Doing what the brain does: how computers learn to listen

Researchers at the Leipzig Max Planck Institute for Human Cognitive and Brain Sciences and the Wellcome Trust Centre for Neuroimaging in London have now developed a mathematical model which could significantly improve the automatic recognition and processing of spoken language. In the future, this kind of algorithms which imitate brain mechanisms could help machines to perceive the world around them.

Many people will have personal experience of how difficult it is for computers to deal with spoken language. For example, people who "communicate" with automated telephone systems now commonly used by many organisations need a great deal of patience. If you speak just a little too quickly or slowly, if your pronunciation isn't clear, or if there is background noise, the system often fails to work properly. The reason for this is that until now the computer programs that have been used rely on processes that are particularly sensitive to perturbations. When computers process language, they primarily attempt to recognise characteristic features in the frequencies of the voice in order to recognise words.

"It is likely that the brain uses a different process", says Stefan Kiebel from the Leipzig Max Planck Institute for Human Cognitive and Brain Sciences. The researcher presumes that the analysis of temporal sequences plays an important role in this. "Many perceptual stimuli in our environment could be described as temporal sequences." Music and spoken language, for example, are comprised of sequences of different length which are hierarchically ordered.

According to the scientist's hypothesis, the brain classifies the various signals from the smallest, fast-changing components (e.g., single sound units like "e" or "u") up to big, slow-changing elements (e.g., the topic). The significance of the information at various temporal levels is probably much greater than previously thought for the processing of perceptual stimuli. "The brain permanently searches for temporal structure in the environment in order to deduce what will happen next", the scientist explains. In this way, the brain can, for example, often predict the next sound units based on the slow-changing information. Thus, if the topic of conversation is the hot summer, "su?" will more likely be the beginning of the word "sun" than the word "supper".