The influence of positive reinforcement, negative reinforcement and exposure on children's food intake and liking

Young children often consume too few fruits and vegetables, partly due to picky eating. While repeated exposure can improve acceptance, the added value of reinforcement strategies remains unclear. This pre-registered within-subject study investigated whether combining exposure with positive or negative reinforcement (using non-food rewards) enhances intake and liking of unfamiliar vegetables compared to exposure alone or a control condition. Sixty-two children aged 4-6 years participated in a 10-day school-based intervention involving all four conditions: positive reinforcement (tasting earned a cartoon card), negative reinforcement (tasting prevented card loss), exposure (tasting without rewards), and a control condition. Intake and liking of four unfamiliar vegetables (purple carrot, yellow beetroot, blue meat radish, and rutabaga) were measured on days 1 and 10, with intake also recorded during the intervention (days 2-9). Conditions and vegetable order were counterbalanced. The potential influences of reward sensitivity (RS) and punishment sensitivity (PS), and picky eating were also examined. Results from repeated-measures ANOVAs showed that positive reinforcement led to the highest post-intervention intake, followed by negative reinforcement, exposure, and control, with significant differences between all conditions. For liking, only positive reinforcement showed a significant improvement over the other conditions. RS and PS did not moderate outcomes, but higher picky eating was associated with lower intake and liking across all conditions. In conclusion, adding positive reinforcement to exposure most effectively increases young children's intake and liking of unfamiliar vegetables. This low-cost, easily implementable strategy can support parents and educators in promoting healthier eating habits in early childhood.