10.1177/0146167202239046 ARTICLEPERSONALITY AND SOCIAL PSYCHOLOGY BULLETINSheeran, Abraham / INTENTION-BEHAVIOR MODERATORS

Mediator of Moderators: Temporal Stabilityof Intention and the Intention-Behavior Relation

Paschal SheeranUniversity of Sheffield

Charles AbrahamUniversity of Sussex

Intention certainty, past behavior, self-schema, anticipatedregret, and attitudinal versus normative control all have beenfound to moderate intention-behavior relations. It is argued thatmoderation occurs because these variables produce “strong”intentions. Stability of intention over time is a key index of inten-tion strength. Consequently, it was hypothesized that temporalstability of intention would mediate moderation by these othermoderators. Participants (N = 185) completed questionnairemeasures of theory of planned behavior constructs and modera-tor variables at two time points and subsequently reported theirexercise behavior. Findings showed that all of the moderators,including temporal stability, were associated with significantimprovements in consistency between intention and behavior.Temporal stability also mediated the effects of the other modera-tors, supporting the study hypothesis.

Keywords: intention; action; prediction; stability; properties

Several models of the cognitive determinants of socialand health behaviors, including the theory of reasonedaction (Fishbein, 1980; Fishbein & Ajzen, 1975), the the-ory of planned behavior (Ajzen, 1985, 1991), the modelof interpersonal behavior (Triandis, 1980), and protec-tion motivation theory (Rogers, 1983), propose that themost immediate, and important, predictor of behavior isthe person’s intention to perform it (e.g., “I intend to doX” or “I will try to do X”). According to Ajzen (1991),

Intentions are assumed to capture the motivational fac-tors that influence a behavior; they are indications ofhow hard people are willing to try, of how much of aneffort they are planning to exert, in order to perform abehavior. (p. 181)

Evidence supports the view that intention is a reliablepredictor of behavior. For example, Sheeran (2002) con-

ducted a meta-analysis of 10 meta-analyses of the intention-behavior relation and found that the sample-weightedaverage correlation was .53 (based on 422 hypothesesand a total sample size of N = 82,107): Intention ac-counted for 28% of the variance in behavior, on average,in prospective studies.

Although intentions are good predictors of behav-ior, there is often a substantial gap between people’sintentions and their subsequent behavior (Abraham,Sheeran, et al., 1999; Bagozzi, 1992; Orbell & Sheeran,1998). For example, a review of health behaviors indi-cated that 47% of participants with positive intentionssubsequently failed to perform their intended behavior(Sheeran, 2002). Similarly, a review of consumer behav-iors found that purchase intentions were translated intoaction in less than 62% of cases (Young, DeSarbo, &Morwitz, 1998). Ajzen (1985, 1991; Ajzen & Madden,1986) argued that lack of volitional control over a behav-ior could explain these discrepancies and developed thetheory of planned behavior (TPB) to take account of thisproblem—by adding the concept of perceived behav-ioral control (e.g., “How easy or difficult is it for you to doX?”) to the theory of reasoned action. The TPB has sincereceived considerable empirical support (e.g., Ajzen,1991; Armitage & Conner, 2001).

However, people with equivalent intention and per-ceived behavioral control scores may differ in their sub-sequent behavior. This is because important aspects ofpeople’s motivation to perform a behavior are not cap-

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Authors’ Note: We thank Ian Kellar for help with data collection and in-putting. Please direct correspondence concerning this article to Pas-chal Sheeran, Department of Psychology, University of Sheffield,Sheffield S10 2TN, United Kingdom; e-mail: p.sheeran@shef-field.ac.uk.

PSPB, Vol. 29 No. 2, February 2003 205-215DOI: 10.1177/0146167202239046© 2003 by the Society for Personality and Social Psychology, Inc.

tured by standard intention scales (Abraham et al., 1999;Sheeran, Orbell, & Trafimow, 1999). Just as attitudes dif-fer not only in their valence (i.e., positive vs. negative)and extremity (i.e., how positive or negative) but also intheir strength (Petty & Krosnick, 1995), so too intentionsmay differ in their strength and priority (cf. Austin &Vancouver, 1996). Moreover, in the same way that atti-tude strength affects the consistency between attitudesand behavior (cf. Petty & Krosnick, 1995), intentionstrength should moderate the intention-behavior rela-tion. Thus, it may be important to measure intentionstrength to enhance the prediction of behavior byintention.

