- Email: [email protected]
Visual exposure impacts on toddlers’ willingness to taste fruits and vegetables
Appetite 53 (2009) 450–453
Contents lists available at ScienceDirect
Appetite journal homepage: www.elsevier.com/locate/appet
Short communication
Visual exposure impacts on toddlers’ willingness to taste fruits and vegetables Carmel Houston-Price *, Laurie Butler, Paula Shiba School of Psychology & Clinical Language Sciences, University of Reading, Earley Gate, Whiteknights, Reading RG6 6AL, UK
A R T I C L E I N F O
A B S T R A C T
Article history: Received 19 March 2009 Received in revised form 6 July 2009 Accepted 28 August 2009
This study explores the effects of exposure to pictures of fruits and vegetables on young children’s willingness to taste the foods. The parents of 20 toddlers aged 21–24 months were asked to read a picture book about four foods with their child every day for two weeks. In a subsequent ‘taste test’ children displayed a neophobic pattern of behaviour towards foods to which they had not been exposed, but not towards exposed foods. Furthermore, while exposure served to decrease children’s willingness to taste familiar vegetables, it increased their willingness to taste unfamiliar fruits. ß 2009 Elsevier Ltd. All rights reserved.
Keywords: Food choice Exposure Children Fruit and vegetables Willingness to taste
Introduction A variety of factors determine infants’ liking of foods, including genetic predispositions to prefer sweet tastes and avoid unfamiliar foods (‘food neophobia’; Rozin, 1976). Exposure to food plays an important role in determining young children’s preferences; the influence of experience begins with pre-natal exposure through amniotic fluid and continues post-natally through breast milk (Mennella, Jagnow, & Beauchamp, 2001) and via the foods provided during weaning and beyond (Birch, Gunder, GrimmThomas, & Laing, 1998). Exposure to food has therefore been a key feature of attempts to enhance children’s liking of healthy foods. In adults, both positive and negative relationships have been reported between exposure to foods and rated liking of the foods. For example, Pliner (1982) gave participants three unfamiliar fruit juices to taste 5, 10 or 20 times and found that the number of exposures was positively related to participants’ ratings of how much they liked each juice’s taste. Other work has found ‘satiation effects’, whereby repeated taste exposures lead to dislike of the food (Pliner, Polivy, Herman, & Zakalusny, 1980). Pliner (1982) suggests that the discrepancy is due to participants’ initial levels of familiarity with exposed foods; while repeated exposure to unfamiliar foods increases liking, exposure to foods that are already familiar may lead to dislike.
* Corresponding author. E-mail address: [email protected] (C. Houston-Price). 0195-6663/$ – see front matter ß 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.appet.2009.08.012
Research studies involving young children support the potential for exposure to enhance liking and consumption of unfamiliar and disliked foods. For example, Birch and Marlin (1982) provided two-year olds with up to 20 exposures to 5 unfamiliar cheeses (Experiment 1) or 5 unfamiliar fruits (Experiment 2) over a fourweek period and in each case found children’s preferences to be predicted by the number of exposures they had received to each food. In a more recent study, Maier, Chabanet, Schaal, Issanchou, and Leathwood (2007) found that after 16 presentations of an initially disliked pure´ed vegetable, infants of 7 months willingly consumed as much of the vegetable as they did of an initially liked vegetable. Liking of a food’s texture, as well as its taste, is affected by exposure; at 12 months, infants’ intake of chopped carrots is predicted by the frequency with the child has previously been provided with chopped foods (Blossfeld, Collins, Kiely, & Delahunty, 2007). Exposure therefore appears to be a powerful and straightforward solution to the problem of encouraging healthy eating in children. However, 10–15 exposures to a new or disliked food may be required to effect positive changes in preference (Birch & Marlin, 1982; Birch, McPhee, Shoba, Pirok, & Steinberg, 1987), a number ‘‘greater than that most parents are willing or able to provide’’ (Birch et al., 1987, p. 177; Carruth, Ziegler, Gordon, & Barr, 2004). As a result, researchers have sought a means of exposing foods that does not require parents to engage in multiple attempts to persuade their child to taste unwanted foods. One avenue that has been explored is visual exposure. Given that brief television commercials can successfully induce brand preferences in preschoolers (Borzekowski & Robinson, 2001), it is conceivable
C. Houston-Price et al. / Appetite 53 (2009) 450–453
that visual exposure to different foods might impact on children’s liking of them. Very little research has directly explored this question. One exception is a study by Birch et al. (1987), who compared the effects of taste exposure and visual exposure on preschoolers’ liking of a set of six unfamiliar fruits. Each fruit was exposed 5, 10 or 15 times over a 30-day period; 3 of the fruits were tasted at each exposure, while 3 were presented visually for 10 s on each occasion. A few days later, children were presented with a forcedchoice paired comparison task; the six exposed foods and a further unfamiliar food were presented in pairs and children were asked to ‘‘choose the one you like the best’’. The question was posed both before and after the pair of foods were tasted, which Birch et al. termed ‘look judgments’ and ‘taste judgments’, respectively. The number of taste exposures provided correlated with children’s look and taste judgments of the foods, confirming previous reports that taste exposure enhances food liking. Birch et al. also reported a correlation between the number of visual exposures and children’s look judgments, but no relationship between the number of visual exposures and their taste judgments, leading the authors to conclude that visual exposure has no impact on food liking. However, there are grounds for calling for further research into the impact of visual exposure on food liking. First, Birch et al.’s (1987) ‘look’ and ‘taste’ judgments may not have indexed children’s liking of the look and taste of the foods, respectively, because children were, in both