Spatial skills linked to tone deafness

Why are some people tone deaf? This question has long puzzled scientists, but Otago's Psychology researchers have come up with surprising evidence about the brain processes involved.

They have shown, for the first time, that tone-deaf people have poorer spatial skills than people who can distinguish musical notes in a normal way and they believe this difference may underlie problems in musical perception.

Associate Professor David Bilkey, who co-authored the study with student Katie Douglas, says true tone deafness (amusia) affects around four per cent of the population.

"It's not just the inability to carry a tune - people with amusia are often simply unable to tell differences between the musical notes they hear.

"However, they have no problem detecting similar subtle changes in pitch that indicate questions in speech. Nor have studies with MRI scanners shown any abnormal processing in the auditory cortex of amusic brains," he says.

So Bilkey and Douglas investigated whether tone-deaf people have deficits in spatial representation and processing, which involves a different part of the brain.

They conducted experiments with 34 university students, including eight identified as amusical through a standard test. There were two control groups, one composed of 14 musicians and the other of 12 students from non-musical backgrounds.

When asked to perform a task involving mentally rotating three-dimensional objects made up of cubes, the amusical group made significantly more errors than the control groups, says Bilkey.

Two further tests involving simultaneous melodic and spatial elements back up the initial finding, he says.

"In these particular tests, the important result was actually that the amusic group had fewer, rather than greater, difficulties with the tasks than the two control groups.

"This means that the people without amusia were experiencing more cognitive ‘interference' in simultaneously processing spatial and melodic information, indicating that the processing of musical pitch may depend on the same cognitive mechanisms used to process spatial information."

Not only do the findings provide an important insight into the possible causes of amusia, they also raise more general questions about the representation of music in the brain, he says.

"We are all used to thinking about tones as being high or low, but these findings suggest that this could be more than just a metaphor.

"It might be based on something more fundamental to do with the way the brain stores information about the high and low notes in melodies."