Santino, an aggressive chimpanzee who collected and stored a stash(隠し場所、隠したもの)of stones and later hurled them at zoo visitors in fits(激発、一時的興奮)of rage, has confirmed that apes can plan ahead just like humans. The rock gathering took place before the zoo opened in the morning, while he was in a calm state. Only later, when visitors were nearby and the ape became extremely agitated, did he launch his attacks. This suggests that his behavior was not based on an immediate emotional drive and that he collected the rocks in anticipation of a future mental state. Prior to this study, there had been little evidence suggesting that animals are able to plan for future events.