A group of friends are sitting in the garden chatting - but only one of them hears the ice-cream van in the distance.

That person is autistic. He is also able to hear the buzzing of electricity in the walls and, sometimes, finds it overwhelming to be in a very noisy environment.

Our most recent work, published in Cognition, suggests why that might be the case. People on the autistic spectrum can take in more sounds at any given moment, compared with non-autistic people.

Over the past few years, there has been a growing awareness that sensory experiences are different in autism.

What is also becoming clear is that different does not mean worse.

There are many reports of autistic people doing better than non- autistic people in visual and auditory tasks.

For example, compared with non-autistic people, autistic people spotted more continuity errors in videos and were much more likely to have perfect pitch.

We suggest this is because autistic people have a higher perceptual capacity, which means they can process more information at once.

Having this extra processing space would be useful in some situations, but problematic in others. For example, when copying a complicated drawing, you need to take in lots of information as efficiently as possible.

On the other hand, if you do not need much information to perform a task (for example, having a conversation with someone), then the extra capacity automatically processes other things in the room.

This can distract you from what you are trying to do or make you feel overwhelmed by lots of different sensory stimuli. To test this idea, we asked a group of autistic and non-autistic adults to carry out two computer-based tasks.

The first was a listening-search task where having greater perceptual capacity would be useful and help you perform well.

Participants were asked to listen to short bursts of animal sounds - played simultaneously - and figure out if there was a dog's bark or a lion's roar.

At the same time, they also had to listen for the sound of a car, which was there in half of the trials.

The autistic adults were much better than the non-autistic adults at picking out the sound of the car at the same time as doing the animal task correctly.

The second task involved listening to a recording of people preparing for a party and focusing on the women's conversation so as to be able to answer questions about it.

In this case, the task was easy and a person with that extra capacity might be more easily distracted by information that is not needed.

To test if that was the case, an unexpected addition was made to the middle of the scene - a man walking in and saying, "I'm a gorilla", over and over again.

As predicted, many more of the autistic participants (47 per cent) noticed the "gorilla man", compared with 12 per cent of the non- autistic group.

So it seems that increased capacity for processing sounds in autism could be linked to difficulties and enhanced auditory abilities found in the condition.

CHANGING PERCEPTIONS

Understanding that differences in autistic attention might be due to this extra capacity - rather than an inability to filter out irrelevant information - can change the way we understand the condition.

Our findings suggest that to reduce unwanted distraction, autistic people need to fill their extra capacity with information that would not interfere with the task at hand. For example, it might be helpful to listen to music while reading.

This challenges the common approach taken to simplify the classroom environment for autistic children, although care should be taken to avoid a sensory overload.

While we must not downplay the challenges associated with autism, our study raises awareness of a more positive side to the condition.

By promoting evidence of autistic strengths, we undermine the traditional view that autism is associated only with deficits.

•Anna Remington is a senior lecturer in cognitive science at University College London.

•This article first appeared in The Conversation at http://theconversation.com, a website which carries analysis by academics and researchers.