Table 2.

Survey items, related constructs, TDF domains and COM-B categories

COM-B category	TDF domain	Construct	Survey item	Rationale
Psychological capability	Knowledge	n/a	n/a	n/a
	Memory, attention, decision processes	Memory [1]	• I’m likely to forget to take a reusable cup with me	Adapted from O’Brian et al. [30], Cane et al. [19] and Michie et al. [18]
	Behavioural regulation	n/a	n/a	n/a
Physical capability	Skills	n/a	n/a	n/a
Physical opportunity	Environmental context and resources	Resources/material [4]	• I don’t have enough space to carry a reusable cup around with me all day  • Cleaning a reusable cup is too inconvenient  • Reusable cups are too expensive to buy  • There aren’t enough facilities on campus to clean reusable cups	Adapted from Oliveira et al. [31] Cane et al. [19] and Michie et al. [18]
Social opportunity	Social influences	Descriptive norms [1]	• Most of my colleagues/friends don’t use a reusable cup	Adapted from Wakefield et al. [32] and Cialdini et al. [33]
Automatic motivation	Emotion	Affect [1]	• I feel guilty if I buy a drink in a single-use cup	Adapted from Wakefield et al. [32] and Russell et al. [34]
	Reinforcement	Reinforcement [1]	• I don’t like how my drink tastes in a reusable cup	Adapted from Skinner et al. [35] Wakefield et al. [32]
Reflective motivation	Social/professional role and identity	Role/identity [1]	• I feel good about myself when I use a reusable cup	Adapted from Cane et al. [19] and Wakefield et al. [32]
	Beliefs about capabilities	n/a	n/a	n/a
	Beliefs about consequences	Attitudes [4]	• I think reusable cups are good for the environment  • I think single-use cups are harmful for the environment  • Reusable cups don’t look as good as single use cups  • I don’t think reusable cups to be hygienic	Adapted from Wakefield et al. [32] Ajzen et al. [36]
	Optimism	Outcome expectancies [2]	• It makes no difference to the environment whether I use a reusable cup or not  • A reusable cup may leak in my bag	Adapted from Bandura et al. [37] and Wakefield et al. [32]
	Intention	Intention [1]	• ‘Would you like to own a reusable cup?’ [Definitely yes/Probably yes/Not sure/Probably not/Definitely not]	Adapted from Cane et al. [19] and Ajzen et al. [36]
	Goals	Priorities [1]	• I have too many other things to think about other than the type of cup I buy my hot drinks in	Adapted from West et al. [38] and Wakefield et al. [32]