It's been well-described and well-observed in primates, but you also see it in rats, and wherever you find it -- humans, primates, rats -- you find it associated with things like tickling.
Taj je fenomen detaljno  opisan i uočen u primata, ali i u štakora. Gdje god na njega naišli - kod ljudi, primata, štakora - uvijek je povezan  sa stvarima poput škakljanja.