some consequence i (thus,bi is the subjective probability that the behaviour has the consequence i). ei is the evaluationof consequence i, and p is the number of salient consequences over which this values aresummed.Fishbein (1993) claims equation 3 is not a model of process but is a computationalrepresentation aimed to capture the output of a process that occurs automatically as afunction of learning. This part of the model, the relationship between attitudes and beliefs isbased on Fishbein´s summative model of attitudes. It is assumed that a person may possess alarge number of beliefs about a particular behaviour, but that at any one time only some ofthese are likely to be salient. It is the salient beliefs which are assumed to determine aperson´s attitude.Determinants of subjective normSubjective norm is a function of normative beliefs, which represent perceptions of specificsignificant other´s preferences about whether one should or should not engage in behaviour,multiplied by the person´s motivation to comply with that referent´s expectation.SN = (4)It should be noted that the distinction between behavioural beliefs and normative beliefs issomewhat arbitrary, and there is often considerable correlation between the two.Determinants of perceived behavioural controlJudgements of perceived behavioural control are influenced by beliefs concerning whetherone has access to the necessary resources and opportunities to perform the behavioursuccessfully, weighted by the perceived power of each factor. The perceptions of factors likelyto facilitate or inhibit the performance of the behaviour are referred to as control beliefs.These factors include both internal (information, personal deficiencies, skills, abilities,emotions) and external (opportunities, dependence on others, barriers) control factors. Ajzen
  4. 4. (1991) has suggested that each control factor is weighted by its perceived power to facilitateor inhibit performance of the behaviour.PBC = (5)Commentary Behaviour is determined by intention to engage in the behaviour and perceptions of controlover performance of the behaviour.Intention is determined by attitude towards the behaviour, subjective norms and perceivedbehavioural controlAttitude is determined by perceptions of the likelihood of salient outcomes and theirevaluation.Subjective norm is determined by normative beliefs and motivation to comply with salientreferents.PBC is determined by the perceived presence or absence of requisite resources andopportunities and the perceived power of these factors to facilitate or inhibit performance ofthe behaviour. Actual control influences the impact of PBC on intention and behaviour.External variablesDemographic Attitude(age, sex, Behaviouraloccupation, Beliefssocioeconomicstatus, religion,education) Intention Behaviour SubjectivePersonality traits Normative Beliefs norm(extraversion,agreeableness,conscientiousness, neuroticism,openness) Control Beliefs PBCEnviromentalinfluences(access, physical Actualenvironment) Behavioural control3-. Summary of researchKey issues raised in reviews of the TPBThe majority of studies have demonstrated that the background factors influence intentionsand behaviour indirectly by their effects on behavioural, normative or control beliefs. Onecommon criticism of the TRA/TPB has been that it assumes that all behaviour is rational andfails to take account of other non-cognitive or irrational determinants of human behaviour.This criticism highlights potential problems with the way in which typical TRA/TPB studies areconducted. In particular, differences may exist between the contemplation of a behaviour (e.g.when filling in a TPB questionnaire) and its actual performance in a real-life context. It may beparticularly difficult for individuals to correctly anticipate the strong emotions that drive theirbehaviour in real life. This would lead to problems with incorporating emotional factors withintypical TRA/TPB applications.
