That's one of those it depends which study you read questions I'm afraid. It's hard to get a definitive answer because you cant really just go ask a baby. Some studies suggest that a baby can recognize it's mother from birth, within a few hours a baby can see about 18cm in front of him and can recognize it's mother both by appearance and the smell of the breast milk. This is part of the reason why so much emphasis is put on breast feeding, it's part of the bonding process with the baby. After about 8 months the baby can recognize you from a distance. With regard to other people, Grandparents, family friends etc exposure is the key element here. If you see the baby a few times a month it can take several months for a baby to start to fully recognize you but if you see the baby on a daily basis this will happen much quicker, especially if you spend time holding the baby, feeding it etc. Studies have shown that young babies have a very short memory 1 or 2 days, maybe slightly more depending on who you believe and this will gradually increase to about 2 weeks by the time they are 5 months old. This can often leave people who do not see the baby very often (aunts, cousins etc) with the feeling that the baby does not like them or has not bonded with them, when in fact, the baby simply doesn't necessarily remember them. Another good example of how, as adults, we tend to attach quite complex adult thoughts and feelings to babies. Its not about like or not like babies just don't have the faculties to remember you for that long. Their hippocampus, the part of the brain that does this just isn't mature enough yet.
