I think the whole subject is very interesting, but the nature/nurture thing cannot definitively be proven one way or the other.
However I do think folk (generally) are very scathing about the amount that babies understand (in general).
I was always very talkative with my daughter, starting off by 'converstaions' where I'd chit chat to her babble, and leave pauses for 'replies'. She picked up words easily and tried to sound them till she could say them. I paid for a course in baby sign language (which was considered the 'new thing' about 18 years ago) however she was already speaking quite a few words by 9 months so rather than learn the sign she spoke the word! Shealso could speak in short sentences of her own (not repeated ones someone else said) by her 1st birthday eg 'airplane up there' when Concorde went over.
So of course I tried the same thing with my friend's 10 month old non-talker son, she said to offer him a biscuit so before going in the kitchen to get the jar I said to him (with no biscuits in sight) 'would you like a plain biscuit or would you prefer a chocolate one' Of course he tried his hardest to say 'cokolat' because he knew exactly what he wanted, friend was amazed that a) he understood, when there were no biscuits in sight and b) that he could actually say this (and we had to repeat a few times with more biscuits to prove it wasn't a one off, he also knew a plain biscuit he was given was 'not cokolat' and refused it).
When my daughter was tiny I always did 'right sock first and the left one is the one left till last', same with shoes, gloves, arms in sleeves etc. really just as something to say as we're dressing. Obviously by 2-3 she was dressing herself mostly so I dropped it, but was interested to note that at infant school they did a play at Christmas that involved marching soldiers who had to turn on the stage and the teacher said she was one of the only ones to relaiably know her left from right! Now did all that sock business teach her left and right? I think so, she rides and can memorise 2 or 3 dressage tests in a day (with circles and changes of pace as well as lefts and rights), and has no problem with directions when driving. Many of her friends still struggle.
I do so very much wish I had recited her 7 or 8 times table to a silly tune every time I did a nappy change, then she might be a maths genius! Anyone with a newborn up for trying this?
Incidentally I support a local charity www.abctoread.org.uk/ who help encourage non or poor readers from an early age, by going in to primary schools and giving additional reading support to those that need it. It has made a huge difference to many children locally.