By age 3, typical children have passed predictable language learning milestones; one of the earliest is babbling. By the first birthday, a typical toddler says words, turns when he or she hears his or her name, points when he or she wants a toy, and when offered something distasteful, makes it clear that the answer is "no." Speech development in people with autism takes different paths. Some remain mute throughout their lives while being fully literate and able to communicate in other ways—images, sign language, and typing are far more natural to them. Some infants who later show signs of autism coo and babble during the first few months of life, but stop soon afterwards. Others may be delayed, developing language as late as the teenage years. Still, inability to speak does not mean that people with autism are unintelligent or unaware. Once given appropriate accommodations, many will happily converse for hours, and can often be found in online chat rooms, discussion boards or web sites and even using communication devices at autism-community social events such as Autreat.
Those who do speak often use language in unusual ways, retaining features of earlier stages of language development for long periods or throughout their lives. Some speak only single words, while others repeat the same phrase over and over. Some repeat what they hear, a condition called echolalia. Sing-song repetitions in particular are a calming, joyous activity that many autistic adults engage in. Many people with autism have a strong tonal sense, and can often understand spoken language. Some children may exhibit only slight delays in language, or even seem to have precocious language and unusually large vocabularies, but have great difficulty in sustaining typical conversations. The "give and take" of non-autistic conversation is hard for them, although they often carry on a monologue on a favorite subject, giving no one else an opportunity to comment. When given the chance to converse with other autistic's, they comfortably do so in "parallel monologue"—taking turns expressing views and information. Just as "neurotypicals" (people without autism) have trouble understanding autistic body languages, vocal tones, or phraseology, people with autism similarly have trouble with such things in people without autism. In particular, autistic language abilities tend to be highly literal; people without autism often inappropriately attribute hidden meaning to what people with autism say or expect the person with autism to sense such unstated meaning in their own words.
The body language of people with autism can be difficult for other people to understand. Facial expressions, movements, and gestures may be easily understood by some other people with autism, but do not match those used by other people. Also, their tone of voice has a much more subtle inflection in reflecting their feelings, and the auditory system of a person without autism often cannot sense the fluctuations. What seems to non-autistic people like a high-pitched, sing-song, or flat, robot-like voice is common in autistic children. Some autistic children with relatively good language skills speak like little adults, rather than communicating at their current age level, which is one of the things that can lead to problems.
Since non-autistic people are often unfamiliar with the autistic body language, and since autistic natural language may not tend towards speech, autistic people often struggle to let other people know what they need. As anybody might do in such a situation, they may scream in frustration or resort to grabbing what they want. While waiting for non-autistic people to learn to communicate with them, people with autism do whatever they can to get through to them. Communication difficulties may contribute to autistic people becoming socially anxious or depressed.