A systematic review and meta-analysis of visual cues and primes for nudging consumption-related behaviours

Healthy diets are crucial for maintaining overall well-being and reducing risk of health complications. Visual cues and primes are popular implicit nudging techniques for promoting healthier consumption habits. The present review and meta-analysis was conducted and reported according to PRISMA guidelines. It aimed to evaluate the effectiveness of these cues and primes for nudging consumption-related behaviours. Six electronic databases were comprehensively searched for experimental studies on the use of non-marketing-based visual cues/primes on food/beverage consumption. Sixty-six studies from 52 articles were included, resulting in 205 comparisons categorised into seven groups for separate analyses: (1) healthy food- and (2) body-related nudges, and (3) unhealthy food- and (4) body-related nudges, versus neutral controls; (5) mixed-health food- and (6) body-related comparisons; and (7) nudges not inherently health-related. Overall, nudges effectively influenced consumption-related behaviours. Healthier food- and body-nudges encouraged healthier behaviours relative to neutral controls and less healthy nudges, and unhealthy food-nudges, relative to neutral controls. Non-health-related nudges influenced behaviours in the expected direction, relative to comparison/control conditions. Nudge effectiveness, especially for unhealthy food-nudges, was moderated by participant age and weight, nudge timing (prime/cue) outcome measure (intake/choice), health (mixed/healthy/unhealthy), and whether the outcome was real or hypothetical. A range of participant, nudge, and outcome-related mechanisms proposed to underlie nudge effectiveness were also identified. Findings supported the efficacy of visual cues and primes for eliciting changes in consumption-related behaviours, indicating they may be effective for encouraging healthier consumption, when the right nudges are used. Results also indicated that different forms of nudges may be more appropriate in different circumstances (e.g., for different types of participants or food-related outcomes). Further research is needed to thoroughly comprehend the mechanisms underlying these nudges and their effectiveness.