Several moderators of the intention-behavior relationhave been identified, including intention certainty (Bassili,1995), past behavior (e.g., Kashima, Gallois, & McCamish,1993), self-schemas (e.g., Kendzierski & Whitaker,1997), anticipated regret (Abraham & Sheeran, in press-a; Sheeran & Orbell, 1999), and attitudinal versus nor-mative control (Sheeran, Norman, & Orbell, 1999).However, the possibility that these variables affect theconsistency between intentions and behavior becausethey affect intention strength has not been tested. Inten-tion strength may be indexed by temporal stability(Sheeran, Orbell, & Trafimow, 1999), and a recent meta-analytic review showed reliable moderation of theintention-behavior relation by intention stability (Cooke& Sheeran, in press). The aim of the present study was toprovide a simultaneous test of these six moderators toclarify the mechanism responsible for moderation of theintention-behavior relation. More specifically, we pro-pose that because temporal stability is a key indicator ofintention strength, and because the other moderatorsaffect intention strength, intention stability will medi-ate the effects of other moderators of the intention-behavior relation.

Temporal Stability of Intentionas an Index of Intention Strength

Research on attitude strength (see Petty & Krosnick,1995, for a review) can provide useful insights into thenature of intention strength. Attitude strength does notinvolve a single underlying dimension (e.g., Krosnick,Boninger, Chuang, Berent, & Carnot, 1993; Prislin,1996). For example, Krosnick and Petty (1995) distin-guished between defining and strength-related proper-ties. The two defining features of strong attitudes are asfollows: (a) They are durable and (b) they have impact.Durability and impact both have two manifestations.Durability embraces both temporal stability (the extentto which an attitude persists over time regardless ofwhether it is challenged) and resistance (the extent towhich an attitude can withstand challenge). Impact, onthe other hand, involves how well an attitude predicts

behavior and how much an attitude affects informationprocessing and judgment. Thus, according to Krosnickand Petty’s analysis, temporal stability should be con-strued as a defining feature of intention strength.

Krosnick and Petty (1995) acknowledged that littleresearch has been devoted to understanding the rela-tionship between durability and impact and that, con-sequently, it is unclear whether either, or both, fea-tures characterize strong attitudes/intentions.However, a second distinction—between antecedentversus consequent properties (cf. Abelson, 1988; Bassili,1996; Fazio, 1995)—is relevant here. Although it is possi-ble to construe temporal stability as a consequence ofstrong attitudes (see, e.g., Prislin, 1996) and to regardbehavioral impact as antecedent to strong attitudes (see,e.g., Kiesler, 1971), there are theoretical and practicalgrounds for supposing that temporal stability is anteced-ent to behavioral impact. At the theoretical level,Fishbein and Ajzen have repeatedly stressed that inten-tion stability is a precondition of a causal relationshipbetween intention and behavior (e.g., Ajzen, 1991;Fishbein, 1980). The assumption is that participants withstable intentions are less likely to exhibit intentionchange prior to performance of the behavior (e.g., as aresult of new information) compared to participantswith unstable intentions. Consequently, greater stabilityof intention should enhance the impact of intention onbehavior (see also Abraham & Sheeran, in press-b). Atthe practical level, it is also important to construe behav-ioral impact as a consequence because many appliedsocial psychologists are concerned with maximizing theprediction of health and prosocial behaviors in order todesign interventions to promote these behaviors (see,e.g., Abraham, Sheeran, & Johnson, 1998).

The distinction between operative and meta-judgmentalproperties of attitudes (Bassili, 1996) is also instructive.Meta-judgmental properties refer to people’s percep-tions of (e.g., how certain is their attitude) and are typi-cally measured by self-reports (e.g., “My attitude to X iscertain/uncertain”). Operative properties, on the otherhand, refer to cognitive processes responsible for attitu-dinal responses and are indexed by implicit measures ofsuch processes rather than by subjective reports. Bassili(1996) demonstrated that operative properties providedbetter prediction of key dependent variables than didmeta-judgmental measures. Bassili argued that this wasbecause operative measures reflect underlying cognitiveprocesses, whereas meta-judgmental measures have lit-tle cognitive foundation. Temporal stability refers to thepersistence of attitude/intention in memory and is typi-cally measured by within-participants correlationsbetween measures taken at two time points (e.g., Batista-Foguet & Saris, 1997; Sheeran, Orbell, & Trafimow,1999). As such, it is an operative rather than a meta-judg-

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mental property and should, therefore, have particular“impact” in Krosnick and Petty’s terms.

In summary, because temporal stability can be con-strued as a defining, antecedent, and operative propertyof intention, this property constitutes a key indicator ofintention strength. Consequently, temporal stabilityshould affect how well intentions predict behavior. Evi-dence supports this view. For example, Sheeran, Orbell,and Trafimow (1999) found that intention stability mod-erated both intention-behavior and past behavior–future behavior relations. When intentions were unsta-ble, intention did not predict behavior and past behaviorwas the strongest predictor. Conversely, intentionstrongly predicted behavior, and past behavior was not asignificant predictor, when intentions were stable.Intention stability also moderated intention-behaviorconsistency in studies of health screening (Conner,Sheeran, Norman, & Armitage, 2000, Study 1), diet(Conner et al., 2000, Study 2; Conner, Norman, & Bell,2002), video game play (Doll & Ajzen, 1992), and dona-tions to charity (Cooke & Sheeran, 2002). Moreover,moderation by intention stability may be long lasting.In a recent study, Conner et al. (2002) observed signifi-cant moderation over a 6-year time interval betweenintention and behavior.1

Distal Moderators ofIntention-Behavior Relations

Intention certainty, attitudinal versus normative con-trol, past behavior, self-schemas, and anticipated regrethave all been found to moderate the intention-behaviorrelation. We propose that these are distal moderators,that is, they enhance intention-behavior consistencybecause they are associated with intention stability.

