[MUD-Dev] Law of Diminishing Marginal Utility [was Boredom]

Ron Gabbard rgabbard at swbell.net
Sat May 25 06:16:43 New Zealand Standard Time 2002

From: "Ben Chambers"

> What do you do to prevent players getting bored?  It is inevitable
> that at some point they will become so good that the areas and
> monsters you have made just don't challenge them... Generated
> quests just won't be difficult enough, and you won't be able to
> churn out new areas to explore and new scripted/programmed quests
> to do.  How do you keep a player like that entertained?

I've actually thought about this exact topic a lot as a means for
analyzing different in-game systems and procedures.

As you stated, every player of every game will eventually become
bored and leave.  It's inevitable given the Law of Diminishing
Marginal Utility that states that every unit consumed of a good will
give a lower level of satisfaction (utility) than the previously
consumed unit.  While the downward sloping line will have a
different shape for each person, it's a fact that every player's
line slopes downward and that they have a horizontal line on this
graph that represents the level of utility of other options for the
use of their leisure time. The player will leave the game when the
utility received from playing a particular MUD falls below that

As a game developer, there are only two things that you can offer
the player -- mental stimulation and emotional satisfaction through
the acquisition of virtual wealth, skill wealth, and human capital
in a challenging and immersive environment.

Imagine a MUD that has only one facet -- level up the character.  In
this MUD, the satisfaction from earning level 2 is higher that
earning level 3 which is higher than that for earning level 4, and
so on.  The result is that the amount of time a player is willing to
invest in earning each subsequent level becomes less and less
corresponding to the utility gained from acquiring that next level.
This is counter to the standard XP curve that requires a larger and
larger investment of time for each subsequent 'level'.

So, the developer adds new skills to the game where the player is
rewarded for achieving certain 'levels'.  In this example, let's say
that at level 5 the player receives the spell Fireball and they can
put away that bloodied stick they have been using to whack the local
flora and fauna.  Thus, you get a spike in mental stimulation and
emotional satisfaction (thus, overall utility) because the player
now has a new skill to learn and can more effectively destroy the
local flora and fauna.  Now, this is where using skills to add
utility gets tricky.

Assume that this MUD's player progression model is such that the
player gets new skills every five levels.  This model will result in
a spike in the player's overall utility curve every 5 levels when
they get their new skill.  However, if the new skill is just an
upgraded version of the skill gained at level 5, the marginal
utility will be less than if it were a completely new skill.  For
example... If the player learned Fireball1 at level 5 that is able
to do 30% damage to mobiles his/her level, learning Fireball2 that
is able to do 30% damage to mobiles his/her level will give less
satisfaction than learning 'Invisibility' or some other spell that
offers new utility.  This is the trap that many MUDs fall into where
player skills increase by X% and the corresponding mob difficulty
also increases by X% (or even X+1%).  Thus, the player stays in the
status quo (or is penalized) and the 'spike' in utility from gained
new skills becomes negligible as it is also affected by the Law of
Diminishing Marginal Utility.

Thus, the game developer adds loot to their MUD.  Loot is often
implemented in the same manner that Skills are implemented in MUDs
and is a primary reason why a 'robust' economy is so important.  A
level 1 mobile will drop X coin, a level 2 mob will drop 2X, etc.
The developer also adds 'rare drops' that a player can get when
receiving a particular level.  However, like skills, these items
typically just maintain the status quo in terms of overall player
effectiveness.  In addition, the real use for coin (number of
purchasable items with a greater utility than previously purchased
items) decreases over time due to shallow economies.  Eventually,
the incremental value of that next gold piece becomes minimal and
the next 'phat loot' is needed just to maintain a player's
effectiveness.  The Law of Diminishing Marginal Utility sets in
again and drives down the satisfaction gained from loot.

The same thing happens with the addition of mobiles, mob_Y and
mob_Z.  There is a spike in overall utility as the player gains
mental stimulation from fighting the new beasts (even moreso if the
new mobiles have a different AI).  However, the marginal utility
gained from killing mobiles Y & Z starts downward as well after the
first killing.

The next facet is immersiveness.  While not a tangible/quantifiable
aspect of the game, immersiveness has a drastic impact on the
utility curve for most players.  The greater the immersiveness, the
longer the player goes before hitting that "it's just a game" phase
of optimization, i.e., the overall utility curve doesn't start
sloping downward as soon and not as steeply as a game with a low
level of immersiveness.  Immersiveness can't completely counter the
Law of Diminishing Marginal Utility forever but it can definitely
lengthen the amount of time a player will play a game.

The last part is the 'Human Capital' aspect of
MUD's... socialization and friendships.  In my opinion, this is the
most critical area for encouraging player longevity in a MUD as it's
the only aspect that is not impacted by the Law of Diminishing
Marginal Utility.  The value of the relationship between Bubba the
Warrior and Frank the Thief is greater after 3 months playing
together than it was after 2 days... and continues to increase over
time.  While the impact of Human Capital will vary from player to
player, the 'cost' to the player of leaving those friends by
quitting the game lowers the value of their best alternative
activity, (that horizontal line representing the point at which they

This is why I am puzzled why so many commercial MUDs are striving
for 'soloability' of characters and minimal downtime.  While I don't
know if I totally agree with Raph's "50% downtime" model, time for
socialization certainly needs to be greater than the "almost zero"
downtime found in some of the more recently released commercial
MUDs.  And, it needs to be 'quality' downtime for socialization and
not downtime where the player goes AFK for 15 minutes (as in the
case of the 'boat' in EQ).

In short, I don't think the 'boredom' factor can be removed from
MUDs...  it's inherent with every activity no matter how fun.
However, player development, skill progression, and the economy can
be developed in such a way that the effect of the Law of Diminishing
Marginal Utility is lessened by always keeping a 'carrot' in front
of the player.



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