What's interesting is how humans react to things like progress bars.

I remember designed Google Flights come back with results instantly by spending absurd amounts to pre-compute and cache results long before people requested them. Some of the other flight shopping websites had progress bars that suggested they were doing a deep search for the best possible deals. People trusted the slower website with progress bars more because it seemed like it had worked harder, even though the reality was that it was just slower and less thorough.