There's a pretty good chance your earliest memory isn't based on a real event, researchers say.
Nearly 40 percent of us claim to have memories from before the age of two, according to a new study, which scientists say just isn't possible.
What we're actually recalling is a constructed version of reality based on old photographs or things our parents told us which, over time, have turned into what we think are real memories.
"When people are told that their memories are false they often don't believe it," says Martin Conway, director of the Centre for Memory and Law at City University of London.
Prof Conway and his team surveyed 6641 people, and found 38.6 percent claim to have memories from before they turned two. More than 13 percent said they could remember events from before their first birthday.
"The systems that allow us to remember things are very complex, and it's not until we're five or six that we form adult-like memories due to the way that the brain develops and due to our maturing understanding of the world," says Prof Conway.
Current research suggests the first real memories we make are from around the age of three-and-a-half.
Middle-aged and older people are more likely to claim they can remember events from their infancy, which provides a clue as to what's going on.
"These fictional memories are based on remembered fragments of early experience - such as a pram, family relationships and feeling sad - and some facts or knowledge about their own infancy or childhood which may have been derived from photographs or family conversations," City University of London said in a release.
"As a result, what a rememberer has in mind when recalling these early memories is a mental representation consisting of remembered fragments of early experience and some facts or knowledge about their own childhood, instead of actual memories.
"Over time, such mental representations come to be recollectively experienced when they come to mind, and so for the individual they quite simply are 'memories' with content strongly tied to a particular time."
Previous research has found memories change over time because each time it's recalled, imperfections creep in. The more often your brain brings it out of storage, the more it changes.
"Your memory of an event can grow less precise even to the point of being totally false with each retrieval," researcher Donna Bridge of the Northwestern University Feinberg School of Medicine said in 2012, after releasing her findings.
"When you think back to an event that happened to you long ago - say your first day at school - you actually may be recalling information you retrieved about that event at some later time, not the original event."
Prof Conway says many early 'memories' are based around things common to most of us - prams, toys and mothers.
"This type of memory could have resulted from someone saying something like 'mother had a large green pram'. The person then imagines what it would have looked like. Over time these fragments then becomes a memory and often the person will start to add things in such as a string of toys along the top.
"Crucially, the person remembering them doesn't know this is fictional."
The latest research was published in journal Psychological Science on Tuesday.