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A controlled evaluation of an eating disorders primary prevention videotape using the Elaboration Likelihood Model of Persuasion
Journal of Psychosomatic Research 53 (2002) 1021 – 1027
A controlled evaluation of an eating disorders primary prevention videotape using the Elaboration Likelihood Model of Persuasion Giselle F. Withersa, Kylie Twigga, Eleanor H. Wertheima,*, Susan J. Paxtonb a
School of Psychological Science, La Trobe University, Bundoora (Melbourne), Vic. 3083, Australia b Department of Psychology, University of Melbourne, Parkville, Vic., Australia
Abstract Objective: The aim was to extend findings related to a previously reported eating disorders prevention program by comparing treatment and control groups, adding a follow-up, and examining whether receiver characteristics, personal relevance and need for cognition (NFC), could predict attitude change in early adolescent girls. Method: Grade 7 girls were either shown a brief prevention videotape on dieting and body image (n = 104) or given no intervention (n = 114). All girls completed pre-, post- and 1-month follow-up questionnaires. Results: The intervention
group resulted in significantly more positive changes in attitude and knowledge at post-intervention, but only in knowledge at follow-up. There was no strong evidence that pre-intervention characteristics of recipients predicted responses to the videotape intervention when changes were compared to the control group. Conclusion: This prevention videotape appeared to have positive immediate effects, but additional intervention (e.g., booster sessions) may be required for longer-term change. D 2002 Elsevier Science Inc. All rights reserved.
Keywords: Body image; Dieting; Eating disorders; Persuasion; Prevention
Introduction The primary prevention of eating disorders in adolescent girls has received increasing attention over the past 10 years. Prevention programs have typically aimed to reduce body concerns and unhealthy dieting practices in adolescent girls, using psychoeducation and interactive presentations in a school classroom setting [1– 10]. Overall, the findings of these programs have been mixed. While more recent interventions achieved better results than earlier studies, changes have been small and rarely maintained [10 –13]. Several criticisms of these studies have been made. First, many programs lack a control group or follow up testing [1,4,9,14]. Second, programs fail to recognise the effects of individual differences on program effectiveness. Third, programs often lack a theoretical framework upon which to organise and present program material, thus, ineffective message components (e.g., in content or delivery) have not been isolated and identified. In response to these criticisms, the current study aims to (a) re-evaluate a
* Corresponding author. E-mail address: [email protected] (E.H. Wertheim).
previously reported prevention program [1] using a control group and follow up testing, (b) integrate theories of persuasion and attitude change to examine the effects of individual differences on program effectiveness and (c) promote a theoretical framework within which various intervention factors can be systematically evaluated. Social influence and persuasion theories posit that persuasive messages can be divided into at least four components: message source, content, mode of delivery and recipient characteristics [15]. While previous prevention programs have varied in types of presenters (e.g., school teachers [5,9,14] and experts [1,13]), in time lengths (e.g., single [1,4,5] to multiple session [2,6,7,11,13,14]), methods of delivery (e.g., videotapes [1,5], role plays [10,14] and classroom presentations [4,6,9,16]), information content (e.g., media literacy [12], self-esteem [17], healthy eating [9] and combination approaches [1 –14]) and target audiences (e.g., high risk vs. low risk girls [2,13]), few direct comparisons between these variations have been made. In a unique study, Heinze et al. [1] addressed this issue by directly comparing differences in presenter characteristics and receiver characteristics of girls participating in the intervention. Differences in the perceived identity of the presenter (expert, recovered anorexic, peer or no-identity)
0022-3999/02/$ – see front matter D 2002 Elsevier Science Inc. All rights reserved. PII: S 0 0 2 2 - 3 9 9 9 ( 0 2 ) 0 0 4 9 3 - 2
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and differences in the grade level of recipients (Grade 7 vs. Grade 10) were examined for their influence on program effectiveness. The researchers used a videotape intervention, a format that had achieved some success previously [5]. Overall, small significant improvements were found on knowledge, drive for thinness, size discrepancy (current – ideal size) and intention to diet. No significant differences were found between girls exposed to different presenter characteristics. Grade 7 girls, however, appeared to benefit more from the preventative video intervention on some measures than did Grade 10 girls. The Heinze et al. [1] study was an important beginning to the systematic evaluation of different message components within a social influence framework. It also suggested that small changes could be achieved from a relatively short videotape intervention. Advantages of videotaped presentations are that they are convenient for reaching many schools and students, who may not have otherwise been able to implement such a program and, in the research context, they ensure well-controlled interventions that can be standardised across settings. However, a limitation of the study was that it lacked a control group and a follow up measure, so it was not clear that positive changes were due to the intervention per se or were lasting. Receiver characteristics While receiver characteristics have been ignored in most eating disorder prevention research, several studies have examined differential effects of an intervention on characteristics including age [1] and risk status [2,13,16,17]. Ideally, in primary prevention ideology, it is best to intervene at a time point early enough to thwart the possible development of pathology. In terms of eating problems specifically, there is some evidence that dieting behaviours become relatively entrenched by the time girls reach Grade 8 [18]. Therefore, Grade 7 girls were chosen for the current study as an appropriate age for intervention. In the current study, receiver characteristics identified in the well-established social influence model, the Elaboration Likelihood Model of Persuasion (ELM) [19], were used to predict responses to a prevention program. In the ELM, Petty and Cacioppo [19] argued that individuals process persuasive messages in one of two ways. Some individuals actively think about and elaborate on message arguments (high elaboration), whereas others tend to use some peripheral cues, such as attractiveness of presenter, to evaluate a message (low elaboration). The model postulates that active information processing, or high elaboration, is the ‘‘cental route’’ to attitude change. Through this central route, when individuals carefully consider and think through all the arguments presented in a message, the attitudinal outcome is likely to be long lasting and resistant to future counterarguments. On the other hand, peripheral information processing or low elaboration is the ‘‘peripheral route’’ to attitude change. When message arguments are not likely
to be considered, and individuals rely on superficial cues for decision making, the end decision is likely to be short-lived and easily influenced by other peripheral cues, such as attractiveness of source presenting a counter-argument. Petty and Cacioppo therefore suggested that the most effective, long-lasting persuasion will occur for individuals who engage in higher levels of elaboration. Degree of elaboration depends on two main elements: individual differences in motivation to elaborate and situational characteristics that affect the ability to elaborate. While both are important elements, the current study will focus on individual characteristics relevant to the motivation to elaborate. In the ELM, two individual characteristics predictive of motivation are need for cognition (NFC) and personal relevance. NFC is the degree to which an individual engages in and enjoys cognitive activity and personal relevance is the level of interest or relevance an issue has to a person. Individuals with either high personal relevance or high NFC tend to make greater and longer lasting attitude changes than individuals low in these characteristics, assuming the arguments in the message are strong [21 –27]. In summary, the first part of the current study aims to reevaluate the videotaped intervention used by Heinze et al. [1] by comparing the response of Grade 7 girls who view the videotape to a parallel nonintervention control group immediately post-intervention and at 1-month follow-up. It is hypothesised that the intervention group will show greater changes on the outcome variables compared to the control group and that these changes will be maintained at a 1-month follow-up. The second part of the study aims to use the ELM to determine whether the receiver characteristics, personal relevance and NFC, moderate attitude change following the videotape intervention. It is expected that girls with high elaboration likelihood (high NFC or high personal relevance) will make greater attitude changes that will be longer lasting than girls with low elaboration likelihood.
