In comparison, the happy banana signage increased hourly sales of single bananas from 2.02 to 2.13 (5.4%), making the sad banana signage almost 50% more effective than the happy banana signage.

Sad banana signs above single bananas encouraged shoppers to buy the left-behind fruit and cut food waste, in a study by the University of Bath, RWTH Aachen University and Goethe University ...

On average, the number of single bananas sold per hour increased from 2.02 when the emotionless banana sign was displayed to 3.19 with the sad banana sign – an increase of 58%.

We made three signs to display above the single banana crates. One showed a "sad" banana with a down turned mouth and the message: "We are sad singles and want to be bought as well".