Image via Deviantart user GtkShroom (Image credit: GtkShroom)

Loot boxes are everywhere. They're in shooters, RPGs, card games, action games and MOBAs. They also take the form of packs, chests and crates. They're filled with voice lines, weapon skins, new pants or materials to get you more loot boxes. They're in free games and paid ones, singleplayer and multiplayer. They can be free to open and paid for with real money. You may feel an almost violent antipathy to the very idea of them, but you've probably also opened a fair few.

The appeal isn't hard to grasp. Opening a loot box is a rush: a moment of anticipation followed by release. That colourful animated flurry is often accompanied by disappointment, but is sometimes with the joy of getting exactly the item that you wanted. And then you feel the gambler's pull to open another, pushing you back into the game to grind or digging into your wallet to earn or buy your next one.

"It's that moment of excitement that anything's possible," Ben Thompson, art director on Hearthstone, tells me. "In that moment I could be getting the cards I've been looking for for ten or 20 packs. That anticipation has always been a key point in games in general; successful games build on anticipation and release, whether a set of effects or in gameplay."

Loot boxes' ubiquity might be fairly new, but they've been around rather longer than you might think. Economic sociologist Vili Lehdonvirta has suggested that they appeared in their modern form first in the Chinese free-to-play MMO ZT Online in around 2006 or 2007. A Chinese newspaper described how for a yuan you would buy a key : "When the key is applied to the chest, the screen will display a glittering chest opening. All kinds of materials and equipment spin inside the chest like the drums on a slot machine as the wheel of light spins." Yep, sounds like a loot box.

But they've also been around far longer in the form of baseball cards and Magic: The Gathering packs, and, if you think about it, even in identifying magic items in D&D. In each case you experience the same notes of suspense and reveal, and also the way the reward is separated from the action you took to earn them. That's an important distinction. Loot boxes aren't quite the same as the shower of loot you get for killing an elite monster in Diablo. There's more of a build-up, and rather than being focused on moment-to-moment play, your view is being pulled out far wider, into the meta game, into the larger systems that give you reasons to keep swinging your sword.

Loot boxes are appearing in more triple-A games, like Gears of War 4.

The psychology of loot

Why do loot boxes provide such a dark compulsion? Psychologists call the principle by which they work on the human mind 'variable rate reinforcement.' "The player is basically working for reward by making a series of responses, but the rewards are delivered unpredictably," says Dr Luke Clark, director at the Center for Gambling Research at the University of British Columbia. "We know that the dopamine system, which is targeted by drugs of abuse, is also very interested in unpredictable rewards. Dopamine cells are most active when there is maximum uncertainty, and the dopamine system responds more to an uncertain reward than the same reward delivered on a predictable basis."

We know that the dopamine system, which is targeted by drugs of abuse, is also very interested in unpredictable rewards. Dr. Luke Clark

What's more, the effect of variable rate reinforcement is very persistent. Psychologist B.F. Skinner conducted trials during the early 1930s in which he conditioned animals to respond to certain stimuli in closed chambers that became known as Skinner Boxes, and showed that even when the rewards were removed, the subject would continue responding for sometimes hundreds of trials, trying to recreate the circumstances in which it got its reward before.

"Modern video games then amplify this idea by having many overlapping variable ratio schedules," says Clark. "You're trying to level up, advance your avatar, get rare add-ons, build up game currency, all at the same time. What this means is that there is a regular trickle of some kind of reinforcement." Whether you're watching your XP climb up to the next level in Overwatch, or you're collecting scraps in Battlefield 1 by breaking down skins, there's a constant sense of reward leading to reward.

The clever—or insidious—bit is how a loot box is wired into a game, and how it doles out its baubles, keeping a player on the knife-edge between feeling hungry and feeling rewarded. One such system is Battlefield 1’s Battlepacks. Standard Battlepacks are earned by playing multiplayer matches. They used to be randomly awarded, but they recently switched to an Overwatch-like progression bar system for more regular drops. Each one is a guaranteed weapon skin or one of a number of pieces of a unique weapon. So that would seem satisfying, if it wasn’t for the scrap system.

Here, you can turn your skins into scraps an in-game currency called Scraps, which will buy you more Battlepacks. And they’re the only way without spending real money that you can access Superior and Enhanced Battlepacks, two upper tiers which have rather better chances of dropping Distinguished or Legendary weapon skins. The result is a system which ekes out rewards and then asks you to question them and wonder: should you dispose of them in the interests of getting better stuff?

It’s a complex system with a lot to get your head around, and remember: Battlefield 1 is meant to primarily be an FPS, not a lottery game. In other games, loot systems sit more centrally, and few are more central as the card packs in Hearthstone. Since it’s a collectible card game, they’re perhaps so fundamental to the game that it's inaccurate to consider them loot boxes in the same vein as the controversial packs of skins and items added to recent big-budget games like Destiny 2 and Middle-earth: Shadow of War . Still, they're a great example of the loot box's principles.

