In many toilets there is a device that allows for a full flash and a partial flash in order to save water. The design is that the larger pedal or lever is for a full flash and the smaller lever or pedal is for a partial flash.
Although this may save a little on education as people would intuitively understand that big button is for more water and small button is for less water I think it is a usability disaster.
If I would design it I would make the big button (easiest to use, default use) the half flash and the harder to use smaller button on the side for a full flash. The aim is to make people press on the half flash more often than on the full flash. For that it has to be more accessible.
I think that in reality people press on the full flash button most of the time because it is easier.
To make people do something you need to make it easier and more accessible making it an automatic decision.
