The McGurk effect

McGurk was hearing dada when baba had been dubbed on to gaga. Summerfield (1987) explained this as occurring due to the sound being perceived is compatible with the auditory and visual information presented. As baba is said and gaga is mimed a conflict arises due to the marked differences in mouth movement when both are presented. The result is different from either spoken word. This represents strong evidence for the belief that speech perception is a result of a combination of top down processing and bottom up processing working together. Lip reading in this instance generally is the source of knowledge that creates the conflict in speech perception. This act of lip reading generally occurs unconsciously as does the processing of speech perception - to the effect that the perceiver does not think about what they are doing most of the time. .
             Even though lip reading is usually done unconsciously it is also a recognised method of improving the quality of hearing - speech reception. Lip reading is a technique employed by impaired listeners and listeners with normal hearing to improve speech reception at any given time. Two previous studies have shown lip reading to have a varied level of success in improving speech reception. Grant and Braida (1991) discovered whilst using a speech to noise ratio of -10dB the majority of listeners could only identify 10% of the words correctly. If the speaker's face was made visible and the listener could see the lips move in time with the spoken words beneath the noise the range of words correctly identified ran from 30% - 70%. Grant and Braida (1991) formed a number of conclusions due to their findings. The first being at different noise levels and for a number of people lip reading can increase the amount of the message understood significantly. They also discovered that the ability to lip read for persons with cochlear damage was very similar in skill.