You Have a Friend Who Has a 12-Month-Old Son and You

You have a friend who has a 12-month-old son and you have an 18-month-old son. You have been getting together each week for a couple of months for them to socialise and so that you can talk. Your friend is concerned that his son is not very advanced because your son systematically and deliberately separates his various toys into categories while he plays and his son is oblivious to any categories. What would you tell your friend?

A) That his son should probably start going to a high-quality day care
B) That his son will most likely also categorise when he is 18 months old
C) That your son is very advanced since children generally do not categorise until they are at least 24 months old
D) That infants are very different in their development