Testing verbal quantifiers for social norms messages in cancer screening: evidence from an online experiment.

Background: Studies have shown that presenting correct information about group norms to correct misperceptions of norms can influence health behaviours. In two online studies we investigated how different ways of communicating the current uptake of 43% of the English Bowel Scope Screening (BSS) programme affects intention among disinclined men and women.
Methods: In the first study, 202 participants were asked to interpret eight quantifiers for 43% uptake ('few', 'many', 'a considerable number', 'a large number', 'a great number', 'a lot', 'numerous' and 'nearly half') and to indicate how misleading they perceived each of them to be. In the second study, with 1245 participants, we compared the motivational impact of two quantifiers ('a large number' and 'nearly half' which were associated with the highest perceived uptake (48.9%) and considered least misleading in study 1 respectively) with a control message that did not contain any information on uptake, and a message which communicated actual uptake as a proportion (43%).
Results: While we found that both verbal quantifiers increased screening intentions compared with the control group (from 7.8 to 12.5%, aOR 1.72; 95%CI 1.00-2.96 in the case of 'a large number' and 14.3%, aOR 2.02; 95%CI 1.20-3.38 for 'nearly half'), simply communicating that 43% do the test, however, had no impact on intentions (9.9% vs. 7.8% aOR 1.25; 95%CI 0.73-2.16).
Conclusion: Verbal quantifiers can be used to improve the perception of low uptake figures and avoid a demotivating effect.