From a report at the link below:
Two fifths of people have a fictional first memory based on fragments of early experiences, psychologists have found.
Scientists questioned participants in a survey that identified more than 2,000 individuals claiming to have memories from the age of two or younger.
Current research suggests that memories cannot be formed before about three-and-a-half years.
Yet 893 of those taking part in the survey said they had memories extending to before their first birthday.
Full report here.