Game Development Reference
In-Depth Information
8
Marginal Utility
In Chapter 7, we discussed how objects or actions can have relative merits that
may differ from their values. Different items have different utilities to different
people or even in different situations. However, going a bit further, the same item
may have a
different
utility to the same person at a different
time
. This complicates
our calculations significantly. We cannot simply count on something having a
particular utility any time we encounter it. We experience a constant ebb and flow in
the relative utilities of those items. How, then, can we use utility in our calculations?
If the utility is always changing, what is something
really
worth? That is the struggle
with trying to quantify utilities.
For instance, when I get up in the morning, having a can of caffeinated pop is
pretty high on my priority list. I have to admit that, at that point in my day, even the
idea of my wife's coffee-flavored milk (latte) is almost attractive to me (although
still a little peculiar). That early in the day, caffeine of
any
sort has a higher appeal.
I figure I'm not alone in this assessment. At a different time of the day, however, my
utility for caffeine is not as great. The can size is the same, the milligrams of caffeine
per ounce are the same—everything about my intake of the product is the same.
The difference is that it's just not that important to me at that time. The utility has
changed simply based on the time of day.
Moving one square further down this path, even the changes in the amount of
something that someone
already has
in an item can represent different increases in
utility. As I mentioned, I like that first can of pop in the morning. In fact, I like it
about as much as I can like any can of pop during the day (100% value). I like the
second shot of caffeine quite a bit as well. It isn't the same as getting that first dose,
however. There has been a drop-off in the utility that I have for it. As the day pro-
gresses, each additional can of pop has a smaller utility for me (Figure 8.1). I am still
gaining utility from each can, just not as much as the one before, and certainly not
as much as I received from the first can. Eventually, I get to a point where the util-
ity of a can of pop is next to zero. I am not getting any utility out of it at all. I could
take it or leave it.
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