Effort Justification
Effort justification is the finding that we value what cost us something, and revise our judgement of the thing upward to justify what we paid. Elliot Aronson and Judson Mills demonstrated it in 1959 and explained it through cognitive dissonance: having gone through an unpleasant initiation, the only comfortable conclusion left is that the group was worth it. The record since is genuinely split. A conceptual replication using electric shock succeeded; a later attempt did not. The studies pre-date preregistration and this publication grades the concept accordingly.
What it is
Aronson and Mills recruited women for a discussion group and required them, before admission, to pass a screening of varying unpleasantness. Some faced a severe embarrassment, some a mild one, some none. They then listened to the same deliberately dull discussion and rated it. The women who had paid the highest entry price liked it most.
The explanation is dissonance. Two thoughts sit badly together: I went through that, and this is tedious. One of them can be revised at no cost, and it is not the memory of the ordeal. So the group improves in retrospect.
What makes the effect interesting is that nothing about the group changed. The manipulation was entirely on the entry side, and the revision happened on the valuation side.