I was thinking about this and couldn't figure this out. In Diablo you kill enemies and they drop random things. But usually the drops are worthless to you relative to what you already have equipped. Why bother building a drop system that gives you crappy drops? Maybe I'm not communicating my question well so I'll provide an alternative implementation:

Instead of frequently dropping crappy items and rarely dropping good items, why not only rarely drop good items?

I guess that crappy items adds to the addictive-ness somehow, but I don't understand why. Why is dropping crappy items part of the design? What does that add?

Edit: FWIW, I have been referring to Diablo 2 as my reference, not D3. But it's still interesting to see answers explaining why D2 was more addictive.

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    \$\begingroup\$ Well for starters, dropping crappy items most of the time communicates to the player that something will drop. That way something always drops, versus a system where the majority of the time you get nothing. \$\endgroup\$
    – jhocking
    Commented Aug 6, 2013 at 17:50
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    \$\begingroup\$ It's operant conditioning using a variable-ratio schedule, known to psychologists to be the most addictive type of reward schedule. It's the same principle that underlies the lottery and slot machines. \$\endgroup\$ Commented Aug 6, 2013 at 18:03
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    \$\begingroup\$ @NathanReed: So what you're saying is that it's half-assed game designers playing on psychological peculiarities rather than using good game design to make the game actually enjoyable. \$\endgroup\$ Commented Aug 6, 2013 at 19:20
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    \$\begingroup\$ You might want to take a look at this. It's an examination of exactly this type of behavior. \$\endgroup\$ Commented Aug 6, 2013 at 19:38
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    \$\begingroup\$ @NicolBolas: Abusing psychological peculiarities is what makes games "actually enjoyable." Enjoyability has no meaning outside of psychology. \$\endgroup\$
    – Phoshi
    Commented Aug 6, 2013 at 20:04

8 Answers 8


Usually, they're not totally worthless. While they're not better than what you have equipped, the items you can' wear can usually be sold or broken down and used in crafting. However, the psychology behind it is interesting.

These small, mostly worthless items are called reinforcers(more). They strengthen desired activity. In this case, playing the game and killing baddies.

Mindless, repetitive tasks are more enjoyable with small frequent rewards, instead of rare large rewards. Giving players a "physical" reward works well, even if it's not worth much. The "physical" part is important. XP or money are really just numbers, not an actual object (in game object) that the player can see. The psychological effect very similar to grinding XP or gold however, it's a reward schedule that keeps the player coming back for more.

Getting these small frequent low interest items, increases the desire to continue playing, since the good reward is right around the corner right? This likely takes advantage of the Gambler's Fallacy.

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This is a big reason people continue to buy scratch off tickets, or continue to pour money into a slot machine. Since they haven't won yet, they believe the probability of winning big is getting larger and larger.

Further, it's expected, and it should be. If players are continuously opening up the loot window, only to find no loot, they're going to stop looking and they're going to stop feeling rewarded. Even something little, not worth much, will show the player that they got something for their effort.

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    \$\begingroup\$ @tieTYT I've edited to clean up my meaning. The small reward is the almost worthless item. The "physical" reward is something that's an actual object (in game), and has a bit more meaning than meta-physical things like XP or currency. Yes, it could be argued that currency in game is a "physical" object, like gold coins. But it really just goes to increasing a value somewhere, so I call it meta-physical in this sense. \$\endgroup\$
    – House
    Commented Aug 6, 2013 at 20:26
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    \$\begingroup\$ @Byte56 Thanks! FWIW, your comment here really helped solidified what you were communicating more than your edit alone did. I'm saying that so that you don't delete it later :) \$\endgroup\$ Commented Aug 6, 2013 at 21:04
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    \$\begingroup\$ Actually slot machines and scratch off tickets regularly give small rewards, and both are very good at showing the player "how close they were" to winning. Sunk Costs also likely play a role in continuing to gamble (or in this case "grind" for loot). \$\endgroup\$
    – House
    Commented Aug 7, 2013 at 15:38
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    \$\begingroup\$ Another point: the probability of eventually getting a good loot usually does increase as you add more drops, unless e.g. the algorithm specifically reduces that probability for each subsequent drop. The crux of the matter is not that people are wrong in thinking that after the next drop the chances get better cumulatively, but in that they vastly overestimate this effect, or add "magical thinking" like the Gambler's Fallacy. \$\endgroup\$
    – mikołak
    Commented Aug 8, 2013 at 0:58
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    \$\begingroup\$ The chances get better on an average per-drop basis, but that's irrelevant. All the really matters is the probability on the next drop, which hasn't changed. Playing something like Star Pirates which has amazingly tiny probabilities on the best loot brings this home. \$\endgroup\$
    – Almo
    Commented Aug 15, 2013 at 12:11

Because there has to be a heirarchy of stuff. Common, uncommon, rare and ultra rare. It hooks into that primal part of people that likes getting stuff, and gets frustrated if it doesn't.

Slot machines are built this way. They pay out often, but only occasionally give the big prizes. The big prizes could be bigger if they only ever paid about big prizes. But then people wouldn't play, because losing 100 times in a row makes them quit. But if they win a buck here and 10 bucks there, they keep playing.

So you do the same with your loot drops. The player gets used to the hope every time something drops that it's something good.


Besides the obvious psychological aspect in Byte56's answer, I wanted to add something. There are a few interesting things regarding your example, Diablo 3.

Blizzard made quite and experiment with their auction house, which effects the way they made items and item stat rolls behave. I don't want to insinuate anything, but it is in Blizzard's interest that the chances a player finds an upgrade to their gear gets smaller, the better their gear gets. It makes players depend on the auction house, and of course animates them to use the real money auction house.