  5. 5. 4-. DevelopmentsMultiple component view of the TPBComponents of intentions:Intentions capture the motivational factors that influence behaviour, how hard people arewilling to try, how much effort they would exert to perform the behaviour or the self-instructions individuals give themselves to act.Warshaw and Davis (1985) made the distinction between measures of behavioural intentionsand self-predictions.Sheppard et al´s (1988) meta-analysis indicated the latter to be more predictive of behaviour.Beyond this, Bagozzi (1992) has suggested that attitudes may first be translated into desireswhich then develop into intentions to act, which direct action.The meta-analysis of Armitage and Conner found that intentions and self-predictions werestronger predictors of behaviour than desires when PBC was included as a predictor.Ajzen and Fishbein (2005) also argue that willingness to perform behaviour, personal normwith respect to the behaviour or identification with the behaviour are each closely related tointention.Components of attitudes:In the TRA/TPB attitudes towards behaviours are measured by semantic differential scales.However, research on attitudes towards objects has used such measures to distinguishbetween affective and cognitive measures of attitudes, with the suggestion that the former aremore closely related to behaviour. It is now recognized that similar components of an attitudetowards a behaviour can be distinguished in the TRA/TPB. In particular, it has been noted thatan attitude may contain instrumental (e.g. desirable-undesirable, valuable-worthless) as wellas experiential or affective (e.g. Pleasant-unpleasant, interesting-boring) aspects.This is problematic because some research has indicated that intentions may be more closelyrelated to affective than cognitive measures of attitudes. Ajzen and Fishbein (2005) indicatedthat appropriate attitude measures for use in the TPB should contain items representing theinstrumental and affective or experiential components of attitudes. The two components dotend to be correlated with one another but can be discriminated based on their underlyingbelief systems, their different functions and empirical differences. However, in order tomaintain the parsimony of the TPB is has also been suggested that it is useful to distinguishbetween a higher order construct of attitude and these differentiated components of attitudeat a lower order. Thus, in relation to instrumental and experiential attitudes, a higher orderconstruct of attitude is invoked to explain the shared variance between these twocomponents.Two forms of such models have been recently proposed. In the first, the higher orderconstructs are “caused” by their lower order components. In the second, it is the higher orderconstruct which “causes” the lower order components.
  6. 6. In the TRA/TPB attitudes are held to be determined by underlying salient behavioural beliefs. Itis assumed that a person may possess a large number of beliefs about a particular behaviour,but that at any one time only some of these are likely to be salient. It is the salient beliefswhich are assumed to determine a person´s attitude.Towriss (1984) noted that while the theory would suggest the use of individually salientbeliefs, respondents are normally presented with modal salient beliefs based on pilot work.This procedure has a number of disadvantages. First, procedures for sampling “behaviouralbeliefs” about specific behaviours may sample an excessively cognitive subset (i.e.Instrumental beliefs) of the influences that actually play on people´s attitudes, and fail to elicitbeliefs which are more difficult to articulate (affective or moral influences), yet potentiallyimportant influences on attitude formations. A second problem is that the TPB is primarilyconcerned with individuals ‘beliefs. The supplying of beliefs by researcher may not adequatelycapture the beliefs salient to the individual. Another problem related to the use of modalbeliefs concerns the relative importance of beliefs. A number of authors have suggested thatthe prediction of attitudes might be improved by adding a measure of importance or relevanceof the attribute to the attitude towards the behaviour. (population stratified by key beliefs).Components of norms:Armitage and Conner (2001) noted that subjective norms were the weakest predictor ofintentions in the TPB. Similarly , Sheppard et al (1988) and Van den Putte (1991) noted thatsubjective norms were weak predictors of intentions across the TRA.However, at least partly, this appeared to be attributable to the use of single item measureswith lower reliability. Where studies employed reliable multi-item measures subjective normswere significantly stronger predictors of intentions, although still weaker than attitudes orPBC. Another explanation of the weak predictive power of normative measures in the TRA/TPBis the conceptualization of norms used. Cialdini et al (1991) call the normative beliefs used inthe TRA/TPB injunctive social norms as they concern the social approval of others whichmotivates action through social reward/punishment, and distinguish them from descriptivesocial norms which describe perceptions of what others do.Most recently, Fishbein (1993) and Ajzen and Fishbein (2005) suggested that both subjectivenorms and descriptive norms be considered indicators of the same underlying concept, socialpressure. Similarly to attitudes one might conceive of social