cases, asked to ‘‘choose the one they liked the best’’. When foods were first presented children’s choices were thought to reflect their liking of the look of the foods, but their judgments may have been influenced by their memory of the taste of the foods they had tasted before. Similarly, the selections children made after they had tasted the two foods may have been determined by their liking of the taste of the foods, but their responses may also have been influenced by the look or smell of the food. One cannot, therefore, be certain that children’s liking of the look and taste of the exposed foods were tapped into by the questions asked. It could also be argued that visual exposure would be unlikely to directly enhance liking of a food’s taste, and that one should look elsewhere for evidence of a positive influence of visual exposure, such as in a greater willingness to taste an unfamiliar food. Birch et al.’s (1987) finding that visual exposure enhanced children’s ‘look judgments’ suggests that this type of exposure may induce more positive attitudes towards exposed foods. Recent research by Houston-Price et al. (2009) shows that repeated exposure to pictures of foods in books leads toddlers to preferentially attend to exposed over non-exposed foods in a visual preference test. By enhancing children’s attitudes towards the appearance of foods and/or their willingness to explore them visually, visual exposure might also reduce children’s reluctance to taste previously unfamiliar foods. The potential to enhance children’s willingness to taste new foods through visual exposure is, therefore, an exciting avenue of research that deserves exploration. This article describes a preliminary investigation into the effects of exposure to pictures of familiar and unfamiliar foods on toddlers’ willingness to taste them. We hypothesised that children would be more willing to taste unfamiliar foods if they were repeatedly visually exposed to these foods before they were invited to try them. Method Participants Twenty toddlers, 10 boys and 10 girls, with a mean age of 23.2 months (range = 21.4–24.7) were recruited from the University’s Child Development Group database, a list of parents who had
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expressed an interest in taking part in research with their child. Parents gave informed consent to participate with their child in this study. Participants were rewarded with travel expenses and a certificate. Design This study was approved by the University’s Research Ethics Committee and conformed to the standards prescribed by the 1964 Declaration of Helsinki. Parents were sent one of two books about four foods to read with their child every day for two weeks. Each book contained pictures and information about two familiar foods (one fruit, one vegetable) and two unfamiliar foods (one fruit, one vegetable). Following the exposure period, children took part in a ‘taste test’ in which they were offered all eight foods shown in the two books: the four vegetables followed by the four fruits. We recorded the number of foods children tasted and the order in which they did so. Note that, in this design, each food serves as an exposed food and as a non-exposed food for different children, thus controlling for any preferences for specific foods that children may have had. Materials The fruits and vegetables to be included in exposure books were selected on the basis of parents’ responses to a Food Familiarity Questionnaire. This is a list of 83 commonly available fruits and vegetables, which parents are asked to rate in terms of how often their child encounters each food on a 3-point scale: rarely or never (less than once per month); sometimes (less than once per week but more than once per month); or often (at least once per week). After excluding foods that could not be eaten raw, we selected as stimuli the two fruits parents rated as most familiar (grape and strawberry) and least familiar (blueberry and lychee) and the two vegetables rated most familiar (carrot and sweetcorn) and least familiar (radish and watercress). Two books were created, each about two fruits and two vegetables, with one of each food type likely to be familiar to children and one likely to be unfamiliar (Book A: grape, blueberry, sweetcorn and radish; Book B: strawberry, lychee, carrot and watercress). Books included a page about each food, with one large photograph and several smaller photographs showing how the food grows, what it looks like inside and what the prepared food might look like, with sentences for parents to read. Books were produced in a colourful, child-friendly A4 format, laminated and bound. The eight foods depicted in the books served as stimuli in the taste test. Foods were washed and provided either whole (radish, blueberry, and grape), cut in half (strawberry and lychee) or in pieces (sweetcorn kernels, carrot stick, and small sprig of watercress). A video camera was used to record test sessions. Procedure Children were randomly assigned to receive one of the two books; 11 children received Book A and 9 received Book B. Parents were sent the relevant book and instructions to read the book with their child for 5 min every day for two weeks. The day after the exposure period ended, parents (in all cases, mothers) and toddlers visited the University to take part in the taste test. Mothers were asked to choose one of two vegetables (cherry tomato or cucumber stick) and one of two fruits (pineapple chunk or mandarin orange segment) to eat during the taste test, to ensure that their child felt comfortable about eating. Mothers were told that a piece of the foods they had selected would be placed in the centre of each of the child’s food plates and that they should
