The Perception of 'Random' on the iPod

Robaato writes "Stephen Levy writes in the Guardian about the perception of randomness, or the lack thereof, on an iPod set to shuffle." From the article: "My first iPod loved Steely Dan. So do I. But not as much as my iPod did.... I didn't keep track of every song that played every time I shuffled my tunes, but after a while I would keep a sharp ear out for what I came to call the LTBSD (Length of Time Before Steely Dan) Factor. The LTBSD Factor was always perplexingly short." My first iPod shuffle refused to let me delete (sigh) Weird Al's Polkamon off of the flash memory.

Comments

And Zonk dupes himself... again...

[Anonymous Coward]

Is the iPod Shuffle Playing Favorites?

How about an analysis of the randomness of Zonk dupes. I guess I should be happy it's not a games story.

Bias

[Anonymous Coward]

http://en.wikipedia.org/wiki/Confirmation_bias

Re:Bias

[pchan-]

This is exactly what is going on. Good call, AC.

Some years ago, I worked on an mp3 playing device (no, not Apple). Our users were quite often complaining that our random was not truly random, and seems to be clustering, favoring, disliking some thing or another. Some would swear that there was some intelligence to it, picking particular songs. I've seen the shuffle code, it's a simple array swap. I ran a numerical simulation on the output and found that the distribution of the array elements from their original position equal throughout. Further, there seemed to be no specific clustering, as the probability that any item would end up next to any of its peers was again equally distributed throughout. We had some of the customers submit their own ideas and tried them out in code. In general, we found that we never outperformed the simple array swap in terms of randomness, though most results were about the same.

The conclusion that we reached: If you have a lot of Jimmy Buffet, you're going to hear a lot of Jimmy Buffet. And on that one occassion that two Buffet songs play back to back, you're going to think to yourself "this random sucks". But it is, in fact, all in your head.

*I'm sure someone will want to bring up the seed issue. Let's just say that we had it covered.

OCD

[eldavojohn]

Or - and here is the nub of an issue that would consume me for more than a year - was the shuffle function, meant to mix up my music collection in a random fashion, actually not random at all?

There there, Mr. Levy, we'll get you all the randomness you want. In fact, we have a special place filled with randomness and padded white walls! You're going to like it there.

You know, instead of wasting your interviewee's time, you could have installed a five song list on your iPod and set it to shuffle. You'd have to carefully mark down the track number being played and listen to it for 100 songs. Do this a few times and make sure you're very methodical about what you do. Wipe the iPod, put five songs on it in order and then listen to a hundred songs "randomly." If you start to see a pattern developing or one song is obviously favored over the other, it will begin to show up.

But on the more technical side, they have to seed the random variable with something. Whether or not it's an internal clock, I'm not sure. Either way, they have to derive a random number and it's possible that their seed isn't good enough or has too few states or is prone to being seeded at the same state, etc. Based on this information, I hate to break it to you but it is very hard to be truly random.

Re:OCD

[monoqlith]

Not OCD. Sub-clinical schizophrenia. . Read all the way to the end of the article(I'm new here). If you don't want to, I'll summarize: It's more about randomness than the iPod. He eventually realizes his suspicions of programmer malfeasance are in fact an expression of his own favoritism, not the iPod's. In other words, its all in his head. So a worthwhile, interesting article, and even if he could have benefitted by experimenting himself, that wouldn't have made for a very fun read, or an interesting question to ask Steve Jobs while he had the chance.

People are Pattern seekers

[BigDiz]

Humans innately seek patterns in things that are random. That's why so many people wear smelly socks because they think they're lucky. Once you identify a supposed "pattern" i.e. non-randomness, you're going to keep noticing instances that fit that pattern, and ignore instances that do not. This is deeply ingrained.

Think about it, if you're at the roulette table and black has come up four times in a row, how likely are you to bet black? Most people would bet red, because, I mean hey, there's got to be a pattern. But (as I'm sure you all can understand) black has the same probability of occurring again as red does.

People have had this complaint about all sorts of playlist randomizers (not just iPod), it's just people seeing what isn't there.

Humans and dictionaries define random differently

[jonadab]

Except for mathematicians and programmers, most think of "random" in a *very* different way from its technical definition. To most humans, saying that a particular sequence is "random" means *guaranteeing* certain things about it. Among them: the same element does not occur back-to-back, EVER, even if there are only a few elements total to choose from. Even more, if there are more than about half a dozen elements, the same element never occurs twice within about five positions. (So if you've got songs 1 through 7 on your iPod, and the first seven played are 5, 3, 7, 2, 4, 1, 6, then the next one has to be 5 or 3, or _maybe_ 7, or it doesn't seem "random" to most people. Yet, the order can't be the same every time through, either.) No element occurs substantially more often than any other element, even over the short term. If the elements have a natural order (e.g., alphabetical), then no three elements that are adjascent in that order can ever occur together in that order, nor should they occur together in the reverse order. (This gets particularly difficult to guarantee when the elements have more than one natural order, e.g., if the elements are people, you can't have three of them in a row by either name or age, or people notice and decide that the order is not random.) Even worse, if the elements can all be categorized into a small number of categories (e.g., by gender), you can't have "too many" from one category in a row. (How many is too many depends on the ratio, but if half of the elements are male and half female, having four of either in a row will make people cry foul, the order is not "random".) If certain elements stand out from the others in some significant way, they can neither occur first nor last. (For instance, if test questions are being drawn from a question bank, neither the easiest nor the hardest question should be first or last; if it is, people will say the order was not random.)

I could go on and on, but what it really amounts to is that when most people say "random" they mean "carefully arranged in a thoroughly mixed-up order". This is almost the *opposite* of what a mathematician or computer programmer thinks the word "random" means.

For this reason, when describing a mathematically-random sequence to an end user, I never EVER use the word "random". I generally call it something like "arbitrary" or "unpredictable". This greatly reduces complaints.

Now, as far as song frequency, I like to rate my tracks on a scale of 1-10, and rig my playlist so that anything under a 6 never plays unless I specifically select it, tracks rated 7 play twice as often as those rated 6, and the frequency keeps going up the higher my rating is. (I only have eight tracks rated as a 10, and they're all things I don't mind hearing back-to-back.) Then if I find a track is playing more often than I like, I figure I rated it too high and cut back its rating.