McGurk effect an auditory illusions resulting from inferences – 11/08/2023 – Luciano Melo

An important discovery for neuroscience happened in 1976. Psychologist Harry McGurk and his assistant John MacDonald noticed that many people, when they saw lips moving silently to say “ga”, but synchronized with the sound “ba”, heard “da”. This phenomenon is recognized as the McGurk effect, with many variations easily found in videos on the internet, ready to convince you, skeptical reader.

But it’s not just what you see that can get in the way of what you hear. The McGurk effect can come to light at the expense of tactile stimulation. A vent in the neck increases the chances of perceiving a sound that requires exhalation of air, for another that does not. In this way, English volunteers understood “p” as “b” expressed in a British accent.

Friendly reader, I am not saying that we understand speech due to the influence of air blown onto the neck. But the brain integrates information relevant to language awareness, no matter the sensory modality.

This fusion gives rise to a unified conscious experience. Therefore, what we perceive of the world is an addition and average of the environmental elements computed in our neurons. Our consciousness emerges from a probabilistic work, the more coincident in time and space the emergence of two or more sensory stimuli, the greater the possibility of their origins being in the same external event, and, therefore, the greater the chance of them being integrated into our mass. grey.

Our memory stores lip movement patterns for certain vocal sounds. We can read lips because we remember and recognize these patterns. We are also capable of the opposite movement, based on a phoneme, we can imagine how the mouth moves. But when there is incongruity between synchronous stimuli, integration fails, and the brain creates an impression that best meets the sum of the two perceptions, and harmonizes them. We are not aware of the inconsistency. We will not say, “I saw your lips move to such a sound, but the fact is that I heard something else.”

The McGurk effect appears to be shielded from cognition, as people will still report its influence even if previously warned that they will hear something incompatible with what they see. But it’s not entirely like that. For example, the effect loses its strength if visual attention is attenuated. Practical advice: at certain times, closing your eyes can be a good way to listen reliably. People are better at picking up on others’ emotions when they focus on their voice rather than their actions.

By uncovering the neural bases of the McGurk effect, we better understand the brain. This organ saves energy by not having to constantly understand what is happening, in second-by-second updates. It is an inference machine more than a perceptual machine. External stimuli are integrated into a mental map, previously constructed by memories and previous experiences to format a coherent and understandable conception of the world. The result is brilliant, as we are able to interact in an orderly manner with our environment. But sometimes our deductions are inaccurate, even though our vivid sensations make us think otherwise. This mentally constructed coherence in the discordance between perception and reality is a source of errors beyond the McGurk effect.

And if the subject is error, I’ll put a topic in this chronicle that I can’t resist, here I go. There are real reasons to distrust the forces that drive interests in selling medicines. From this simple observation, it is easy to infer that the pharmaceutical industry is a villain, which invents physical and biological bases for mental illnesses to justify the lucrative pharmaceutical trade.

This cognitive trap is probably the center of the thoughts that paraded in this UOL video. There is even a lost reference to a compilation of studies – the so-called meta-analysis – that points to the ineffectiveness of the antidepressant fluoxetine against depression. The deep-rooted inference of pharmaceutical banditry, and other biases, eclipsed all evidence about the real benefits of fluoxetine, which liquidated the dubious meta-analysis.

The cute video has well-accepted and superficial clichés and also helps to stigmatize people who use psychostimulants to treat their attention deficit hyperactivity disorder.

Here is the lesson we can learn from the psychologist duo Harry McGurk and John MacDonald: it is better not to believe everything we hear, and from time to time, to distrust the final product of our conclusions.

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References

McGurk H, MacDonald J. Hearing lips and seeing voices. Nature. 1976 Dec 23-30;264(5588):746-8. doi: 10.1038/264746a0. PMID: 1012311

Gick, B., Derrick, D. Aero-tactile integration in speech perception. Nature 462, 502–504 (2009). Dias, James W., Theresa C. Cook, and Lawrence D. Rosenblum, ‘The McGurk Effect and the Primacy of Multisensory Perception’, in Arthur G. Shapiro, and Dejan Todorovic (eds), The Oxford Compendium of Visual Illusions (New York, 2017; online edn, Oxford Academic, 22 June 2017),

Iqbal, ZJ; Shahin, A.J.; Bortfeld, H.; Backer, K.C. The McGurk Illusion: A Default Mechanism of the Auditory System. Brain Sci. 2023, 13, 510.

Anne-Marie Muller, Tyler C. Dalal, Ryan A. Stevenson,Schizotypal personality traits and multisensory integration: An investigation using the McGurk effect,Acta Psychologica,Volume 218, 2021, 103354, ISSN 0001-6918,

Tiippana K, Andersen TS, Sams M. Visual attention modulates audiovisual speech perception. European Journal of Cognitive Psychology. 2004 May 1;16(3):457–72.

Kraus MW. Voice-only communication enhances empathetic accuracy. Am Psychol. 2017 Oct;72(7):644-654. doi: 10.1037/amp0000147. PMID: 29016168.

Getz LM, Toscano JC. Rethinking the McGurk effect as a perceptual illusion. Atten Percept Psychophys. 2021 Aug;83(6):2583-2598. doi: 10.3758/s13414-021-02265-6. Epub 2021 Apr 21. PMID: 33884572.