I would disagree, since society measure's one's knowledge or level of smartness on such things as can a baby eat, roll, or babble, I think that these small (to us adults) physical abilities do show a great deal of intellect and knowledge on a babies part. If at all, it shows that the baby has learned to adapt itself to the world to survive and to me that's a pretty significant achievement.
Otherwise, what are all the homes for mentally or physically ill people for. Although, these people can be very smart inside, they lack the skills to feed, dress, or even take care of themselves sometimes and yet we as a society consider them to be not as "knowledgeable" or "smart" as the rest of us. Thus we are basing someone's knowledge on their physical abilities.

As far as Locke goes, I think that someone's personality does play a role in his philosophies, because he's a believer in sense experiences and it's these sense experiences that teach children how to respond and act in certain situations, thus giving them a personality. For example, if a child's hit each time he cries, he's prone to be a timid and angry child in personality because he's learned through his senses that abuse comes with crying.

Just my thoughts, but good question to bring up!