Echolalia is a speech disorder in which a person repeats words, phrases and sounds spoken by another person. It is commonly referred to as 'parrot-like' echoing behavior and is experienced by children and adults with problems such as autism, Asperger Syndrome, Tourette Syndrome, aphasia, schizophrenia, other brain disorders or developmental disabilities.
There are two forms of echolalia: immediate and delayed. Immediate echolalia is where the person repeats something that someone has said immediately prior, while delayed echolalia is where the person repeats a word or phrase hours, days or even weeks after they were first heard. The causes of echolalia are not exactly certain, but it is seen as a functional tool for people learning to communicate. In fact, echolalia in children is normal for language development, as the repetition of words and phrases is a fast way of learning the meaning of words. Most children grow out of this and develop the ability to generate sentences themselves without having to repeat pre-learned sentences.
For children with autism, however, echolalia can occur much more frequently and last for a longer period of time. This is because they lack the ability to create spontaneous responses to situations and often resort to using phrases they have heard before to communicate what they want to say in the present. For example, a child may feel anger but not know how to express it in the appropriate manner; the anger is then likely to trigger a memory of a different time when they were angry and they may use an echoed phrase from that previous situation to communicate how they are feeling now. In this way, echolalia can be a useful way for children to communicate when they lack the ability to do so in a normal way, provided that the people they are speaking to can understand what the child is trying to say.
Another reason for some children to have echolalia is that it can be like a coping mechanism for them under stressful situations. Autistic children do not adapt to change well and find it difficult to think and make decisions in high pressure situations, so it is comforting for them to repeat familiar and often-used phrases. My little sister, who was diagnosed with mild autism as an infant, has a habit of repeating phrases when she is in tense situations which require her to make decisions quickly. For example, when doing maths homework on a worksheet, she can easily complete the problems (being eight years old, she only has to learn her times tables). However, when we test her on the times tables in a rapid-fire quiz, she always has to repeat "I'm thinking, I'm thinking, I'm thinking", even when it is obvious that she actually already knows the answer. Repetition of the phrase allows her more time to thoroughly think through the question and assures her that she can eventually communicate the correct answer.
Echolalia amongst adults is common in people with schizophrenia, Alzheimer's and other brain degenerative disorders because they are lacking the ability to comprehend others and respond accordingly. For example, if someone asks them "Would you like an apple?" and they cannot actually understand what is being offered to them, they may respond immediately with the repeated phrase "Would you like an apple?", often with exactly the same intonation used as the original speaker.
Other examples of echolalia include when people suffering from Tourettes spontaneously starts repeating a string of words with no coherent meaning, or in patients with aphasia, which is a brain disorder which causes damage to the language areas of the brains and impairs a person's ability to communicate effectively.