The self-reported certainty with which an intention isheld (e.g., “My intention to do X is certain/uncertain”)is an important meta-judgmental property of attitudes/intentions (cf. Bassili, 1996). Bagozzi and Yi (1989),Bassili (1993), and Pieters and Verplanken (1995) testedwhether intention certainty moderated the intention-behavior relation; all three studies found that greatercertainty was associated with improved consistencybetween intentions and behavior. There is also evidencethat certainty is related to temporal stability. Bassili(1996) measured certainty of participants’ attitudestoward employment quotas for women and laws on por-nography and followed up participants 10 or more dayslater. For both issues, certainty predicted attitude stabil-ity even after other properties of attitudes had beentaken into account.

Intentions also differ in the extent to which they aredetermined by one’s evaluation of the behavior (atti-tude) versus social pressure from significant others (sub-jective norm; see Trafimow, 1998; Trafimow & Finlay,

1996). Attitudinal versus normative control parallels a dis-tinction made by self-determination theory (e.g., Deci &Ryan, 1985; Ryan & Connell, 1989; Ryan, Sheldon,Kasser, & Deci, 1996) between autonomous versus con-trolled motivation. Autonomous motivation involvesintentions that are experienced as self-chosen and ema-nating from the self, whereas controlled intentions areinitiated and pursued because of pressures external tothe self (such as approval from significant others). Self-determination theory suggests that goal achievement ismore likely when people’s motivation is autonomouscompared to when motivation is controlled (e.g.,Chatzisarantis, Biddle, & Meek, 1997; Sheldon & Elliott,1998; Williams, Grow, Freedman, Ryan, & Deci, 1996).Sheeran, Norman, and Orbell (1999) examinedwhether attitudinal versus normative control moderatedintention-behavior consistency in a study of 30 behav-iors. Findings for both attitudinally versus normativelycontrolled people, and attitudinally versus normativelycontrolled behaviors (determined by within-participantsanalyses and between-participants analyses, respec-tively), showed that attitudinal control was associatedwith improved prediction of behavior by intention.There is also suggestive evidence that attitudinally con-trolled intentions are more stable than are normativelycontrolled intentions (Chatzisarantis & Biddle, 1998;Chatzisarantis et al., 1997; Sheldon & Elliott, 1998),which suggests that the effects of attitudinal versus nor-mative control could be mediated by intention stability(see also Sheeran, 2002).

Numerous studies have shown that a measure of pastbehavior has a direct relationship with behavior evenafter intention and perceived behavioral control havebeen taken into account (e.g., Abraham, Clift, &Grabowski, 1999; Armitage & Conner, 1999; Bagozzi &Kimmel, 1995; Conner & McMillan, 1999; Norman,Conner & Bell, 1999; Perugini & Bagozzi, 2001;Sheeran & Orbell, 2000), a finding that is consistent withthe idea that behaviors vary in the extent to which theyare under habitual versus intentional control (Ouellette &Wood, 1998; Triandis, 1980). However, two lines of evi-dence suggest that past behavior may moderate theintention-behavior relation such that intentions basedon greater experience better predict behavior than dointentions based on less experience. First, a direct test byKashima et al. (1993) showed that the more participantshad used condoms in the past, the greater the predictivevalidity of their intentions to use condom in the future.Second, Sheeran, Orbell, and Trafimow (1999) andConner et al. (2000) both found that past behavior wasassociated with greater stability of intention and thatintention stability, in turn, was associated with improvedintention-behavior consistency. In sum, evidence sug-gests that past behavior moderates the intention-behavior

Sheeran, Abraham / INTENTION-BEHAVIOR MODERATORS 207

relation and that past behavior is related to intentionstability.

Self-schemas (Markus, 1977) are core self-conceptionsthat reflect domains of enduring importance to a per-son. They are typically measured by descriptiveness andimportance ratings on traits relevant to a domain (e.g.,Kendzierski, 1988, 1990, used ratings of “physicallyactive,” “exercises regularly,” and “keeps in shape” to mea-sure participants’ exercise self-schema). Kendzierski andWhitaker (1997) and Sheeran and Orbell (2000) bothfound that self-schemas moderated intention-behaviorconsistency, even after the effects of past behavior hadbeen controlled. Sheeran and Orbell also showed that itwas the importance dimension of self-schemas (and notdescriptiveness) that was responsible for the effect. Self-schemas are thought to moderate the relationshipbetween intention and behavior through their effects onthe temporal stability of intention (Sheeran & Orbell,2000). Formal tests of mediation have not been con-ducted, but Kendzierski and Whitaker (1997) found thatthe intentions of schematic participants were more sta-ble over an 8-week period than intentions of aschematicparticipants.

