- Email: [email protected]
Chocolate cravings are susceptible to visuo-spatial interference
Eating Behaviors 6 (2005) 101 – 107
Chocolate cravings are susceptible to visuo-spatial interference Eva Kemps*, Marika Tiggemann, Georgina Hart School of Psychology, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia Received 11 May 2004; accepted 31 August 2004
Abstract The study investigated the specificity of visuo-spatial working memory-based techniques as a means to reduce chocolate cravings. Twenty-four self-identified chocolate cravers and 24 non-cravers formed and maintained images of chocolate-containing foods elicited by pictures, while performing a visuo-spatial task (loading the visuospatial sketch pad) or an auditory task (loading the phonological loop). Vividness and craving intensity were rated for each image. Concurrent visuo-spatial processing was found to render chocolate images significantly less vivid and cravings less intense compared to concurrent verbal processing, for both cravers and non-cravers. Chocolate cravers did, however, report higher levels of chocolate craving and intake than non-cravers. It was concluded that visuo-spatial tasks provide an effective craving reduction mechanism for the management of chocolate cravings. Such techniques may be particularly useful in populations for whom eating problems are triggered by chocolate craving. D 2004 Elsevier Ltd. All rights reserved. Keywords: Chocolate cravings; Imagery; Working memory; Visuo-spatial processing
1. Introduction Chocolate has a prominent yet unique place in the Western world. No other food evokes quite as much ambivalence as does chocolate. On the one hand, it has been praised for its health benefits (KrisEtherton & Etherton, 1999; Waterhouse, Shirley, & Donovan, 1996) and is offered as gifts or rewards (James, 1990). On the other hand, it is considered an indulgence that should be eaten with restraint * Corresponding author. Tel.: +61 8 8201 3963; fax: +61 8 8201 3877. E-mail address: [email protected] (E. Kemps). 1471-0153/$ - see front matter D 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.eatbeh.2004.08.006
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(Rogers, 1994). Indeed, chocolate often constitutes the bforbidden fruitQ in weight-loss diets (Knight & Boland, 1989). The hedonic appeal of chocolate derives from its creamy, melt-in-the-mouth texture and its ideal sugar-to-fat ratio (Drewnowski & Greenwood, 1983). Thus, it is not surprising that chocolate has been found to be the most commonly and intensely craved food in Western cultures (Weingarten & Elston, 1990). Chocolate cravings occur largely in response to psychological triggers, such as depression (Willner et al., 1998) and stress (Benton, Greenfield, & Morgan, 1998), rather than as a result of psychopharmacological deficiencies (Pelchat & Schaeffer, 2000). Interestingly, there is no substitute for chocolate when it is craved (Polivy, Coleman & Herman, submitted for publication; Weingarten & Elston, 1991). Other sweet foods, including white bchocolate,Q cannot fully satisfy chocolate cravings (Michener & Rozin, 1994). Although occasional chocolate cravings occur among a large proportion of the general population without any problem (Lafay et al., 2001), for some people, they can pose various health risks. Cravings for chocolate, like those for substances such as alcohol, drugs, and cigarettes, introduce the potential for abuse (Rozin, Levine, & Stoess, 1991) and addiction (Hetherington & Macdiarmid, 1993). Moreover, excessive chocolate consumption in response to cravings has been shown to produce feelings of guilt and ambivalence (Macdiarmid & Hetherington, 1995). Chocolate cravings have also been linked to binge eating episodes in bulimics (Kales, 1990; Mitchell, Hatsukami, Eckert, & Pyle, 1985) and overeating in obese women (Bjoervell, Roennberg, & Roessner, 1985). Therefore, the development of techniques for the reduction of chocolate cravings is of considerable practical importance. To date, only a handful of studies have focused on potential craving reduction techniques. The available intervention tools involve suppression of craving-related thoughts (Johnston, Bulik, & Anstiss, 1999) or unreinforced exposure to food cues (Hetherington, 2001) and have not proven very successful. Instead, Kemps, Tiggemann, Woods, and Soekov (in press) proposed a craving reduction paradigm based on recent observations that mental imagery is a key element of food craving experiences (Green, Rogers, & Elliman, 2000; Harvey, Kemps, & Tiggemann, in press). They adopted a working memory approach to investigate whether interfering with the cognitive processes used to construct and maintain craving-related images could suppress food cravings. The working memory model (Baddeley, 1990) comprises an overarching central executive responsible for coordinating the activities of two limitedcapacity slave systems, the visuo-spatial sketch pad and the phonological loop. The visuo-spatial sketchpad and the phonological loop are responsible for setting up and manipulating visual and auditory images, respectively. Kemps et al. showed that loading the visuo-spatial sketch pad with a concurrent task while imaging highly desired foods (e.g., cake, pizza) reduced the vividness of, and craving reactivity to, food images. This finding was replicated for personalised food craving images (McClelland, Kemps & Tiggemann, submitted for publication). The aim of the present study was to investigate whether frequent and intense cravings for highly palatable and potentially addictive foods, in this case chocolate, would also be responsive to concurrent visuo-spatial processing. To the extent that food cravings involve specifically visual imagery, we would not expect loading the other slave system (the phonological loop) to affect cravings. However, the specificity of concurrent visuo-spatial processing as a craving reduction mechanism has not yet been demonstrated. Thus, the current study sought to compare the efficacy of the visuo-spatial technique of dynamic visual noise (watching a flickering pattern of random black and white dots; Quinn & McConnell, 1996) with its auditory counterpart, irrelevant speech (foreign language spoken material), a task known to load the phonological loop (Salame´ & Baddeley, 1982).
