How Headphones Changed the World by Derek Thompson - The Atlantic:

Science says we’re full of it. Listening to music hurts our ability to recall other stimuli, and any pop song — loud or soft — reduces overall performance for both extraverts and introverts. A Taiwanese study linked music with lyrics to lower scores on concentration tests for college students, and other research have shown music with words scrambles our brains’ verbal-processing skills. “As silence had the best overall performance it would still be advisable that people work in silence,” one report dryly concluded.

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There is evidence that music relaxes our muscles, improves our mood, and can even moderately reduce blood pressure, heart rate, and anxiety. What music steals in acute concentration, it returns to us in the form of good vibes.

That brings us finally to our final cultural answer: Headphones give us absolute control over our audio-environment, allowing us to privatize our public spaces. This is an important development for dense office environments in a service economy. But it also represents nothing less than a fundamental shift in humans’ basic relationship to music.