Kleefstra syndrome in humans is characterized by a general delay in development, intellectual disability and autistic features. The mouse model of this disease (Ehmt1^(±)) expresses anxiety, autistic-like traits, and aberrant social interactions with non-cagemates. To investigate how Ehmt1^(±) mice behave with unfamiliar conspecifics, we allowed adult, male animals to freely interact for 10 min in…