Method Participants Participants were 242 girls in Grade 7 (aged 12 – 13 years) from three private girls’ secondary schools in Melbourne, Australia. The schools were all of middle to upper socioeconomic status. All girls in Grade 7 at each school were invited to participate (N = 325). Of the 242 (74.5%) girls who agreed to participate, 115 girls were in the intervention group and 127 girls in the control group. Twenty-four girls (11 intervention and 13 control) were not present at either Time 1 or 2 of the intervention and were excluded from the analysis. Analyses were therefore performed on 104 girls in the intervention group and 114 girls in the control group. The mean age of girls in the intervention group and control group was 12.7 years (0.41) and
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13.3 years (0.65), respectively. The mean body mass index (BMI; kg/m2) for the intervention group and control group was 18.49 (0.29) and 19.46 (0.34), respectively. Data collection for the intervention group began in the first half of the school year and the control groups began in the second half of the year. Materials Consistent with Heinze et al. [1], the pre-video questionnaire included five knowledge items, based on the videotaped message, which were rated from 1 (definitely do not agree) to 5 (definitely agree). The items were: ‘‘Around puberty most girls put on weight around the tummy, hips and bottom,’’ ‘‘Models can be up to 25% under weight for their height,’’ ‘‘Magazines often change pictures of models to make them look thinner than they really are,’’ ‘‘The ‘ideal’ female body shape has changed over time and is different across cultures’’ and ‘‘Research has shown that most dieters end up putting back on the weight they lose.’’ The body dissatisfaction and drive for thinness subscales of the Eating Disorders Inventory (EDI) [28] were used, together with a glossary of the terms ‘‘preoccupied’’ (to think about all the time) and ‘‘magnify’’ (to make something bigger than it really is), as recommended for younger participants [29]. Given the nonclinical nature of the sample, untransformed responses were summed for each scale to create total scale scores for the analyses [30]. The Contour Drawing Rating Scale [31] portrayed two sets of nine female figure outline sketches ranging from very thin to very large, which were rated from 1 to 17 with odd numbers under figures and even numbers half way between. Girls selected the figure that best represented their own body size (current figure) and the body size they would like to be (ideal figure). Size discrepancy was measured by calculating current figure minus ideal figure. Current and ideal figure ratings have been found to be stable (r = .88) over a 5-week period in an adolescent sample [29]. Three items measured current dieting behaviour, by asking how often girls have dieted, how old they were when they first dieted, and what behaviours they use to diet. Intention to diet was measured by a single item ‘‘How likely are you to go on a weight loss diet in the future?,’’ rated from 1 (definitely unlikely) to 5 (definitely likely) [1]. To measure subjective personal relevance, the 16-item shortened Personal Involvement Inventory (PII) [32] originally developed by Zaichkowsky [33], was adapted for use. At pretest, girls were informed that they would be viewing a videotape on body image and dieting and then responded to ‘‘I think the videotape (on body image) will be. . .’’ using the 16 items of the PII, which were rated from 1 (e.g., not needed by me) to 5 (e.g., needed by me). Munson and McQuarie [32] found satisfactory levels of internal consistency (a=.95), test – retest reliability and convergent and predictive validity.
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The shortened version of the Need for Cognition Scale [34] included 18 self-statements (e.g., ‘‘I prefer simple to complex problems’’) rated from 1 (definitely do not agree) to 5 (definitely agree). The internal consistency and splithalf reliability were reported by the authors to have reached acceptable levels of significance, and convergent and discriminant validity was also supported [20]. The post-video questionnaire consisted of the same knowledge items, body dissatisfaction, drive for thinness and intention to diet items, described in the prevideo questionnaire. The preventative videotape The 22-min videotape was designed and constructed by Heinze et al. [1] for a previous intervention study. Content included (1) determinants of body size and shape, variation in the ‘‘normal’’ female appearance, natural weight gain during puberty; (2) historical and sociocultural influences on female appearance, the media’s role in shaping this ideal; (3) the negative effects of extreme dieting, eating disorders and their harmful consequences, emotional eating and its triggers; (4) healthy eating habits, the importance of healthy eating; and (5) suggestions for creating a healthy body image and boosting self-image. Procedure Following approval from relevant ethics committees, all Grade 7 girls at three private girls’ schools were invited to participate in the study. Only girls at one school were shown the videotape and the other two schools were used as the control group. Separate schools were used for the intervention group and the control groups to reduce potential contamination effects related to girls within one school but in different treatment groups discussing the study and exchanging information. All students and parents were fully informed of the study and signed consent forms prior to testing day. Students’ identity was protected by an identification code, provided by the school, which girls wrote on all three questionnaires for future matching. At Time 1, girls filled in the 20-min Pre-Video Questionnaire. One week later (Time 2), the videotape was shown to all girls in the intervention group, followed by the 20-min Post-Video Questionnaire. The control group was not shown the video and simply completed their Time 2 questionnaire. One month later (Time 3), the Follow-Up Questionnaire was administered to the participants in the intervention group and control group. Girls self-reported their height and weight on the Time 2 questionnaires. Girls were assisted by group facilitators to measure their height (without shoes) and weighing scales were provided for girls to weigh themselves. Previous research has found high correlations between self-reported weights and actual weights [35,36].
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Results Table 1 shows means and standard deviations of outcome measures for intervention and control groups at the three time points. To guard against Type I error when performing multiple ANOVAs, the a level was set at P = .01 for all analyses. A one-way ANOVA at Time 1 was performed to examine whether there were differences at baseline between intervention and control groups for each dependent variable. No significant differences were found between the control group and intervention group on any dependent variables. The control group had slightly higher ages, F(1,214) = 67.04, P < .001 and BMIs, F(1,203) = 9.79, P < .01, than the intervention group, which was likely due to data collection occurring somewhat later in the year in the control group. In order to control for within group differences in initial scores on each of the variables, post-intervention change scores were calculated as Time 1 minus Time 2 score on each dependent variable. All change score variables satisfied assumptions of normality, linearity and homogeneity. There were no significant correlations between either age or BMI and any of the outcome variable change scores. A one-way ANOVA on the Times 1 – 2 change scores on the five dependent variables revealed that the students in the intervention group made significantly more changes on drive for thinness, F(1,208) = 7.01, P < .01, and intention to diet, F(1,211) = 8.38, P < .005, than the control group. Due to Table 1 Means and standard deviations for outcome measures for intervention (intervent) and control groups at Times 1 – 3
Variable
Time 1
Time 2
Time 3
n
n
n
M (S.D.)
M (S.D.)
M (S.D.)
