How does the iPod Shuffle play songs randomly?

Even before the iPod Shuffle was introduced in 2005, some people had considered adding a random play feature to the iPod. Many people complained that the music played on their MP3 players was not random at all - every time they created a new playlist, the iPod would always choose the same song from the same artist and album. It was as if the iPod had its own likes and dislikes, and was particularly fond of certain songs. This caused some controversy in forums, and some even believed that Apple had rigged the iPod to make it easier to play songs downloaded from the iTunes Music Store. Of course, Apple denied this [source: CNET].

It's important to remember that you can set the degree of randomness of the iPod Shuffle yourself. In iTunes settings, you can choose to have the iPod play "no repeats" or you can rate songs so that the iPod plays more of the ones with the highest ratings.

Some people believe that our brains are more likely to remember things that follow a certain order and pattern than things that are chaotic and random. This is true. People like to describe clouds as different faces or animals, look for the image of Jesus on burnt toast, and marvel at a number - most viewers of the American TV series "Lost" are familiar with the last situation.

Likewise, we don't like to admit some coincidences. Take the birthday paradox, for example. You'd think it's highly unlikely that two people in the same room would have the same birthday, right? You'd be right -- the odds are only 1 in 365, or 0.3%. So how many people would you need to put in the room to make that probability 50%? Most people would say a lot. When asked how many people you would have to cram into a room for two people to have the same birthday, college students gave an average answer of 385 [source: CompuServe].

What's the correct answer? You only need 23 people to make it 50%. Considering there are 365 days in a year, that number seems ridiculously low.

David Wooley/Getty Images (Family Photo) The probability that two of these seven people share a birthday is 6%. However, if you add just a few more people, that probability rises dramatically.

Therefore, even though an iPod Shuffle can hold 500 songs, if you consider the same artist or album as "the same birthday", you will find that the possibility of iPod selecting several songs from the same artist is much higher than we think.