Anticipated regret refers to people’s expectationsabout the extent of regret, tension, or upset they wouldfeel if they did not perform a behavior. Richard and col-leagues (e.g., Richard et al., 1995, 1998; Richard, van derPligt, & de Vries, 1996; see also Parker et al., 1995) dem-onstrated that anticipated regret captures a significantincrement in the variance in intention after TPB vari-ables have been controlled. Sheeran and Orbell (1999)speculated that anticipated regret could increase thestability of participants’ intentions and therebyenhance the consistency between intention andbehavior. This analysis was supported by findings thatshowed that the predictive validity of intention to playthe lotto increased when participants anticipatedgreater levels of regret about not playing. More recently,Abraham and Sheeran (in press-a) obtained equivalentfindings in correlational and experimental studies ofexercise behavior. Abraham and Sheeran also confirmedthat anticipated regret was associated with greater tem-poral stability of intention.

Rationale and Hypotheses

The literature reviewed above provides the followingrationale for the present study: (a) Although intentionprovides good prediction of behavior there is consider-able scope for improving intention-behavior, consistency,and (b) evidence suggests that intention certainty, attitu-dinal versus normative control, past behavior, self-schema, and anticipated regret moderate the intention-behavior relation and that these variables are related to akey indicator of intention strength (temporal stability of

intention); however, the possibility that intention stabil-ity mediates moderation by these variables has not beentested.

The hypotheses tested here are as follows:

Hypothesis 1: Intention stability, intention certainty, attitudi-nal versus normative control, past behavior, self-schema,and anticipated regret will each moderate the relation-ship between intention and behavior.

Hypothesis 2: Intention stability will mediate the effects of theother five moderator variables.

METHOD

Participants and Procedure

Undergraduates at two United Kingdom universitiesvoluntarily completed questionnaires at three timepoints separated by 2 weeks (N = 185). At Time 1 andTime 2, participants completed identical questionnairesthat measured constructs from the TPB and moderatorvariables in relation to exercise. At Time 3, participantsreported their exercise behavior.

Consistent with previous research (e.g., Norman &Smith, 1995), a brief definition of exercise was printedon the front of the questionnaires to reduce ambiguityabout the meaning of the word exercise (“Exerciseinvolves at least 20 min of moderate/vigorous physicalactivity. Exercise includes activities such as aerobics, bad-minton, jogging, rugby, etc., but not activities whichform part of your daily life such as walking to the busstop, dancing at discos, etc.”).

A pilot study showed that N = 4 was the median num-ber of times that potential participants would exerciseover a 2-week period. Consequently, all of the measuresspecified exercising “at least four times over the next 2weeks.” Unless otherwise stated, responses to items weremade on 7-point scales.

Time 1 and Time 2 Questionnaires

Intentions to exercise were measured by five items: “Iintend to exercise at least four times over the next 2weeks” (strongly agree to strongly disagree), “I will try to exer-cise at least four times over the next 2 weeks” (stronglyagree to strongly disagree), “I will definitely exercise at leastfour times over the next 2 weeks” (strongly agree to stronglydisagree), “I intend to exercise at least four times over thenext 2 weeks” (definitely no to definitely yes), and “Howlikely is it that you will exercise at least four times over thenext 2 weeks” (very unlikely to very likely). Reliability wassatisfactory (α = .93). Attitudes were assessed byresponses to the stem “For me to exercise at least fourtimes in the next 2 weeks would be . . . ” on six bipolarscales (pleasant to unpleasant, fun to boring, good to bad,important to unimportant, enjoyable to not enjoyable, worth-while to not worthwhile) (α = .85). Subjective norms were

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measured by two items: “Most people who are importantto me think that I should exercise at least four times inthe next 2 weeks” (strongly agree to strongly disagree) and“Most people who are important to me think that Ishould exercise at least four times in the next 2 weeks”(unlikely to likely) (α = .89). Perceived behavioral controlwas measured by five items: “For me to exercise at leastfour times in the next 2 weeks would be . . . ” (easy to diffi-cult), “How much control do you have over exercising atleast four times in the next 2 weeks?” (no control to com-plete control), “If I wanted to I could easily exercise at leastfour times in the next 2 weeks” (strongly agree to stronglydisagree), “I feel in complete control of whether or not Iexercise at least four times over the next 2 weeks”(strongly agree to strongly disagree), and “I am confidentthat I will be able to exercise at least four times in thenext 2 weeks” (strongly agree to strongly disagree) (α = .82).Past behavior was measured by two items: “How often doyou generally exercise (5-point scale: never to most days)and “How many days did you exercise in the last 2weeks?” (α = .69). Intention certainty was measured by asingle item: “How certain is your intention to exercise atleast four times in the next 2 weeks?” (certain to uncer-tain). Anticipated regret was measured by two items: “If Idid not exercise at least four times in the next 2 weeks, Iwould feel regret” and “If I did not exercise at least fourtimes in the next 2 weeks, I would feel upset” (definitely yesto definitely no). Reliability was moderate (α = .68).Finally, the exercise self-schema measure was based onthe measure developed and validated by Kendzierski(1990). Participants rated the importance of the phrases“physically active,” “exercises regularly,” and “keeps inshape” “to the image you have of yourself, regardless ofwhether or not it describes you” (11-point scale, not allimportant to very important; α = .84).