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2. Method 2.1. Participants Participants were recruited into the study as self-identified chocolate cravers (n=24) or non-cravers, who nevertheless liked chocolate (n=24). All were female undergraduate students at Flinders University aged between 18 and 35 years (M=20.92, S.D.=4.14). Participants abstained from eating and drinking (water was allowed) for at least 2 h prior to testing. Chocolate cravers (M=50.58, S.D.=26.34) and noncravers (M=43.29, S.D.=25.08) did not differ in terms of self-reported hunger, tb1, as measured on a 100-mm visual analogue scale, ranging from bnot at all hungryQ to bextremely hungry.Q 2.2. Design A two-way 23 mixed factorial design was used with the between-subjects factor of craving status (2: chocolate cravers, non-cravers) and the within-subjects factor of concurrent task (3: control, dynamic visual noise, irrelevant speech). 2.3. Materials and procedure Participants were tested individually in a session lasting approximately 35 min. They were first asked to indicate the number of chocolate bars and chocolate-containing food items eaten per week. Participants then performed the imagery task, followed by self-report measures of habitual (trait) chocolate craving and imaging ability. 2.3.1. Imagery task Stimuli were 21 coloured pictures taken from food magazines. These portrayed images of seven chocolate-containing food categories: chocolate cake, chocolate bars, chocolate pudding, chocolate ice cream, chocolate drinks, chocolate mousse, and chocolate brownies. There were three different pictures per food category. The 21 pictures were presented on white A4 cards and divided into three equivalent sets each comprising one picture from each of the seven categories. Stimulus sets were counterbalanced across concurrent task conditions. In each concurrent task condition, participants were seated approximately 45 cm in front of a 17-in. computer screen. On each trial, a stimulus picture was presented against the screen for 5 s. During presentation, participants formed an image of the stimulus. They then retained the image for another 8 s while looking at the blank computer screen (control condition) or performing either of the concurrent tasks. In the dynamic visual noise condition, participants watched a 1717-cm matrix, comprising 80 black or white squares in each row and column. Random squares changed from black to white or white to black at a rate of 640 changes every second. In the irrelevant speech condition, participants heard a recording of a female voice reading a passage from a Dutch newspaper. None of the participants understood Dutch. Following the retention interval, participants rated the vividness of their image on a 100-mm visual analogue scale, ranging from bno image at allQ to bimage perfectly clear—as vivid as normal vision.Q They also rated their chocolate craving intensity using a similar scale, ranging from bno desire or urge to eat chocolateQ to bextremely strong desire or urge to eat chocolateQ.
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2.3.2. Chocolate craving General chocolate craving was assessed by the 10-item Craving subscale of the Attitudes to Chocolate Questionnaire (Benton et al., 1998), but using a 7-point Likert scale, ranging from 1 (dnot at all like meT) to 7 (dvery much like meT). Internal reliability was very high for the present sample (a=.91). 2.3.3. Imaging ability Imaging ability was assessed by the Vividness of Visual Imagery Questionnaire (Marks, 1973). Participants generated images of 16 familiar scenes (e.g., the sun rising above the horizon into a hazy sky) and rated the vividness of their imagery on a 5-point scale, with lower ratings indicating greater imaging ability. In the present sample, internal reliability was high (a=.88).
3. Results 3.1. Participant characteristics Descriptive and inferential statistics of sample characteristics are presented in Table 1. Chocolate cravers reported significantly higher levels of habitual chocolate craving than non-cravers. Moreover, their weekly consumption of chocolate bars and chocolate-containing foods was approximately double that of non-cravers. These observations confirm our designation of two clearly discernible groups on the basis of chocolate craving and intake. Importantly, the chocolate cravers and non-cravers did not differ on imaging ability. 3.2. Imagery task Vividness and craving ratings were analysed separately by two-way (craving statusconcurrent task) mixed-design ANOVAs. For each analysis, ratings were averaged over the seven stimulus pictures in each concurrent task condition. Table 2 presents the mean ratings for the craving statusconcurrent task conditions. 3.2.1. Imagery vividness There was no main effect of craving status, F(1,46)=1.87, pN.15. There was, however, a significant main effect of concurrent task, F(2,92)=34.10, pb.001. Mean vividness ratings were 78.78 (S.D.=10.52) in the control condition, 59.37 (S.D.=18.73) in the dynamic visual noise condition, and 70.55 Table 1 Descriptive and inferential statistics of sample characteristics Chocolate craving No of chocolate bars p/w No of chocolate-containing foods p/w Imaging ability * pb.001. ** pb.01.
