Is iTunes’ Shuffle Mode Truly Random?

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image copyright Apple Inc.

ITunes' shuffle feature makes a random path through your iTunes music library, jumping from song to artist to album with no logic or order. Or does it? Some people swear that it does, others claim to see patterns all the time. But where does the truth lie?

It lies in the spaces between our expectations, our perceptions, and our understanding of the difference between shuffle and random, in turns out.

What we may expect out of a "shuffle" feature is not necessarily what it's designed to do.

According to Newsweek's Steven Levy, who has written a book on the iPod and is one of the leading chroniclers of all things Apple, the shuffle feature works this way:

“When an iPod does a shuffle, it reorders the songs much the way a Vegas dealer shuffles a deck of cards, then plays them back in the new order. So if you keep listening for the week or so it takes to complete the list, you will hear everything, just once.”

But note that you need to listen to the entire library all the way through without stopping for the randomness of shuffle to make itself apparent.

As Levy points out, most people don't do this, leading the "deck" to be reshuffled constantly, creating new paths through their libraries each time they listen on shuffle, thus causing some tracks or orders of tracks to appear to repeat or group together.

The shuffle order can also be affected by user settings. In iTunes' iTunes DJ mode, users can ask iTunes to play songs that are highly rated more often, thus skewing the randomness. Songs can also be marked "Skip When Shuffling" so that they're excluded from all shuffles in iTunes DJ or a regular shuffle.

The other thing that causes shuffle to look less than random has to do with statistics and probability. Take the instance of a coin flip. While it's not very likely that one person flipping a coin 10 times would get heads every time, it's statistically – and even actually – possible (as illustrated in the opening to Tom Stoppard's "Rosencrantz and Guildenstern Are Dead"). This is because each coin flip is a distinct event, with probabilities reset each time. The events only look related to humans observing it.

The the last element that causes us to suspect that iTunes Shuffle isn't truly random is our brains. The human brain is wired to seek out and see patterns – sometimes even where they don’t exist. This is an important function of the brain and makes our brains pretty powerful tools, but it can mislead us when examining questions like this.

Ultimately there's no simple answer to whether iTunes' shuffle function is truly random. It's just too deeply influenced by our perception, expectation, iTunes settings, and use. Still, it's fun to see what songs come after each other in iTunes when shuffling and create our own patterns and explanations.

For further reading on this subject, with far more math, science, and hard data than I’ve provided, check out these articles:

My iPod for a Random Playlist