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immediately take this food and eat it when the plate was offered. Mothers were instructed that they should not name, point to, touch or eat any of the other foods on either plate. The child was then seated at a low table in a communal area with their mother close by. The vegetable plate was offered first. This contained two pieces of each of the four vegetables depicted in the two books and the mother’s chosen vegetable in the centre. After the mother had eaten her food, children were encouraged to eat by the experimenter, who was blind to the specific book to which the child had been exposed. When a period of 5 min had elapsed, or earlier if the child had eaten all the foods or refused to eat any more, the plate was removed and the fruit plate was presented. Again, two pieces of each of the four fruits shown in the books were provided, with the mother’s fruit in the centre of the plate; once the mother had taken her piece of fruit children were encouraged to eat what they wanted. The experimenter recorded whether, and in what order, children placed the foods on each plate in their mouths. Test sessions were recorded on video camera. Results Each child had the opportunity to taste eight foods in a 2 (fruit vs. vegetable) 2 (familiar vs. unfamiliar) 2 (exposed vs. nonexposed) within-subjects design. Three children (all boys) refused to taste any of the foods offered and were excluded from analyses. Remaining children tasted an average of 5.0 of the 8 foods (SD = 2.4), of which 2.41 were vegetables (SD = 1.37) and 2.59 were fruit (SD = 1.23). The numbers of each food type that children tasted are presented in Table 1. The data were first entered into a 2 (familiarity) 2 (exposure) repeated measures ANOVA, collapsing across food category (fruit vs. vegetable). The analysis revealed a significant main effect of familiarity, F(1, 16) = 4.70, p = .046, partial h2 = .23, reflecting children’s food neophobia; children tasted more familiar foods (mean = 2.76, SD = 1.20) than unfamiliar foods (mean = 2.24, SD = 1.44). There was no main effect of exposure, F(1, 16) = .26, p = .62, partial h2 = .02; overall, children did not taste more exposed foods (mean = 2.4, SD = 1.4) than non-exposed foods (mean = 2.6, SD = 1.5). However, there was a significant interaction between familiarity and exposure, F(1, 16) = 5.2, p = .037, partial h2 = .25. As can be seen in Table 1, exposure exerted different effects on children’s willingness to taste foods depending on the food’s status as familiar or unfamiliar. Our hypothesis was that children would be more likely to taste previously unfamiliar foods if they had been exposed to pictures of these. A tendency to taste more exposed than non-exposed foods was evident for unfamiliar foods, but this effect was not significant, t(16) = 0.94, p = .36. Unexpectedly, children tasted fewer of the familiar foods to which they had been exposed compared to those to which they had not, t(16) = 2.14, p = .049. Non-parametric analyses revealed that this negative effect was due to children’s behaviour towards familiar vegetables (Wilcoxon Z = 2.45, p = .014) rather than familiar fruit
Table 1 The mean number of foods children tasted, according to whether foods were initially familiar or unfamiliar and whether they had been visually exposed or not, with standard deviations in brackets. Familiar
Vegetables Fruits Total foods
Unfamiliar
Total
Exposed
Nonexposed
Exposed
Nonexposed
0.47 (0.51) 0.71 (0.47) 1.18 (0.73)
0.82 (0.39) 0.76 (0.44) 1.59 (0.71)
0.65 (0.49) 0.59 (0.51) 1.24 (0.83)
0.47 (0.51) 0.53 (0.51) 1.00 (0.94)
2.41 (1.37) 2.59 (1.23) 5.00 (2.45)
(Z = .45, p = .66). Thus, repeated visual exposure to already familiar vegetables reduced children’s willingness to taste them in our test. We further explored the interaction by examining whether children’s overall preference for familiar over unfamiliar foods was displayed equally towards exposed and non-exposed foods. As can be seen in Table 1, children displayed a strong preference for familiar non-exposed foods over unfamiliar non-exposed foods (overall: t(16) = 3.05, p = .008; vegetables: Wilcoxon Z = 2.45, p = .007, 1-tailed; fruits: Z = 1.63, p = .05). However, no such preference was seen for exposed foods (overall: t(16) = .32, p = .75; vegetables: Z = 1.13, p = .26; fruit: Z = .82, p = .41). If children’s preference for familiar foods over unfamiliar foods reflects their natural unwillingness to taste new foods, exposure appears to reduce this food neophobia. Finally, we examined the order in which children tasted the unfamiliar foods on each plate. There was no effect of exposure on the order in which vegetables were tasted. However, exposed fruits were tasted before non-exposed fruits (Wilcoxon Z = 2.07, p = .019, 1-tailed). Importantly, this finding was exhibited for both of the fruits concerned. Children who had been exposed to blueberries tasted them earlier than children who had not (Mann– Whitney U = 1.81, p = .036, 1-tailed), and children who had been exposed to lychees tasted them earlier than children who had not (U = 2.00, p = .023, 1-tailed). Moreover, children tasted the exposed unfamiliar fruit before the exposed familiar fruit (Wilcoxon Z = 2.16, p = .031), demonstrating a complete reversal of the neophobic pattern of behaviour displayed towards nonexposed foods. Discussion Previous work has demonstrated that prior visual exposure affects the time toddlers spend looking at pictures of foods (Houston-Price et al., 2009) and their ratings of how much they like the foods (Birch et al., 1987). The current study adds to this literature by providing preliminary evidence that visual exposure impacts on children’s willingness to taste foods. However, the role of visual exposure in determining a child’s willingness to taste a food does not seem to be straightforward. Children did not simply taste more of the exposed foods in this study. Rather, the impact of exposure seems to depend on children’s familiarity with the exposed foods. The literature has shown that food selection is determined by a variety of factors, including experience with foods; children typically exhibit neophobia, an aversion to unfamiliar foods until they have been shown to be ‘safe’ (Rozin, 1976). Half of the foods used in the current study were selected because children were likely to be familiar with them, while the remainder were selected to be unfamiliar. Children tasted significantly more familiar foods, displaying typical neophobic behaviour and providing support for our categorisation of the eight foods as familiar or unfamiliar. The question of interest is how visual exposure interacted with children’s natural aversion towards unfamiliar foods. We found several indications that visual exposure might serve to reduce food neophobia. First, children displayed neophobia – as indexed by their relative preference for familiar over unfamiliar foods – only towards non-exposed foods and were equally likely to taste exposed foods regardless of their status as familiar or unfamiliar at the start of the study. Thus, the visual exposure manipulation overcame children’s natural aversion towards unfamiliar foods. We also investigated the order in which children tasted the foods on each plate as a potentially more sensitive measure of their willingness to consume the foods. Exposure exerted an effect on the order in which the unfamiliar fruits were selected: whichever book children had been exposed to, they tasted the exposed fruit before the non-exposed fruit. In addition, children’s typical
