placebo effect

The placebo effect is when some form of intervention has an effect even when the intervention doesn't actually do anything in itself, but the user thinks it does. The term comes from medicine, when patients given a placebo, a pill that looks like the real drug but is inactive, still respond as if they had been treated. This is clearly connected with the belief of the patient receving the treatment, but weirdly still persists weakly even when the person knows thay have taken a placebo. Similar effects are seen in experiments with digital technology, for example, if people are told a system is 'intelligent', they may be more likely to accept its suggestions, compared with if they are told it is a simple algorithm.

There is a similar nocebo effect when people believe that the true intervention is likely to have negative consequences; in the medical domain experiencing side effects even if given a neutral treatment.