OH thats got quite a few studies referenced, I cant read all of them now.
There is certainly mention on stuff that I have read (will try and find so i can link) that cognitive development takes off between 3-4 months, ie, that a baby understands a difference in environment, or an action enough to react to it.
It does say that between 6-10 weeks it is vital to meet a babies needs in order that it mustnt feel neglected, which I knew already, not mentioning any names , so yes, that is important. Absolutely.
But all things being equal, weaning a baby is, a choice, whereas behaviours that you display to your baby isnt something you consciously choose to do. Breaking lifetime habits are far more difficult to do, because they are ingrained and we dont realise we are doing them (as displayed in your post regarding your son telling you to stop whining when you cried), rather than simply Just Not Weaning.
Failure to thrive is one of the most common reasons for infants being hospitalised, and allergies and bowel conditions are steadily increasing in the UK, so, from that point of view nutrition is paramount in my mind.
Im not dismissing the importance of emotional development at all, just saying that it is not somethign you'd be as reactive to as you would the sudden changes in nutritional development in early months as hinderences in emotional development are not really possible to detect at the time.
Am happy to read more if you have more links? This stuff fascinates me.