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neophobic response was reversed by exposure: children tasted the unfamiliar fruit before the familiar fruit. Visual exposure therefore had two positive effects on children’s willingness to taste foods in this study: It reduced children’s aversion to unfamiliar foods relative to familiar foods and, in the case of unfamiliar fruits, children were more eager to taste exposed foods than non-exposed foods, as indexed by their order of food selection. The data therefore suggest that visual exposure may prove a useful additional tool in the battle to increase children’s consumption of healthy foods. If parents find it less demanding to provide repeated visual exposures to new foods than it is to provide repeated taste exposures (Carruth et al., 2004), their attempts to introduce new foods into their child’s diet may be facilitated by an initial period of picture-book exposure. Further research should explore whether visual exposure also works to reduce the number of taste exposures required to elicit positive liking of the food’s taste. By enhancing children’s willingness to taste a food, it is possible that fewer than the 10–15 taste exposures previously found to be necessary (Birch et al., 1987) might be needed to introduce a food following visual exposure. It is important to note, however, that visual exposure to foods that were familiar did not increase children’s willingness to taste these. In fact, children were less willing to taste familiar foods that had been repeatedly exposed, especially for vegetables. Further research should elucidate whether this negative effect is longlasting or only short-lived. Children may have become bored with repeatedly looking at familiar foods, leading to a temporary lack of interest in the foods at the time of the taste test. However, it is worth noting the parallel between the negative effect of exposure to familiar foods in this study and the ‘satiation effects’ reported for adults who were repeatedly exposed to the taste of a familiar food (Pliner et al., 1980). If visual exposure satiates children’s appetite for foods with which they are already familiar (and which may already be liked), this should be taken into account in interventions employing visual exposure as a tool for enhancing food liking. The potential to enhance children’s willingness to taste new foods through visual exposure is clearly an avenue of research that requires further investigation. Given that our hypotheses were only partially supported in this study – positive effects of exposure were found for fruits, but not vegetables – further research should explore whether the categorical status of fruits and vegetables is the cause of these discrepant findings or whether differences in children’s familiarity with or liking of these food groups may be responsible. For example, if children were less familiar with the unfamiliar fruits than with the unfamiliar vegetables, there would have been more scope for visual exposure to impact on their liking of fruits. In fact, the opposite is likely to be true. Although we selected as stimuli the two foods reported to be most familiar and least familiar in each category, scrutiny of parents’ questionnaire responses reveals that the foods selected to be unfamiliar were not well-matched. While the proportions of children who were reported to have at least monthly contact with the four familiar foods were highly similar (carrots, 100%; sweetcorn, 97%; grapes, 100%; and strawberries, 97%), one of the unfamiliar foods was much more likely to be regularly encountered than the others (radish, 15%; watercress, 17%; lychees, 9%; and blueberries, 70%). The identical pattern of results seen for lychees and blueberries would suggest that children’s differing familiarity with these two foods did not influence their tasting behaviour in this study, however. Alternatively, what appear to be qualitatively different responses to exposure to fruits and vegetables may reflect quantitative differences in children’s initial liking of each food.
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Adults report decreasing levels of desire to eat highly liked foods, such as chocolate, with repeated taste exposures (Hetherington, Pirie, & Nabb, 2002), a finding that is at odds with the positive effect for the better-liked food group (fruit) in the current study. However, in the social psychology literature, negative exposure effects have been induced by repeated exposure to individuals who are associated with negative experiences (Swap, 1977). Children’s natural dislike of the bitter taste of vegetables might similarly lead to negative exposure effects for this food category; the fact that a negative effect was seen only for familiar vegetables, which children would have tasted before, fits well with such an account. Further research is clearly required to tease apart the factors that determine the success of picture-book exposure, including the food’s status as a fruit or vegetable, liked or disliked and familiar or unfamiliar food Finally, although unanticipated, it is worth noting that the negative effect of exposure to familiar foods corroborates the potential for visual exposure to directly impact on children’s willingness to taste foods. If, under certain conditions (such as prior familiarity), exposure can lower children’s food consumption, there are likely to be conditions under which exposure promotes consumption. Researchers should seek out these conditions, for a successful visual exposure manipulation could make a significant contribution to parents’ efforts to provide their child with a healthy diet.
Acknowledgements The authors would like to thank the parents and toddlers who participated in this study and the School Research Committee for funding the project.