pressure as a higher order factorwith injunctive and descriptive norms lower order measures. However, it is unclear whether aformative model with injunctive and descriptive norms producing overall social pressure or areflective model with social pressure producing injunctive and descriptive norms is moreappropriate.A further distinction in relation to the normative component of the TPB has been made byresearchers applying a social identity theory/self-categorization approach. For example, Terryand Hogg (1996) demonstrated that group norm measures were more predictive of intentionswhen they employed a measure of group identification (e.g. I identify with my friends withregard to smoking”) rather than motivation to comply. Group norms have beenoperationalized as either what members of the group are perceived to do (e.g. “Most of my
  7. 7. friends smoke”; i.e. Descriptive norms) or to think (i.e. “Most of my friends think smoking is agood thing to do”, sometimes referred to as group attitude). Studies using this approach tendto report interactive effects between group norms and group identification rather than maineffects.In particular, for referent groups not defined by the behaviour an interactive model betweengroup attitude (or descriptive norm) and group identification may be appropriate.There has also been a work examining normative beliefs. It should be noted that thedistinction between behavioural beliefs and normative beliefs is somewhat arbitrary, andthere is often found to be considerable correlation between the two. However, there is somemerit in maintaining a distinction between the determinant of behaviour that are attributes ofthe person and those which are attributes of the social environment.Other researchers have suggested that rather than the way normative influences is tapped; itis measurement of compliance with this pressure which needs attention. There has beendebate about the most appropriate level of specificity to use in the wording of the motivationto comply item. For example, should motivation to comply be in general, specifying a group ofbehaviour or be specific to the behaviour in question (the principle of compatibility mightsuggest this last alternative?). Alternatively, as we noted earlier in relation to social identitytheory, a measure of group identification rather than motivation to comply might be moreappropriate.Components of PBC:The difference between the TRA and the TPB lies in the control component (i.e. PBC) of theTPB. Meta-analytic evidence has generally supported the power of PBC to explain additionalvariance in intentions and behaviour after controlling for the component of the TRA. Theoverlap in definition of PBC with Bandura´s definition of self-efficacy is striking. Ajzen (1991)argued that the PBC and self-efficacy constructs were synonymous and more recently “quitesimilar”. There is controversy surrounding the nature and measurement of PBC which has anumber of threats. A first thread concerns disparities in the definitions and operationalizationsused with respect to PBC and the possibility that it represents a multidimensional construct. Asecond threat has questioned the discriminant validity of some operationalizations of the PBCas distinct from other components of the TPB.Early definitions of the PBC construct were intended to encompass perceptions of factors thatwere both internal (e.g. Knowledge, skills, willpower) and external (e.g. time availability,cooperation of others) to the individual.The items used to tap PBC included both perceptions of difficulty and perceptions of controlover the behaviour. In the majority of early applications of the TPB studies tended to employ“mixed” measures of PBC that included both components. However, more recently opinionappears to have coalesced around the idea of PBC being a multidimensional constructconsisting of two separate but related components. In particular, Ajzen argues that PBC can beconsidered as a second-order construct that consists of two components which he labelsperceived self-efficacy and perceived controllability.
  8. 8. Self-efficacy component of PBC, Ajzen has suggested that this component can be tapped bytwo types of items: first, the perceived difficulty of the behaviour; second, the perceivedconfidence the individual has to perform the behaviour.A second threat to research with the PBC construct has focused on discriminant validity.Fishbeing and colleagues note two problems with employing perceived difficulty items to tapPBC: first, there is no necessary association between individual´s perceptions of how difficult abehaviour is held to be and how much they perceive control over performing it; second, easy-difficult items overlap conceptually and empirically with semantic differential items designedto tap affective attitudes.This review of existing research suggests at least three possibilities in relation to measuringPBC within the TPB. First, the use of formative research within a behavioural domain can resultin the appropriate selection of items with a unidimensional structure. Second, measures canexplicitly tap the two components of PBC identified by Ajzen: perceived self-efficacy andperceived controllability. Third, measures of PBC could be selected which explicitly avoidperceived difficulty items because of concerns about overlap with affective attitudes. Anotherissue in relation to the PBC component of the TPB is the assessment of underlying controlbeliefs. These beliefs are assumed to be based upon various forms of previous experience withthe behaviour. Control beliefs are tapped by items assessing the frequency with which afacilitator or inhibitor of the behaviour occurs, e.g. “I can climb in an area that has goodweather”(likely-unlikely) weighted by its perceived power to facilitate or inhibit performanceof the behaviour, e.g “Good weather makes mountain climbing...”