Seeing is not always believing -- visual speech (mouth movements) mismatched with auditory speech (sounds) can result in the perception of an entirely different message. This mysterious illusion is known as the McGurk effect.
According to one of the researchers at the Baylor College of Medicine, even though our senses are constantly blitzed with information, our brain easily chooses the verbal and nonverbal speech of our conversation partners from this dissonance. The McGurk effect is an example of when this goes wrong. It happens when mouth movements that are seen can override what is heard, causing a person to perceive a different sound than what is actually being said. Only when the eyes are closed, and when the sound is being heard, can the correct message be perceived. Information regarding an algorithm developed to further study this phenomenon was published in the PLOS Computational Biology.