References Birch, L. L., Gunder, L., Grimm-Thomas, K., & Laing, D. G. (1998). Infants’ consumption of a new food enhances acceptance of similar foods. Appetite, 30, 283–295. Birch, L. L., & Marlin, D. W. (1982). I don’t like it; I never tried it: effects of exposure on two-year-old children’s food preferences. Appetite: Journal for Intake Research, 3, 353–360. Birch, L. L., McPhee, L., Shoba, B. C., Pirok, E., & Steinberg, L. (1987). What kind of exposure reduces children’s food neophobia? Appetite, 9, 171–178. Blossfeld, I., Collins, A., Kiely, M., & Delahunty, C. (2007). Texture preferences of 12month-old infants and the role of early experiences. Food Quality and Preference, 18, 396–404. Borzekowski, D. L. G., & Robinson, T. N. (2001). The 30-second effect: an experiment revealing the impact of television commercials on food preferences of preschoolers. Journal of the American Dietetic Association, 101, 42–46. Carruth, B. R., Ziegler, P. J., Gordon, A., & Barr, S. I. (2004). Prevalence of picky eaters among infants and toddlers and their caregivers’ decisions about offering a new food. Journal of the American Dietetic Association, S57–S64. Hetherington, M. M., Pirie, L. M., & Nabb, S. (2002). Stimulus satiation: effects of repeated exposure to food on pleasantness and intake. Appetite, 38, 19–28. Houston-Price, C., Burton, E., Hickinson, R., Inett, J., Moore, E., Salmon, K., et al. (2009). Visual exposure elicits positive visual preferences in toddlers. Journal of Experimental Child Psychology, 104, 89–104. Maier, A., Chabanet, C., Schaal, B., Issanchou, S., & Leathwood, P. (2007). Effects of repeated exposure on acceptance of initially disliked vegetables on 7-month old infants. Food Quality and Preference, 18, 1023–1032. Mennella, J. A., Jagnow, C. P., & Beauchamp, G. K. (2001). Prenatal and postnatal flavor learning by human infants. Pediatrics, 107, e88. Pliner, P. (1982). The effects of mere exposure on liking for edible substances. Appetite: Journal for Intake Research, 3, 283–290. Pliner, P., Polivy, J., Herman, C. P., & Zakalusny, I. (1980). Short-term intake of overweight individuals and normal weight dieters and non-dieters with and without choice among a variety of foods. Appetite: Journal for Intake Research, 1, 203–213. Rozin, P. (1976). The selection of foods by rats, humans and other animals. In Rosenblatt, J. S., Hinde, R. A., Shaw, E., & Beer, C. (Eds.), Advances in the study of behaviour. Vol. 6 (pp.21–76). New York: Academic Press Swap, W. C. (1977). Interpersonal attraction and repeated exposure to rewarders and punishers. Personality and Social Psychology Bulletin, 3, 248–251.
.
Contents lists available at ScienceDirect
Appetite journal homepage: www.elsevier.com/locate/appet
Short communication
Visual exposure impacts on toddlers’ willingness to taste fruits and vegetables Carmel Houston-Price *, Laurie Butler, Paula Shiba School of Psychology & Clinical Language Sciences, University of Reading, Earley Gate, Whiteknights, Reading RG6 6AL, UK
A R T I C L E I N F O
A B S T R A C T
Article history: Received 19 March 2009 Received in revised form 6 July 2009 Accepted 28 August 2009
This study explores the effects of exposure to pictures of fruits and vegetables on young children’s willingness to taste the foods. The parents of 20 toddlers aged 21–24 months were asked to read a picture book about four foods with their child every day for two weeks. In a subsequent ‘taste test’ children displayed a neophobic pattern of behaviour towards foods to which they had not been exposed, but not towards exposed foods. Furthermore, while exposure served to decrease children’s willingness to taste familiar vegetables, it increased their willingness to taste unfamiliar fruits. ß 2009 Elsevier Ltd. All rights reserved.
Keywords: Food choice Exposure Children Fruit and vegetables Willingness to taste
Introduction A variety of factors determine infants’ liking of foods, including genetic predispositions to prefer sweet tastes and avoid unfamiliar foods (‘food neophobia’; Rozin, 1976). Exposure to food plays an important role in determining young children’s preferences; the influence of experience begins with pre-natal exposure through amniotic fluid and continues post-natally through breast milk (Mennella, Jagnow, & Beauchamp, 2001) and via the foods provided during weaning and beyond (Birch, Gunder, GrimmThomas, & Laing, 1998). Exposure to food has therefore been a key feature of attempts to enhance children’s liking of healthy foods. In adults, both positive and negative relationships have been reported between exposure to foods and rated liking of the foods. For example, Pliner (1982) gave participants three unfamiliar fruit juices to taste 5, 10 or 20 times and found that the number of exposures was positively related to participants’ ratings of how much they liked each juice’s taste. Other work has found ‘satiation effects’, whereby repeated taste exposures lead to dislike of the food (Pliner, Polivy, Herman, & Zakalusny, 1980). Pliner (1982) suggests that the discrepancy is due to participants’ initial levels of familiarity with exposed foods; while repeated exposure to unfamiliar foods increases liking, exposure to foods that are already familiar may lead to dislike.
* Corresponding author. E-mail address: [email protected] (C. Houston-Price). 0195-6663/$ – see front matter ß 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.appet.2009.08.012
Research studies involving young children support the potential for exposure to enhance liking and consumption of unfamiliar and disliked foods. For example, Birch and Marlin (1982) provided two-year olds with up to 20 exposures to 5 unfamiliar cheeses (Experiment 1) or 5 unfamiliar fruits (Experiment 2) over a fourweek period and in each case found children’s preferences to be predicted by the number of exposures they had received to each food. In a more recent study, Maier, Chabanet, Schaal, Issanchou, and Leathwood (2007) found that after 16 presentations of an initially disliked pure´ed vegetable, infants of 7 months willingly consumed as much of the vegetable as they did of an initially liked vegetable. Liking of a food’s texture, as well as its taste, is affected by exposure; at 12 months, infants’ intake of chopped carrots is predicted by the frequency with the child has previously been provided with chopped foods (Blossfeld, Collins, Kiely, & Delahunty, 2007). Exposure therefore appears to be a powerful and straightforward solution to the problem of encouraging healthy eating in children. However, 10–15 exposures to a new or disliked food may be required to effect positive changes in preference (Birch & Marlin, 1982; Birch, McPhee, Shoba, Pirok, & Steinberg, 1987), a number ‘‘greater than that most parents are willing or able to provide’’ (Birch et al., 1987, p. 177; Carruth, Ziegler, Gordon, & Barr, 2004). As a result, researchers have sought a means of exposing foods that does not require parents to engage in multiple attempts to persuade their child to taste unwanted foods. One avenue that has been explored is visual exposure. Given that brief television commercials can successfully induce brand preferences in preschoolers (Borzekowski & Robinson, 2001), it is conceivable