Chocolate cravers
Non-cravers
t(46)
4.82 2.58 4.08 2.35
2.61 0.89 2.06 2.45
7.89* 2.79** 3.08** 0.53
(1.04) (2.86) (2.70) (0.58)
(0.89) (0.86) (1.73) (0.73)
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Table 2 Mean imagery vividness and food craving ratings as a function of craving status and concurrent task condition (standard deviations in parentheses) Ratings
Concurrent task
Craving status Chocolate craver
Non-craver
Imagery vividness
Control Dynamic visual noise Irrelevant speech Control Dynamic visual noise Irrelevant speech
81.45 60.63 74.30 78.30 62.85 71.10
76.12 58.11 66.79 40.53 31.72 34.92
Craving intensity
(10.32) (18.03) (16.77) (17.10) (20.14) (19.50)
(10.25) (19.71) (18.44) (22.16) (20.18) (21.41)
(S.D.=17.84) in the irrelevant speech condition. Planned comparisons (one-tailed modified Bonferroni test with a=.025; Keppel, 1991) indicated that images in both experimental conditions were rated as less vivid than those in the control condition, t(47)=7.57, pb.001 (dynamic visual noise), and t(47)=4.56, pb.001 (irrelevant speech). Vividness ratings were significantly lower in the dynamic visual noise condition than in the irrelevant speech condition, t(47)=4.32, pb.001. The craving statusconcurrent task interaction was not statistically significant, Fb1. 3.2.2. Craving intensity As expected, there was a significant main effect of craving status, F(1,46)=46.32, pb.001, whereby chocolate cravers (M=70.75, S.D.=15.90) reported higher craving ratings than non-cravers (M=35.73, S.D.=19.57). There was also a significant main effect of concurrent task, F(2,92)=13.38, pb.001. Mean craving ratings were 59.41 (S.D.=27.34) in the control condition, 47.29 (S.D.=25.40) in the dynamic visual noise condition, and 53.01 (S.D.=27.29) in the irrelevant speech condition. Planned contrasts showed that craving ratings were significantly lower in both experimental conditions than in the control condition, t(47)=4.37, pb.001 (dynamic visual noise), and t(47)=4.34, pb.001 (irrelevant speech). More importantly, cravings were rated as less intense in the dynamic visual noise condition than in the irrelevant speech condition, t(47)=2.22, pb.05. There was no significant interaction between craving status and concurrent task, F(2, 92)=1.09, pN.30. 3.2.3. Relationship between imagery vividness and craving intensity Pearson product-moment correlations were performed to determine whether vividness of chocolate images was associated with craving intensity. There was a significant positive correlation between vividness and craving ratings in all three concurrent task conditions, r=.30, pb.05 (control), r=.33, pb.05 (dynamic visual noise), and r=.31, pb.05 (irrelevant speech). Interestingly, when the sample was divided into the two groups, there was a significant correlation between vividness and craving ratings for chocolate cravers, r=.40, pb.05, but not for non-cravers, r= .03, pN.85.
