Autism is a pervasive developmental disorder, a group of illnesses that involve delays in the development of basic skills, including the ability to socialize, use imagination, and communicate.  Children on the autism spectrum may have trouble bonding with parents and family members, and have problems understanding the world around them and may appear to be atypically self-absorbed.

There can be a lot of variability in the way that autism is expressed from one child to another.  Here's why:

1. No two children are alike, whether they have autism or not.  In the same way, each child with autism is an individual, with his or her own personality and unique characteristics.
2. Each child with autism displays a range of behaviors, some of which look like what we expect for his or her age and some of which are different, or unusual, compared to other children.  This behavior variability is exactly what makes autism hard to identify in young children.

Whatever the range, intensity, or frequency of symptoms, they will include atypical development in these three primary areas:  social skills, language and communication skills, and repetitive and restricted behaviors.  Although the symptoms in each area can vary from one child with autism to the next, we can take a look at what is typically found in these children.

Symptom 1:  Impaired Social Skills

Humans instinctively interact with each other.  Even in infancy, babies are interested in faces; they like close physical contact; they turn toward voices and smile with recognition at familiar family members.  As they grow, babies learn how to be social and interactive by watching how others talk, play and relate to each other.  They enjoy the give-and-take of social engagement and will initiate, maintain and respond to interactions with others.  In fact, they seek out these interactions.

Children with autism, however, often do not show the expected development of early social interaction skills.  They seem not to have the same "drive" to interact socially as their peers do.  In fact, impaired social interactions are the hallmark of autism and are present in all children with this diagnosis.

These social impairments affect children's interactions with adults as well as with other children.  They affect children's ability to initiate interactions with others as well as to respond to interactions that are initiated by others.  For example, unlike other children, children with autism may not:

    Pay attention to adults, even when they are close by
    Smile in response to praise or an adult's smile
    Respond when an adult calls their name
    Initiate social interactions with adults or peers
    Show enjoyment in interactive or turn-taking games 
    Imitate actions of adults
    Repeat actions that adults respond to with praise or attention
    Show interest in other children
    Join another child in play
    Play interactive, back-and-forth games with other children
    Show an interest in making friends
    Initiate the actions of other children
    Initiate play with other children, such as greeting them

As always, each of the symptoms of social impairment may vary in frequency and intensity from one child with autism to another, but social deficits are an important marker of the disorder.

Symptom 2:  Impaired Language and Communication Skills

Problems with language and communication can take many forms in children with autism.  To understand these symptoms better, you need to understand the difference between communication, language and speech:

    Communication is a process through which someone conveys a message to another
    person.  Communication can be verbal, which involves using words, or nonverbal, 
    which involves using other behaviors, such as crying, reaching, gesturing, or facial
    expressions.  In contrast, language refers to a system of communication in which
    conventional symbols are used to convey a message.  Examples of conventional
    symbols are sign language, gestures, and words.  Crying is not a symbol, nor is
    pulling on an adult's hand.  speech refers specifically to a form of language in 
    which spoken words are used to communicate.

The most commonly recognized characteristic of autism in the domain of language and communication is the delayed development of spoken language.  Nearly all children with autism are delayed in reaching their language milestones.  But the problems often go deeper than just language.  Many children with autism do not understand the process of communication at all, they don't seem to know that there is a way for them to convey their needs and desires to other people.  They don't know how to ask for help or ask for more or make a choice, other than by fussing or crying.

Similar to their impairments in the social domain, children with autism have difficulty initiating communication as well as responding to the communication of others.  Children with autism may not:

    Look at people in the eye during playful interactions
    Follow another person's point by looking in the direction indicated
    Express their needs or desires to others in conventional ways
    Use nonverbal gestures, such as waving good-bye or nodding
    Look at other people's faces to seek information
    Communicate for the purpose of sharing their interests or achievements with others
    Engage in back-and-forth babble "conversations"

Even children with autism who eventually develop spoken language still have impairments in this areas.  Like many children learning to speak, they may echo back words and phrases they hear.  But unlike other children, those with autism may mimic the exact intonation of the speaker and persist in this echoing long after other children have moved on to interactive speech, usually by three years of age.

Sometimes children with autism echo words or phrases they have just heard; this is called immediate echolalia.  An example is a child's answering the question, "Do you want to go outside?" with "Go outside".  Another type of echolalia occurs when children repeat things they have heard in another context (delayed echolalia).  Examples of delayed echolalia occur when children repeat dialogue from videotapes or things that they have heard their teacher say at school.  One of the most baffling things about autism is that some children can repeat long segments from favorite videotapes or books, but cannot use words functionally, to achieve their goals, such as by requesting a cookie or favorite snack.

Symptom 3:  Restricted Interested and Repetitive Activities

Some children with autism become preoccupied with a particular activity, toy, or interest in a way that is unusual in its intensity.  They may, for example, spend hours opening and closing the door on a toy car.  Or the may line up puzzle pieces over and over again - never actually putting them into the puzzle.

These children may also find comfort and security in repetition of certain routines, patterns, or rituals.  They may insist on following a certain pattern during dressing:  socks first, pants next, then shirt, and so on.  They may need to have the same plate and cup during mealtime.  Sometimes, if their set routing is changed, they will explode in a temper tantrum of frustration.

Young children with autism may also show unusual repetitive movements that seem to serve no particular function.  For example, some children may repeatedly flap their hands, flick their fingers, or spin around in a circle.  Much more rarely, they may show self-injurious behaviors such as banging their heads or biting their hands.

Some children with autism also demonstrate unusual sensory responses, which may vary widely from child to child.  For example, some children enjoy rubbing certain surfaces or are hypersensitive to the feel of new clothes.  Many children avoid foods that have certain textures.  Some children are very attentive to small details, such as a piece of thread on the floor, yet stumble over large objects in their paths.  Some children appear distressed when they hear certain sounds, such as a vacuum cleaner or hair dryer, yet do not respond when a parent calls their name.

Despite the variation in the types and extent of restricted interests and repetitive activities, some examples of behaviors that may be observed are:

    Engaging in repetitive play activities, such as lining up toys or spinning objects
    Acting out repetitive movements, such as running in circles or flicking their fingers
    Showing prolonged visual interest in objects, such as flapping objects in front of their    
        eyes or staring at mirrors or objects that spin
    Having overly focused interest in one object or activity, such as a fascination with     
        boats or bugs
    Demanding rigid adherence to rituals or routines
    Focusing attention on small parts of toys, such as the wheels on a toy truck, rather
        than the whole

Repetitive activities often go hand in hand with impaired play skills.  Around the age of eighteen months, most children will flex their imaginations by turning a banana into a telephone, a bowl into a hat, or a clothespin into a little man.  Because young children with autism often have very literal thinking patterns, they may not be able to see that a stick is anything more than a stick - not a sword, or totem pole, as other children may imagine.  They may not pretend that their teddy bear in injured and in need of a hug.

With respect to play skills, children with autism may not:

    Play with a variety of toys
    Use toys the way they're designed to be used
    Arrange toys in their intended scheme
    Show functional play with dolls, stuffed animals, or toy figures
    Create play sequences 
    Play with toys in a variety of ways

Early problems related to the development of social skills, language and communication skills, and restricted and repetitive interests and activities are the primary symptoms used to diagnose autism.