Of musical interest

My kids were playing "recording studio" today. They were taking turns making up songs and digitally recording them, in the hopes that mommy will help them make a CD ;-) Anyway, one of dd10's songs involved her singing a phrase, and little bro echoing her. It was interesting to note that he perfectly echoed what she sang, note for note and word for word, but where she used syncopated rhythm, he consistently sang it straight. Hmmmmm, I wonder what that means, LOL?