Visually stimulating activities, such as checking one’s smartphone, reading a book or gaming, can leave people temporarily deaf, a recent study commissioned by the Wellcome Trust has revealed.
The findings, detailed in the Journal of Neuroscience, have sprung from research conducted by a team of British experts at University College London, led by Nilli Lavie, director of the Attention and Cognitive Control laboratory, and Maria Chait, Reader in Auditory Cognitive Neuroscience, at the Ear Institute.
A group of 13 subjects took part in this trial, which consisted in carrying out complex tasks requiring visual concentration.
More precisely, the respondents were asked to be on the lookout for specific letters in a larger set of characters being briefly displayed on a screen, as random melodies were being played in their headphones.
MEG (magnetoencephalography) images of their brains were captured, as those activities were under way. Upon analyzing these scans, scientists discovered a statistically significant reduction in the participants’ ability to detect sounds and respond to them.
As study authors point out, it’s not that the participants actively chose to disregard auditory cues: in fact, they couldn’t even hear them properly anymore.
Apparently, excessive attention awarded to a visually engrossing task made it virtually impossible to be aware of one’s surroundings, at least as far as environmental noise was concerned.
This disruption in the brain’s ability to identify and process sounds didn’t persist however when less demanding instructions had to be executed, such as identifying a certain letter without others being displayed simultaneously.
In such instances, it was much easier for subjects to perceive auditory stimuli and react to them, even though the cues were at the same frequency and amplitude as in the prior experiment.
A term has actually been coined so as to describe this phenomenon of being unaware of sounds when taking part in a challenging task requiring visual alertness: “inattentive deafness”.
A clear explanation for this human peculiarity hasn’t been found, but researchers speculate it may be caused by the fact that visual and auditory signals may be processed by the same part of the brain and may be competing for the same “bandwidth”.
Therefore, the overwhelming presence of one such stimulus may interfere with the ability to perceive a different type of input being received concomitantly.
Prior research, such as the one conducted by Daniel Simons, renowned experimental psychologist and bestselling author of “The Invisible Gorilla”, had also shown that, due to information overload, the brain tends to miss important details, while being overly preoccupied with other cues.
This occurrence, further emphasizing human beings’ actual inability to multitask, may be responsible for traffic accidents which occur when pedestrians are overly distracted by their mobile devices, to the point where they become oblivious of incoming cars revving their engines.
In addition, the fact that some stimuli may take precedence over others, confusing the brain, may also explain why drivers or bikers can get so easily distracted by road signs and billboards.
Another situation when inattentive deafness can have even life-threatening consequences can be encountered during surgeries, when doctors may fail to distinguish changes in the sounds of hospital machines, such as the heart rate monitor.
In a less frightful scenario, this recently discovered oddity may explain why gamers or bookworms have trouble responding while being engaged in their favorite activity: it’s not that they are purposefully trying to be rude by snubbing their interlocutor.
They may simply be so captivated by their visually demanding task that their sense of hearing is no longer able to function at normal parameters.
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