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Autism Brief – Early Indicators of Autism (Red Flags for ASD) in Infants and Toddlers

Maryann Trott MA, BCBA

Autism and Other Developmental Disabilities Division

Download a printable version of this post here.

One of the questions most often asked of the individuals that work in the Autism programs is “How early can you tell if a child has autism?” followed by “What are the signs?”

According to Dr. Lauren Elder who is the assistant director of dissemination science at Autism Speaks, it is a complicated question because of the variation in the way that children develop and the signs of autism are manifested. That said, some of the early behavioral signs may begin to emerge as early as 6 to 12 months. Most professionals who specialize in the diagnosis of autism, however, hesitate to make a definite diagnosis until 18 months. Sometimes, the signs of autism appear to emerge or fade away until about 24 months. Some children may appear to develop in a typical way until about 18 months and then lose skills or regress. Other 18 month old babies may seem be behind developmentally but then “catch up” by the time they are 24 months old. For some infants, behavioral signs may be quite apparent close to the first birthday. In these cases, an experienced professional may make a diagnosis so that the infant will begin to receive early intervention services as soon as possible. One more thing to consider is that some children with autism are not diagnosed until they enter school and begin to struggle with social demands.

Early diagnosis of autism is essential as early intervention can change the way the brain develops. For further information about early screen and diagnosis, see the CDD information brief “The Importance of Early Screening for Autism Spectrum Disorder”.

What are the early signs of autism in babies and toddlers?

Recognizing that every infant is different from every other infant and that some of the “signs” of autism may be present in infants who may have other disabilities or even in infants who may turn out not to have any disability, there are some signs that warrant a discussion with a pediatrician and a possible closer look at the infant’s overall development.

In the area of language development:

  • Diminished babbling (especially back and forth babbling that looks like the baby is “talking” to another person).
  • No single words by 16 months
  • Odd first words
  • No two word phrases by 24 months
  • Limited response to name by 12 month
  • Repeat words or phrases over and over (echolalia)
  • Abnormal tone of voice (flat, robotic or sing-song)

In the area of nonverbal communication:

  • May avoid eye contact or look at people/things in unusual ways
  • Little or no joint attention (baby and an-other person are both interested in the same item or event and both understand that the other is interested). It is not joint attention if the purpose is to get some-thing (non– social) Joint attention emerges about 9 months and should be well established by 18 months
  • Less positive affect or joyful expressions (flat or inappropriate expression)
  • Limited or absent social smile
  • Infrequent use of gestures such as pointing by about 14 months

In the area of social development:

  • Limited shared enjoyment including showing something to another person or engaging in back and forth activities such as waving, reaching by 12 months
  • May prefer to play alone
  • May resist or avoid physical contact
  • Only interacts to get something s/he wants

In the area of play

  • May be repetitive such as lining things up or spinning things
  • May not be interested in functional play (making cars go vroom; pounding with a toy hammer, eating toy food)
  • Odd play such as spinning the wheels on a car rather than making the car go
  • Plays with toys the same way over and over (and may become upset if others at-tempt to join in)
  • “Obsessive” interests
  • May be more interested in parts of objects
  • Does not pretend

In the area of body use & sensory differences:

  • Repetitive movements such as hand or finger posturing, flapping, spinning
  • Seeks out or avoids certain textures, sounds or movements
  • Visual differences (fixating on objects or certain kinds of stimuli such as the light coming through blinds, looking at things in odd ways or tracking such things as fan blades, etc. )
  • Unusual reactions to food tastes or textures
  • Unusual response to smells or sounds


  • Has to follow certain routines
  • Gets excessively upset by minor changes on a regular basis
  • Very difficult to comfort
  • May dislike physical contact

Please remember that none of these concerns by themselves, or even several taken together, indicate that a child has an Autism Spectrum Disorder. Also, many of these indicators may be present in children who have other developmental concerns. This is not to say “wait and see.” If in doubt or if you are wondering about a baby’s development, do not delay. Ask for an appointment with a pediatrician or developmental specialist as soon as possible.

  1. Get Regular Well-Child Check-ups: It is important for a child to get regular check-ups with a primary care doctor to monitor development . Be sure to bring up any concerns about a child’s progress, and don’t hesitate to ask questions.
  2. Know what to look for: Know the developmental milestones for each stage of a child’s development and talk to the doctor if the child is not reaching those milestones. Learn the early signs or “red flags” for ASD in young children and request an evaluation if there are concerns.
  3. Don’t take the “wait and see” approach: There is no time for the “wait and see” approach when there are concerns about a child’s development, and there is no harm done in screening or seeking a referral. Remember, early identification leads to early intervention. The age that intervention begins does matter!


  1. Autism Video Glossary
  2. Early Childhood Evaluation Program (ECEP): Age 0-3 years Center for Development and Disability, University of New Mexico, E-mail: (505) 272-9846 or Toll Free at 1-800-337-6076
  3. Centers for Disease Control and Prevention: Learn the Signs & Act Early
  4. Steiner, A.M., Goldsmith, T.R., Snow, A.V., & Chawarska, K. (2012). Practitioners guide to assessment of autism spectrum disorders in infants and toddlers. Journal of Autism and Developmental Disorders, 42:1183-1196.

About the Author:

Maryann Trott MA, is a Special Educator and BCBA who manages several projects for the Autism Programs at the University of New Mexico, Center for Development and Disability, Autism Programs.

A University Center for Excellence in Developmental Disabilities Education, Research and Service
Publication 15-12

Supported in part by the NM DOH|DDSD, the NM DOH|FIT & the NM PED