The study looked at the abilities of 14,000 children, and found a big gap in academic ability between richer and poorer youngsters.
By the age of five, children with wealthier, degree educated parents have, on average, a vocabulary 18 months ahead of their poorer peers. They are also 13 months ahead when it comes to problem-solving skills, with the biggest gap between the ages of three and five years.
The study, Growing up in Scotland, also found children whose parents are educated to a lower level perform poorly and are less likely to catch up with their rich classmates before or after starting school.
Angela Constance, the Scottish Children's Minister, said the research was welcomed as it could help improve children's life chances:
'This research will play a crucial role in informing what we need to do to improve the life chances for all of Scotland's children.
'A child's chances in life begin to be shaped before they are even born. Our priority is to create a fairer start for all.'