Have you ever wished on all the stars above and a few below that you could be one of the lucky people? One of the few, proud owners of super rare horse poop?

Not real horse poop. Gross. I mean virtual horse poop.1 Back towards the end of the last century, Ultima Online was pushing boundaries and becoming one of the first commercially successful massively multiplayer online games. To help dress its virtual windows, UO designers littered a few stables with horse plop. But due to the way the game was designed, the horses didn’t generate new poop. And once players figured out that the horse poop that was there would be all there ever would be (at a supply of one piece per 30,000 players), it became a highly coveted collector’s item.2 It didn’t do anything. No beneficial stats, no quest rewards, nothing. It was just desirable to have in your inventory.

But why?

Well, let’s explore that question. Because a lot of us are familiar with collecting in the real world and we can kind of intuit why people want to gather up sets of physical objects like salt shakers, celebrity memorabilia, and trading cards. As marketing researchers Rebecca Mardon and Russel Belk note, it often comes down to two factors:3

Elusiveness – The likelihood and difficulty of acquiring an object, which makes you feel a sense of accomplishment when you track it down. This gives you the “thrill of the hunt” as you comb through antique stores, flea markets, and auction listings in search of that rare piece.

Authenticity – The extent to which an object is seen as “the real thing” based on how close in time or space it was to a significant person, event, or thing. It gives the object a uniqueness based on its history.

All this makes sense for physical objects, but it starts to get dodgy when you think of virtual items like skins, weapons, equipment, and other things you would find in a video game. Even achievements and UI elements like player banners, portraits, and pips next to your name could be lumped into this category. All of these things are just computer code. As such, they present obstacles to designers who might want to motivate players to play and pay through their desire to collect them. Most if not all of the things that make physical objects desirable to collectors can be swept away if a virtual object is infinitely reproducible, indistinguishable from other copies, and available for purchase all the time.

And yet people collect things in video games all the time. Some of it is horse poop. So what have game designers figured out about the psychology of collecting virtual goods that make amassing them desirable despite the deck of Pokemon cards stacked against them?

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Elusiveness

As mentioned, this characteristic of goods deals with how hard something is to get. This can be because it’s rare (first editions of books), far away from you (fridge magnets from different cities you visit), limited in quantity (limited edition sneakers), or available only at certain times (special holiday drinking glasses).

But digital goods are potentially limitless and don’t care about physical distance. There need not necessarily be old copies of a cosmetic item. No first editions. No mint condition when every copy is mint condition. And digital goods can be freely available 24/7 on an easily accessible storefront, thus robbing collectors of the thrill of the hunt.

So video game developers have come up with ways around these limitations to elusiveness. As Mardon and Belk note,4 they offer things like:

Time aristocracy

• Artificially limited availability
• Location-based availability
• Social-based availability
• Skill-based availability

“Time aristocracy” is a great term that means that an item is available to those who put in a lot of time to get it. Think grinding out currencies or faction reputation in order to unlock items.

Artificially limited availability relates to putting artificial constraints of time or numbers around the virtual items. Overwatch, for example, limits many of its avatar skins to seasonal events around Halloween, Christmas, or Chinese New Year. Team Fortress 2 limited the number of “earbud” cosmetic items in circulation by making them available for a limited time when the game came out on Mac. And, of course, the Ultima Online horse dung fits in here.

Location-based availability is more unusual, but you saw it in 2016 when millions of people wandered around the landscape in search of rare Pokemon in Pokemon Go. Mobile games like this can require that players be in certain locations to get items.

Social-based availability is also rare, but you sometimes see it in the form of “contagious” achievements like playing an online match with the game’s developer in order to unlock an achievement. Or playing so many matches with people on your friend’s lists in Heroes of the Storm in order to unlock a special skin.

Finally, there are some digital items that you just have to be skillful enough to get. Like achieving a certain killstreak in a game of Call of Duty or beating a raid boss to get the gear it drops.

Authenticity

Authenticity deals with how something has to be the real thing. Even an item that’s identical to all other copies can feel different and irreplaceable if it is imbued with a special meaning based on who owned it before you, where it came from, who gave it to you. The item’s history can be vastly important.

But again, virtual items often undermine this feature. Digital items can’t be physically close to any person or event. They don’t age or develop a patina5 Virtual items won’t necessarily develop an essence or history in the same way that physical ones do.

To get around this, game developers have learned to do the following:

• Letting virtual items develop a “digital patina”
• Surfacing metadata about objects
• Creating unique or special copies of items

Developing digital patinas involves letting players understand the developing history of an item that makes each copy of it unique. Tracking the number of kills scored with a weapon in a first-person shooter accomplishes this, and once again Team Fortress 2 does this by appending special descriptors to guns as you use them more and more.

Metadata about items can make an item feel more collectible if the player is aware of it. Pokemon Go does this by showing you where each Pokemon was collected. Players can then engage with a meta-game where they try to collect a Pokemon –even a mundane one– from each city they visit. Even seeing who gave you an item and when you got it can create a history for it, which makes it seem more valuable than otherwise identical copies.

Finally, creating special copies isn’t something I’ve seen a whole lot of, though some games might do it by letting players append signatures to their weapons, or making other modifications based on limited time events. Or having items of which only one is allowed to exist on any given MMO server.

So there you have it. You now know how to engage in a little mental judo to take virtual items that defy collectability and make players want to acquire them for all the same reasons we collect stupid stuff outside of games. If you have any examples of any of these other tricks in games, I’d love to hear about them in the comments below or on Twitter at @JamieMadigan.

Also, if you want a way more in-depth dive into this topic, I had one of the authors of the main paper I referenced throughout this piece on the podcast as a guest.