title: Adding a reward increases the reinforcing value of fruit.
abstract: Adolescents' snack choices could be altered by increasing the reinforcing value (RV) of healthy snacks compared with unhealthy snacks. This study assessed whether the RV of fruit increased by linking it to a reward and if this increased RV was comparable with the RV of unhealthy snacks alone. Moderation effects of sex, hunger, BMI z-scores and sensitivity to reward were also explored. The RV of snacks was assessed in a sample of 165 adolescents (15·1 (sd 1·5) years, 39·4 % boys and 17·4 % overweight) using a computerised food reinforcement task. Adolescents obtained points for snacks through mouse clicks (responses) following progressive ratio schedules of increasing response requirements. Participants were (computer) randomised to three experimental groups (1:1:1): fruit (n 53), fruit+reward (n 60) or unhealthy snacks (n 69). The RV was evaluated as total number of responses and breakpoint (schedule of terminating food reinforcement task). Multilevel regression analyses (total number of responses) and Cox's proportional hazard regression models (breakpoint) were used. The total number of responses made were not different between fruit+reward and fruit (b -473; 95 % CI -1152, 205, P=0·17) or unhealthy snacks (b410; 95 % CI -222, 1043, P=0·20). The breakpoint was slightly higher for fruit than fruit+reward (HR 1·34; 95 % CI 1·00, 1·79, P=0·050), whereas no difference between unhealthy snacks and fruit+reward (HR 0·86; 95 % CI 0·62, 1·18, P=0·34) was observed. No indication of moderation was found. Offering rewards slightly increases the RV of fruit and may be a promising strategy to increase healthy food choices. Future studies should however, explore if other rewards, could reach larger effect sizes.
authors.affiliation: 1Department of Food Safety and Food Quality,Ghent University,Coupure Links 653,Ghent,Belgium.
authors.forename: Nathalie
authors.initials: N
authors.lastname: De Cock
authors.affiliation: 2Department of Developmental, Personality and Social Psychology,Ghent University,Henri Dunantlaan 2,Ghent,Belgium.
authors.forename: Leentje
authors.initials: L
authors.lastname: Vervoort
authors.affiliation: 1Department of Food Safety and Food Quality,Ghent University,Coupure Links 653,Ghent,Belgium.
authors.forename: Patrick
authors.initials: P
authors.lastname: Kolsteren
authors.affiliation: 3Poverty, Health and Nutrition Division,International Food Policy Research Institute,2033 K Street,Washington,DC 20006,USA.
authors.forename: Lieven
authors.initials: L
authors.lastname: Huybregts
authors.affiliation: 4Department of Public Health,Ghent University,De Pintelaan 185A,Ghent,Belgium.
authors.forename: Wendy
authors.initials: W
authors.lastname: Van Lippevelde
authors.affiliation: 5Leuven School for Mass Communication Research,KU Leuven,Parkstraat 45 - Box 3603,Leuven,Belgium.
authors.forename: Jolien
authors.initials: J
authors.lastname: Vangeel
authors.affiliation: 5Leuven School for Mass Communication Research,KU Leuven,Parkstraat 45 - Box 3603,Leuven,Belgium.
authors.forename: Melissa
authors.initials: M
authors.lastname: Notebaert
authors.affiliation: 5Leuven School for Mass Communication Research,KU Leuven,Parkstraat 45 - Box 3603,Leuven,Belgium.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Beullens
authors.affiliation: 2Department of Developmental, Personality and Social Psychology,Ghent University,Henri Dunantlaan 2,Ghent,Belgium.
authors.forename: Lien
authors.initials: L
authors.lastname: Goossens
authors.affiliation: 3Poverty, Health and Nutrition Division,International Food Policy Research Institute,2033 K Street,Washington,DC 20006,USA.
authors.forename: Lea
authors.initials: L
authors.lastname: Maes
authors.affiliation: 4Department of Public Health,Ghent University,De Pintelaan 185A,Ghent,Belgium.
authors.forename: Benedicte
authors.initials: B
authors.lastname: Deforche
authors.affiliation: 2Department of Developmental, Personality and Social Psychology,Ghent University,Henri Dunantlaan 2,Ghent,Belgium.
authors.forename: Caroline
authors.initials: C
authors.lastname: Braet
authors.affiliation: 5Leuven School for Mass Communication Research,KU Leuven,Parkstraat 45 - Box 3603,Leuven,Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Eggermont
authors.affiliation: 1Department of Food Safety and Food Quality,Ghent University,Coupure Links 653,Ghent,Belgium.
authors.forename: John
authors.initials: J
authors.lastname: Van Camp
authors.affiliation: 1Department of Food Safety and Food Quality,Ghent University,Coupure Links 653,Ghent,Belgium.
authors.forename: Carl
authors.initials: C
authors.lastname: Lachat
mesh_terms: D000293:Adolescent; D004032:Diet; D005260:Female; D005518:Food Preferences / Q000523:psychology*; D005638:Fruit; D015438:Health Behavior; D006801:Humans; D008297:Male; D016016:Proportional Hazards Models; D012201:Reward; D062410:Snacks / Q000523:psychology*
keywords:  BAS DRV BAS drive;  FRT food reinforcement task;  HR hazard ratio;  PR progressive ratio;  RV reinforcing value;  SR sensitivity to reward;  zBMI BMI z-scores; Adolescents; Fruits; Reinforcing value; Rewards; Snacks