4. Discussion Consistent with previous findings (Benton et al., 1998; Macdiarmid & Hetherington, 1995), participants who identified themselves as chocolate cravers clearly differed from non-craving participants on measures of chocolate consumption and craving. Chocolate cravers ate almost twice
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as many chocolate bars and chocolate-containing foods per week than did non-cravers and reported much higher levels of trait chocolate craving. Nevertheless, non-cravers also reported cravings for chocolate, although to a lesser extent, confirming that chocolate cravings are indeed experienced by the population at large (Lafay et al., 2001). Fortuitously, there was no difference in reported hunger between chocolate cravers and non-cravers. Although cravings are not invariably related to hunger (Cornell, Rodin, & Weingarten, 1989), some studies do suggest a link between these two internal sensations (Hill & Heaton-Brown, 1994; Hill, Weaver, & Blundell, 1991). As an extension of our previous findings for food cravings in general (Kemps et al., in press; McClelland et al., submitted for publication), dynamic visual noise reduced the vividness and associated craving in response to chocolate images. According to working memory theory, dynamic visual noise has its craving reduction effect by interfering with food-related visual images held in the visuo-spatial sketchpad. Contrary to our expectation, irrelevant speech also reduced imagery vividness and craving intensity. This could be the result of a general distraction mechanism, or the fact that images of chocolate (and probably food in general) may involve not only visual content but also incorporate auditory elements (e.g., the sound of unwrapping a chocolate bar or the sound of teeth munching). In working memory terms, chocolate cravings may also engage, to some extent, the phonological loop. Most importantly, however, the study found that dynamic visual noise was clearly much more effective in reducing vividness and craving ratings than was irrelevant speech. It seems that tasks that target the visuo-spatial sketchpad of working memory provide more effective food craving reduction techniques than those that tap the phonological loop. This finding demonstrates that the craving reducing effect of visuo-spatial tasks such as dynamic visual noise cannot be attributed to general cognitive distraction. It also supports the predominantly visual, rather than auditory, content in craving-related images. Our experimental finding is consistent with recent survey data concerning everyday cravings for a range of desired substances, including food (May, Andrade, Panabokke, & Kavanagh, in press). The descriptive statement, bI am visualising it,Q was highly endorsed by respondents as characterising their craving episodes, whereas the statement ,bI can hear myself having it,Q was not. In the present experiment, the chocolate cravers reported higher levels of craving than did the noncravers in the imagery task, but similar levels of imagery vividness. Perhaps as a consequence, vividness and craving ratings were significantly correlated for chocolate cravers, but not for non-cravers. Although the dynamic visual noise task reduced chocolate craving ratings for both groups, the correlations suggest that visuo-spatial tasks may be particularly effective for individuals for whom chocolate is a salient urge cue (chocolate cravers). Future research needs to determine the efficacy of these techniques for chocolate daddicts,T as well as for individuals with eating problems triggered by chocolate cravings. References Baddeley, A. D. (1990). Human memory: Theory and practice. Hove7 Lawrence Erlbaum Associates. Benton, D., Greenfield, K., & Morgan, M. (1998). The development of the attitudes to chocolate questionnaire. Personality and Individual Differences, 24, 513 – 520. Bjoervell, H., Roennberg, S., & Roessner, S. (1985). Eating patterns described by a group of treatment seeking overweight women and normal weight women. Scandinavian Journal of Behaviour Therapy, 14, 147 – 156. Cornell, C. E., Rodin, J., & Weingarten, H. (1989). Stimulus-induced eating when satiated. Physiology and Behavior, 45, 695 – 704. Drewnowski, A., & Greenwood, M. R. C. (1983). Cream and sugar: Human preferences for high-fat foods. Physiology and Behavior, 30, 629 – 633.
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Green, M. W., Rogers, P. J., & Elliman, N. A. (2000). Dietary restraint and addictive behaviors: The generalizability of Tiffany’s cue reactivity model. International Journal of Eating Disorders, 27, 419 – 427. Harvey, K., Kemps, E., and Tiggemann, M. (in press). The nature of imagery processes underlying food cravings. British Journal of Health Psychology. Hetherington, M. M. (2001). Food cravings and addiction. Surrey, UK7 Leatherhead Publishing. Hetherington, M. M., & Macdiarmid, J. I. (1993). Chocolate addiction: A preliminary description and report of its relationship to problem eating. Appetite, 21, 233 – 246. Hill, A. J., & Heaton-Brown, L. (1994). The experience of food craving: A prospective investigation in healthy women. Journal of Psychosomatic Research, 38, 801 – 814. Hill, A. J., Weaver, C. F., & Blundell, J. E. (1991). Food craving, dietary restraint and mood. Appetite, 17, 187 – 197. James, A. (1990). The good, the bad and the delicious: The role of confectionery in British society. Sociological Review, 38, 666 – 688. Johnston, L., Bulik, C. M., & Anstiss, V. (1999). Suppressing thoughts about chocolate. International Journal of Eating Disorders, 26, 21 – 27. Kales, E. F. (1990). Macronutrient analysis of binge eating in bulimia. Physiology and Behavior, 48, 837 – 840. Kemps, E., Tiggemann, M., Woods, D., & Soekov, B. (2004). Reduction of food cravings through visuospatial processing. International Journal of Eating Disorders, 36, 31 – 40. Keppel, G. (1991). Design and analysis: A researcher’s handbook (3rd ed.). Englewood Cliffs, NJ7 Prentice Hall. Knight, L. J., & Boland, F. J. (1989). Restrained eating: An experimental disentanglement of the disinhibiting