The system, known as the Picture Exchange Communications System, is being trialled by 30 youngsters after being developed in the United States.

Some users believe the method is the most effective yet for alleviating problems associated with autism. Typically these include aggressive and attention-seeking behaviour, and tantrums because of the child’s frustration at the inability to communicate.

Pecs, which was developed by educational psychologists in Delaware, relies on finding out what the child wants. This might include toys, food or drinks consistently sought by the youngster.

Colour pictures are made of the article, and the children are taught to place them in their carer’s hand to indicate what they want.

Initially, childen work with trainers who help them physically pick up the picture and put it into an adult’s hand. However, as they learn to associate the items with the pictures, more images are added and the children are expected to seek out the adult to get what they want.

It is thought that although children are expected to do very little, the actual skills acquired by the process do much to enhance communication. Each child is forced to interact with another person instead of trying to obtain the item alone, and by initiating the action is not dependent on being prompted by adults.

In some cases, autistic children have learned to speak in simple words or short sentences as a progression of breaking down the barriers of communication with another person.

Sue Baker, from the West Sussex Educational and Psychology Portage Services, who brought the system to Britain and organised a conference last week, said: “This system is not designed to help the autistic child to speak but to unlock their silent world. If they learn to speak as a result then it is a bonus.

“Many different methods have been tried but so far this appears to be the best.”

Sandra Hunter, who is using Pecs with her five-year-old grandson, said he had appeared different from his peers when he was 18 months old. “He was displaying a lack of curiosity and seemed very isolated. At first we thought he was deaf but at the age of two-and-a-half he was diagnosed as autistic.

“He has been on Pecs since February but already he is happier and less frustrated. He can’t speak but I am confident he will.”