(easier-more difficult) withboth items scored as bipolar items.Additional predictorsA number of additional constructs to be added have been suggested, we consider fouradditional constructs:1-. Anticipated regret:The traditional method for eliciting behavioural beliefs may fail to elicit affective outcomesassociated with performance of the behaviour. Such anticipated affective reactions to theperformance or non-performance of a behaviour may be important determinants of attitudesand intentions, especially in situations where the consequences of the behaviour areunpleasant or negatively affectively laden. Anticipated regret is a negative, cognitive-basedemotion that is experienced when we realize or imagine that the present situation could havebeen better had we acted differently. Studies have demonstrated that regret is distinct fromother component of the TPB. For regret to be further considered as an additional predictor ofintentions we need research demonstrating independent effects for anticipated regret whencontrolling for both instrumental and experiential attitudes.2-. Moral norms:Cialdini et al (1991) distinguished between injunctive, descriptive and moral norms. The firsttwo might usefully be considered components of a social norms construct. The latter are theindividual´s perception of the moral correctness or incorrectness of performing a behaviour
  9. 9. and take account of “...personal feeling of...responsibility to perform, or refuse to perform, acertain behaviour”. Moral norms might be expected to have an important influence on theperformance of those behaviours with a moral or ethical dimension. Ajzen suggested thatmoral norms work in parallel with attitudes, subjective norms and PBC, and directly influenceintentions. These findings imply that moral norm would be a useful addition to the TPB, atleast for those behaviours where moral considerations are likely to be important.3-. Self-identity:It may be defined as the salient part of an actor´s self which relates to a particular behaviour. Itreflects the extent to which an actor sees him or herself fulfilling the criteria for any societalrole. Ajzen and Fishbein (2005) suggest self-identity might be best considered as an alternativemeasure of intentions.4-. Past behaviours:It is argued that many behaviours are determined by one´s previous behaviour rather thancognitions such as described in the TRA/TPB (Sutton 1994). The argument is based on theresults of a number of studies showing past behaviour to be the best predictor for futurebehaviour. What is of particular interest is the contribution of past behaviour to thepredictions of intentions and behaviour once the TPB variables are taken into account. Despitethe strong effects of pas behaviour within the TPB we should be cautious in giving pastbehaviour the same status as other predictors in the TPB. It is clear that past behaviour cannotbe used to explain future performance of an action (i.e. individuals do not perform a behaviourbecause they have performed in the past), although habit may be one way of conceptualizingthis effect (Sutton 1994).5-. Operationalization of the ModelThe present text provides (a) some examples of measures applied to somewhat differentbehaviours within a common theme, and (b) the variation between research studies in thelevel of specificity and in adherence to the Target, Action, Context, Time (TACT) principle.Behaviour:Developing a clear conceptualization of the behaviour or behavioural categories we wish topredict. The principle of compatibility indicates that measures of behaviours and componentsof the TPB need to be formulated at the same level of specificity with regard to action, target,context and time. Specification of the action, target, context and time frame for the behaviourwill greatly assist the specification of the TPB measures. Assessment of such a behaviour mightinvolve simple self-reports or whether the behaviour was performed in the specified contextover the appropriate time period (in this example, behaviour is assessed on the following day): I walked for an hour in the countryside yesterday. Definitely did not 1 2 3 4 5 6 7 Definitely didThe reliability of self-report measures may be expected to vary as a function of the behaviourand context in question.