Body dissatisfaction Intervent 104 29.44 (11.74) 104 28.18 (11.06) Control 112 32.95 (11.90) 112 32.83 (11.01)
99 28.24 (11.24) 94 32.27 (12.00)
Drive for thinness Intervent 104 17.12 (9.15) Control 112 18.73 (9.58)
99 15.53 (7.74) 95 17.97 (8.98)
104 15.27 (7.86) 112 18.58 (2.93)
Table 2 One-way ANOVAs for differences in change scores on intervention and control outcome measures Group main effect Change scores
df
F
P
Times 1 – 2 Body dissatisfaction Drive for thinness Size discrepancy Intention to diet Knowledgea
207 208 199 211 141
0.69 7.01* 2.96 8.83* 33.88**
.406 .009 .087 .004 .000
Times 1 – 3 Body dissatisfaction Drive for thinness Size discrepancy Intention to diet Knowledge
186 186 183 196 194
0.153 2.26 1.76 3.11 9.44*
.696 .134 .192 .079 .002
a
Full knowledge scale data only available for 40 control group girls. * P < .01. ** P < .001.
an error on the knowledge scale in the Time 2 control group questionnaire, only two of the five items were measured for 74 control group participants. For participants who answered the full knowledge scale (n = 141), there were significantly more positive changes for the intervention group than the control group, F(1,140) = 33.88, P < .001. On the two knowledge items answered by all girls, the intervention made significantly more changes on each knowledge item compared to the control group, F(1,214) = 17.2, P < .001 and F(1,214) = 10, P < .002. No significant differences were found for size discrepancy or body dissatisfaction. To determine whether these changes were maintained 1 month later, follow-up change scores were calculated as Time 1 minus Time 3 scores. A one-way ANOVA revealed that, at Time 3, the intervention group made greater changes than the control group only on knowledge, F(1,194) = 9.44, P < .002. See Table 2 for summary of ANOVA results. Receiver characteristics analyses
Size discrepancy Intervent 104 1.78 (2.40) Control 97 2.28 (2.92)
104 109
1.48 (2.18) 2.36 (2.71)
99 98
1.46 (2.27) 2.19 (2.73)
Current size Intervent 104 Control 97
8.17 (3.29) 8.76 (3.19)
104 109
8.16 (2.92) 8.81 (3.13)
99 99
8.19 (3.03) 8.43 (3.13)
Ideal size Intervent 104 Control 97
6.39 (2.37) 6.48 (2.23)
104 109
6.68 (1.93) 6.45 (2.37)
99 98
6.72 (1.83) 6.24 (2.22)
Intention to diet Intervent 104 2.94 (1.16) Control 112 3.02 (1.25)
104 111
2.66 (1.12) 3.16 (1.15)
99 101
2.61 (1.15) 2.97 (1.31)
Knowledge Intervent 104 19.13 (2.73) Control 111 18.58 (2.93)
115 21.86 (2.28) 114 17.39 (2.94)
99 20.54 (2.55) 100 18.95 (3.02)
The aim of the second part of the analyses was to determine whether girls higher in elaboration likelihood receiver characteristics made greater and longer lasting attitude changes than girls lower on these variables. Level of elaboration likelihood was measured by using subjective personal relevance scores (subjective PR) measured by scores on the PII [32], objective personal relevance (objective PR) represented by the body dissatisfaction score, NFC or a combined personal relevance and NFC variable (subjective PR NFC = elaboration likelihood (EL)). The analyses were conducted on the intervention data only. First, initial change from pre to post was assessed using Times 1– 2 change scores (Time 1 minus Time 2). These change scores were correlated with elaboration likelihood variables, subjective PR, objective PR, NFC and EL. As
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Table 3 Correlations among elaboration likelihood receiver characteristics and Times 1 – 2 change scores and Times 1 – 3 change scores in the intervention group Variables
1
2
3
4
5
1. Subjective PR 2. Objective PR 3. NFC 4. EL 5. Ch 1 – 2 BDIS 6. Ch 1 – 2 DFT 7. Ch 1 – 2 size 8. Ch 1 – 2 ITD 9. Ch 1 – 2 KNOW 10. Ch 1 – 3 BDIS 11. Ch 1 – 3 DFT 12. Ch 1 – 3 size 13. Ch 1 – 3 ITD 14. Ch 1 – 3 KNOW
6
.31** .19 .88** .24y .24* .13 .21y .11 .16 .22y .08 .09 .02
.02 .25* .39** .22y .30* .08 .02 .34** .37** .24y .05 .03
.62** .00 .01 .01 .09 .06 .06 .17 .05 .05 .08
.18 .18 .12 .20 .13 .10 .24 .09 .09 .06
.22y .30* .11 .07 .10 .13 .08 .68** .11 .20y .56** .18 .01 .03 .03 .01 .09
7
8
9
10
.06 .00 .17 .08 .63** .10 .08
.09 .18 .01 .04 .56** .08
.06 .07 .21y .02 .15 .08 .09 .59** .10
11
12
13
.04 .03 .02
.08 .02
.09
PR = personal relevance, NFC = need for cognition, EL = elaboration likelihood (PR NFC), Ch = change score between the two time points, DFT = drive for thinness, Size = size discrepancy, ITD = intention to diet, KNOW = knowledge, BDIS = body dissatisfaction; Times 1 – 2: n = 104, Times 1 – 3: n = 99. * P < .01. ** P < .001 (two-tailed). y P < .05.
seen in Table 3, there was a significant positive correlation between subjective PR and Times 1– 2 changes in drive for thinness, r = .24, P < .01. Although not statistically significant, subjective PR also positively correlated with body dissatisfaction, r = .24, P = .015 and intention to diet, r = .21, P = .03, indicating that girls who believed the videotape would be personally relevant to them tended to report the greatest positive changes in attitudes. Objective PR (Time 1 body dissatisfaction) was correlated with change scores for body dissatisfaction, r = .39, P < .001, and size discrepancy, r = .30, P < .002, and while not significant, tended to do so for drive for thinness, r = .22, P = .03; NFC and EL did not correlate with changes made on any of the variables. Correlations between Times 1– 3 changes and elaboration likelihood receiver characteristics were also conducted. Subjective PR had a nonsignificant tendency with change in drive for thinness, r = .22, P = .03. Objective personal relevance significantly correlated with change in body dissatisfaction, r = .34, P < .001, drive for thinness, r = .37, P < .001, and size discrepancy, r = .24, P < .001. There were no significant correlations between Times 2 –3 change scores and any of the receiver characteristics. Given that maintenance of change implies some change took place (between Times 1 and 2), a second set of analyses only examined the 50 girls who made a positive change on body dissatisfaction at Time 2. Again, for this subset, none of the Times 2 –3 change scores correlated significantly with subjective PR, objective PR, NFC and ELM. A series of 2 (intervention/control) 2 (high/low relevance) ANOVAs were used to examine group differences on Times 1 – 2 and Times 1– 3 change scores that significantly correlated with subjective or objective relevance. Two high/low relevance variables were created using a median split on subjective PR and objective PR, respectively. No
relevance by group interaction effects were found for any change scores, but there were significant main effects for ‘‘high/low’’ objective PR for Times 1– 2 changes in body dissatisfaction, F(1,208) = 13.8, P < .001, and size discrepancy, F(1,196) = 6.16, P < .01, and for Times 1 –3 changes in drive for thinness, F(1,184) = 7.73, P < .01, and body dissatisfaction, F(1,188) = 15.3, P < .001. This suggests that girls higher in objective relevance made greater changes on these variables regardless of whether or not they participated in the intervention.
