Cleaner fish and other wrasse match primates in their ability to delay gratification

Humans are outstanding in their ability to achieve mutual cooperation for direct benefits. One often-quoted factor driving our unique skills is delay gratification future benefits, which supposedly linked advanced cognitive abilities relative other species. The established experimental paradigm used test delayed primates and birds give subjects access a small food reward, can be exchanged larger (quantitative task) or better quality (qualitative reward after time delay. Here we this primarily the cleaner fish Labroides dimidiatus its gratification. specific ecology of cleaners makes them ideal candidates task: remove ectoparasites from visiting ‘client’ reef although they prefer eat client mucus. This eating against preference equivalent as clients that have removed (as opposed mucus) will both stay longer with return it later inspection. Cleaners performed very well quantitative task, i.e. similarly monkeys. In contrast, poorly if was higher quality. Using task wrasse species, found another species noncleaner also well, latter despite no evidence need such cooperate nature. However, only two showed making decisions early on about whether wait directly immediate reward. We conclude does not warrant require endotherm-specific brain morphology, underlying mechanisms vary between