By 4 Months of Age

•  Does not make eye contact or makes little eye contact

•  Does not seem interested in other people
• Does not react by looking at people when they are makingsocial “sounds,” such as humming or clapping
•  Does not show as much interest in people as objects

• Does not have a social smile (does not smile back at someone who smiles at them)

• Does not show interest in watching people’s faces

By 12 Months of Age

•  Does not combine eye contact with smiling

•  Does not babble (or the babble doesn’t sound like “talking”)

•  Does not look at objects that another person is looking at

•  Does not try to engage other people in what he or she is looking at or doing
•  Does not engage in interactive gestures, such as giving,showing or reaching for parents
•  Does not respond when his or her name is called
•  Does not show a caring or concerned reaction to other people crying

• Does not use gestures, such as waving “hi” or “bye,” or use the index finger to point

By 24 Months of Age

• Does not look toward an object that is pointed to

• Does not point to share interests with others, such as pointing to an appealing toy

• Does not imitate common activities of others, such as sweeping the floor

• Does not learn simple, new interactive routines
• Does not develop pretend or make-believe play, such as feeding a doll
• Does not use single words by 16 months; does not spontaneously use meaningful two-word phrases (“go car” or “look doggie”) by 24 months

Other Early Signs

• Experiences a significant loss of language or social skills that he or she once had

• Echoes what others say (echolalia) without regular spontaneous speech

• Demonstrates speech that sounds mechanical, almost robotic 
•  Uses limited or atypical facial expressions

• Prefers to play alone or does not show interest in other children

• May not enjoy cuddling or being touched, unless it is on his or her own terms

• Displays repetitive body movements (hand flapping,spinning)

• Fixates upon a single object, such as a spoon or book

• Cannot tolerate change in routine or environment, such as a new toothbrush or a replacement for a lost toy

• Demonstrates difficulties with sensory regulation (light, texture, sound, taste, smell)

• Lines items up or puts things in order, repeatedly

• Has excessive tantrums and is difficult to console

• Walks on tiptoes

• Has delayed motor skills (late walking, riding a tricycle or learning to jump)