C. Houston-Price et al. / Appetite 53 (2009) 450–453
that visual exposure to different foods might impact on children’s liking of them. Very little research has directly explored this question. One exception is a study by Birch et al. (1987), who compared the effects of taste exposure and visual exposure on preschoolers’ liking of a set of six unfamiliar fruits. Each fruit was exposed 5, 10 or 15 times over a 30-day period; 3 of the fruits were tasted at each exposure, while 3 were presented visually for 10 s on each occasion. A few days later, children were presented with a forcedchoice paired comparison task; the six exposed foods and a further unfamiliar food were presented in pairs and children were asked to ‘‘choose the one you like the best’’. The question was posed both before and after the pair of foods were tasted, which Birch et al. termed ‘look judgments’ and ‘taste judgments’, respectively. The number of taste exposures provided correlated with children’s look and taste judgments of the foods, confirming previous reports that taste exposure enhances food liking. Birch et al. also reported a correlation between the number of visual exposures and children’s look judgments, but no relationship between the number of visual exposures and their taste judgments, leading the authors to conclude that visual exposure has no impact on food liking. However, there are grounds for calling for further research into the impact of visual exposure on food liking. First, Birch et al.’s (1987) ‘look’ and ‘taste’ judgments may not have indexed children’s liking of the look and taste of the foods, respectively, because children were, in both cases, asked to ‘‘choose the one they liked the best’’. When foods were first presented children’s choices were thought to reflect their liking of the look of the foods, but their judgments may have been influenced by their memory of the taste of the foods they had tasted before. Similarly, the selections children made after they had tasted the two foods may have been determined by their liking of the taste of the foods, but their responses may also have been influenced by the look or smell of the food. One cannot, therefore, be certain that children’s liking of the look and taste of the exposed foods were tapped into by the questions asked. It could also be argued that visual exposure would be unlikely to directly enhance liking of a food’s taste, and that one should look elsewhere for evidence of a positive influence of visual exposure, such as in a greater willingness to taste an unfamiliar food. Birch et al.’s (1987) finding that visual exposure enhanced children’s ‘look judgments’ suggests that this type of exposure may induce more positive attitudes towards exposed foods. Recent research by Houston-Price et al. (2009) shows that repeated exposure to pictures of foods in books leads toddlers to preferentially attend to exposed over non-exposed foods in a visual preference test. By enhancing children’s attitudes towards the appearance of foods and/or their willingness to explore them visually, visual exposure might also reduce children’s reluctance to taste previously unfamiliar foods. The potential to enhance children’s willingness to taste new foods through visual exposure is, therefore, an exciting avenue of research that deserves exploration. This article describes a preliminary investigation into the effects of exposure to pictures of familiar and unfamiliar foods on toddlers’ willingness to taste them. We hypothesised that children would be more willing to taste unfamiliar foods if they were repeatedly visually exposed to these foods before they were invited to try them. Method Participants Twenty toddlers, 10 boys and 10 girls, with a mean age of 23.2 months (range = 21.4–24.7) were recruited from the University’s Child Development Group database, a list of parents who had
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expressed an interest in taking part in research with their child. Parents gave informed consent to participate with their child in this study. Participants were rewarded with travel expenses and a certificate. Design This study was approved by the University’s Research Ethics Committee and conformed to the standards prescribed by the 1964 Declaration of Helsinki. Parents were sent one of two books about four foods to read with their child every day for two weeks. Each book contained pictures and information about two familiar foods (one fruit, one vegetable) and two unfamiliar foods (one fruit, one vegetable). Following the exposure period, children took part in a ‘taste test’ in which they were offered all eight foods shown in the two books: the four vegetables followed by the four fruits. We recorded the number of foods children tasted and the order in which they did so. Note that, in this design, each food serves as an exposed food and as a non-exposed food for different children, thus controlling for any preferences for specific foods that children may have had. Materials The fruits and vegetables to be included in exposure books were selected on the basis of parents’ responses to a Food Familiarity Questionnaire. This is a list of 83 commonly available fruits and vegetables, which parents are asked to rate in terms of how often their child encounters each food on a 3-point scale: rarely or never (less than once per month); sometimes (less than once per week but more than once per month); or often (at least once per week). After excluding foods that could not be eaten raw, we selected as stimuli the two fruits parents rated as most familiar (grape and strawberry) and least familiar (blueberry and lychee) and the two vegetables rated most familiar (carrot and sweetcorn) and least familiar (radish and watercress). Two books were created, each about two fruits and two vegetables, with one of each food type likely to be familiar to children and one likely to be unfamiliar (Book A: grape, blueberry, sweetcorn and radish; Book B: strawberry, lychee, carrot and watercress). Books included a page about each food, with one large photograph and several smaller photographs showing how the food grows, what it looks like inside and what the prepared food might look like, with sentences for parents to read. Books were produced in a colourful, child-friendly A4 format, laminated and bound. The eight foods depicted in the books served as stimuli in the taste test. Foods were washed and provided either whole (radish, blueberry, and grape), cut in half (strawberry and lychee) or in pieces (sweetcorn kernels, carrot stick, and small sprig of watercress). A video camera was used to record test sessions. Procedure Children were randomly assigned to receive one of the two books; 11 children received Book A and 9 received Book B. Parents were sent the relevant book and instructions to read the book with their child for 5 min every day for two weeks. The day after the exposure period ended, parents (in all cases, mothers) and toddlers visited the University to take part in the taste test. Mothers were asked to choose one of two vegetables (cherry tomato or cucumber stick) and one of two fruits (pineapple chunk or mandarin orange segment) to eat during the taste test, to ensure that their child felt comfortable about eating. Mothers were told that a piece of the foods they had selected would be placed in the centre of each of the child’s food plates and that they should