Discussion The first aim of the present study was to replicate and extend findings made by Heinze et al. [1] in which significant improvements in drive for thinness, intention to diet and knowledge were found following a brief eating disorder prevention videotape. The present study extended their research by including a nonintervention control group and 1-month follow-up. Findings demonstrated that compared to a nonintervention control group, girls who watched the prevention videotape made small, but significant, positive changes in drive for thinness and intention to diet and had improved scores on knowledge items, thus confirming on a larger Grade 7 sample and strengthening the findings of Heinze et al. [1]. At 1-month follow-up, only changes in knowledge were maintained. These findings are an improvement to earlier studies, many of which did not find attitude changes and are consistent with more successful recent interventions [10,12]. The poor maintenance of these attitude changes is also consistent with previous research, which has often found short-term changes fail to be sustained at follow-up.
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It appears that despite the immediate positive effects of intervention programs, other sociocultural, media or psychological factors remain powerful influences on the body image attitudes of adolescent girls. Nevertheless, the fact that a very brief videotape intervention demonstrated positive short-term changes in attitude and intention to diet and longer term improvements in knowledge is promising. The videotape could potentially be used as a component of a broader prevention program, which includes additional interventions and booster sessions to maintain positive changes. Further research is needed to explore this possibility. The second aim of the study was to examine whether receiver characteristics based on the ELM, specifically personal relevance and NFC, influenced the persuasiveness of the prevention program. The study found that when participants in the intervention program only were examined, girls who were higher in personal involvement (both objective and subjective) reported greater positive changes on several variables between pre-intervention and both postvideo and 1-month follow-up. However, the positive relationship between relevance and attitude change in the intervention group was not significantly different from that in the control group, suggesting that either any intervention (including just questionnaires) may cause a positive effect in relevant individuals, or alternatively that a regression to the mean effect occurred on certain measures over repeated assessment. NFC and elaboration likelihood (NFC subsubjective personal relevance) did not predict greater or longer lasting changes on the dependent variables in the intervention group. These findings therefore offer only weak support for the ELM hypotheses, that the receiver characteristic, personal relevance, can influence the amount of attitude change after a persuasive message, and no support that NFC was predictive. Two additional design considerations would be useful for future research into the question of relevance. First, the measure of subjective relevance was taken prior to the videotape and, while this is the best measure of a true ‘‘predictor’’ variable, the videotape may actually have been more relevant than many girls expected initially. Thus, in future research, a measure of subjective relevance taken both before and after the intervention might better predict maintenance of change. Second, the present study was designed to assess the importance of prior individual characteristics related to elaboration proneness in a given context. However, the design was such that even though certain girls may have had individual characteristics predicting that they would be more motivated to elaborate upon the messages in the videotape, they did not have a great deal of opportunity to elaborate. As measures were taken immediately after the videotape was shown, girls did not have the opportunity to discuss or elaborate on the content of the video in any systematic way. Thus, any attitude change may have been ‘‘peripheral’’ vs. ‘‘central’’ for almost all girls. If girls were unable to elaborate and changed their attitudes via the
‘‘peripheral route,’’ this would explain the overall poor maintenance of change. Future research needs to address the issue of providing further opportunities and guidance in elaboration. It is clear from the present study that, just because an individual possesses characteristics suggesting that they would be prone to elaborate on messages, does not mean they will benefit more from a particular intervention program. The provision of opportunities for elaboration of the videotape content could involve post-videotape discussion groups or written exercises to follow the intervention videotape, which (a) provide girls with the opportunity to elaborate on the prevention arguments, thus, theoretically increasing the potential for central route attitude change and (b) assess which types of elaboration most successfully increase the benefits of a basic preventive message (i.e., the videotape). Our research team is currently in the process of collecting such data. Other limitations of the study were that the control group had slightly higher mean ages and BMI scores than the intervention group. It is likely this was due to slight differences in time of year that data was collected. As expected, higher BMI was associated with greater Time 1 scores in body dissatisfaction, drive for thinness, intention to diet and size discrepancy. However, as neither age nor BMI were associated with differences in changes scores, the group differences were unlikely to have confounded the analyses. Finally, a limitation familiar to most prevention research is the timing of follow up measurement. The 1-month followup period used in the current study was useful for examining short-term maintenance, but an insufficient measure of the long-term benefits of a primary prevention program and longer follow up measures are desirable. Despite these limitations, this study can serve as a model for an approach that includes the systematic evaluation of the message factors proposed in theories of social influence. It is hoped that future prevention research will continue to examine each of these message components so that the most effective style of presenter can deliver the most persuasive arguments (content), in the most engaging and captivating format, to the most relevant audience. In summary, in this study, girls who watched an eating disorders primary prevention videotape made small but significantly more changes in drive for thinness, knowledge and intention to diet, than girls who received no intervention. However, at 1-month follow-up, only changes in knowledge were maintained. Recipient NFC levels did not predict amount of change or maintenance of change. It was also found that personal relevance predicted amount of change in the intervention group, but analyses comparing control and intervention participants suggested this relationship did not appear to be a function of the intervention itself. The pre – post attitude changes are promising considering that the videotape intervention was only 22 min in length and no active involvement of the girls was required. Videotaped prevention messages are potentially an effective
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method of intervention as they are both cost effective and easily used in schools. Future research needs to examine the long-term impact when this program is combined with further interventions that provide the opportunity for girls to discuss and think through the arguments in the videotape.
Acknowledgments Funding from the Australian Rotary Health Research Fund supported this research. We thank the following individuals: Tracey Holt, Emma Twigg, Jessica Stean and Debbie Barned for their help with data collection in the schools; Linda Tilgner for her assistance with data analysis; Vanessa Heinze and Lisa Robins for the use of the videotape; Glenda Message and Wendy Jones for their enthusiasm and assistance with the organization of testing. We would also like to thank the participating schools and students.
