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History
Tit for tat
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Tit for tat is an English saying meaning "equivalent retaliation". It developed from "tip for tap", first recorded in 1558.
In Western business cultures, a handshake when meeting someone is a signal of initial cooperation.
In Western business cultures, a handshake when meeting someone is a signal of initial cooperation.
Reciprocal altruism
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In evolutionary biology, reciprocal altruism is a behaviour whereby an organism acts in a manner that temporarily reduces its fitness while increasing another organism's fitness, with the expectation that the other organism will act in a similar manner at a later time.
Cleaning symbiosis: a small cleaner wrasse (Labroides dimidiatus) with advertising coloration services a big eye squirrelfish (Priacanthus hamrur) in
Cleaning symbiosis: a small cleaner wrasse (Labroides dimidiatus) with advertising coloration services a big eye squirrelfish (Priacanthus hamrur) in an apparent example of reciprocal altruism.
Eurasian jay, Garrulus glandarius, gives loud alarm calls from its tree perch when it sees a predator.
Eurasian jay, Garrulus glandarius, gives loud alarm calls from its tree perch when it sees a predator.
Arctic terns protect their offspring extremely aggressively by very quick drop-downs from a stationary flight over their enemies. Other birds often be
Arctic terns protect their offspring extremely aggressively by very quick drop-downs from a stationary flight over their enemies. Other birds often benefit from this behavior by breeding very close to the Arctic terns.