(Summary) Ease-of-use: Efficiency vs. Intuitiveness

29 Nov 2004 - 1:16am
1244 reads
Elizabeth Bacon

Quote from Dave:
But when I hear someone try to say that "intuitive", "efficient",
"effective" should have different more generic meanings in our space, it
really upsets me.
Intuition is about pre-learning, so it can't be equated to "learnable". If I
use my "intuition" to do something it means that it didn't require anything
to learn. Efficiency, is efficiency ... Effectiveness:effort derived.
Effective is about end result.

-- dave

Liz: I really don't understand your reaction, Dave. Nobody is trying to say
that these words "should have different, more generic meanings in our
space," although at the end of your message it seems like what you're
doing - "Effectiveness:effort derived"?? On the contrary, efforts to answer
our discipline's questions about defining "ease of use" need a lot of
careful consideration, and as the leading Interaction Design Group, I say we
need to use the terms "efficiency" and "intuitiveness" with ever greater
precision and carefulness. Please also listen to yourself thinking: "If I
use my "intuition" to do something it means that it didn't require anything
to learn" - you have just provided the definition of why we can MEASURE the
level of LEARNING to assess how "intuitive" something is (learning = zero,
then it's totally intuitive).

Quote from Dan:
Why would we want to vary from the term as it is commonly used though?
Maybe I'm dense, but I see a gap between effective (meeting user goals)
and efficient (doing so with the smallest expenditure of user effort).
They aren't the same thing and can be at odds. As Lada pointed out, a
system can be effective without being efficient.


Liz: Maybe I made too big a leap in my attempted summation without exposing
what I think are some of the underlying assumptions pertinent to this

0) We can assume that we are Interaction Designers designing interactive
systems that should fulfill a given purpose for a given person.

1) We can assume that "ease-of-use" is always a target characteristic of
these products we design for people.

2) We can assume that a user would define "ease-of-use" for a product as
having it properly serve their goals for a given scenario in a given
context. (For example, "I was able to renew my subway pass without having to
wait for the next train" or "I fired the missile knowing that I was fully
informed about the battle situation and the commander confirmed the

3) We can assume that an Interaction Designer can define a given product's
"ease-of-use" by measuring or at least assessing the system's "efficiency"
and "intuitiveness" (to at least a large degree).

4) Given the insanely wide variation we're dealing with in the systems we
design -- made for different people doing different things in different
contexts -- we can assume that the specific "efficiency" of an interactive
system is only *meaningful* in terms of how that system *satisfies its
target user's goals*.

Thusly, it seemed to me that to get anywhere on this issue, we can discuss
"efficiency" in the more real-world terms of serving the user's goals, which
can also be expressed as the system's "effectiveness". Isn't "effectiveness"
a much more human and helpful expression of efficiency than ... what,
mathematical calculations determining the "right" number of input options
for a screen display size? It's not "fewer buttons" or "more buttons" or
anything numerically quantifiable in the same way for all situations - even
time isn't necessarily going to be a standardizable unit for efficiency if
one considers potentially desirable product characteristics like the
engrossing "fun factor" that could lead to long-term customer loyalty, and
other subtleties depending on your application.

-- Similarly, we can and should discuss "intuitiveness" in more concrete
terms like learnability or familiarity. The optimum level of "intuitiveness"
for a given product will not always be "learning = zero"; it will depend on
your context and users and application posture and marketing strategy and
other design constraints.

Ultimately, I am concluding that "efficiency" and "intuitiveness" are in a
balancing act in each designed system, but it's not one "vs" the other by
any means. Intuitiveness is more important in the short-term or initial
usage of a system, while efficiency is more important in the long-term or
ongoing usage of a system. I'll stand by these points while y'all argue


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