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Favaro A. A preventive intervention program in adolescent schoolgirls: a longitudinal study. Psychother Psychosom 1999;68:46 – 50. Carter J, Stewart D, Dunn V, Fairburn C. Primary prevention of eating disorders: might it do more harm than good? Int J Eating Disord 1997;22:167 – 72. McGuire W. Personality and susceptibility to social influence. In: Borgatta EF, Lambert WW, editors. Handbook of personality theory and research. Chicago: Rand McNally and Company, 1968. Neumark-Sztainer D, Butler R, Palti H. Eating disturbances among adolescent girls: evaluation of a school based primary prevention program. J Nutr Educ 1995;27:24 – 31. O’Dea J, Abraham S. Improving the body image, eating attitudes, and behaviours of young male and female adolescents: a new educational approach that focuses on self-esteem. Int J Eating Disord 2000;28: 43 – 57. Wertheim E, Koerner J, Paxton S. Longitudinal predictors of restrictive eating and bulimic tendencies in adolescent girls: age differences between early and middle adolescence in predictions of change. J Youth and Adol 2001;30:69 – 81. Petty R, Cacioppo J. The Elaboration Likelihood Model of Persuasion. Adv Experim Soc Psychol 1986;19:123 – 205. Cacioppo J, Petty R. The need for cognition. J Pers Soc Psychol 1982;42:116 – 31. Andrew J, Shimp T. Effect of involvement, argument strength, and source characteristics on central and peripheral processing of advertising. Psychol Market 1990;7:195 – 214. Petty R, Cacioppo J. Involvement and persuasion: tradition versus integration. Psychol Bull 1990;10:367 – 74. Petty R, Cacioppo J. Attitudes and persuasion: classic and contemporary approaches. Dubuque (IA): W.C. Brown, 1981. Petty R, Cacioppo J. Central and peripheral routes to persuasion. An application to advertising. In: Percy L, Woodside A, editors. Advertising and consumer psychology. Lexington (MA): Health, 1983. pp. 3 – 23. Neimeyer G, Guy J, Metzler A. Changing attitudes regarding the treatment of disordered eating: an application of the elaboration likelihood model. J Soc Clin Psychol 1989;8:70 – 86. Cacioppo J, Petty R, Morris K. Effects of need for cognition on message evaluation, recall, and persuasion. J Pers Soc Psychol 1983;45:805 – 18. Haugtvedt C, Petty R, Cacioppo J. Need for cognition and advertising: understanding the role of personality variables in consumer behaviour. J Consumer Psychol 1992;1:239 – 60. Garner DM, Olmstead MP, Polivy J. Development and validation of a multidimensional eating disorder inventory for anorexia nervosa and bulimia. Int J of Ed 1983;2:15 – 34. Banasiak S, Wertheim E, Koerner J, Voudouris N. Test – retest reliability and internal consistency of a variety of measures of dietary restraint and body concerns in a sample of adolescent girls. Int J Eating Disord 2001;29:85 – 9. Schoemaker C, van Strien T, van der Staak C. Validation of the Eating Disorders Inventory in a non-clinical population using transformed and untransformed responses. Int J Eating Disord 1994;15:387 – 93. Thompson M, Gray J. Development and validation of a new bodyimage assessment tool. J Pers Assess 1995;64:258 – 69. Munson J, McQuarrie E. The factorial and predictive validities of a revised measure of Zaichkowsky’s Personal Involvement Inventory. Educ Psychol Measur 1987;47:773 – 82. Zaichkowsky JL. Measuring the involvement construct. J Consumer Res 1985;12:341 – 52. Petty R, Cacioppo J. Communication and persuasion: central and peripheral routes to attitude change. New York: Springer-Verlag, 1986. Fairburn C, Beglin S. The assessment of eating disorders: interview or self-report questionnaire. Int J Eating Disord 1994;16:363 – 70. Davis H, Gergen PJ. Self-described weight status of Mexican – American adolescents. J Adolesc Health 1994;15:407 – 9.
A controlled evaluation of an eating disorders primary prevention videotape using the Elaboration Likelihood Model of Persuasion Giselle F. Withersa, Kylie Twigga, Eleanor H. Wertheima,*, Susan J. Paxtonb a
School of Psychological Science, La Trobe University, Bundoora (Melbourne), Vic. 3083, Australia b Department of Psychology, University of Melbourne, Parkville, Vic., Australia
Abstract Objective: The aim was to extend findings related to a previously reported eating disorders prevention program by comparing treatment and control groups, adding a follow-up, and examining whether receiver characteristics, personal relevance and need for cognition (NFC), could predict attitude change in early adolescent girls. Method: Grade 7 girls were either shown a brief prevention videotape on dieting and body image (n = 104) or given no intervention (n = 114). All girls completed pre-, post- and 1-month follow-up questionnaires. Results: The intervention
group resulted in significantly more positive changes in attitude and knowledge at post-intervention, but only in knowledge at follow-up. There was no strong evidence that pre-intervention characteristics of recipients predicted responses to the videotape intervention when changes were compared to the control group. Conclusion: This prevention videotape appeared to have positive immediate effects, but additional intervention (e.g., booster sessions) may be required for longer-term change. D 2002 Elsevier Science Inc. All rights reserved.
Keywords: Body image; Dieting; Eating disorders; Persuasion; Prevention
Introduction The primary prevention of eating disorders in adolescent girls has received increasing attention over the past 10 years. Prevention programs have typically aimed to reduce body concerns and unhealthy dieting practices in adolescent girls, using psychoeducation and interactive presentations in a school classroom setting [1– 10]. Overall, the findings of these programs have been mixed. While more recent interventions achieved better results than earlier studies, changes have been small and rarely maintained [10 –13]. Several criticisms of these studies have been made. First, many programs lack a control group or follow up testing [1,4,9,14]. Second, programs fail to recognise the effects of individual differences on program effectiveness. Third, programs often lack a theoretical framework upon which to organise and present program material, thus, ineffective message components (e.g., in content or delivery) have not been isolated and identified. In response to these criticisms, the current study aims to (a) re-evaluate a
* Corresponding author. E-mail address: [email protected] (E.H. Wertheim).
previously reported prevention program [1] using a control group and follow up testing, (b) integrate theories of persuasion and attitude change to examine the effects of individual differences on program effectiveness and (c) promote a theoretical framework within which various intervention factors can be systematically evaluated. Social influence and persuasion theories posit that persuasive messages can be divided into at least four components: message source, content, mode of delivery and recipient characteristics [15]. While previous prevention programs have varied in types of presenters (e.g., school teachers [5,9,14] and experts [1,13]), in time lengths (e.g., single [1,4,5] to multiple session [2,6,7,11,13,14]), methods of delivery (e.g., videotapes [1,5], role plays [10,14] and classroom presentations [4,6,9,16]), information content (e.g., media literacy [12], self-esteem [17], healthy eating [9] and combination approaches [1 –14]) and target audiences (e.g., high risk vs. low risk girls [2,13]), few direct comparisons between these variations have been made. In a unique study, Heinze et al. [1] addressed this issue by directly comparing differences in presenter characteristics and receiver characteristics of girls participating in the intervention. Differences in the perceived identity of the presenter (expert, recovered anorexic, peer or no-identity)
0022-3999/02/$ – see front matter D 2002 Elsevier Science Inc. All rights reserved. PII: S 0 0 2 2 - 3 9 9 9 ( 0 2 ) 0 0 4 9 3 - 2
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and differences in the grade level of recipients (Grade 7 vs. Grade 10) were examined for their influence on program effectiveness. The researchers used a videotape intervention, a format that had achieved some success previously [5]. Overall, small significant improvements were found on knowledge, drive for thinness, size discrepancy (current – ideal size) and intention to diet. No significant differences were found between girls exposed to different presenter characteristics. Grade 7 girls, however, appeared to benefit more from the preventative video intervention on some measures than did Grade 10 girls. The Heinze et al. [1] study was an important beginning to the systematic evaluation of different message components within a social influence framework. It also suggested that small changes could be achieved from a relatively short videotape intervention. Advantages of videotaped presentations are that they are convenient for reaching many schools and students, who may not have otherwise been able to implement such a program and, in the research context, they ensure well-controlled interventions that can be standardised across settings. However, a limitation of the study was that it lacked a control group and a follow up measure, so it was not clear that positive changes were due to the intervention per se or were lasting. Receiver characteristics While receiver characteristics have been ignored in most eating disorder prevention research, several studies have examined differential effects of an intervention on characteristics including age [1] and risk status [2,13,16,17]. Ideally, in primary prevention ideology, it is best to intervene at a time point early enough to thwart the possible development of pathology. In terms of eating problems specifically, there is some evidence that dieting behaviours become relatively entrenched by the time girls reach Grade 8 [18]. Therefore, Grade 7 girls were chosen for the current study as an appropriate age for intervention. In the current study, receiver characteristics identified in the well-established social influence model, the Elaboration Likelihood Model of Persuasion (ELM) [19], were used to predict responses to a prevention program. In the ELM, Petty and Cacioppo [19] argued that individuals process persuasive messages in one of two ways. Some individuals actively think about and elaborate on message arguments (high elaboration), whereas others tend to use some peripheral cues, such as attractiveness of presenter, to evaluate a message (low elaboration). The model postulates that active information processing, or high elaboration, is the ‘‘cental route’’ to attitude change. Through this central route, when individuals carefully consider and think through all the arguments presented in a message, the attitudinal outcome is likely to be long lasting and resistant to future counterarguments. On the other hand, peripheral information processing or low elaboration is the ‘‘peripheral route’’ to attitude change. When message arguments are not likely
to be considered, and individuals rely on superficial cues for decision making, the end decision is likely to be short-lived and easily influenced by other peripheral cues, such as attractiveness of source presenting a counter-argument. Petty and Cacioppo therefore suggested that the most effective, long-lasting persuasion will occur for individuals who engage in higher levels of elaboration. Degree of elaboration depends on two main elements: individual differences in motivation to elaborate and situational characteristics that affect the ability to elaborate. While both are important elements, the current study will focus on individual characteristics relevant to the motivation to elaborate. In the ELM, two individual characteristics predictive of motivation are need for cognition (NFC) and personal relevance. NFC is the degree to which an individual engages in and enjoys cognitive activity and personal relevance is the level of interest or relevance an issue has to a person. Individuals with either high personal relevance or high NFC tend to make greater and longer lasting attitude changes than individuals low in these characteristics, assuming the arguments in the message are strong [21 –27]. In summary, the first part of the current study aims to reevaluate the videotaped intervention used by Heinze et al. [1] by comparing the response of Grade 7 girls who view the videotape to a parallel nonintervention control group immediately post-intervention and at 1-month follow-up. It is hypothesised that the intervention group will show greater changes on the outcome variables compared to the control group and that these changes will be maintained at a 1-month follow-up. The second part of the study aims to use the ELM to determine whether the receiver characteristics, personal relevance and NFC, moderate attitude change following the videotape intervention. It is expected that girls with high elaboration likelihood (high NFC or high personal relevance) will make greater attitude changes that will be longer lasting than girls with low elaboration likelihood.
