Does the sound of nails scratching chalkboard makes you squirm? Don’t worry it happens with most of the people. But why does it happen? It is just not you or me who has this question but this one weird behavior has plagued even the scientific community for years. At last, they have found something shocking and unbelievable.
There are many reasons why we react the way we react to the sound of scratching nails on chalkboard or blackboard. Our ears are designed in such a way that frequencies from 2000 – 4000 Hz are emphasized more. This happens because human speech falls under that frequency but unfortunately, this nail or fork or squeaky chalk scratching also falls within that frequency range, thereby making us more vulnerable to the such aversive sounds. Our ear canal is also to be blamed for this behavior of aversiveness.
Another reason for our dislike towards such sounds is of evolutionary origin, the sound of nails scratching a blackboard is similar to screaming or a crying baby. This forces humans to act for survival. As all these are under one group we dislike these sounds and try to avoid them as much as possible.
Research on Sound of Nails Scratching Chalkboard
A study claimed that it is shape our ear canals and our own perceptions that are to be blamed when it comes to our hatred to shrill sounds. The participants of the study rated nails on a chalkboard sound and running a chalk on blackboard as the worst sounds from other sounds like Styrofoam squeaking or running a fork against a slate. The researchers then made some modifications in these sounds and removed some frequencies which caused considerable irritation. They told half of the participants that the sound is part of contemporary music and told the other half the original source of the sound. The researchers measured the participants’ heartbeat, BP and skin conductivity. The researchers found out that our skin conductivity changes when we hear such sounds and we tend to produce physical reaction similar to the physical reaction when we are under stress.
Michael Oehler, a professor of media and music management at Macromedia University of Applied Sciences in Germany and one of the researchers, said that when the participants were told that the sound was a part of music, they rated the sound of nails scratching chalkboard more pleasantly than the ones who knew the real source of the sound. However, all the participants reacted physically in the same way they reacted to stress in general.
Another research in 2012 published in Journal of Neuroscience suggested that two parts of the brain communicate when we hear these screechy sounds like chalkboard writing sound or scratching nails on a chalkboard sound. The part which controls hearing communicate with the part which controls emotions. 13 participants were asked to rate 74 sounds in pleasantness parameter.
Researchers used fMRI (functional Magnetic Resonance Imaging) to see how participants’ brains respond to sounds. When the participants heard such squeaky sounds both parts of their brains – the auditory cortex which processes sound and the amygdala which controls negative emotions – interacted. It was further seen that when the sound was more aversive the interaction between these parts was stronger. Fingernail scratching chalkboard was one of the most unpleasant sounds whereas flowing water, sound of a laughing baby etc. were rated as few of the most pleasant sounds.
Ig Noble Prize – That’s a Parody Prize
A study published in 1986 in the journal “Perception & Psychophysics” was awarded Ig Noble Prize (Ig Noble Prize is a parody of Noble Prize awarded for the researches which are funny or trivial but sometimes which makes us think) in 2006. In that study, the researchers recorded the sound of a garden tool scraping over a chalkboard. Then they modified the sound and removed the higher frequencies, middle and lower frequencies one at a time. They found out that when higher frequencies were removed, unpleasant feeling among participants didn’t go away. However, it was the middle and sometimes the lower frequencies which caused this displeasure and removing those frequencies got rid of some unpleasant feeling.
A warning call of a chimp is almost similar to these kinds of sounds like the sound of nails scratching chalkboard or chalkboard writing sound. So, it is assumed that we have this reflex to consider these sounds (no matter they cause no trouble) as harmful and run away or avoid and survive.
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