Why do little girls like pink ?

Probably because of social pressure. In Britain and the USA, older girls like pink more than boys do, but they could already have been influenced by expectations. So studies have tested one- to two-year-old's by using the ‘preferential looking task’, which measures what the children like to look at the most. The studies found that preference for toys differ by sex, with boys looking longer at cars and girls at dolls, but preference for color do not. So perhaps it’s not surprising that back in 1918 the trade publication Earnshaw’s Infants’ Department wrote that babies’ clothes should be pink for a boy and blue for a girl.