Behaviour Change Techniques (BCTs) are strategies used in the field of psychology that help an individual change their behaviour; in this case to promote sustainable grocery shopping. An example of a Behaviour Change Technique is: a pop-up window with motivational messages at the beginning of each shop.
This section explains in detail how Envirofy was developed using both behaviour change theory (Behaviour Change Wheel, BCW)  and multidisciplinary evidence to support consumers in shopping sustainably.
The first steps of the BCW focus on understanding the problem; in this case environmentally damaging food consumption. Stating the problem in behavioural terms helps to define the target of the intervention . This involves considering first all relevant behaviours by relevant groups (step 1); selecting from these to identify a single target behaviour (step 2); and specifying that behaviour as thoroughly and precisely as possible, using pre-specified prompts provided by the BCW (step 3). The final behaviour is specified in Table 1.
|Who needs to perform the behaviour?||Individuals who purchase food from supermarkets online.|
|What do they need to do differently?||Select and purchase the most sustainable option from a range of available food products.|
|When do they need to do it?||When they are choosing food items, at the point-of-purchase.|
|Where do they need to do it?||On supermarket websites, using their device, in locations with internet access.|
|How often do they need to do it?||Every time they visit the online supermarket website.|
|With whom do they need to do it?||Alone or with members of the same household.|
A core step of the BCW is to identify barriers that are currently stopping individuals from doing the specified behaviour. This helps to understand what problems the intervention should solve and how it should work. A narrative literature review was conducted to identify various barriers to purchasing environmentally friendly foods. APEASE criteria  were then systematically applied to each barrier to judge whether it was likely to be Affordable; Practical; Effective/cost-effective; Acceptable to users; and Equitable, to target within an online shopping environment. The resulting barriers targeted by Envirofy are reported in Table 2, column 1. The BCW provides multiple theoretical tools to interpret and synthesise barriers: (i) COM-B was used to first understand whether, broadly, barriers related to individuals’ “Capability”, “Opportunity”, and/or “Motivation” to engage in a Behaviour (eco-friendly food shopping) (Table 2, column 2) (ii) The Theoretical Domains Framework (TDF)  was then used to describe these barriers in more theoretical detail (Table 2, column 3). In summary, Envirofy targets barriers relating to individual shoppers': knowledge and skills in choosing environmentally friendly foods (i.e. psychological capability); exposure to environmentally friendly foods and opportunity to access these (i.e. physical opportunity); and beliefs relating to "perceived consumer effectiveness" i.e. whether their choices will make an environmental impact (i.e. "reflective motivation").
|Barriers identified in literature||Broad COM-B category||Detailed theoretical description (TDF)|
|Limited awareness of the association between food choices and environment . Limited factual knowledge about impact of specific food types . Limited skills and understanding of eco labels [5,6].||Capability (psychological)||Behavioural regulation (i.e. monitoring food choices in relation to their environmental impact)\newline Knowledge (i.e. of the environmental impact of food groups and individual products)\newline Cognitive and interpersonal skills (I.e. in understanding and using environmental information)|
|Perceived lack of time [7, 8, 9, 10, 11] to use environmental information and limited availability of eco-friendly foods [12, 13, 14].||Opportunity (physical)||Environmental Context and Resources|
|Belief that actions will not have an impact (Perceived Consumer Effectiveness, PCE) [4, 7, 15].||Motivation (reflective)||Beliefs about consequences; Beliefs about capabilities|
The BCW provides theoretical links between the barriers identified, and the kinds of interventions that are likely to be effective in addressing them. Following this process, Envirofy was designed to target the barriers identified (see step 4) through Education (to improve knowledge on the environmental impact of food choices), Training (to improve skills in selecting products according to environmental labels), Environmental Re-structuring (to improve exposure to and accessibility of environmentally friendly products), and Persuasion (to target beliefs on perceived consumer effectiveness). The delivery mode (i.e. "digital") and policy ("service provision") were decided in advance. To decide which specific behaviour change techniques (``BCTs'') to embed in this digital tool we again applied APEASE criteria and consulted the multidisciplinary evidence base, including HCI literature, on ways these had been operationalised. The final BCTs and related evidence are reported for each component in Envirofy your Shop: Development of a Real-time Tool to Support Eco-friendly Food Purchases Online
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