3. No joyful expression
By the age of 9 months, babies usually begin to show expression and illustrate their happiness with a smile and/or a laugh. Joyful expressions are meaningful interactions, and for most children with autism, social skills are affected. If your little one isn’t smiling or laughing by the age of 9 months, it’s not necessarily a cause for alarm, as development varies from person to person. However, if your child is not exhibiting joy by the age of 1, there may be a cause for concern.