[1] It is typically demonstrated in a paradigm in which some participants in an experiment are randomly assigned to own a good ("owners") by receiving it for free.
Other participants are randomly assigned to simply evaluate the same good without receiving it.
It is not necessary to actually own a good to exhibit the mere ownership effect.
Simply touching[2] or imagining that one owns a good[3] is enough to instantiate the mere ownership effect.
[4] Two routes have been proposed to explain the mere ownership effect.