Washington, Feb 11: Canadian researchers have developed a new technique that uses infrared light brain imaging to decode a person's preference.

The tool might ultimately open the world of choice to children who can''t speak or move.

In a study Bloorview scientists demonstrated the ability to decode a person''s preference for one of two drinks with 80 per cent accuracy by measuring the intensity of near-infrared light absorbed in brain tissue.

"This is the first system that decodes preference naturally from spontaneous thoughts," said Sheena Luu, the University of Toronto PhD student in biomedical engineering who led the study under the supervision of Tom Chau, Canada Research Chair in pediatric rehab engineering.

Although most brain-computer interfaces designed to read thoughts require training, but the nine adults in the current study received no training.

Before the study they rated eight drinks on a scale of one to five.

They wore a headband fitted with fibre-optics that emit light into the pre-frontal cortex of the brain, and were then shown two drinks on a computer monitor, one after the other.

Then they were asked to make a mental decision about which they liked more.

"When your brain is active, the oxygen in your blood increases and depending on the concentration, it absorbs more or less light. In some people, their brains are more active when they don''t like something, and in some people they''re more active when they do like something," said Luu.

They taught the computer to recognize the unique pattern of brain activity linked with preference for each subject, and then accurately predicted which drink the participants liked best 80 per cent of the time.

"Preference is the basis for everyday decisions," said Luu.

In future, Luu is hoping to create a portable, near-infrared sensor that rests on the forehead and relies on wireless technology, opening up the world of choice to children who can''t speak or move.

She pointed out that the brain is too complex to ever allow decoding of a person''s random thoughts.

"However, if we limit the context - limit the question and available answers, as we have with predicting preference - then mind-reading becomes possible," she said.

The study is published in The Journal of Neural Engineering. (ANI)