Range nudges enhance behavioural adherence to safety and health guidelines

Behavioural guidelines sometimes specify only an upper or lower limit, such as speed limits (e.g., '60') or minimum handwashing durations (e.g., '20 s'). Limits can produce anchoring effects, biasing judgments toward the values. The distinction between anchoring arising from limits that semantically imply a range (e.g., speed limit '60' implying '0-60 km/h') and those arising from an explicitly stated range (e.g., '0-60') provides insights into how presentation formats affect anchoring. Here, we show that explicitly stating both limits acts as an additional anchor; the Range Nudge-reframing a single limit as a range-reduces non-adherence behaviour compared to presenting only one limit. In online (Study 1: n = 112) and simulated driving tasks (Study 2: n = 31), while the speed limits '60' and '0-60' are logically equivalent, the range led to lower incidences of speeding. Similarly, in handwashing tasks conducted in online (Study 3a: n = 163; Study 3b: n = 484), field (Study 4: n = 38), lab (Study 5a: n = 19), and individual home settings (Study 5b: n = 442), although the limit ('more than 20 s') covered a broader time span than the range ('20-60 s'), the latter prompted a longer handwashing duration. The results suggest that individuals consider limits as recommendations, but the Range Nudge reduces this tendency. Although the findings (seven experiments, total n = 1199) stem from controlled experiments rather than large-scale real-world applications, they offer theoretical insights and practical guidance for using the Range Nudge to enhance adherence to safety and health guidelines.