What unsustainable behavior needs to change:
Toilets are more and more equipped with a dual-flush option. While the design varies widely between different manufacturers, the principle remains the same. There is an option to flush with a full flush (generally supposed to flush faeces) and an option to flush with a partial flush (generally supposed to flush liquids). One of the designs often seen is that of a small and a big button next to each other. While many people have learned to understand that big button = big flush and small button = small flush, this does not hold true from a nudging point of view.
Considering that biologically speaking, the small flushing button should be used considerably more often than the big flushing button, the nudging principles of option composition (as identified by Mertens et al. 2022) and more specifically sizing (as identified by Wee et al. 2021) are not adhered to. This is to say that the big flushing button draws more attention than the small button at the generally short decision-making time when picking a flushing button. This consequently leads to excessive use of that big flushing button. Using a full flush with often twice the amount of water as a partial flush when it isn’t necessary is a wasteful use of freshwater and should be prevented as much as possible.
The Green Nudge:
To address this issue right at the moment of decision-making prior to flushing the toilet, Chiel Verstappen developed an interactive prototype known as „The Button Nudger.“
An unmissable message was presented to the toilet user just before flushing: the nudge text (see image) – based on the principle of conveying the norm (as per Byerly et al. 2018), was humoristic by design and had the added benefit of informing users who are not at all familiar with the dual-flush setup. In users who are familiar, it obviously acted as a gentle reminder to perform a certain action (in this case, consider the small flushing button if it would suffice) as is often the case in nudging. Next to a textual cue, an additional cue based on coloured lighting (centred around the influence of colour on mood/feeling) was given to aid the message.
The result: The pilot test showed that “The Button Nudger” did have an influence on flushing behaviour. Some toilets showed greater effect than others, with a maximum water reduction of 10.7% and an average water reduction of 6.17%. Taking the average water reduction, a yearly water reduction of 3,180 litres per toilet could be achieved at the University of Twente.
Are you aware of any other nudges that help to conserve water? Feel free to comment or get in touch: firstname.lastname@example.org