(1) Autistic children usually show symptoms within 30-36 months. Early symptoms often appear during the infant stage and they become apparent during 12-30 months. This usually show up as regression in language skills and gradual loss of vocabularies acquired at the earlier stage. This is also accompanied by typical autistic symptoms. Under normal circumstances, parents usually will have a very hard time to discern whether the child is autistic because parents are not paying enough attention to the infant and lack the knowledge related to infant psychological and behavioral development process.

(2) Clinical symptoms of autism are lack of social interactions, interest in language and games, repeat monotonic actions and obsessive-compulsively maintain the same living environment and lifestyle.

1. Impaired Social Interaction

Most autistic children lack interest in other people during their infant stage. For example, when mother hug them to feed them milk, they would not get close to the mother or smile at the mother. When they reach 6-7 months old, they could not distinguish between family members and outsiders. They could not mumble like normal infants and could only cry or be quiet. Even if they appear to develop normally up to 1-2 years old, at the onset of autistic symptoms, they would not come to parents’ side and ask for consolation when they are hungry, in pain or in discomfort. Instead they pull their parents’ hands to get their desired items for them without saying a word. They often have no reaction to parents’ departure or return. Even if parents are around, they would not interact nor have eye contact with them, thus they appear to be antisocial. Autistic children similarly lack social skills, do not know how to interact with other kids and could not form any long term relationship.

2. Impaired Language and Communication Skills

Impaired language and communication skills is the most obvious autistic symptom. In particular, it manifests ifself in the following aspects:

(1) Autistic patients usually use crying or screaming to convey their needs. Older patients may pull adult’s hand and lead the adult to the item they need. Nevertheless, they are lacking the corresponding facial expression and usually appear to be stoned, ie seldom nod, shake their head or body to convey their wishes.

(2) Delayed language development or no language development: Autistic children develops slower than children at the similar age. Some of them do not even have language development. About half of the autistic children very often stay silent. They can only resort to using hand gestures or
other means to express their wishes. Some autistic children while able to develop language skills before 2-3 years old, their language skills usually loss gradually or even completely over time.

(3) Abnormal way of speaking: Even if autistic children know the language well,  they will still encounter many problems, for example, they use their toes to walk. They would not proactively talk to people. They would not ask questions or they would repeatedly obsess about the same topic and do not care about other people’s response. It can be said that they often talk ”to” people but not talk “with” people. Monotonic, repetitive and imitative speech is often observed. When speaking with autistic children, they often repeats what you said, what is said on TV and radio or what other people said. Some autistic children would talk to themselves or mumble in broken words while seemingly having fun with themselves. In addition, autistic children can have problems in pronuciation, tone, word stress, speed and rhythm such that their speech sound strange and without emotion. Some autistic children make mistakes on pronouns, they often misuse “I” as “you” or “he/she” as “I”.

3. Limited interests

Insist on using the same format and ritual to do things

(1) Limited interest and abnormal obsession: Autistic children often show no interest in the toys and games played by typical children, especially
games that require imagination. Instead, they are more likely to be interested in items that are not considered as toys, for example, wheels, bottle cap or other rotatable items. Some others might be interested in plastic bags, door locks and fruits. There was a case of a 3-years old female patient that hugs a 2.5kg red brick all day long. She would not let loose the brick even during her sleep. If you attempt to remove the brick from her, she would become irritated and angry. This type of patients seldom show interests in living and moving things.

(2) Reluctant to change daily routine: Autistic children stubbornly maintain the status quo. They become anxious when any change happens. They react similar for daily routines as well. For example, some patients only eat certain food and insist on sitting at the sample place in every meal. Some like to arrange toys or objects in a row and feel painful or irritated when the row is disrupted. Nearly all autistic children refuse to learn or participate in new activities.

(3) Ritualistic or compulsive behavior: For example, bending or tapping finger, clapping hands. Some patients spend a lot of time to remember
weather forecast, capitals of some countries, birthdates of family member or so on. Older patients tend to repetitively ask the same question and
irresistibly touch or smell certain objects. These ritualistic and compulsive behavior are more common in patients with normal intelligence.

4. Feeling and movement disorder

Autistic children are indifferent to pain and outside stimulus. For example, upon hearing a sudden bang, normal children would panic whereas
autistic children would act as if nothing happened. If you talk to them, they would act as if they are deaf. Many parents then take the child to the
clinic and mistakenly think their child is deaf. Even if someone is standing in front of the autistic child, the child would again be indifferent to him/her or just staring at the person’s hand or other parts of the body. Autistic children often resort to rubbing, banging one’s hand or head, biting hard objects, shaking or rotating the body to stimulate their senses. Autistic children are often highly sensitive to particular stimulus, for example, siren sound, vacuum cleaner sound, dog barks and sudden change of light intensity. When exposed to these stimuli, they will become panic or restless. Some autistic children would not complain when they hurt their fingers but they could not bear mind scratch or tickle. Undersensitivity or oversensitive can happen for the same autistic child. Autistic children are often restless and hyperactive. They use toes to walk or prefer run to walk. They look around aimlessly and have a hard time to maintain focus. They like to stick out their neck, make grand or bizarre gesture. Some autistic children laugh or cry without any apparent reasons.

5. Intelligence and cognitive disorder

About 50% autistic children are classified as medium or highly low IQ (IQ<49). About 25% are midly low IQ (50<IQ<70). The remaining 25% are of normal intelligence. Typical cases diagnosed at the hospital are often medium or highly low IQ cases. The mildly low or normal cases often are not referred to the hospitals. No matter the level of intelligence, they all share the major autistic symptoms. However, patients with lower IQ would have more serious problems in social skills, self-mutilation and more likely to have epilepsy. Rutter and Lockyer studied the intelligence of autistic children in 1967. They found that autistic children are better at applied operations, visual space skills and instant quiz. However, they are weak in tests involving symbols, abstract and logical thinking. Other cognitive defects show up in imitation, dexterity, understanding of verbal vocabularies and gestures. Some low IQ patients also exhibit “autistic talent”. They excel in music, counting dates, mechanical memorization and recitation. These patients are often called “idiot genius”.

6. Other characteristics

Autistic children are emotionally flat or overly emotional for the circumstances. They could cry uncontrollably without any reasons and hard to be consoled. They could also laugh for no reasons. Besides, they are not afraid of cars, high raise building or fury animals that are often feared
by normal children. Autistic children can also rotate themselves without feeling dizzy. They often have self-infected wounds. Epilepsy can happen at pre-adolescence or adolescence with the latter time more common.