Method Participants Participants were 242 girls in Grade 7 (aged 12 – 13 years) from three private girls’ secondary schools in Melbourne, Australia. The schools were all of middle to upper socioeconomic status. All girls in Grade 7 at each school were invited to participate (N = 325). Of the 242 (74.5%) girls who agreed to participate, 115 girls were in the intervention group and 127 girls in the control group. Twenty-four girls (11 intervention and 13 control) were not present at either Time 1 or 2 of the intervention and were excluded from the analysis. Analyses were therefore performed on 104 girls in the intervention group and 114 girls in the control group. The mean age of girls in the intervention group and control group was 12.7 years (0.41) and
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13.3 years (0.65), respectively. The mean body mass index (BMI; kg/m2) for the intervention group and control group was 18.49 (0.29) and 19.46 (0.34), respectively. Data collection for the intervention group began in the first half of the school year and the control groups began in the second half of the year. Materials Consistent with Heinze et al. [1], the pre-video questionnaire included five knowledge items, based on the videotaped message, which were rated from 1 (definitely do not agree) to 5 (definitely agree). The items were: ‘‘Around puberty most girls put on weight around the tummy, hips and bottom,’’ ‘‘Models can be up to 25% under weight for their height,’’ ‘‘Magazines often change pictures of models to make them look thinner than they really are,’’ ‘‘The ‘ideal’ female body shape has changed over time and is different across cultures’’ and ‘‘Research has shown that most dieters end up putting back on the weight they lose.’’ The body dissatisfaction and drive for thinness subscales of the Eating Disorders Inventory (EDI) [28] were used, together with a glossary of the terms ‘‘preoccupied’’ (to think about all the time) and ‘‘magnify’’ (to make something bigger than it really is), as recommended for younger participants [29]. Given the nonclinical nature of the sample, untransformed responses were summed for each scale to create total scale scores for the analyses [30]. The Contour Drawing Rating Scale [31] portrayed two sets of nine female figure outline sketches ranging from very thin to very large, which were rated from 1 to 17 with odd numbers under figures and even numbers half way between. Girls selected the figure that best represented their own body size (current figure) and the body size they would like to be (ideal figure). Size discrepancy was measured by calculating current figure minus ideal figure. Current and ideal figure ratings have been found to be stable (r = .88) over a 5-week period in an adolescent sample [29]. Three items measured current dieting behaviour, by asking how often girls have dieted, how old they were when they first dieted, and what behaviours they use to diet. Intention to diet was measured by a single item ‘‘How likely are you to go on a weight loss diet in the future?,’’ rated from 1 (definitely unlikely) to 5 (definitely likely) [1]. To measure subjective personal relevance, the 16-item shortened Personal Involvement Inventory (PII) [32] originally developed by Zaichkowsky [33], was adapted for use. At pretest, girls were informed that they would be viewing a videotape on body image and dieting and then responded to ‘‘I think the videotape (on body image) will be. . .’’ using the 16 items of the PII, which were rated from 1 (e.g., not needed by me) to 5 (e.g., needed by me). Munson and McQuarie [32] found satisfactory levels of internal consistency (a=.95), test – retest reliability and convergent and predictive validity.
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The shortened version of the Need for Cognition Scale [34] included 18 self-statements (e.g., ‘‘I prefer simple to complex problems’’) rated from 1 (definitely do not agree) to 5 (definitely agree). The internal consistency and splithalf reliability were reported by the authors to have reached acceptable levels of significance, and convergent and discriminant validity was also supported [20]. The post-video questionnaire consisted of the same knowledge items, body dissatisfaction, drive for thinness and intention to diet items, described in the prevideo questionnaire. The preventative videotape The 22-min videotape was designed and constructed by Heinze et al. [1] for a previous intervention study. Content included (1) determinants of body size and shape, variation in the ‘‘normal’’ female appearance, natural weight gain during puberty; (2) historical and sociocultural influences on female appearance, the media’s role in shaping this ideal; (3) the negative effects of extreme dieting, eating disorders and their harmful consequences, emotional eating and its triggers; (4) healthy eating habits, the importance of healthy eating; and (5) suggestions for creating a healthy body image and boosting self-image. Procedure Following approval from relevant ethics committees, all Grade 7 girls at three private girls’ schools were invited to participate in the study. Only girls at one school were shown the videotape and the other two schools were used as the control group. Separate schools were used for the intervention group and the control groups to reduce potential contamination effects related to girls within one school but in different treatment groups discussing the study and exchanging information. All students and parents were fully informed of the study and signed consent forms prior to testing day. Students’ identity was protected by an identification code, provided by the school, which girls wrote on all three questionnaires for future matching. At Time 1, girls filled in the 20-min Pre-Video Questionnaire. One week later (Time 2), the videotape was shown to all girls in the intervention group, followed by the 20-min Post-Video Questionnaire. The control group was not shown the video and simply completed their Time 2 questionnaire. One month later (Time 3), the Follow-Up Questionnaire was administered to the participants in the intervention group and control group. Girls self-reported their height and weight on the Time 2 questionnaires. Girls were assisted by group facilitators to measure their height (without shoes) and weighing scales were provided for girls to weigh themselves. Previous research has found high correlations between self-reported weights and actual weights [35,36].