variables of perceived calories and food type. Journal of Abnormal Psychology, 98, 412 – 420. Kris-Etherton, P., & Etherton, T. D. (1999). Cardiovascular health: Role of stearic acid on atherogenic and thrombogenic factors. In I. Knight (Ed.), Chocolate and cocoa: Health and nutrition (pp. 89 – 104). Oxford7 Blackwell. Lafay, L., Thomas, F., Mennen, L., Charles, M.A., Eschwege, E., Borys, J., & Basdevant, A. (2001). Gender differences in the relation between food cravings and mood in an adult community: Results from the Fleurbaix Laventie Ville Sante Study. International Journal of Eating Disorders, 29, 195 – 204. Macdiarmid, J. I., & Hetherington, M. M. (1995). Mood modulation by food: An exploration of affect and cravings in dchocolate addictsT. British Journal of Clinical Psychology, 34, 129 – 138. Marks, D. F. (1973). Visual imagery differences in the recall of pictures. British Journal of Psychology, 64, 17 – 24. May, J., Andrade, J., Panabokke, N., & Kavanagh, D. (2004). Images of desire: Cognitive models of craving. Memory, 12, 447 – 461. McClelland, A., Kemps, E., and Tiggemann, M. (submitted for publication). Reduction of vividness and associated craving in personalised food imagery. Michener, W., & Rozin, P. (1994). Pharmacological versus sensory factors in the satiation of chocolate craving. Physiology and Behavior, 56, 419 – 422. Mitchell, J. E., Hatsukami, D., Eckert, E. D., & Pyle, R. L. (1985). Characteristics of 275 patients with bulimia. American Journal of Psychiatry, 142, 482 – 485. Pelchat, M. L., & Schaeffer, S. (2000). Dietary monotony and food cravings in young and elderly adults. Physiology and Behavior, 68, 353 – 359. Polivy, J., Coleman, J., and Herman, C.P. (submitted for publication). The effect of deprivation on food cravings and eating behaviour in restrained and unrestrained eaters. Quinn, J. G., & McConnell, J. (1996). Irrelevant pictures in visual working memory. Quarterly Journal of Experimental Psychology, 49A, 200 – 215. Rogers, P. J. (1994). Mechanisms of moreishness and food craving. In D. M. Warburton (Ed.), Pleasure, the politics and the reality (pp. 38 – 49). Chichester7 Wiley-Liss. Rozin, P., Levine, E., & Stoess, C. (1991). Chocolate craving and liking. Appetite, 17, 199 – 212. Salame´, P., & Baddeley, A. D. (1982). Disruption of short-term memory by unattended speech: Implications for the structure of working memory. Journal of Verbal Learning and Verbal Behavior, 21, 150 – 164. Waterhouse, A. L., Shirley, J. R., & Donovan, J. L. (1996). Antioxidants in chocolate. Lancet, 87, 311 – 315. Weingarten, H., & Elston, D. (1990). The phenomenology of food cravings. Appetite, 15, 231 – 246. Weingarten, H., & Elston, D. (1991). Food cravings in a college population. Appetite, 17, 167 – 175. Willner, P., Benton, D., Brown, E., Cheeta, S., Davies, G., Morgan, J., & Morgan, M. (1998). Depression increases craving for sweet rewards in animal and human models of depression and craving. Psychopharmacology, 136, 272 – 283.
Chocolate cravings are susceptible to visuo-spatial interference Eva Kemps*, Marika Tiggemann, Georgina Hart School of Psychology, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia Received 11 May 2004; accepted 31 August 2004
Abstract The study investigated the specificity of visuo-spatial working memory-based techniques as a means to reduce chocolate cravings. Twenty-four self-identified chocolate cravers and 24 non-cravers formed and maintained images of chocolate-containing foods elicited by pictures, while performing a visuo-spatial task (loading the visuospatial sketch pad) or an auditory task (loading the phonological loop). Vividness and craving intensity were rated for each image. Concurrent visuo-spatial processing was found to render chocolate images significantly less vivid and cravings less intense compared to concurrent verbal processing, for both cravers and non-cravers. Chocolate cravers did, however, report higher levels of chocolate craving and intake than non-cravers. It was concluded that visuo-spatial tasks provide an effective craving reduction mechanism for the management of chocolate cravings. Such techniques may be particularly useful in populations for whom eating problems are triggered by chocolate craving. D 2004 Elsevier Ltd. All rights reserved. Keywords: Chocolate cravings; Imagery; Working memory; Visuo-spatial processing
1. Introduction Chocolate has a prominent yet unique place in the Western world. No other food evokes quite as much ambivalence as does chocolate. On the one hand, it has been praised for its health benefits (KrisEtherton & Etherton, 1999; Waterhouse, Shirley, & Donovan, 1996) and is offered as gifts or rewards (James, 1990). On the other hand, it is considered an indulgence that should be eaten with restraint * Corresponding author. Tel.: +61 8 8201 3963; fax: +61 8 8201 3877. E-mail address: [email protected] (E. Kemps). 1471-0153/$ - see front matter D 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.eatbeh.2004.08.006
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(Rogers, 1994). Indeed, chocolate often constitutes the bforbidden fruitQ in weight-loss diets (Knight & Boland, 1989). The hedonic appeal of chocolate derives from its creamy, melt-in-the-mouth texture and its ideal sugar-to-fat ratio (Drewnowski & Greenwood, 1983). Thus, it is not surprising that chocolate has been found to be the most commonly and intensely craved food in Western cultures (Weingarten & Elston, 1990). Chocolate cravings occur largely in response to psychological triggers, such as depression (Willner et al., 1998) and stress (Benton, Greenfield, & Morgan, 1998), rather than as a result of psychopharmacological deficiencies (Pelchat & Schaeffer, 2000). Interestingly, there is no substitute for chocolate when it is craved (Polivy, Coleman & Herman, submitted for publication; Weingarten & Elston, 1991). Other sweet foods, including white bchocolate,Q cannot fully satisfy chocolate cravings (Michener & Rozin, 1994). Although occasional chocolate cravings occur among a large proportion of the general population without any problem (Lafay et al., 2001), for some people, they can pose various health risks. Cravings for chocolate, like those for substances such as alcohol, drugs, and cigarettes, introduce the potential for abuse (Rozin, Levine, & Stoess, 1991) and addiction (Hetherington & Macdiarmid, 1993). Moreover, excessive chocolate consumption in response to cravings has been shown to produce feelings of guilt and ambivalence (Macdiarmid & Hetherington, 1995). Chocolate cravings have also been linked to binge eating episodes in bulimics (Kales, 1990; Mitchell, Hatsukami, Eckert, & Pyle, 1985) and overeating in obese women (Bjoervell, Roennberg, & Roessner, 1985). Therefore, the development of techniques for the reduction of chocolate cravings is of considerable practical importance. To date, only a handful of studies have focused on potential craving reduction techniques. The available intervention tools involve suppression of craving-related thoughts (Johnston, Bulik, & Anstiss, 1999) or unreinforced exposure to food cues (Hetherington, 2001) and have not proven very successful. Instead, Kemps, Tiggemann, Woods, and Soekov (in press) proposed a craving reduction paradigm based on recent observations that mental imagery is a key element of food craving experiences (Green, Rogers, & Elliman, 2000; Harvey, Kemps, & Tiggemann, in press). They adopted a working memory approach to investigate whether interfering with the cognitive processes used to construct and maintain craving-related images could suppress food cravings. The working memory model (Baddeley, 1990) comprises an overarching central executive responsible for coordinating the activities of two limitedcapacity slave systems, the visuo-spatial sketch pad and the phonological loop. The visuo-spatial sketchpad and the phonological loop are responsible for setting up and manipulating visual and auditory images, respectively. Kemps et al. showed that loading the visuo-spatial sketch pad with a concurrent task while imaging highly desired foods (e.g., cake, pizza) reduced the vividness of, and craving reactivity to, food images. This finding was replicated for personalised food craving images (McClelland, Kemps & Tiggemann, submitted for publication). The aim of the present study was to investigate whether frequent and intense cravings for highly palatable and potentially addictive foods, in this case chocolate, would also be responsive to concurrent visuo-spatial processing. To the extent that food cravings involve specifically visual imagery, we would not expect loading the other slave system (the phonological loop) to affect cravings. However, the specificity of concurrent visuo-spatial processing as a craving reduction mechanism has not yet been demonstrated. Thus, the current study sought to compare the efficacy of the visuo-spatial technique of dynamic visual noise (watching a flickering pattern of random black and white dots; Quinn & McConnell, 1996) with its auditory counterpart, irrelevant speech (foreign language spoken material), a task known to load the phonological loop (Salame´ & Baddeley, 1982).
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2. Method 2.1. Participants Participants were recruited into the study as self-identified chocolate cravers (n=24) or non-cravers, who nevertheless liked chocolate (n=24). All were female undergraduate students at Flinders University aged between 18 and 35 years (M=20.92, S.D.=4.14). Participants abstained from eating and drinking (water was allowed) for at least 2 h prior to testing. Chocolate cravers (M=50.58, S.D.=26.34) and noncravers (M=43.29, S.D.=25.08) did not differ in terms of self-reported hunger, tb1, as measured on a 100-mm visual analogue scale, ranging from bnot at all hungryQ to bextremely hungry.Q 2.2. Design A two-way 23 mixed factorial design was used with the between-subjects factor of craving status (2: chocolate cravers, non-cravers) and the within-subjects factor of concurrent task (3: control, dynamic visual noise, irrelevant speech). 2.3. Materials and procedure Participants were tested individually in a session lasting approximately 35 min. They were first asked to indicate the number of chocolate bars and chocolate-containing food items eaten per week. Participants then performed the imagery task, followed by self-report measures of habitual (trait) chocolate craving and imaging ability. 2.3.1. Imagery task Stimuli were 21 coloured pictures taken from food magazines. These portrayed images of seven chocolate-containing food categories: chocolate cake, chocolate bars, chocolate pudding, chocolate ice cream, chocolate drinks, chocolate mousse, and chocolate brownies. There were three different pictures per food category. The 21 pictures were presented on white A4 cards and divided into three equivalent sets each comprising one picture from each of the seven categories. Stimulus sets were counterbalanced across concurrent task conditions. In each concurrent task condition, participants were seated approximately 45 cm in front of a 17-in. computer screen. On each trial, a stimulus picture was presented against the screen for 5 s. During presentation, participants formed an image of the stimulus. They then retained the image for another 8 s while looking at the blank computer screen (control condition) or performing either of the concurrent tasks. In the dynamic visual noise condition, participants watched a 1717-cm matrix, comprising 80 black or white squares in each row and column. Random squares changed from black to white or white to black at a rate of 640 changes every second. In the irrelevant speech condition, participants heard a recording of a female voice reading a passage from a Dutch newspaper. None of the participants understood Dutch. Following the retention interval, participants rated the vividness of their image on a 100-mm visual analogue scale, ranging from bno image at allQ to bimage perfectly clear—as vivid as normal vision.Q They also rated their chocolate craving intensity using a similar scale, ranging from bno desire or urge to eat chocolateQ to bextremely strong desire or urge to eat chocolateQ.
