Testing the decoy effect to increase interest in colorectal cancer screening

Abstract

Literature on consumer choice has demonstrated that the inclusion of an inferior alternative choice (decoy) can increase interest in a target product or action. In two online studies, we tested the impact of decoys on the probability of previous non-intenders to have a screening test which could significantly lower their chances of dying of colorectal cancer. We find that the presence of a decoy increased the probability to choose screening at the target hospital (over no screening) from 39% to 54% and 37% to 59% depending on how many hospital attributes were communicated and how strongly the decoy was dominated by the target. We also show that the presence of the decoy was associated with lower levels of reported decisional complexity while not undermining information seeking and knowledge acquisition. These findings offer a ‘proof of principle’ that decoys have the potential to increase screening uptake without negatively influencing informed choice.

Public preferences for using quantitative faecal immunochemical test versus colonoscopy as diagnostic test for colorectal cancer: evidence from an online survey

“…With regards to numeracy, it was important to note that only 55% of responders answered the numeracy question correctly; this was in line with a previous study using a comparable sample of UK adults in a similar age range, 28 which may have to do with specific characteristics of the sample population. However, it also demonstrates the need to review specifically the way that information about risk (often presented in numerical form) is communicated to the public.…”

Offering male endoscopists as decoy option to nudge disinclined women to have colorectal cancer screening

“…Furthermore, we followed their approach to present eligible participants with a short description of flexible sigmoidoscopy, which is offered in England at no cost to men and women aged 55, and then asked them to correctly identify where the scope is inserted (to ensure they had read and understood the description of the screening test). Participants were not able to continue with the survey unless they could correctly answer the comprehension question (Stoffel et al, 2018;von Wagner et al, 2019). Participants were then asked to indicate their intention to undergo flexible sigmoidoscopy screening using the question: 'Would you take up the offer if you were invited to have the bowel scope screening test?'…”

“…Only 309 women (27.7%) indicated that they would 'definitely not' (N=56) or 'probably not' (N=219) do the test and were therefore considered 'disinclined' and randomised to one of the two experimental conditions with equal probability. We chose to test the decoy among disinclined people to minimise ceiling and social desirability effects often associated with self-reported intention measures (Michie & Abraham, 2004) and to simulate a targeted intervention aimed at non-attenders who are in most need of an effective behavioural intervention (Stoffel et al, 2018;Stoffel et al, 2019;von Wagner et al, 2019).…”

“…To date, only a few studies have tested the decoy effect in the context of medical decision making, mainly because of ethical reasons (Rubaltelli et al, 2008;Schwartz & Chapman, 1999;Stoffel et al, 2019;Zenko et al, 2016). As the principle of employing the decoy effect is to guide people towards a target behaviour, researchers must be careful that the target is desirable for both society and the individual.…”

“…Medical treatments often bear benefits and potential harms which can be distressing for the individual. We are only aware of one study exploring whether the decoy effect could be applied to increase interest in CRC screening (Stoffel et al, 2019). The study showed that offering participants an inferior alternative screening appointment at a screening centre that was further away and/or required longer waiting times than the standard screening centre increased screening intentions for the standard appointment.…”