Two studies were reviewed for this summary. Study 1 was conducted in a school setting with children in kindergarten and first grade. Study 2 was conducted in the homes of children attending nursery schools.
Sixteen kindergarten and first-grade classrooms from eight schools were randomly assigned to one of four study conditions: exposure plus tangible reward, exposure plus social reward (i.e., praise), exposure alone, and no-treatment control. The intervention was administered by trained researchers for 15 school days over a period of 3 weeks, with participants in the intervention conditions scheduled for 12 exposure sessions.
On days 1 and 2, each child in every condition was individually shown six vegetables (carrot, red pepper, sugar snap pea, cabbage, cucumber, and celery). The child was asked to taste a small piece of each vegetable and rate how much he or she liked it using a faces scale, which consists of cartoons of three faces with expressions corresponding to "yummy," "just OK," and "yucky". After the child had tasted and rated all of the vegetables, the researcher asked the child to rank them from 1 (most liked) to 6 (least liked). Each child's target vegetable was the one he or she ranked fourth. The child was then invited to eat as much of the target vegetable as he or she wanted, with intake (in grams) assessed by weighing the dish before and after consumption using a digital scale.
From day 3 to day 14, children in the intervention conditions were seen individually and offered a small piece of their target vegetable each day. Children in the exposure plus tangible reward condition were told that if they tasted the vegetable, they could choose a sticker as a reward. Children in the exposure plus social reward condition were praised if they tasted the vegetable (e.g., "Brilliant, you're a great taster"). Children in the exposure alone condition were invited to taste the target vegetable but received minimal social interaction. Children in the control group did not receive taste exposure to the target vegetable during the intervention period. Children's ratings and consumption of their target vegetable were also assessed on day 15 and at 1- and 3-month follow-up visits.
The study included 99 children in the exposure plus tangible reward condition, 106 in the exposure plus social reward condition, 105 in the exposure alone condition, and 112 in the control condition, for a total of 422 participants. Children were aged 4-6, and 53% were boys.
Families who agreed to participate were randomly allocated to one of three study conditions using blocked randomization: exposure plus tangible reward, exposure plus social reward, and no-treatment control. A researcher visited each family in their home to administer the baseline assessment. Children were presented with six different vegetables (carrot, cucumber, white cabbage, red pepper, celery, and sugar snap peas). The children were asked to taste a small piece of each vegetable and then rank them from 1 (most liked) to 6 (least liked). Each child's target vegetable was the one he or she ranked fourth.
After the baseline assessment and the randomization procedure were conducted, the researcher explained the exposure and reward techniques to parents in the intervention groups. Parents in the exposure plus tangible reward condition were asked to offer their child a small piece of their target vegetable every day for 12 weekdays and to tell the child that he or she could choose a sticker for trying the vegetable each time. Parents in the exposure plus social reward condition were asked to offer the vegetable as described above and to praise their child with phrases such as "Brilliant, you're a great vegetable taster" if the child tasted it. Families assigned to the control group did not perform any daily tastings but were told that they would be taught a special technique to help their child eat more vegetables after the last visit. Children's ratings and consumption of their target vegetable were also assessed in the home by a researcher immediately after the intervention period and at 1- and 3-month follow-up visits.
The study included 58 children in the exposure plus tangible reward condition, 59 in the exposure plus social reward condition, and 56 in the control condition, for a total of 173 participants. Children were aged 3-4, and 52.6% were girls. Parents/primary caregivers were 66.5% White, 2.9% Black (African/Caribbean), 5.8% South Asian (Indian/Pakistani/Bangladeshi), and 24.8% other/missing data.