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2.3.2. Chocolate craving General chocolate craving was assessed by the 10-item Craving subscale of the Attitudes to Chocolate Questionnaire (Benton et al., 1998), but using a 7-point Likert scale, ranging from 1 (dnot at all like meT) to 7 (dvery much like meT). Internal reliability was very high for the present sample (a=.91). 2.3.3. Imaging ability Imaging ability was assessed by the Vividness of Visual Imagery Questionnaire (Marks, 1973). Participants generated images of 16 familiar scenes (e.g., the sun rising above the horizon into a hazy sky) and rated the vividness of their imagery on a 5-point scale, with lower ratings indicating greater imaging ability. In the present sample, internal reliability was high (a=.88).
3. Results 3.1. Participant characteristics Descriptive and inferential statistics of sample characteristics are presented in Table 1. Chocolate cravers reported significantly higher levels of habitual chocolate craving than non-cravers. Moreover, their weekly consumption of chocolate bars and chocolate-containing foods was approximately double that of non-cravers. These observations confirm our designation of two clearly discernible groups on the basis of chocolate craving and intake. Importantly, the chocolate cravers and non-cravers did not differ on imaging ability. 3.2. Imagery task Vividness and craving ratings were analysed separately by two-way (craving statusconcurrent task) mixed-design ANOVAs. For each analysis, ratings were averaged over the seven stimulus pictures in each concurrent task condition. Table 2 presents the mean ratings for the craving statusconcurrent task conditions. 3.2.1. Imagery vividness There was no main effect of craving status, F(1,46)=1.87, pN.15. There was, however, a significant main effect of concurrent task, F(2,92)=34.10, pb.001. Mean vividness ratings were 78.78 (S.D.=10.52) in the control condition, 59.37 (S.D.=18.73) in the dynamic visual noise condition, and 70.55 Table 1 Descriptive and inferential statistics of sample characteristics Chocolate craving No of chocolate bars p/w No of chocolate-containing foods p/w Imaging ability * pb.001. ** pb.01.
Chocolate cravers
Non-cravers
t(46)
4.82 2.58 4.08 2.35
2.61 0.89 2.06 2.45
7.89* 2.79** 3.08** 0.53
(1.04) (2.86) (2.70) (0.58)
(0.89) (0.86) (1.73) (0.73)
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Table 2 Mean imagery vividness and food craving ratings as a function of craving status and concurrent task condition (standard deviations in parentheses) Ratings
Concurrent task
Craving status Chocolate craver
Non-craver
Imagery vividness
Control Dynamic visual noise Irrelevant speech Control Dynamic visual noise Irrelevant speech
81.45 60.63 74.30 78.30 62.85 71.10
76.12 58.11 66.79 40.53 31.72 34.92
Craving intensity
(10.32) (18.03) (16.77) (17.10) (20.14) (19.50)
(10.25) (19.71) (18.44) (22.16) (20.18) (21.41)
(S.D.=17.84) in the irrelevant speech condition. Planned comparisons (one-tailed modified Bonferroni test with a=.025; Keppel, 1991) indicated that images in both experimental conditions were rated as less vivid than those in the control condition, t(47)=7.57, pb.001 (dynamic visual noise), and t(47)=4.56, pb.001 (irrelevant speech). Vividness ratings were significantly lower in the dynamic visual noise condition than in the irrelevant speech condition, t(47)=4.32, pb.001. The craving statusconcurrent task interaction was not statistically significant, Fb1. 3.2.2. Craving intensity As expected, there was a significant main effect of craving status, F(1,46)=46.32, pb.001, whereby chocolate cravers (M=70.75, S.D.=15.90) reported higher craving ratings than non-cravers (M=35.73, S.D.=19.57). There was also a significant main effect of concurrent task, F(2,92)=13.38, pb.001. Mean craving ratings were 59.41 (S.D.=27.34) in the control condition, 47.29 (S.D.=25.40) in the dynamic visual noise condition, and 53.01 (S.D.=27.29) in the irrelevant speech condition. Planned contrasts showed that craving ratings were significantly lower in both experimental conditions than in the control condition, t(47)=4.37, pb.001 (dynamic visual noise), and t(47)=4.34, pb.001 (irrelevant speech). More importantly, cravings were rated as less intense in the dynamic visual noise condition than in the irrelevant speech condition, t(47)=2.22, pb.05. There was no significant interaction between craving status and concurrent task, F(2, 92)=1.09, pN.30. 3.2.3. Relationship between imagery vividness and craving intensity Pearson product-moment correlations were performed to determine whether vividness of chocolate images was associated with craving intensity. There was a significant positive correlation between vividness and craving ratings in all three concurrent task conditions, r=.30, pb.05 (control), r=.33, pb.05 (dynamic visual noise), and r=.31, pb.05 (irrelevant speech). Interestingly, when the sample was divided into the two groups, there was a significant correlation between vividness and craving ratings for chocolate cravers, r=.40, pb.05, but not for non-cravers, r= .03, pN.85.
