optimistically unchoke상대의 이전 행동이 협조적이었으면 협조하고, 비협조적이었으면 협조하지 않음으로써 보복하는 전략 Tit for tatTit for tat is an English saying meaning "equivalent retaliation". It developed from "tip for tap", first recorded in 1558.https://en.wikipedia.org/wiki/Tit_for_tat