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Results Table 1 shows means and standard deviations of outcome measures for intervention and control groups at the three time points. To guard against Type I error when performing multiple ANOVAs, the a level was set at P = .01 for all analyses. A one-way ANOVA at Time 1 was performed to examine whether there were differences at baseline between intervention and control groups for each dependent variable. No significant differences were found between the control group and intervention group on any dependent variables. The control group had slightly higher ages, F(1,214) = 67.04, P < .001 and BMIs, F(1,203) = 9.79, P < .01, than the intervention group, which was likely due to data collection occurring somewhat later in the year in the control group. In order to control for within group differences in initial scores on each of the variables, post-intervention change scores were calculated as Time 1 minus Time 2 score on each dependent variable. All change score variables satisfied assumptions of normality, linearity and homogeneity. There were no significant correlations between either age or BMI and any of the outcome variable change scores. A one-way ANOVA on the Times 1 – 2 change scores on the five dependent variables revealed that the students in the intervention group made significantly more changes on drive for thinness, F(1,208) = 7.01, P < .01, and intention to diet, F(1,211) = 8.38, P < .005, than the control group. Due to Table 1 Means and standard deviations for outcome measures for intervention (intervent) and control groups at Times 1 – 3
Variable
Time 1
Time 2
Time 3
n
n
n
M (S.D.)
M (S.D.)
M (S.D.)
Body dissatisfaction Intervent 104 29.44 (11.74) 104 28.18 (11.06) Control 112 32.95 (11.90) 112 32.83 (11.01)
99 28.24 (11.24) 94 32.27 (12.00)
Drive for thinness Intervent 104 17.12 (9.15) Control 112 18.73 (9.58)
99 15.53 (7.74) 95 17.97 (8.98)
104 15.27 (7.86) 112 18.58 (2.93)
Table 2 One-way ANOVAs for differences in change scores on intervention and control outcome measures Group main effect Change scores
df
F
P
Times 1 – 2 Body dissatisfaction Drive for thinness Size discrepancy Intention to diet Knowledgea
207 208 199 211 141
0.69 7.01* 2.96 8.83* 33.88**
.406 .009 .087 .004 .000
Times 1 – 3 Body dissatisfaction Drive for thinness Size discrepancy Intention to diet Knowledge
186 186 183 196 194
0.153 2.26 1.76 3.11 9.44*
.696 .134 .192 .079 .002
a
Full knowledge scale data only available for 40 control group girls. * P < .01. ** P < .001.
an error on the knowledge scale in the Time 2 control group questionnaire, only two of the five items were measured for 74 control group participants. For participants who answered the full knowledge scale (n = 141), there were significantly more positive changes for the intervention group than the control group, F(1,140) = 33.88, P < .001. On the two knowledge items answered by all girls, the intervention made significantly more changes on each knowledge item compared to the control group, F(1,214) = 17.2, P < .001 and F(1,214) = 10, P < .002. No significant differences were found for size discrepancy or body dissatisfaction. To determine whether these changes were maintained 1 month later, follow-up change scores were calculated as Time 1 minus Time 3 scores. A one-way ANOVA revealed that, at Time 3, the intervention group made greater changes than the control group only on knowledge, F(1,194) = 9.44, P < .002. See Table 2 for summary of ANOVA results. Receiver characteristics analyses
Size discrepancy Intervent 104 1.78 (2.40) Control 97 2.28 (2.92)
104 109
1.48 (2.18) 2.36 (2.71)
99 98
1.46 (2.27) 2.19 (2.73)
Current size Intervent 104 Control 97
8.17 (3.29) 8.76 (3.19)
104 109
8.16 (2.92) 8.81 (3.13)
99 99
8.19 (3.03) 8.43 (3.13)
Ideal size Intervent 104 Control 97
6.39 (2.37) 6.48 (2.23)
104 109
6.68 (1.93) 6.45 (2.37)
99 98
6.72 (1.83) 6.24 (2.22)
Intention to diet Intervent 104 2.94 (1.16) Control 112 3.02 (1.25)
104 111
2.66 (1.12) 3.16 (1.15)
99 101
2.61 (1.15) 2.97 (1.31)
Knowledge Intervent 104 19.13 (2.73) Control 111 18.58 (2.93)
115 21.86 (2.28) 114 17.39 (2.94)
99 20.54 (2.55) 100 18.95 (3.02)
The aim of the second part of the analyses was to determine whether girls higher in elaboration likelihood receiver characteristics made greater and longer lasting attitude changes than girls lower on these variables. Level of elaboration likelihood was measured by using subjective personal relevance scores (subjective PR) measured by scores on the PII [32], objective personal relevance (objective PR) represented by the body dissatisfaction score, NFC or a combined personal relevance and NFC variable (subjective PR NFC = elaboration likelihood (EL)). The analyses were conducted on the intervention data only. First, initial change from pre to post was assessed using Times 1– 2 change scores (Time 1 minus Time 2). These change scores were correlated with elaboration likelihood variables, subjective PR, objective PR, NFC and EL. As
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Table 3 Correlations among elaboration likelihood receiver characteristics and Times 1 – 2 change scores and Times 1 – 3 change scores in the intervention group Variables
1
2
3
4
5
1. Subjective PR 2. Objective PR 3. NFC 4. EL 5. Ch 1 – 2 BDIS 6. Ch 1 – 2 DFT 7. Ch 1 – 2 size 8. Ch 1 – 2 ITD 9. Ch 1 – 2 KNOW 10. Ch 1 – 3 BDIS 11. Ch 1 – 3 DFT 12. Ch 1 – 3 size 13. Ch 1 – 3 ITD 14. Ch 1 – 3 KNOW
6
.31** .19 .88** .24y .24* .13 .21y .11 .16 .22y .08 .09 .02
.02 .25* .39** .22y .30* .08 .02 .34** .37** .24y .05 .03
.62** .00 .01 .01 .09 .06 .06 .17 .05 .05 .08
.18 .18 .12 .20 .13 .10 .24 .09 .09 .06
.22y .30* .11 .07 .10 .13 .08 .68** .11 .20y .56** .18 .01 .03 .03 .01 .09
7
8
9
10
.06 .00 .17 .08 .63** .10 .08
.09 .18 .01 .04 .56** .08
.06 .07 .21y .02 .15 .08 .09 .59** .10
11
12
13
.04 .03 .02
.08 .02
.09
PR = personal relevance, NFC = need for cognition, EL = elaboration likelihood (PR NFC), Ch = change score between the two time points, DFT = drive for thinness, Size = size discrepancy, ITD = intention to diet, KNOW = knowledge, BDIS = body dissatisfaction; Times 1 – 2: n = 104, Times 1 – 3: n = 99. * P < .01. ** P < .001 (two-tailed). y P < .05.