Time 3 Questionnaire

Behavior was measured by two items: “How often didyou exercise in the last 2 weeks?” (5-point scale, never tomost days) and “How many days did you exercise in thelast 2 weeks?” (α = .94).

Measurement of Intention Stability

Consistent with previous operationalizations (e.g.,Conner et al., 2000), there were four indices of intentionstability: (a) the within-participants correlation betweenintention items at Time 1 and Time 2; (b) the sum of theabsolute differences between intention items at the twotime points; (c) the absolute difference between the sumof intention items at both time points; and (d) the num-ber of items that exhibited change. Reliability was satis-factory (α = .78).

Measurement of AttitudinalVersus Normative Control

Attitudinal versus normative control has characteristi-cally been measured by partitioning participants on thebasis of the strength of the within-participants correla-tions between attitude and intention versus subjectivenorm and intention (e.g., Sheeran, Norman, & Orbell,1999; Trafimow & Finlay, 1996). Because this approachwas not feasible here, we adopted an alternative strategybased on whether intention scores more closely matchedattitude scores or more closely matched subjective normscores. In particular, we computed the absolute differ-ence between intention and attitude scores and betweenintention and subjective norm scores for each partici-pant. When subjective norm scores were more discrep-ant from intention scores than were attitude scores, par-ticipants were deemed to be under “attitudinal control.”Conversely, when attitude scores were more discrepantfrom intention scores than were subjective norm scores,participants were deemed to be under “normative con-trol.” Using this procedure, the intentions of 51% of thesample (n = 95) were under attitudinal control.

RESULTS

Moderation of theIntention-Behavior Relation

In all analyses, the Time 2 measures of the TPB andthe moderator variables were used to predict behavior atTime 3 (the Time 1 data were used only to compute themeasure of intention stability). Table 1 presents themeans, standard deviations, and intercorrelations forstudy variables. There were reliable associations betweenbehavior and both the TPB variables and moderatorvariables.

We used the procedure recommended by Aiken andWest (1991) to test whether intention stability, intentioncertainty, past behavior, self-schema, anticipated regret,and attitudinal versus normative control moderated therelationship between intention and behavior. Thisinvolved a three-step hierarchical regression analysis foreach moderator; behavior was regressed on intention atthe first step, on intention and the focal moderator vari-able at the second step, and on intention, the moderatorvariable, and the multiplicative intention by moderatorvariable (interaction term) at the final step. Moderationcan be said to obtain when the interaction term has a sig-nificant regression coefficient and is associated with asignificant increment in the explained variance. Prior toall analyses, variables were standardized to reduce poten-tial multicollinearity (Aiken & West, 1991).

Table 2 shows that intention stability, intention cer-tainty, past behavior, self-schema, anticipated regret, and

Sheeran, Abraham / INTENTION-BEHAVIOR MODERATORS 209

attitudinal versus normative control were all significantmoderators of the intention-behavior relationship. Ineach case, the inclusion of the interaction between themoderator variable and intention was associated with asignificant increment in the variance explained inbehavior (.01 < ∆R2 < .02; 4.56 < ∆F < 7.71; all ps < .05).The interaction terms had significant betas in all six finalequations.

Simple slopes analyses were used to decompose theinteractions (Aiken & West, 1991). For the continuousmoderator variables, we computed slopes for the regres-sion of behavior on intention at three levels of the mod-erator variable: 1 standard deviation below the mean(low), the mean level (moderate), and 1 standard devia-tion above the mean (high). Attitudinal versus norma-tive control is a dichotomous variable, so the slope for

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TABLE 1: Means, Standard Deviations, and Intercorrelations for Study Variables (N = 185)

1 2 3 4 5 6 7 8 9 10 11

1. Behavior 1.00 .67*** .52*** .16* .63*** .14* .41*** .80*** .28*** .44*** .27***2. Intention 1.00 .70*** .23*** .67*** .06 .57*** .76*** .40*** .57*** .34***3. Attitude 1.00 .34*** .51*** –.17* .35*** .62*** .52*** .50*** .134. Subjective norm 1.00 .22** –.03 .15* .13 .23** .14 .125. Perceived control 1.00 .10 .42*** .62*** .26*** .28*** .28***6. Intention stability 1.00 .26*** .11 –.08 .08 .16*7. Intention certainty 1.00 .49*** .25*** .29*** .20**8. Past behavior 1.00 .34*** .47*** .23***9. Self-schema 1.00 .41*** .03