Since the announcement of the release of the console version, it was clear that they went a complete different way. There will be no auction house included at all, instead players are more likely to find items with stats they actually need. If they would have just removed the auction house and implemented the same loot system, players would become very frustrated at some point.

So it might not be just a loot system, but a business model.


Most drops will be crap because you are comparing them the best drop you've gotten so far.

Roll a die 50 times. Most rolls will be lower than the best roll so far, simply because you're going to roll maximum pretty soon; then all other possible rolls will be "bad".

The only way to get away from that is to constantly increase the maximum and minimum roll. You could for instance add the number of rolls you've made so far to the die roll. But even then, unless the increase per roll is high compared to the variance, most rolls will still be low as it takes many increases for one good roll to be negated. (I won't do the math now, but I suspect +1 per roll is still in the "most rolls are lower"-category.)

In Diablo et cetera you will of course continuously get better loot, as it scales to your level, but it doesn't improve fast enough to cancel this effect.

It is possible to design a "loot-curve" such that new items are better than old ones, but there are issues with that. You have to ramp up the power level of items quickly, or have very little randomness in how good each item is or give out loot only rarely.

As to why such loot-curves are rare: they don't suit a majority of games.

First of all, it's hard to rate different abilities against each other, even a two stat weapon, speed and damage, is hard to rate, given preferences of players, interaction with armour et cetera.

Secondly, most games expect a long playtime, so power gain must be spread out over a long time. Nethack, in my opinion, has mostly useful loot; but has short playtime and your powerlevel goes from worthless tourist to demigod capable of killing Death.

Third: such a loot system isn't very interesting. http://progressquest.com/ is a good example of such a system. There are no choices to make: anything you pick up is better than what you had before.

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    \$\begingroup\$ This seems like flawed logic to me. The developers write the drop algorithm and they can do it any way they want. If they wanted to, they could have made it so that the randomness is about "how much better than your current equipment will the next drop be?" EG: look at the current strength of your weapon and the next drop is currentStrength + 0-N. That's a very easy thing to do. They intentionally chose not to. \$\endgroup\$ Commented Aug 8, 2013 at 16:51
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    \$\begingroup\$ @tieTYT Yes, I mentioned that it is possible to design a loot system such that new items are better, by ramping power, lowering variance or reducing rate. The exact mechanism is unimportant, your method seems like a combination of faster power and lower variance. Also, it is not easy to rate your current gear, in a system like Diablo: is +19HP better than +1% exp or +10 damage? \$\endgroup\$
    – Odalrick
    Commented Aug 9, 2013 at 9:18

On topic of Diablo III's Auction House:

Low drop rates encouraged players to use the auction house at first, but in the end AH was the main reason for people quitting the game. I didn't really understand the reason behind this (my personal opinion was "just don't use AH if you don't like it"), but after reading the answers here I think I can finally see the problem.

AH had too great of an an impact on what the players considered a "good gear" to be. Let's say there's a new player who played about 10 hours without touching the auction house. Assuming the drop rates are set to low, the player's gear is most likely pretty bad at this point. But the player doesn't know that. He is happy for every new, ever so slightly stronger item that drops. However, this all changes after visiting the AH. The player suddenly realizes that most of his gear is very bad, and buys some new stuff from the auction house. He goes back to playing... but now an item which would be previously considered an improvement can't compare to the shiny gear bought on auction house. And this is the point where the whole "psychological addiction magic" disappears because the game rewards just don't feel good enough, all the drops start to feel "annoyingly worthless".

The scale of the game probably escalated this problem even further. Lets say a "rare good item" is something that drops averagely once per 20 hours of gameplay. When the playerbase is high enough those items turn out to be quite common and cheap on the auction house. They are easy to buy so a player might think they are easy to find... But they aren't. A single player still needs to play those 20 hours. Well, now that's discouraging...


I just wanted to mention this study which provides a scientific basis for Byte56's answer and everyone else talking abut the link with gambling.

The game was simple: when an icon on the left-hand reel lined up with the same icon on a right-hand one, the volunteer won a cash prize of 50 pence (75 cents). [...] A near miss came [when] the right-hand reel [...] eventually stopped within a space or two of lining up with a matching icon on the left.

The researchers found that those who scored highest in gambling severity also showed the most activity in the midbrain area in response to near misses. (They did not differ in their response to real wins, however.)

Note that near-misses gave no reward at all.

Almost winning in the context of loot drops means finding a neat sword that could be really good, casting identify on it, but finding it's not magic or anything. You're just going to sell it at the next shop (or if you're already rich in the game you might just trash it to make room for more loot), but if you'd received a drop of equivalent gold it wouldn't have that "near-miss" feeling.


Worthless items in my opinion can be categorized as vendor trash, and a means to actually make the player feel more accomplished when they actually get a good item.

There are a series of reasons why a lot of popular ARPGs spawn a lot of items rather than a select few. First of all, it makes the good items feel more valuable than they actually are. Second of all, randomly spawned items are a lot like gambling where players feel like the more they grind the better their chances are at getting a good item. Although, I honestly would not suggest spawning a lot of vendor trash to them, because games like Diablo III really messed up on this. You also should not have item affixes that are worthless and just there to promote vendor trash. Look at games more like Torchlight and Path of Exile in terms of item generation, because they did a lot better job at it. Good luck!


The simplest answer? To get you to keep playing. If everything had an equal weight in terms of rarity or probability or usefulness, you wouldn't have to play very long to collect everything in the game. This is doubly so when the amount of time you play is directly related to how much money you are willing to spend per month.


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