How Blizzard designs loot boxes

The clever—or insidious—bit is how a loot box is wired into a game, and how it doles out its baubles, keeping a player on the knife-edge between feeling hungry and feeling rewarded.

You can buy packs in Hearthstone with an in-game currency called gold. There are several ways to earn it, but the key methods are that every third game you win awards you with 10 gold, and for each daily quest you complete, such as winning games with a certain class, you'll get at least 40 gold. A card pack costs 100, so you can expect to earn at least one every couple of days. This system is subtly integrated into play; most quests gently encourage you to try classes and playstyles you're not used to, while also rewarding you for simply playing the way you like. Or you can just buy card packs with real money. Classic card packs cost $3 for two, $10 for seven, and the scale goes up to $70 for 60. Despite the pride some take in being free-to-play, most will spend money at some point, while those who don't get the reward of telling themselves they're saving money by playing.

The five cards you get in each pack will be taken from across all the game's classes, at least one of which will be 'rare' quality. "We're just straightforward with it," says Thompson, but it has other benefits. "People are more inspired to try different and new things. So if I get a number of Shaman cards, maybe it's interesting for me to start to build a Shaman deck? Or I can craft them into cards I do want in the game. We allow player agency to dictate it, but we also avoid putting them in a position where they choose themselves out of experiences."

The loot box's place in Overwatch is quite different since they contain cosmetic items—skins, emotes, voice lines and victory poses—rather than the very thing you play with. But you acquire them in a similar way: play with any character and you earn XP, with various bonuses granted, for example, by playing with friends and for good performance. Level up, which is possible every hour or so, and you earn a loot box.

"We aimed for players earning a box or two in a gaming session, so that you wouldn't walk away from a session empty-handed," principal designer Michael Heiberg tells me. "An earlier version of the game's progression system had per-hero experience levels, with rewards at various hero levels. In testing, though, we saw players picking heroes based on these hero level rewards instead of picking based on what the team needed, or even what they felt like playing. It was a bust, and we knew we needed to disassociate your hero picks from the rewards. Based on that, we shifted to a system with randomized rewards that you could earn by playing as any hero."

Overwatch's loot box is a masterpiece of audio-visual design. "It's all about building the anticipation. When the box is there you're excited at the possibilities of what could be inside," says senior game designer Jeremy Craig. Click the ‘Open loot box’ button and the box bursts open, sending four disks into the sky. Their rarity is indicated by coloured streaks to further build the suspense. "Seeing purple or gold you start to think about what specific legendary or epic you've unlocked. This all happens so fast, but it was those discrete steps that we felt maximized excitement and anticipation."

Hearthstone's opening animation is likewise engineered to trigger anticipation, and also to make the cards desirable objects and to imbue them with a sense of value. From the start it was important that they'd evoke real collectible cards. As Thompson says: "Ripping that foil pack and feeling it give, that moment of excitement that anything's possible."

Rather than hitting a button and watching, as you do when opening most loot boxes, from Battlefield 1 to Overwatch, you have to drag a pack over to what Blizzard calls the altar. There's a brief moment as blue magical power builds, and then, in the case of the classic packs, the cards suddenly burst out in a shower of glitter and gold. With Journey to Un'goro packs, they emerge in a crackle of lightning (which echoes its evolve mechanic), and a shattering of ice in the Knights of the Frozen Throne packs.

The challenge was to design a sequence that would feel special to those opening a single pack while not wearying those opening 50 in a row. "If you buy that many you don't want to spend half your day opening them, you want to get them open and start building decks and experience the real focus of the game," says Thompson. "As much ceremony as we want to put into the pack opening, we need to keep it concise." The sweet spot, it turns out, is about two seconds.

As Overwatch does, Hearthstone indicates the rarity level of the cards you'll be getting before the cards are actually revealed. Mouse over their backs and you'll see a colored glow on rare, epic or legendaries. "We don't immediately flip them, we let player agency take a seat in the sense of controlling what order they flip them in, how they flip them, the time between each flip."

Loot makes you superstitious

That hint of control is quietly important to the design of Hearthstone's card packs. "What we found in talking to people is that superstition sets in," says Thompson. "What you'll find in psychology is that if the outcome is of high import, you know like, 'Gosh I hope I get a legendary in this,' and if player agency is unclear in terms of your ability to manifest any kind of change in the outcome and there's a little bit of randomness involved, superstition takes hold. That agency and sense of involvement and choice is super important in terms of the experience and the enjoyment of it."

