That's most probably a very good point Berrme. Boys are generally slower to talk than girls, I don't think this slowness of language development in comparison reflects on their intelligence any more than girls having smaller sized brains makes them less intelligent than boys. The idea of intelligence can be such a subjective thing. Einstein for instance, didn't start talking until he was 3. I think most people would agree that him being slow of speech didn't make him slow of mind.

I think you make a good point Nai, motivation to communicate plays a big factor.