First author Dr Shazia Akhtar, from the University of Bradford, said: 'We suggest that what a rememberer has in mind when recalling fictional improbably early memories is an episodic-memory-like mental representation consisting of remembered fragments of early experience and some facts or knowledge about their own infancy/childhood.
We all know that memory isn't the most reliable of things and this study certainly gives weight to that - frankly, it's made us question our own "first memories".
But if that memory is from before the age of two, it's nearly certainly fictional, researchers said.
This means that they're not memories that got muddled in time because they mention prams, cribs or wanting to communicate before knowing how to talk. They were told the memory should not be linked to photos of themselves, a family story, or any other source apart from direct experience.
As the person continues to re-imagine this fictional first memory, it gets reinforced to the point where it's truth - at least to him - and he'll correct anyone who contradicts him.
Generally speaking, scientists believe that memories start to form at age 3 or 3 1/2.
Interestingly, the person remembering doesn't realize the memory is fake and the researchers found that when participants were told their first memory was false they didn't believe it, showing just how deeply ingrained mental representations of early events are.
This comes despite four in 10 (40 percent) people claiming to have clear memories from the first couple of years of their life.
However, the new study found that 38.6% of a survey of 6,641 people claimed to have memories from two or younger, with 893 people claiming memories from one or younger.
Additionally, details may be inferred or added later, Akhtar said.
Then the researchers examined the content, language, nature and details of these earliest memories and evaluated the likely reasons why people would claim to have memories from an age when memories can not be formed.
They said 30% were about family relationships such as "my parents were going on holiday" and a further 18% remembered "feeling sad".
Researchers found it was particularly prevalent among middle-aged people and older adults.
It is important to understand that the people are not even aware that his early memories - fiction. "This partly due to the fact that 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". The findings are published in Psychological Science.