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How many times does the chorus repeat[br]in your favorite song?

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And, take a moment to think,[br]how many times have you listened to it?

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Chances are you've heard that chorus[br]repeated dozens, if not hundreds, of times,

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and it's not just popular songs in the West[br]that repeat a lot.

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Repetition is a feature that music from[br]cultures around the world tends to share.

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So, why does music rely[br]so heavily on repetition?

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One part of the answer come from what[br]psychologists call the mere-exposure effect.

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In short, people tend to prefer things[br]they've been exposed to before.

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For example, a song comes on the radio[br]that we don't particularly like,

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but then we hear the song at[br]the grocery store, at the movie theater

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and again on the street corner.

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Soon, we are tapping to the beat,[br]singing the words,

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even downloading the track.

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This mere-exposure effect doesn't[br]just work for songs.

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It also works for everything [br]from shapes to Super Bowl ads.

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So, what makes repetition so[br]uniquely prevalent in music?

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To investigate, psychologists asked[br]people to listen to musical compositions

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that avoided exact repetition.

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They heard excerpts from these pieces[br]in either their original form,

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or in a version that had been digitally[br]altered to include repetition.

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Although the original versions[br]had been composed by

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some of the most respected [br]20th century composers,

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and the repetitive versions had been[br]assembled by brute force audio editing,

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people rated the repetitive versions[br]as more enjoyable, more interesting

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and more likely to have been[br]composed by a human artist.

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Musical repetition is deeply compelling.

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Think about the Muppets classic,[br]"Mahna Mahna."

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If you've heard it before,

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it's almost impossible after I sing,[br]"Mahna mahna,"

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not to respond, "Do doo do do do."

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Repetition connects each bit of music[br]

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irresistibly to the next bit [br]of music that follows it.

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So when you hear a few notes,[br]you're already imagining what's coming next.

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Your mind is unconsciously singing along,

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and without noticing,[br]you might start humming out loud.

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Recent studies have shown that when[br]people hear a segment of music repeated,

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they are more likely to move[br]or tap along to it.

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Repetition invites us into music[br]as imagined participants,

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rather than as passive listeners.

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Research has also shown

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that listeners shift their attention[br]across musical repetitions,

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focusing on different aspects of[br]the sound on each new listen.

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You might notice the melody[br]of a phrase the first time,

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but when it's repeated, your attention[br]shifts to how the guitarist bends a pitch.

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This also occurs in language,[br]with something called semantic satiation.

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Repeating a word like atlas ad nauseam

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can make you stop thinking about [br]what the word means,

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and instead focus on the sounds:[br]the odd way the "L" follows the "T."

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In this way, repetition can [br]open up new worlds of sound

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not accessible on first hearing.

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The "L" following the "T" might not be[br]aesthetically relevant to "atlas,"

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but the guitarist pitch bending[br]might be of critical expressive importance.

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The speech to song illusion[br]captures how simply

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repeating a sentence a number of times[br]shifts listeners attention

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to the pitch and temporal[br]aspects of the sound,

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so that the repeated spoken language

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actually begins to sound[br]like it is being sung.

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A similar effect happens with [br]random sequences of sound.

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People will rate random sequences[br]they've heard on repeated loop

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as more musical than a random[br]sequence they've only heard once.

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Repetition gives rise to a kind of[br]orientation to sound

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that we think of as distinctively musical,[br]where we're listening along with the sound,

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engaging imaginatively with the note[br]about to happen.

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This mode of listening ties in with our[br]susceptibility to musical ear worms,

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where segments of music[br]burrow into our head,

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and play again and again,[br]as if stuck on repeat.

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Critics are often embarrassed[br]by music's repetitiveness,

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finding it childish or regressive,

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but repetition, far from an embarrassment,[br]is actually a key feature

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that gives rise to the kind of experience[br]we think about as musical.