A racially diverse group of mates in your childhood years could help you tell people of other races apart as an adult.
New research suggests learning the ability to recognise individuals of other races cuts off at 12 years of age.
The Australian National University study released on Friday said prejudice didn't influence a person's ability to tell people of other races apart.
Researchers also found that even if a person developed a more racially diverse circle of friends later in life, they would still struggle to tell people of other races apart.
The study examined the "other-race effect", where people struggle to distinguish people of a race other than their own.
The paper said this could lead to poor social interactions, inaccurate eyewitness testimony, racial bias and inaccurate face-to-photo matching.
Researchers compared the inability to "learn" this later in life to how hard it was for people to learn another language as they got older.
Co-author and social psychologist Professor Kate Reynolds said researchers asked adults to note how many people of other races they knew as kids and now, before asking them to recall different faces.
She said Australia's migration history meant researchers could find people ranging from those who were exposed to people of other races when they were young, to people with almost no exposure.
"There was something quite unique about the Australian circumstance," Prof Reynolds said.
Adults who struggled with the "other-race effect" could learn to tell people of other races apart more easily, but it would be hard, Prof Reynolds said.
"They can be trained, but it's kind of like picking up a second language," Prof Reynolds said.
An adult might never become "fluent" in distinguishing between people of other races, she said.
She said parents who didn't want their children to have the "other-race effect" should expose them to ethnically diverse classrooms and the earlier they do that, the better.
She said it was possibly a link between learning another language and being able to tell people of other races apart, with a similar cut-off age for both.
Australian Associated Press