Scientists have confirmed that the noise of fingernails being dragged across a chalkboard is genuinely unpleasant. Subjects displayed the same physiological signs of distress whether they thought they were listening to nails on a board or a musical composition, suggesting that the unpleasantness isn't simply a matter of expectations and conditioning. Researchers also found that the highest frequencies of the sound were not the most unpleasant part, as listeners' reactions improve more when lower frequencies were removed from the sound.

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