Children who have autism process language and sound more slowly than do other children, according to recent US research.

The researchers used brain imaging techniques to measure language processing delays in child study subjects.

The new magnetoencephalography (MEG) techniques will allow researchers to diagnose autistic infants, as well as to look for new preventive measures.

The new methods may also allow researchers to refine their observations about various types of autism.

Timothy P.L. Roberts, a radiology researcher at Children's Hospital in Philadelphia, said that research needed to be done before the technique could become a standard tool.

He said that, if that were done, the delayed brain response pattern could be refined into the first imaging biomarker for autism.

Autism spectrum disorders (ASDs) are a group of disorders impairing the neurological development of children.

Scientists lack objective biological measurements they can use to diagnose ASDs, and children with ASDs often reach school age before they are spotted.

For the purposes of the study, the researchers used MEG to observe the magnetic fields at work in children's brains while they processed language.

They studied 25 children with ASDs, whose average age was 10 years.

As a control, they also included 17 age-matched children who showed no signs of developing ASDs.

They discovered that children who have ASDs recognise sounds up to 11 milliseconds later than children who are apparently unaffected by the disorder.

Roberts said that the delay his team measured meant that a child with ASD would still be processing the ‘el’ sound after hearing the word 'elephant,' where other children would understand the word already.

He said that the delays also cascade as a conversation progresses.

Symptoms of ASDs range from mild problems with social interaction to severe behaviour difficulties.

Gina Gómez de la Cuesta, a researcher at the National Autistic Society, said that the results were useful because many children still had to wait years for a diagnosis of autism, a thing which greatly hindered their progress in life.

In another study, the researchers also showed that the development of white matter in the brain corresponds with faster auditory responses.