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immediately take this food and eat it when the plate was offered. Mothers were instructed that they should not name, point to, touch or eat any of the other foods on either plate. The child was then seated at a low table in a communal area with their mother close by. The vegetable plate was offered first. This contained two pieces of each of the four vegetables depicted in the two books and the mother’s chosen vegetable in the centre. After the mother had eaten her food, children were encouraged to eat by the experimenter, who was blind to the specific book to which the child had been exposed. When a period of 5 min had elapsed, or earlier if the child had eaten all the foods or refused to eat any more, the plate was removed and the fruit plate was presented. Again, two pieces of each of the four fruits shown in the books were provided, with the mother’s fruit in the centre of the plate; once the mother had taken her piece of fruit children were encouraged to eat what they wanted. The experimenter recorded whether, and in what order, children placed the foods on each plate in their mouths. Test sessions were recorded on video camera. Results Each child had the opportunity to taste eight foods in a 2 (fruit vs. vegetable) 2 (familiar vs. unfamiliar) 2 (exposed vs. nonexposed) within-subjects design. Three children (all boys) refused to taste any of the foods offered and were excluded from analyses. Remaining children tasted an average of 5.0 of the 8 foods (SD = 2.4), of which 2.41 were vegetables (SD = 1.37) and 2.59 were fruit (SD = 1.23). The numbers of each food type that children tasted are presented in Table 1. The data were first entered into a 2 (familiarity) 2 (exposure) repeated measures ANOVA, collapsing across food category (fruit vs. vegetable). The analysis revealed a significant main effect of familiarity, F(1, 16) = 4.70, p = .046, partial h2 = .23, reflecting children’s food neophobia; children tasted more familiar foods (mean = 2.76, SD = 1.20) than unfamiliar foods (mean = 2.24, SD = 1.44). There was no main effect of exposure, F(1, 16) = .26, p = .62, partial h2 = .02; overall, children did not taste more exposed foods (mean = 2.4, SD = 1.4) than non-exposed foods (mean = 2.6, SD = 1.5). However, there was a significant interaction between familiarity and exposure, F(1, 16) = 5.2, p = .037, partial h2 = .25. As can be seen in Table 1, exposure exerted different effects on children’s willingness to taste foods depending on the food’s status as familiar or unfamiliar. Our hypothesis was that children would be more likely to taste previously unfamiliar foods if they had been exposed to pictures of these. A tendency to taste more exposed than non-exposed foods was evident for unfamiliar foods, but this effect was not significant, t(16) = 0.94, p = .36. Unexpectedly, children tasted fewer of the familiar foods to which they had been exposed compared to those to which they had not, t(16) = 2.14, p = .049. Non-parametric analyses revealed that this negative effect was due to children’s behaviour towards familiar vegetables (Wilcoxon Z = 2.45, p = .014) rather than familiar fruit
Table 1 The mean number of foods children tasted, according to whether foods were initially familiar or unfamiliar and whether they had been visually exposed or not, with standard deviations in brackets. Familiar
Vegetables Fruits Total foods
Unfamiliar
Total
Exposed
Nonexposed
Exposed
Nonexposed
0.47 (0.51) 0.71 (0.47) 1.18 (0.73)
0.82 (0.39) 0.76 (0.44) 1.59 (0.71)
0.65 (0.49) 0.59 (0.51) 1.24 (0.83)
0.47 (0.51) 0.53 (0.51) 1.00 (0.94)
2.41 (1.37) 2.59 (1.23) 5.00 (2.45)
(Z = .45, p = .66). Thus, repeated visual exposure to already familiar vegetables reduced children’s willingness to taste them in our test. We further explored the interaction by examining whether children’s overall preference for familiar over unfamiliar foods was displayed equally towards exposed and non-exposed foods. As can be seen in Table 1, children displayed a strong preference for familiar non-exposed foods over unfamiliar non-exposed foods (overall: t(16) = 3.05, p = .008; vegetables: Wilcoxon Z = 2.45, p = .007, 1-tailed; fruits: Z = 1.63, p = .05). However, no such preference was seen for exposed foods (overall: t(16) = .32, p = .75; vegetables: Z = 1.13, p = .26; fruit: Z = .82, p = .41). If children’s preference for familiar foods over unfamiliar foods reflects their natural unwillingness to taste new foods, exposure appears to reduce this food neophobia. Finally, we examined the order in which children tasted the unfamiliar foods on each plate. There was no effect of exposure on the order in which vegetables were tasted. However, exposed fruits were tasted before non-exposed fruits (Wilcoxon Z = 2.07, p = .019, 1-tailed). Importantly, this finding was exhibited for both of the fruits concerned. Children who had been exposed to blueberries tasted them earlier than children who had not (Mann– Whitney U = 1.81, p = .036, 1-tailed), and children who had been exposed to lychees tasted them earlier than children who had not (U = 2.00, p = .023, 1-tailed). Moreover, children tasted the exposed unfamiliar fruit before the exposed familiar fruit (Wilcoxon Z = 2.16, p = .031), demonstrating a complete reversal of the neophobic pattern of behaviour displayed towards nonexposed foods. Discussion Previous work has demonstrated that prior visual exposure affects the time toddlers spend looking at pictures of foods (Houston-Price et al., 2009) and their ratings of how much they like the foods (Birch et al., 1987). The current study adds to this literature by providing preliminary evidence that visual exposure impacts on children’s willingness to taste foods. However, the role of visual exposure in determining a child’s willingness to taste a food does not seem to be straightforward. Children did not simply taste more of the exposed foods in this study. Rather, the impact of exposure seems to depend on children’s familiarity with the exposed foods. The literature has shown that food selection is determined by a variety of factors, including experience with foods; children typically exhibit neophobia, an aversion to unfamiliar foods until they have been shown to be ‘safe’ (Rozin, 1976). Half of the foods used in the current study were selected because children were likely to be familiar with them, while the remainder were selected to be