Now, either we're all just becoming really grumpy as we get older, or it may mean that as you understand laughter better, and you are getting better at doing that, you need more than just hearing people laugh to want to laugh.
Ou perdemos o bom humor à medida que envelhecemos, ou isso significa que, como entendemos melhor o riso — e ficamos cada vez melhores nisso — para nos rirmos, precisamos mais do  que ouvir pessoas a rir.