10. Anticipated regret 1.00 .17*11. Attitudinal control 1.00M 0.00 4.36 5.40 4.38 4.93 –0.02 4.46 0.00 7.05 3.87 —SD 0.97 1.87 1.17 1.59 1.35 1.02 1.95 0.87 2.80 1.88 —

NOTE: Behavior and past behavior are the mean of two Z scores. Intention stability is the mean of four Z scores. Attitudinal versus normative controlis a dichotomous variable (attitudinal control = 1, normative control = 0).*p < .05. **p < .01. ***p < .001.

TABLE 2: Moderated Regression Analyses for Intention Stability, Past Behavior, Anticipated Regret, Intention Certainty, Self-Schema, and Atti-tudinal Versus Normative Control

Beta

Step Variable Entered Step 1 Step 2 Step 3 R2 Model F R2 F

1. Intention .67*** .66*** .63*** .45 149.96***2. Intention stability .12* .11* .47 79.15*** .02 5.05*3. Stability × Intention .15** .49 56.73*** .02 6.81**1. Intention .67*** .65*** .61*** .45 149.96***2. Intention certainty .04 .08 .45 74.90*** .00 0.363. Certainty × Intention .15** .47 54.34*** .02 7.71**1. Intention .67*** .16* .24** .45 149.96***2. Past behavior .68*** .56*** .65 167.48*** .20 102.12***3. Past Behavior × Intention .13* .66 116.42*** .01 5.68*1. Intention .67*** .67*** .63*** .45 149.96***2. Self-schema .02 –.00 .45 74.62*** .00 0.073. Self-Schema × Intention .12* .46 52.25*** .01 4.56*1. Intention .67*** .62*** .67*** .45 149.96***2. Anticipated regret .09 .05 .46 76.17*** .01 1.763. Regret × Intention .15** .48 54.75*** .02 6.95**1. Intention .67*** .65*** .47*** .45 149.96***2. Attitudinal control .05 .05 .45 75.19*** .00 0.683. Attitudinal Control × Intention .23** .47 53.87*** .02 6.61**

*p < .05. **p < .01. ***p < .001.

intention was computed separately for attitudinally con-trolled versus normatively controlled participants(Aiken & West, 1991).

Table 3 presents the unstandardized regression coef-ficients for intention at different levels of the moderatorvariables. Findings for all moderators confirmed expec-tations. The predictive validity of intention improved asscores on each moderator increased from low to moder-ate and from moderate to high (or from low to high inthe case of attitudinal control).2

Mediation of Moderators ofthe Intention-Behavior Relation

According to Baron and Kenny (1986), mediationcan be said to occur when three conditions are satisfied:First, the independent variable should be associatedwith the dependent variable; second, the independentvariable should be associated with the mediating vari-able; and third, in a regression of the dependent vari-able on both the independent variable and the media-tor, the independent variable should be reduced tononsignificance, whereas the mediator should besignificant.

The findings in Table 3 satisfy the first criterionbecause the interactions between intention and inten-tion stability, intention certainty, past behavior, self-schema, anticipated regret, and attitudinal versus nor-mative control were significantly associated withbehavior. We tested the second criterion by regressingintention stability (the proposed mediating variable) oneach moderator and its associated interaction term.Results showed that, with one exception, the independ-ent variables accounted for a significant proportion ofthe variance in intention stability (.02 < R2 < .15; 3.40 < ∆F< 15.58; all ps < .04). The exception was attitudinal versusnormative control where the regression equation fellshort of conventional significance, F(2, 182) = 2.28, p <.10. Of importance, however, the beta for attitudinal ver-sus normative control was significant in this equation (β =.16, p < .05). Moreover, the bivariate correlation betweenattitudinal versus normative control and intention stabil-ity was reliable (r = .16, p < .04, two-tailed). These find-ings satisfy Baron and Kenny’s second criterion; theindependent variables (in this case, moderators of theintention-behavior relationship) are associated with themediator.

To test the third criterion, we conducted a series ofhierarchical regression analyses. To provide a stringenttest, variables from the TPB entered the equation at thefirst step and one of the moderator variables, its interac-tion term, intention stability, and the stability interactionterm were entered at the second step (forced entrymethod was employed in all equations). Table 4 showsthat findings were consistent across analyses. When

intention stability and its interaction with intention wereincluded in the equation, other interactions with inten-tion were nonsignificant. In every case, the addition ofthe stability interaction term was associated with a signifi-cant increment in the variance (.01 < ∆R2 < .02; 2.130 <∆F < 3.99; all ps < .05), and the Intention × Intention Sta-bility interaction had a significant beta in the final equa-tion (the beta was marginally significant in one case, p <.08 in step 2f). Interactions with intention certainty, pastbehavior, self-schema, anticipated regret, and attitudinalversus normative control were no longer significantwhen the temporal stability interaction term wasincluded in the equation. In sum, these findings indicatethat intention stability mediates the effects of other mod-erators of the intention-behavior relation.

