Man hears people speak before seeing lips move

• Autores: Helen Thomson
• Localización: New scientist, ISSN 0262-4079, Nº. 2924, 2013, pág. 11
• Idioma: inglés
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• Resumen

  • Light and sound travel at different speeds, so when someone speaks, visual and auditory inputs arrive at one's eyes and ears at different times. The signals are then processed at different rates in the brain. Despite this, people perceive the events as happening simultaneously. How this happens, however, is unclear. To investigate, Elliot Freeman at City University London and colleagues performed a temporal order judgment test. The team then carried out a second, more objective test based on the McGurk illusion. They were surprised to get the result: presenting the voice 200 ms earlier than the lip movements triggered the illusion, suggesting that the brain was processing the sight before the sound in this particular task. Freeman says his implies that the same event in the outside world is perceived by different parts of the brain as happening at different times. This suggests that, rather than one unified "now", there are many clocks in the brain--two of which showed up in the tasks--and that all the clocks measure their individual "flows" relative to their average.