Vending machine backgrounds: nudging healthier beverage choices.

Soft drink overconsumption is a growing public health concern. The present research investigated whether priming nudges could decrease soft drink choices from a vending machine. We compared the effect of six vending machine wraps (Mount Franklin ™ logo, Coca-Cola™ logo, picture of water, picture of soft drink, blue, red) on beverage choice against a black (control) computerised vending machine display. In two studies, young adult participants (17 - 25 years) were recruited from [removed for blind review] (Study 1, n  = 142, Study 2, n  = 232). Participants were randomly allocated to choose a beverage from one of the wrap conditions. They also rated how much the beverage was liked and how often it was consumed (Study 1), or rated the refreshing value, healthiness, taste, and energy of each beverage in the vending machine (Study 2). We predicted that wraps referencing water would produce healthier choices and those referencing soft drink would result in unhealthier choices. Contrary to these predictions, the type of vending machine wrap did not significantly influence beverage choice in Study 1. However, viewing the black vending machine wrap resulted in significantly more caffeine-based selections in Study 2. Other significant predictors of the choice of beverage were how often the beverages were consumed and how much they were liked (Study 1), as well as their perceptions of the taste, healthiness and refreshing value (Study 2). The finding that the black vending machine produced more caffeine-based beverage choices demonstrates, in principle, that color-based priming nudges could influence beverage choices.