Teachers are six times more likely to identify boys as having autism spectrum disorder (ASD) than girls, with parents twice as likely to make the same assessment.
But a study by University College London found autistic traits were more common in girls than previously thought, News.com.au reported.
Researchers used a series of tests to analyse emotional reactions in more than 3500 participants in the Children of the 90s study at the University of Bristol.
In the tests, participants were asked to identify emotions of people as happy, sad, angry or scared.
They were then asked to attribute one of the same four emotions to an animated triangle and circle moving around a screen.
Boys and girls previously identified as having attributes of autism were more likely to make mistakes when identifying sad and scared faces and wrongly identify faces as happy.
When the genders were contrasted, girls with autistic traits were found to be better at recognising emotions in the photographs, but fared less well with the triangle and circle cartoons.
This suggests girls may be better at masking the signs of autism in social situations, but are less able to do so in unfamiliar settings, the study reports.
Lead author of the study Dr Radha Kothari said that the findings have important implications for current assessment of clinical ASD in girls.
The study is published in the Journal of the American Academy of Child and Adolescent Psychiatry.