4. Discussion Consistent with previous findings (Benton et al., 1998; Macdiarmid & Hetherington, 1995), participants who identified themselves as chocolate cravers clearly differed from non-craving participants on measures of chocolate consumption and craving. Chocolate cravers ate almost twice
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as many chocolate bars and chocolate-containing foods per week than did non-cravers and reported much higher levels of trait chocolate craving. Nevertheless, non-cravers also reported cravings for chocolate, although to a lesser extent, confirming that chocolate cravings are indeed experienced by the population at large (Lafay et al., 2001). Fortuitously, there was no difference in reported hunger between chocolate cravers and non-cravers. Although cravings are not invariably related to hunger (Cornell, Rodin, & Weingarten, 1989), some studies do suggest a link between these two internal sensations (Hill & Heaton-Brown, 1994; Hill, Weaver, & Blundell, 1991). As an extension of our previous findings for food cravings in general (Kemps et al., in press; McClelland et al., submitted for publication), dynamic visual noise reduced the vividness and associated craving in response to chocolate images. According to working memory theory, dynamic visual noise has its craving reduction effect by interfering with food-related visual images held in the visuo-spatial sketchpad. Contrary to our expectation, irrelevant speech also reduced imagery vividness and craving intensity. This could be the result of a general distraction mechanism, or the fact that images of chocolate (and probably food in general) may involve not only visual content but also incorporate auditory elements (e.g., the sound of unwrapping a chocolate bar or the sound of teeth munching). In working memory terms, chocolate cravings may also engage, to some extent, the phonological loop. Most importantly, however, the study found that dynamic visual noise was clearly much more effective in reducing vividness and craving ratings than was irrelevant speech. It seems that tasks that target the visuo-spatial sketchpad of working memory provide more effective food craving reduction techniques than those that tap the phonological loop. This finding demonstrates that the craving reducing effect of visuo-spatial tasks such as dynamic visual noise cannot be attributed to general cognitive distraction. It also supports the predominantly visual, rather than auditory, content in craving-related images. Our experimental finding is consistent with recent survey data concerning everyday cravings for a range of desired substances, including food (May, Andrade, Panabokke, & Kavanagh, in press). The descriptive statement, bI am visualising it,Q was highly endorsed by respondents as characterising their craving episodes, whereas the statement ,bI can hear myself having it,Q was not. In the present experiment, the chocolate cravers reported higher levels of craving than did the noncravers in the imagery task, but similar levels of imagery vividness. Perhaps as a consequence, vividness and craving ratings were significantly correlated for chocolate cravers, but not for non-cravers. Although the dynamic visual noise task reduced chocolate craving ratings for both groups, the correlations suggest that visuo-spatial tasks may be particularly effective for individuals for whom chocolate is a salient urge cue (chocolate cravers). Future research needs to determine the efficacy of these techniques for chocolate daddicts,T as well as for individuals with eating problems triggered by chocolate cravings. References Baddeley, A. D. (1990). Human memory: Theory and practice. Hove7 Lawrence Erlbaum Associates. Benton, D., Greenfield, K., & Morgan, M. (1998). The development of the attitudes to chocolate questionnaire. Personality and Individual Differences, 24, 513 – 520. Bjoervell, H., Roennberg, S., & Roessner, S. (1985). Eating patterns described by a group of treatment seeking overweight women and normal weight women. Scandinavian Journal of Behaviour Therapy, 14, 147 – 156. Cornell, C. E., Rodin, J., & Weingarten, H. (1989). Stimulus-induced eating when satiated. Physiology and Behavior, 45, 695 – 704. Drewnowski, A., & Greenwood, M. R. C. (1983). Cream and sugar: Human preferences for high-fat foods. Physiology and Behavior, 30, 629 – 633.
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