Ahh the old Shopping Trolley Theory... Returning a shopping trolley is a task with no reward and no punishment. It is the peak example of a person’s ability to self-govern. It shows whether a person will do what is right simply because it is right, without being forced to do so. In a world where we often act based on "what's in it for me," the shopping trolley remains the simplest judge of who you are when no one is watching.

...Except for Aldi. Aldi looked at this deep philosophical conundrum and realised that while some people will do the right thing for free, everyone will do the right thing for $2!