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What Are the Earliest Signs of Autism?

Signs of autism in infants and toddlers can be easy to miss — unless you know what you’re looking for

Writer: Molly Hagan

Clinical Expert: Cynthia Martin, PsyD

Autism is a developmental disorder that impacts how a child learns to communicate and interact with the world. According to recent data, the average age for diagnosis of autism spectrum disorder (ASD) is about 5 or 6, even though it can be diagnosed in children as young as 12 months. That might sound quite young, but autism is an early-onset disorder that is lifelong. An early diagnosis allows kids to get the support they need during the critical period of development that occurs before a child turns 5.

Dr. Cynthia Martin, a psychologist and the senior director of the Autism Center at the Child Mind Institute says that there can be signs of autism in babies as young as six months old. “That’s not going to be the case for all kids,” she says. “But in general, for the majority of kids, symptoms associated with ASD are going to be present somewhere between six months and three years.” 

But those signs of autism in infants and toddlers can be easy to miss — unless you know what you’re looking for. 

At any age, symptoms of autism are grouped into two main categories: social-communication challenges and restrictive, repetitive behaviors (RRBs). Even in very young children, Dr. Martin says, we can see the absence of typical social-communication skills and the presence of atypical behaviors, or RRBs. Autism shares a number of traits with other disorders, which is why it is frequently misdiagnosed, or diagnosed late. But children with ASD display traits from both categories — like Charlie, who received an autism diagnosis just after he turned three.  

Social-Communication Challenges 

When Charlie’s mom, Jamé, brought him in for his two-year check-up, his pediatrician said Charlie had a speech delay and recommended speech therapy. 

“I was a little surprised, but it wasn’t a bad surprise,” Jamé says. “At that point, he wasn’t quite pointing and gesturing, or even making sounds and intonations. But it wasn’t something that as parents we worried about, really. I guess because neither of us have had kids before.” 

Jamé and her partner may be first-time parents, but they weren’t alone in how they thought about their child’s development. “So often parents don’t know about social communication milestones,” Dr. Martin says. These milestones are subtle, but the skills they demonstrate are the building blocks of communication and language.  

Children with autism develop these prelinguistic, social communication skills at a delayed and inconsistent rate compared to their typically developing peers.  

For instance, infants with ASD may struggle to distinguish the faces of their caregivers from strangers or avoid eye contact — two of the earliest indicators of a social communication deficit. But a wealth of research suggests that a limited use of gesture, as one study put it, is one of the most “robust” signs of autism in infants and very young children.  

Gestures are closely tied to the development of speech and language. Before learning to speak, children typically learn to communicate using gestures to express their thoughts and desires.  

“We should see about 16 gestures or ways of communicating non-verbally to another person by 16 months,” Dr. Martin says. 

Communication autism symptoms in babies and toddlers

So, what are some things parents should be looking for? 

  • Pointing: Babies with autism tend to point less than typically developing children — either with an open palm or an index finger, a slightly more advanced skill. One reason a child points at an object is to say, “I want that.” This is called imperative pointing. Instead of pointing, some children with ASD will use an adult’s hand as a tool to communicate to what they want; this is called hand-leading.  
  • Showing and Giving: Another reason a child points to an object is to say, “Look at that.” This is called declarative pointing, and it facilitates a very important skill called joint attention. Look at that dog! look at the airplane in the sky! When a child initiates joint attention, they are beginning to understand that communication is an act of sharing. Children with autism can be very interested in objects, but don’t tend to show objects to others. Along the same lines, they might less frequently give objects to others. 
  • Gesture + Speech Combinations: Toddlers who have acquired some language skills might begin using word-gesture combinations, like saying the word “more” and pointing to a cup of juice. This is called supplemental gesture, and it is a particularly challenging skill for kids with ASD. 

Repetitive and restrictive behaviors 

RRBs are patterns of behavior that occur in greater frequency among autistic people than the general population. RRBs can include hand flapping, spinning, or holding a particular body posture. They can also include the idiosyncratic way a child plays with their toys, a fixation on one particular interest, and sensory processing issues

In children with autism, RRBs are intense and narrowly focused behaviors that shape the way they interact with the world. As Dr. Martin puts it, “What is the child missing out on because they are focusing on something more intensely than those around them, rather than what the others in the environment are focusing on?” 

Jamé knew that Charlie liked to stack and arrange his toys, and that he liked the squishy feeling of potting soil in his hands. But when he entered preschool, his patterns of behavior became more pronounced, making it difficult for him to adjust. “His teachers were like, ‘He will not wear his shoes,’” Jamé recalled. “If they had circle time, he would kind of be walking around the room doing something else.” Charlie also struggled to transition from one activity to the next — a common challenge for kids with autism triggered by various factors, including RRBs.

For some kids, RRBs present at the same time as social communication deficits. For other kids there’s a pretty big lag, which for a younger child means six to 12 months later,” Dr. Martin says.  

“The challenge is that some repetitive behaviors are very common in young kids because their nervous systems are still developing,” she adds. “They can get what’s called motor overflow, where there is some excitement, and you see some brief posturing or some hand flapping.” 

But for young children with ASD, repetitive behaviors persist and present as a pattern.

Behavioral autism symptoms in babies and toddlers

Some of these patterns can emerge as early as a child’s first year.  

  • Unusual interaction with objects: Very young children with autism might show more interest in objects than people or display what is called a “non-functional use of objects” — for example, holding a toy in their hand instead of playing with it. Another sign, says Dr. Martin, is when a child examines an object in an unusual way. “Maybe they’re bringing things up really closely to their eyes or looking at them from the side of their eyes,” she says.  
  • Intense Interests: Some toddlers with autism begin to develop unusually intense and specific interests. Perhaps they fixate numbers, letters, shapes, or water. “But the way they show they are interested in water is not just wanting to play at the splash pad, they also want to see the water in the toilet bowl flush,” Dr. Martin explains. “Or they want to see the water in the washing machine, or when they hear the water faucet go on in the bathroom or the kitchen, they go running towards it.” 
  • Strong responses to sensory stimuli: Some RRBs are in response to sensory stimuli. Charlie doesn’t like to wear shoes, Jamé theorizes, because shoes make it harder for him to run and climb. “He’s pretty much moving from the moment he gets up until he takes a nap,” Jamé says. Charlie’s compulsion to move is a sensory-seeking behavior, as is his love for squishing potting soil in his hands. But other children with autism, even those that seek sensory stimuli, also exhibit sensory-avoidant behaviors. They might cover their ears, avoid certain foods or have an aversion to certain textures or tags in clothing. 

Jamé had some reservations about pursuing an autism diagnosis for Charlie at such a young age. His needs and behaviors, while unusual to others, seemed only human. But the early intervention and diagnosis has given Charlie access to a needed network of support. “He’s a little kid, but he’s a super clever kid and I am super proud of him,” Jamé says. “I just want him to get whatever he needs to help him be more independent when I’m not with him.” 

This article was last reviewed or updated on January 3, 2024.