My MA is in Applied Linguistics, but I wouldn't be able to shed much light on this, as it goes much deeper than simply 'size of language = more descriptive use of wordplay'. All I can say is there are many examples of cultures which have a smaller vocabulary and more basic grammatical system who still display a fondness for wordplay (ie; the Vietnamese are known for it, albeit with a more poetic nuance than humour-focused). Likewise, children are very imaginative with their use of language, despite not possessing that which adults do. With regards to humour, not all the cultures who share the same language will share the same humour, eg; Britain and America. I would imagine level of education, and also shared cultural reference play a big part.