seen in Table 3, there was a significant positive correlation between subjective PR and Times 1– 2 changes in drive for thinness, r = .24, P < .01. Although not statistically significant, subjective PR also positively correlated with body dissatisfaction, r = .24, P = .015 and intention to diet, r = .21, P = .03, indicating that girls who believed the videotape would be personally relevant to them tended to report the greatest positive changes in attitudes. Objective PR (Time 1 body dissatisfaction) was correlated with change scores for body dissatisfaction, r = .39, P < .001, and size discrepancy, r = .30, P < .002, and while not significant, tended to do so for drive for thinness, r = .22, P = .03; NFC and EL did not correlate with changes made on any of the variables. Correlations between Times 1– 3 changes and elaboration likelihood receiver characteristics were also conducted. Subjective PR had a nonsignificant tendency with change in drive for thinness, r = .22, P = .03. Objective personal relevance significantly correlated with change in body dissatisfaction, r = .34, P < .001, drive for thinness, r = .37, P < .001, and size discrepancy, r = .24, P < .001. There were no significant correlations between Times 2 –3 change scores and any of the receiver characteristics. Given that maintenance of change implies some change took place (between Times 1 and 2), a second set of analyses only examined the 50 girls who made a positive change on body dissatisfaction at Time 2. Again, for this subset, none of the Times 2 –3 change scores correlated significantly with subjective PR, objective PR, NFC and ELM. A series of 2 (intervention/control) 2 (high/low relevance) ANOVAs were used to examine group differences on Times 1 – 2 and Times 1– 3 change scores that significantly correlated with subjective or objective relevance. Two high/low relevance variables were created using a median split on subjective PR and objective PR, respectively. No
relevance by group interaction effects were found for any change scores, but there were significant main effects for ‘‘high/low’’ objective PR for Times 1– 2 changes in body dissatisfaction, F(1,208) = 13.8, P < .001, and size discrepancy, F(1,196) = 6.16, P < .01, and for Times 1 –3 changes in drive for thinness, F(1,184) = 7.73, P < .01, and body dissatisfaction, F(1,188) = 15.3, P < .001. This suggests that girls higher in objective relevance made greater changes on these variables regardless of whether or not they participated in the intervention.
Discussion The first aim of the present study was to replicate and extend findings made by Heinze et al. [1] in which significant improvements in drive for thinness, intention to diet and knowledge were found following a brief eating disorder prevention videotape. The present study extended their research by including a nonintervention control group and 1-month follow-up. Findings demonstrated that compared to a nonintervention control group, girls who watched the prevention videotape made small, but significant, positive changes in drive for thinness and intention to diet and had improved scores on knowledge items, thus confirming on a larger Grade 7 sample and strengthening the findings of Heinze et al. [1]. At 1-month follow-up, only changes in knowledge were maintained. These findings are an improvement to earlier studies, many of which did not find attitude changes and are consistent with more successful recent interventions [10,12]. The poor maintenance of these attitude changes is also consistent with previous research, which has often found short-term changes fail to be sustained at follow-up.
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It appears that despite the immediate positive effects of intervention programs, other sociocultural, media or psychological factors remain powerful influences on the body image attitudes of adolescent girls. Nevertheless, the fact that a very brief videotape intervention demonstrated positive short-term changes in attitude and intention to diet and longer term improvements in knowledge is promising. The videotape could potentially be used as a component of a broader prevention program, which includes additional interventions and booster sessions to maintain positive changes. Further research is needed to explore this possibility. The second aim of the study was to examine whether receiver characteristics based on the ELM, specifically personal relevance and NFC, influenced the persuasiveness of the prevention program. The study found that when participants in the intervention program only were examined, girls who were higher in personal involvement (both objective and subjective) reported greater positive changes on several variables between pre-intervention and both postvideo and 1-month follow-up. However, the positive relationship between relevance and attitude change in the intervention group was not significantly different from that in the control group, suggesting that either any intervention (including just questionnaires) may cause a positive effect in relevant individuals, or alternatively that a regression to the mean effect occurred on certain measures over repeated assessment. NFC and elaboration likelihood (NFC subsubjective personal relevance) did not predict greater or longer lasting changes on the dependent variables in the intervention group. These findings therefore offer only weak support for the ELM hypotheses, that the receiver characteristic, personal relevance, can influence the amount of attitude change after a persuasive message, and no support that NFC was predictive. Two additional design considerations would be useful for future research into the question of relevance. First, the measure of subjective relevance was taken prior to the videotape and, while this is the best measure of a true ‘‘predictor’’ variable, the videotape may actually have been more relevant than many girls expected initially. Thus, in future research, a measure of subjective relevance taken both before and after the intervention might better predict maintenance of change. Second, the present study was designed to assess the importance of prior individual characteristics related to elaboration proneness in a given context. However, the design was such that even though certain girls may have had individual characteristics predicting that they would be more motivated to elaborate upon the messages in the videotape, they did not have a great deal of opportunity to elaborate. As measures were taken immediately after the videotape was shown, girls did not have the opportunity to discuss or elaborate on the content of the video in any systematic way. Thus, any attitude change may have been ‘‘peripheral’’ vs. ‘‘central’’ for almost all girls. If girls were unable to elaborate and changed their attitudes via the
‘‘peripheral route,’’ this would explain the overall poor maintenance of change. Future research needs to address the issue of providing further opportunities and guidance in elaboration. It is clear from the present study that, just because an individual possesses characteristics suggesting that they would be prone to elaborate on messages, does not mean they will benefit more from a particular intervention program. The provision of opportunities for elaboration of the videotape content could involve post-videotape discussion groups or written exercises to follow the intervention videotape, which (a) provide girls with the opportunity to elaborate on the prevention arguments, thus, theoretically increasing the potential for central route attitude change and (b) assess which types of elaboration most successfully increase the benefits of a basic preventive message (i.e., the videotape). Our research team is currently in the process of collecting such data. Other limitations of the study were that the control group had slightly higher mean ages and BMI scores than the intervention group. It is likely this was due to slight differences in time of year that data was collected. As expected, higher BMI was associated with greater Time 1 scores in body dissatisfaction, drive for thinness, intention to diet and size discrepancy. However, as neither age nor BMI were associated with differences in changes scores, the group differences were unlikely to have confounded the analyses. Finally, a limitation familiar to most prevention research is the timing of follow up measurement. The 1-month followup period used in the current study was useful for examining short-term maintenance, but an insufficient measure of the long-term benefits of a primary prevention program and longer follow up measures are desirable. Despite these limitations, this study can serve as a model for an approach that includes the systematic evaluation of the message factors proposed in theories of social influence. It is hoped that future prevention research will continue to examine each of these message components so that the most effective style of presenter can deliver the most persuasive arguments (content), in the most engaging and captivating format, to the most relevant audience. In summary, in this study, girls who watched an eating disorders primary prevention videotape made small but significantly more changes in drive for thinness, knowledge and intention to diet, than girls who received no intervention. However, at 1-month follow-up, only changes in knowledge were maintained. Recipient NFC levels did not predict amount of change or maintenance of change. It was also found that personal relevance predicted amount of change in the intervention group, but analyses comparing control and intervention participants suggested this relationship did not appear to be a function of the intervention itself. The pre – post attitude changes are promising considering that the videotape intervention was only 22 min in length and no active involvement of the girls was required. Videotaped prevention messages are potentially an effective
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method of intervention as they are both cost effective and easily used in schools. Future research needs to examine the long-term impact when this program is combined with further interventions that provide the opportunity for girls to discuss and think through the arguments in the videotape.
Acknowledgments Funding from the Australian Rotary Health Research Fund supported this research. We thank the following individuals: Tracey Holt, Emma Twigg, Jessica Stean and Debbie Barned for their help with data collection in the schools; Linda Tilgner for her assistance with data analysis; Vanessa Heinze and Lisa Robins for the use of the videotape; Glenda Message and Wendy Jones for their enthusiasm and assistance with the organization of testing. We would also like to thank the participating schools and students.
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