  10. 10. Behavioural intention: I intend to exercise at X health club at least four times each week during the next two weeks. Definitely do 1 2 3 4 5 6 7 Definitely do not I make an effort to exercise at X health club at least four times each week during the next two weeks. Definitely do 1 2 3 4 5 6 7 Definitely do not I try to exercise at X health club at least four times each week during the next two weeks. Definitely do 1 2 3 4 5 6 7 Definitely do notMultiple-item measures are more appropriate than single-item measures because of increasedreliability.Attitudes:Attitudes are a person´s evaluation of the target behaviour and are typically measured byusing items such as:My taking regular physical activity over the next 6 months would be: Harmful 1234567 Beneficial Unpleasant 1234567 Pleasant Unenjoyable 1234567 Enjoyable Bad 1234567 Good Foolish 1234567 WiseSemantic differential.Ajzen (2002c) has suggested that steps be taken to ensure that both instrumental (e.g.worthless-valuable; harmful-beneficial; unimportant-important) and experiential (e.g.unpleasant-pleasant; unenjoyable-enjoyable; unsatisfying-satisfying) items should be includedwithin attitude measures. Measurement of instrumental and experiential components ofattitudes allows the analysis of the lower and higher order components of attitudes.Alternatively, attitudes may be assessed by simply asking the respondent more directquestions about their attitudes:My attitude towards my exercising at X health club is: Extremely unfavourable 1 2 3 4 5 6 7 Extremely favourable Extremely negative 1 2 3 4 5 6 7 Extremely positiveSubjective normEarly described as a “person´s...perception that most people who are important to him thinkhe should or should not perform the behaviour in question” and a “person´s perception of the
  11. 11. social pressures put on him to perform or not the behaviour in question”. There is a differencein these two definitions but the construct has traditionally been operationalized as theperson´s subjective judgement concerning whether significant others would want him or herto perform the behaviour or not, using items such as:Most people that are important to me think I: Should 1 2 3 4 5 6 7 Should not take regular physical activity over the next 6 monthsThere are number of well known problems with the use of single items and additional itemshave been suggested to make a multi-item scale, although there is little reliability data on suchmeasures:People who are important to me would: Should 1 2 3 4 5 6 7 Should not of my taking regular physical activity over the next 6 monthsMost people who are important to me want me to take regular physical activity over the next 6 months Should 1 2 3 4 5 6 7 Should notMost recently it has been suggested that measures of subjective norm should include bothinjunctive normative influences (such as those given above which reflect significant othersthink the person should do) and descriptive normative influences (such the items that reflectwhat significant others are perceived to do with respect to the behaviour in question):Most of my friends exercise regularly: Strongly disagree 1 2 3 4 5 6 7 Strongly agreeMost of my family members exercise regularly: Strongly disagree 1 2 3 4 5 6 7 Strongly agreeMeasurement of injunctive and descriptive norm components of subjective norms would allowthe analysis of lower and higher order components of norms.Perceived behavioural controlPBC represents the overall control the individual perceives him or herself to have overperformance of the behaviour:How much control do you have over whether you exercise for at least 20 minutes, three times per week forthe next fortnight? No control 1 2 3 4 5 6 7 Complete controlI feel incomplete control of whether I exercise for at least 20 minutes, three times per week for the nextfortnight. Strongly disagree 1 2 3 4 5 6 7 Strongly agree
  12. 12. For me to exercise for at least 20 minutes, three times per week for the next fortnight will be: Very easy 1 2 3 4 5 6 7 Very difficultI am confident that I can I exercise for at least 20 minutes, three times per week for the next fortnight: Strongly disagree 1 2 3 4 5 6 7 Strongly agreeThe internal reliability of PBC items has frequently been found to be low, such that separateassessment of controllability (the first two items above) and self-efficacy (the second twoitems above) is now recommended. Measurement of controllability and self-efficacycomponents would allow the analysis of the lower and higher order components of PBC.Problem of adequate measurement?Depending on how people conceptualize the notion of “control” and the notion of“difficulty”.People may consider the performance of a behaviour to be “under their control”yet at the same time consider it to be difficult to carry out. Mixing unipolar and bipolar scalesamong PBC items may contribute to this problem.Behavioural beliefsIn the TRA/TPB the relevant behavioural beliefs are those salient to the individual. However,most applications of these models employ modal salient beliefs derived from pilot studies.Examples of belief strength and outcome evaluation items: Belief strength assesses the subjective probability that a particular outcome will be aconsequence of performing the behaviour. Outcome evaluations assess the overall evaluationof that outcome and are generally treated as bipolar and responded to on “bad-good”response formats. Belief strength and outcome evaluation are then multiplicatively combinedand summed (equation 3) to give an indirect measure of attitude. The problem with suchcalculations with interval data has been noted by a number of authors, although no completelysatisfactory solution has been found.Belief strength:My taking regular physical activity would make me feel healthier. Unlikely 1 2 3 4 5 6 7 LikelyMy taking regular physical activity would make me lose weight. Unlikely 1 2 3 4 5 6 7 LikelyOutcome evaluation:Feeling healthier would be... Bad 1 2 3 4 5 6 7 GoodLosing weight would be... Bad 1 2 3 4 5 6 7 GoodNormative beliefsAs with behavioural beliefs, most studies employ modal rather than individually salientreferent groups. Ajzen and Fishbein (1980) suggest that we ask about the groups or individualswho would approve or disapprove of you performing the behaviour or who come to mindwhen thinking about the target behaviour. The most frequently mentioned (modal) referents