DISCUSSION

Although there is often a substantial gap betweenpeople’s intentions and their subsequent behavior(Sheeran, 2002), relatively little research has investi-gated factors that might explain—and, ultimately, helpto bridge—this gap. The present research constitutes anadvance in understanding intention-behavior discrep-ancies in three important respects. First, this is the onlystudy that simultaneously tested six moderator variablesand thereby confirmed that intention stability, intentioncertainty, past behavior, self-schema, anticipated regret,and attitudinal versus normative control are each associ-ated with improved prediction of behavior by intention.Second, the present study provides insight into the rela-tionship between durability and impact as defining fea-tures of intention strength (cf. Krosnick & Petty, 1995).In particular, the findings for temporal stability supportthe view that durability is antecedent to behavioralimpact. Moreover, the consideration that the intentionby stability interaction term, but not intention on itsown, predicted behavior is consistent with Fishbein and

Sheeran, Abraham / INTENTION-BEHAVIOR MODERATORS 211

TABLE 3: Simple Slopes Analyses for Six Moderators of the Intention-Behavior Relation

Level of Moderator Variable

Moderator Variable Low Moderate High

Intention stability .49*** .62*** .76***Intention certainty .46*** .61*** .76***Past behavior .11 .24** .37***Self-schema .57*** .69*** .81***Anticipated regret .52*** .67*** .81***Attitudinal vs.normative control .47*** — .77***

NOTE: Values are unstandardized regression coefficients (Bs) forintention. Attitudinal versus normative control is a dichotomousvariable.*p < .05. **p < .01. ***p < .001.

Ajzen’s theoretical proposal that stability of intention (amanifestation of durability) is a precondition of a causalimpact of intention on behavior (a manifestation ofimpact). Third, and most important, the present find-ings provide new evidence that a single mediator (inten-tion stability) accounts for a wide variety of moderatorsof intention-behavior consistency. The findings showthat intention certainty, past behavior, self-schema,anticipated regret, and attitudinal versus normative con-trol can all be construed as distal moderators that affectthe predictive validity of intention through their associa-tions with intention stability, which is the proximal(mediating) moderator.

Previous research on intention-behavior relations hasbeen concerned predominantly with identifying whatvariables moderate the relationship between intentionsand behavior. The present study focused on why particu-lar variables moderate the intention-behavior relation.Drawing on the literature on attitude strength (Petty &Krosnick, 1995), we reasoned that people are likely tohave strong intentions when they are certain about theirdecision, when they have considerable experience withthe behavior, when they see the behavior as important totheir self-image, when they make decisions based oninternal (i.e., attitudinal) rather than external consider-ations, and when they expect to feel regretful if they donot act. We also argued that temporal stability was a keyindex of intention strength because it is a defining, ante-cedent, and operative property of intentions (cf. Bassili,1996; Krosnick & Petty, 1995). Moreover, a review of liter-

ature indicated that several of the moderator variablesexamined here were associated with more stable behav-ioral intentions. We have provided the missing test of“mediated moderation” (cf. Wegener & Fabrigar, 2000).Our findings support the hypothesis that intention cer-tainty, past behavior, self-schema, anticipated regret, andattitudinal versus normative control affect intention-behavior relations through their effects on intention sta-bility. Intention stability is the mediator of thesemoderators.

Of interest, if one assumes that correlations betweenpast and future behavior reflect the operation of habits(see Ajzen, 2002; Verplanken & Aarts, 1999, for discus-sion), the present findings suggest that exercise is ahabitually, rather than intentionally, controlled behav-ior. Regression of behavior on the TPB showed thatintention and perceived behavioral control explained52% of the variance in behavior. However, the additionof past behavior to the equation increased theexplained variance to 67%, and reduced intention tononsignificance. It is also notable that exercise is likelyto involve behaviors that are frequently performed in sta-ble contexts, that is, circumstances that are conducive tohabit formation (cf. Ouellette & Wood, 1998).

