Bags I loved the look of intense concentration on their wee faces - a look I remember well from my own two and latterly the DGC. I am sure tiny babies know far more than we give them credit for. When you look into their big eyes you can see the intelligence there, when you talk to them seriously you can see them absorbing and processing the information. If you play 'peek-a-boo' they will soon grasp the essentials - look puzzled when Granny disappears, smile when she pops up again. As soon as they can manipulate a blanket they become active participants in the game.
When my DDs returned after 3,4,5, years at college and University they had changed a bit and were certainly knowledgeable about their chosen subjects, but this change was as nothing when compared to the progress they made over the first 3,4,5 years of their life, especially when you remember that half of the time they were asleep (no doubt busy processing information received!). From a blank page at birth, within 5 years most will have mastered walking, talking, swimming, eating, basic counting, drawing, reading and writing, will understand night and day, holidays, TVs, computers, light switches, cooking, recognise people - I could go on and on but it is astonishing. If only one or two children could do these things we would count them as super geniuses, because most children can manage so much so soon, we take it for granted.
Sorry to disagree JO5 but have you never watched a, say, five month old with a BOX - they will do everything in their power to open it. Only thing that stops them before that is lack of motor skills. We keep a toy box at our house and DGS & DGD1 could open it by themselves by the time they were one. DGD2 had a different method - she would bang loudly on the lid until an exasperated GP opened it for her - but all 3 clearly understood the concept of a box and that exciting things might be contained therein.