You've probably dabbled in something like it too, by performing some kind of personal rite before opening a loot box. Here's YouTuber Jordan 'Kootra' Mathewson mass-opening Team Fortress 2 crates his own way. This behaviour is actually common across many species: Skinner discovered in 1947 that even pigeons exhibit it . He observed that they’d practise little rituals in the hope that they’d cause food to appear, including turning around in their cages or nodding their heads, and yet the food was given to them at entirely regular intervals. The absence of any explanation of why the food appeared had conditioned them to believe their actions caused it. On a deep level, our own minds work the same way.

Skinner observed that pigeons practised little rituals in the hope that they’d cause food to appear, including turning around in their cages or nodding their heads.

Overwatch and Hearthstone contrast with the common way loot boxes are presented. The Counter-Strike: Global Offensive model, in which the gun skins in the crate scroll by, slot machine-style, is a direct evolution of the old ZT Online design. Their distinct lack of visual pizazz is compensated for with the graphic way they show you what you could have won, and when the needle just misses the item you wanted, it's hard not to reach for another go, even though as far as CS:GO is concerned it's as black and white a result as rolling a die.

This design closely mirrors the near-misses in many forms of gambling, from horse racing to roulette. As psychologist Luke Clark has said , "A moderate frequency of near-misses encourages prolonged gambling, even in student volunteers who do not gamble on a regular basis. Problem gamblers often interpret near-misses as evidence that they are mastering the game and that a win is on the way."

In most countries, including the US and UK, loot boxes are not legally considered gambling because the winnings have no intrinsic value outside the game (in China, laws have actually forced developers like Blizzard and Valve to publish the drop rates of their loot boxes). But in being expensive to buy and based on the same psychological principles, we have to treat them with the same care.

Why do we love collecting stuff?

Loot boxes also plug into another facet of psychology: collection. In 1991, Dr Ruth Formanek in the Journal of Social Behavior and Personality suggested five reasons we feel the compulsion to collect, including 'extending the self' by obtaining knowledge or having sole control over one's collection, the social benefits of collecting leading to meeting like-minded others, creating a sense of continuity in the world, financial investment, and addiction or compulsion. Alternatively, Freud suggested that it's rooted in a deep desire to reclaim the poo you excreted as a baby.

We don't want players getting frustrated because they're earning none of the best rewards. We also don't want players getting bored because they earned all of the best rewards at once. Michael Heiberg, Overwatch

Whichever theory you go with, loot boxes are almost always filled with collectibles. Overwatch's boards of sprays and percentage counts for completion rates on characters remind you of what you've accrued, and Hearthstone is a collectible card game. Games as a whole highlight an interesting distinction between freeform and structured collection. Collecting, say, baseball caps is freeform collection because you can accrue them indefinitely. But games present a very structured form of collection, tapping into several powerful motivational principles. You're working towards a clear and achievable goal and you can see your progress towards it. During matches you get to show it off to others who are also immersed in collecting the same items, a chance to feel both kinship and bask in the status your collection confers.

And there are systems of scarcity, driving value towards certain items. But managing them is a delicate art. "We use rarity levels primarily to control the frequency of getting our most exciting content," says Overwatch principal designer Heiberg. "We don't want players getting frustrated because they're earning none of the best rewards. We also don't want players getting bored because they earned all of the best rewards at once. Rarity levels give us some control over the pace of these rewards."

Both Overwatch and Hearthstone's designers are careful not to dictate value. "We learned that the value of our cosmetic content varies widely from player to player, and that no distribution of rarities was likely to really jive with everyone," Heiberg continues.

"Some players are super excited about that rare card and the legendary doesn't mean so much, and similarly you'll have someone trying to build an all-Murloc deck and they're going to be more excited about a common Murloc as opposed to the legendary of a class they're not after. We let those moments be fun at every level and not focusing on legendary cards being awesome and how you should get all of them, but rather let the player get excited about any aspect of the opening."

It's easy to feel uncomfortable with loot boxes. They have a powerful capacity to manipulate your behaviour and extract considerable amount of time and money from you with systems that aren't the core game you actually want to play. The bad ones use these tricks to make you value in-game items that you might not choose to in the cold light of day. They can pull you to do things to acquire them that you’ll regret in the long term. But the well-designed ones give you space to find your own value in the trinkets they dole out. That's an indicator that they respect you, and a sign that they recognise—correctly—that collection should be a reward in itself.

"Pack opening is an area that took a fair bit of time to develop because it's a moment players will spend a lot of time with," says Thompson. "More importantly, they'll spend money there and any time our players are investing time and money we want to give them a very fair and honest return. We want people to walk away feeling they got value from it, and that value can come from not just a return on that time or money but also fun. We say we make decisions in Hearthstone based on how much fun players are having, and pack opening is no less of that."