Given that exercise is a habitually controlled behav-ior, it is especially impressive that the interactionbetween stability and intention was a significant predic-tor of behavior after past behavior and additional vari-ables had been controlled. Several studies have shown

212 PERSONALITY AND SOCIAL PSYCHOLOGY BULLETIN

TABLE 4: Mediation of Moderators of the Intention-Behavior Relation by Temporal Stability of Intention

Beta

Step Variables Entered Step 1 Step 2a Step 2b Step 2c Step 2d Step 2e Step 2f

1. Intention .07 .06 .07 .11 .08 .03 –.06Attitude –.03 –.03 –.03 –.02 –.02 –.04 –.03Subjective norm .02 .03 .04 .02 .03 .03 .07Perceived control .20*** .20*** .21*** .18** .19** .21*** .19**Past behavior .64*** .61*** .63*** .55*** .60*** .61*** .61***

2a. Intention stability .06 .08 .05 .06 .06 .06Stability × Intention .10* .11* .10* .11* .09* .09†

2b. Certainty –.07Certainty × Intention –.05

2c. Past Behavior × Intention .072d. Self-schema –.01

Self-Schema × Intention .042e. Anticipated regret .06

Regret × Intention –.012f. Attitudinal control .05

Attitudinal Control × Intention .14R2 .67 .68 .69 .69 .69 .69 .69Model F 72.49*** 54.65*** 42.70*** 48.10 42.24*** 42.46*** 43.41∆R2 — .01 .02 .02 .02 .02 .02∆F — 3.99* 2.47* 3.13* 2.13* 2.29* 3.00*

†p < .08. *p < .05. **p < .01. ***p < .001.

that intention is no longer a significant predictor of exer-cising after past behavior has been taken into account(e.g., Norman et al., 1999; Norman & Smith, 1995), butthese studies offer little insight into what factors mightdecrease exercise behavior among habitual exercisers orincrease exercise behavior among participants who hadnot previously been exercising. The present findings, onthe other hand, indicate that intentional control over“habitual” behaviors is possible—provided that one’sintention remains stable over time.

This is an important implication because most peoplecan identify habits they would prefer not to have (e.g.,snacking between meals) and habits they would like toacquire (e.g., eating more fruit and vegetables). Goodintentions, on their own, may not be sufficient to changebehavior, but our findings suggest that stable intentionsare likely to be translated into action. Admittedly, theeffect size associated with stable intentions was small inthe present study (R2 = .01). However, the deleteriousconsequences of lack of exercise are such that an inter-vention based on intention stability that increased exer-cise behavior by just 1% would have substantial benefitsin terms of mortality and morbidity (e.g., U.S. Depart-ment of Health and Human Sciences, 1996; U.S. Preven-tive Services Task Force, 1989).

The present study also has a number of theoreticalimplications. First, temporal stability is related to animportant manifestation of impact, namely, behavior.Future studies could examine the effects of temporal sta-bility on other manifestations of impact such as informa-tion processing or judgment. For example, the literatureon response effects demonstrates that changes in ques-tion form, wording, and context can dramatically alterparticipants’ responses (e.g., Krosnick & Schuman,1988); it would be useful to determine whether stableintentions are less liable to such response effects com-pared to unstable intentions. The relationship betweenintention stability and resistance to challenge (includingconflict created by competing intentions, cf. Kuhl, 1985)also deserves attention (cf. Eagly & Chaiken, 1995). Inaddition, it would be interesting to explore the implica-tions of temporal stability for goal hierarchies (Austin &Vancouver, 1996; Carver & Scheier, 1998) and actionidentification (Vallacher & Wegner, 1985, 1987). It ispossible that stable intentions are more strongly relatedto higher level goals (principles or “be” goals in Carver &Scheier’s, 1998, terms or higher level identities in actionidentification terms) than are less stable intentions.

In summary, intention stability is an important predic-tor of people’s ability to translate their intentions intoaction and mediates the effects of (at least five) othermoderators of the intention-behavior relationship. Fur-ther research on the determinants and consequences ofintention stability is warranted.

NOTES

1. It is worthwhile discussing why we did not examine the accessibil-ity of intention—another important operative property—alongside, orinstead of, temporal stability. Accessibility refers to the strength of theassociation in memory between an attitude object and its evaluation(or between mental representations of decisions and behaviors, in thecase of intention) and is measured by latency of responses to attitude/intention questions (see Fazio, 1990, 1995, for reviews). Although stud-ies have shown that accessibility moderates both attitude-behavior(e.g., Fazio & Williams, 1986) and intention-behavior relations (Bassili,1993, 1995), recent research indicates that accessibility provides infe-rior moderation of cognition-behavior relations compared to tempo-ral stability. First, a meta-analytic review showed that temporal stabilityprovided significantly better moderation of attitude-behavior relationscompared to accessibility (effect sizes were r = .37 and r = .08, respec-tively, p < .05; see Cooke & Sheeran, in press). Second, the two primaryresearch studies that directly compared temporal stability versus acces-sibility as moderators of the intention-behavior relation both foundthat temporal stability provided superior moderation (Cooke &Sheeran, 2002; Doll & Ajzen, 1992). Consequently, it seems likely thattemporal stability constitutes a better index of intention strength com-pared to accessibility.

2. It is worth noting that a continuous measure of attitudinal versusnormative control moderated the intention-behavior relation in thesame manner as the dichotomous measure.

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