  13. 13. are then incorporated in the final questionnaire. Typically two to six referent groups areincluded. Normative beliefs are a person´s perceptions of whether specific referents wouldwant him or her to perform the behaviour under considerations. Motivation to comply isoperationalized as the person´s willingness to comply with the expectations of the specificreferents. The relevant normative belies and motivations to comply are then multiplicativelycombined and summed (equation 4) to give an indirect measure of normative pressure.Normative belief strength:My friends think I should take regular physical activity. Unlikely 1 2 3 4 5 6 7 LikelyHealth experts think I should take regular physical activity. Unlikely 1 2 3 4 5 6 7 LikelyMotivation to comply:With regard to physical activity, I want to do what my friends think I should do Strongly agree 1 2 3 4 5 6 7 Strongly disagreeWith regard to physical activity, I want to do what health experts think I should do Strongly agree 1 2 3 4 5 6 7 Strongly disagreeControl beliefsOther studies have also used modal control beliefs derived from pilot studies. Ajzen and Driver(1992) suggests that individuals are asked to list the factors and conditions that make it easy ordifficult to performs the target behaviour and the most frequently mentioned (modal) itemsare used in the final questionnaire. Control beliefs assess the presence or absence offacilitating or inhibiting factors are commonly scored on “never-frequently”, “false-true”,“unavailable-available”, or “Unlikely-likely” response formats. Perceived power items assessthe power of the item to facilitate or inhibit performance of the behaviour. The relevant itemsare then multiplicatively combined and summed (equation 5) to give an indirect measure ofthe perceived behavioural control.Control Beliefs:I have free time... Never 1 2 3 4 5 6 7 FrequentlyI am near sports facilities... Never 1 2 3 4 5 6 7 FrequentlyPower:Having free time makes taking regular physical activity. Less likely 1 2 3 4 5 6 7 More LikelyBeing near sports facilities makes taking regular physical activity. Less likely 1 2 3 4 5 6 7 More Likely
  14. 14. 6-. Behavioural intentionsGenerally speaking, there are two stages involved in using the TPB to develop an intervention.First, it is important to determine which variables should be targeted. Second, the messagecontent must be identified. There are some main problems with interpreting these findings,first, many studies did not conduct an initial TPB study to identify appropriate target ofintervention. Second, many studies did not test the effectiveness of interventions in changingtargeted cognitions before examining impacts on intentions and behaviour.What then should we make of the role of the TPB in behavioural change interventions? Thetheory of planned behaviour can provide general guideline...but it does not tell us what kind ofintervention will be most effective. Thus, for example, the popularity of the ElaborationLikelihood Model as a model of persuasion could be used to supplement the TPB inintervention work.There is evidence which indicates that a change in people´s beliefs can bring about changes inattitudes, intentions and/or behaviour lends some support to the basic causal sequence at theheart of the TPB. Objective behaviour measures are often difficult to obtain and the reliabilityof self-report measures merits critical scrutiny. What the TPB does offer is a theory ofvolitional behaviour which posits an explicit causal relationship between people´s beliefs andtheir subsequent actions. It is thus apparent that changes in those beliefs will lead tobehavioural changes, all other things being held equal.In relation to theory development the key issue is the light that intervention studies can throwon supposed causal relationships in the TPB. For such an aim, experimental designs whichallow a focused manipulation of one construct and observation of the effects on otherconstructs are required.7-. Future directionsModerator variables: The role of moderator variables within TPB (i.e. variables that influencethe magnitude of relationships between TPB constructs). A range of moderator variables havebeen examined in relation to the TPB. These can be broadly split into additional variables andproperties of components of the TPB. The former include anticipated regret, moral norms andpast behaviour. The latter include accessibility, direct experience, involvement, certainty,ambivalence, affective-cognitive consistency and temporal stability (to obtain accurateprediction of behaviour, intentions...must remain reasonably stable over time until thebehaviour is performed”).Conclusion:In the broad social environment there will be a number of influences on people´s health andon their behaviour: any of these that do not impinge on people´s perceptions of control willnot be accessible to analysis via the TPB. Health behaviours need to be understood not only interms of people´s beliefs, values, perceived social pressure and perceived control but also interms of the individual´s behaviour history and the broader social pressures that may beoperating. While the TPB is concerned with proximal psychological influences on behaviour,we have to recognize the broader social structure within which these influences develop.