Reducing soft drink consumption using nudges

Author: Ryan Calabro

Calabro, Ryan, 2022 Reducing soft drink consumption using nudges, Flinders University, College of Education, Psychology and Social Work

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The overconsumption of soft drink is an emerging health issue due to its high sugar content. This has led several countries to implement strategies to reduce soft drink consumption, such as taxation, restricting access to soft drinks in certain environments, and introducing health-related warning labels. While each of these strategies has shown varying levels of success, an alternative strategy could have more success without limiting freedom of choice, nor financially disadvantaging those who choose to drink soft drink. One such strategy is a behaviour change strategy called nudging, which has shown success in promoting healthier eating behaviours. The overarching aim of the present thesis was to investigate the socio-cognitive factors associated with soft drink consumption, and design interventions that use nudges to increase healthy beverage choices. The present thesis contained five studies, collated in three chapters.

Study 1 (Chapter 1) presents a systematic literature review and meta-analysis that aimed to identify the socio-cognitive determinants associated with the amount and frequency of sugar-sweetened beverage consumption. The results from the meta-analysis showed that the determinants most strongly associated with sugar-sweetened beverage consumption were those that were part of the Theory of Planned Behaviour (i.e., attitudes, subjective norms, and perceived behavioural control) as well as habits. It was suggested that nudging interventions should be based on the components of the theory and target habits to be maximally effective at reducing sugar-sweetened beverage consumption.

Studies 2 and 3 (Chapter 2) investigated whether subtle wrap-based nudges on a vending machine could influence beverage choices in both a laboratory (Study 2) and an online study (Study 3). Across three types of wrap-based nudges (cues, branding, and colour), there was no significant influence on beverage choice. However, the control vending machine (coloured black) in Study 3 significantly increased caffeine-based choices.

Study 4 (Chapter 3) investigated whether featuring a traffic light system on a vending machine could influence beverage choices. Results showed that it did not. Study 5 expanded the design to include a condition that increased the range of healthy beverages, plus a condition that combined this with traffic lights. Increasing the healthy range resulted in a small but significant increase in healthy beverage choices, and when combined with traffic lights produced a larger increase in healthy beverage choices; in fact, it was the only condition that showed more healthy than unhealthy choices.

Overall, the present thesis provides promising interventions to reduce soft drink consumption by offering a practical and effective approach based on nudging consumers towards healthier beverage choices. The thesis provides evidence that subtle nudges (i.e., branding, pictured beverages, or colours) may be less effective at reducing soft drink choices, whereas using more explicit nudges (i.e., featuring traffic lights, and increasing the healthy range) or combining nudges are likely a more successful approach towards reducing soft drink choices.

Keywords: sugar sweetened beverages, consumption, socio-cognitive determinants,Theory of Planned Behaviour, nudging, vending machine, beverage choice, soft drink, traffic light system, healthy range

Subject: Psychology thesis

Thesis type: Doctor of Philosophy
Completed: 2022
School: College of Education, Psychology and Social Work
Supervisor: Eva Kemps