Estimating the impact of COVID-19 self-test availability and modifications in test-strategy on overall test uptake using an experimental vignette study.

To inform future Dutch COVID-19 testing policies we did an experimental vignette study to investigate whether inclusion of the less reliable lateral flow tests (self-tests) would change test-uptake sufficiently to improve population-level test sensitivity. A representative sample (n = 3,270) participated in a 2-by-2 online experiment to evaluate the effects of test-guidelines including self-testing advice (IV1), and the effects of self-test availability (IV2) on expected test uptake (PCR test, self-test or no test) and sensitivity of the overall test strategy (primary outcome). Across four scenarios, changing test advice did not affect expected testing behaviour. Self-test availability, however, increased the timeliness of testing, the number of people testing, and overall test strategy sensitivity. Based on these findings, we recommend that (national) policy facilitates a supply of self-tests at home, for example through free and pro-active distribution of test-kits during a pandemic. This could substantially enhance the chances of timely detecting and isolating patients.

An experimental investigation of breaking learnt habits with verbal implementation intentions.

The interplay between inflexible habits and flexible goal-directed control can be modelled in lab-settings using the slips-of-action task. In this task, participants are required to selectively respond to still-valuable outcomes while suppressing responding towards no-longer valuable outcomes, thereby overriding learned stimulus-response associations. Here we examined in the slips-of-action task whether learnt habits can be changed using a planning technique - so-called implementation intentions - whereby people instruct themselves to enact a certain behaviour (or not) in the presence of a specific critical stimulus. Such simple 'if-then' instructions have previously been shown to support behavioural change in real-life settings, possibly because people verbally create new stimulus-response associations. Across four experiments we manipulated the intrinsic value of the stimuli and outcomes in the slips-of-action task: abstract stimuli and outcomes (Experiment 1), snack food stimuli and outcomes (Experiment 2), or a combination of both types (Experiment 3-4). Implementation intentions improved the ability to suppress previously learnt responses towards no-longer-valuable abstract outcomes (Experiment 1 and 3). However, when snacks were used as outcomes (Experiment 2 and 4) no beneficial effect of implementation intentions versus goal intentions was observed. The slips-of-action task is thus sensitive to planning techniques under certain circumstances. Yet, the absence of effects when using snacks as outcomes implies the possible importance of its hedonic outcome value for implementation intentions' effectiveness, which warrants further investigation.