Liking bias

Biological Parallel

Vampire bats preferentially share regurgitated blood with roostmates who have groomed them in the past—reciprocal altruism contingent on positive social bonds. Gerald Wilkinson's research showed bats track social debts and withhold aid from non-groomers, demonstrating that liking (grooming investment) directly gates resource allocation. Liking bias evolved as reciprocity enforcement: organisms that allocated resources based on social bonds rather than need ensured cooperation, creating selection pressure for affiliation to influence judgment.