The Westinghouse experiment is an important case study. Initially researchers believed that altering the level of illumination in an office building improved productivity. But later research showed that what matters is novelty - people temporarily react to novelty, but then the effect decays and they return to their previous level of engagement.

Supermarket trolley handles are almost certainly an example of this novelty effect and therefore trolley manufacturers would be very unwise to think about altering their design, especially as the proposed new design would impede concatenation of trolleys and thus defeat storage and movement en mass.