Yesterday I went to an interesting talk on Japanese mimetic words, which are onomatopoeia (擬声語 giseigo / 擬音語 giongo) or words connected to actions, emotions or states (擬態語 gitaigo). For example, くすくす (kusu kusu) – to giggle,ぐずぐず[する] (guzu guzu [suru]) – to procrastinate or dawdle.
Researchers in Japan have found that Japanese mothers use a much higher proportion of mimetic words with young children (60%) than with adults (10%), and their experiments found that children find mimetic verbs (those that use sound symbolism) easier to learn than non-mimetic verbs. They call this process mimetic bootstrapping. They also tested English-speaking children and adults using Japanese mimetic verbs and found that they were able to guess their meanings above the level of chance.
They also mentioned that mimetic words are not just found in Japanese – they are in fact found in the form similar to gitaigo in many of the worlds languages, though are rare in Indo-European languages.