I will both agree and disagree with talkingpeanut
...well, sorta disagree, but not really. You always, always, always want to let the kitten go at its own pace, but early socialization may make the kitten more confident about exploring its environment. THAT will make a difference. But ALWAYS at a pace that the kitten and mama cat set! And don't OVER handle young kittens, either.
I have always socialized kittens right after they are born, only holding them for a few seconds once a day at first, or just let them smell my fingers, longer as they got older, I let them develop at their own pace but it seems to be faster, (I could be wrong) like the kittens I have now are doing things a few days earlier that the kitten development sites say they should, like at 2 1/2 weeks they were up on all 4's trying to run.