unfamiliar. Children tasted significantly more familiar foods, displaying typical neophobic behaviour and providing support for our categorisation of the eight foods as familiar or unfamiliar. The question of interest is how visual exposure interacted with children’s natural aversion towards unfamiliar foods. We found several indications that visual exposure might serve to reduce food neophobia. First, children displayed neophobia – as indexed by their relative preference for familiar over unfamiliar foods – only towards non-exposed foods and were equally likely to taste exposed foods regardless of their status as familiar or unfamiliar at the start of the study. Thus, the visual exposure manipulation overcame children’s natural aversion towards unfamiliar foods. We also investigated the order in which children tasted the foods on each plate as a potentially more sensitive measure of their willingness to consume the foods. Exposure exerted an effect on the order in which the unfamiliar fruits were selected: whichever book children had been exposed to, they tasted the exposed fruit before the non-exposed fruit. In addition, children’s typical
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neophobic response was reversed by exposure: children tasted the unfamiliar fruit before the familiar fruit. Visual exposure therefore had two positive effects on children’s willingness to taste foods in this study: It reduced children’s aversion to unfamiliar foods relative to familiar foods and, in the case of unfamiliar fruits, children were more eager to taste exposed foods than non-exposed foods, as indexed by their order of food selection. The data therefore suggest that visual exposure may prove a useful additional tool in the battle to increase children’s consumption of healthy foods. If parents find it less demanding to provide repeated visual exposures to new foods than it is to provide repeated taste exposures (Carruth et al., 2004), their attempts to introduce new foods into their child’s diet may be facilitated by an initial period of picture-book exposure. Further research should explore whether visual exposure also works to reduce the number of taste exposures required to elicit positive liking of the food’s taste. By enhancing children’s willingness to taste a food, it is possible that fewer than the 10–15 taste exposures previously found to be necessary (Birch et al., 1987) might be needed to introduce a food following visual exposure. It is important to note, however, that visual exposure to foods that were familiar did not increase children’s willingness to taste these. In fact, children were less willing to taste familiar foods that had been repeatedly exposed, especially for vegetables. Further research should elucidate whether this negative effect is longlasting or only short-lived. Children may have become bored with repeatedly looking at familiar foods, leading to a temporary lack of interest in the foods at the time of the taste test. However, it is worth noting the parallel between the negative effect of exposure to familiar foods in this study and the ‘satiation effects’ reported for adults who were repeatedly exposed to the taste of a familiar food (Pliner et al., 1980). If visual exposure satiates children’s appetite for foods with which they are already familiar (and which may already be liked), this should be taken into account in interventions employing visual exposure as a tool for enhancing food liking. The potential to enhance children’s willingness to taste new foods through visual exposure is clearly an avenue of research that requires further investigation. Given that our hypotheses were only partially supported in this study – positive effects of exposure were found for fruits, but not vegetables – further research should explore whether the categorical status of fruits and vegetables is the cause of these discrepant findings or whether differences in children’s familiarity with or liking of these food groups may be responsible. For example, if children were less familiar with the unfamiliar fruits than with the unfamiliar vegetables, there would have been more scope for visual exposure to impact on their liking of fruits. In fact, the opposite is likely to be true. Although we selected as stimuli the two foods reported to be most familiar and least familiar in each category, scrutiny of parents’ questionnaire responses reveals that the foods selected to be unfamiliar were not well-matched. While the proportions of children who were reported to have at least monthly contact with the four familiar foods were highly similar (carrots, 100%; sweetcorn, 97%; grapes, 100%; and strawberries, 97%), one of the unfamiliar foods was much more likely to be regularly encountered than the others (radish, 15%; watercress, 17%; lychees, 9%; and blueberries, 70%). The identical pattern of results seen for lychees and blueberries would suggest that children’s differing familiarity with these two foods did not influence their tasting behaviour in this study, however. Alternatively, what appear to be qualitatively different responses to exposure to fruits and vegetables may reflect quantitative differences in children’s initial liking of each food.
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Adults report decreasing levels of desire to eat highly liked foods, such as chocolate, with repeated taste exposures (Hetherington, Pirie, & Nabb, 2002), a finding that is at odds with the positive effect for the better-liked food group (fruit) in the current study. However, in the social psychology literature, negative exposure effects have been induced by repeated exposure to individuals who are associated with negative experiences (Swap, 1977). Children’s natural dislike of the bitter taste of vegetables might similarly lead to negative exposure effects for this food category; the fact that a negative effect was seen only for familiar vegetables, which children would have tasted before, fits well with such an account. Further research is clearly required to tease apart the factors that determine the success of picture-book exposure, including the food’s status as a fruit or vegetable, liked or disliked and familiar or unfamiliar food Finally, although unanticipated, it is worth noting that the negative effect of exposure to familiar foods corroborates the potential for visual exposure to directly impact on children’s willingness to taste foods. If, under certain conditions (such as prior familiarity), exposure can lower children’s food consumption, there are likely to be conditions under which exposure promotes consumption. Researchers should seek out these conditions, for a successful visual exposure manipulation could make a significant contribution to parents’ efforts to provide their child with a healthy diet.
Acknowledgements The authors would like to thank the parents and toddlers who participated in this study and the School Research Committee for funding the project.
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