So, the first channel that you can use is the same that
I have described in the previous set of examples, which is position.
Position is always the best channel,
and the channel that is available for all kinds of information that you want to express.
So, how do you express order with position?
Well, a good example is anything that resembles a list or a table.
We naturally perceive our list as an ordered set of elements,
of course this could be vertical like this or something horizontal like this,
but the idea is that anything that is expressed as a list
or a table is actually perceived as an ordered set of elements.
So, position is a very powerful,
is actually the most powerful channel you can use to express the idea of order.
Now, if we want to use other channels,
there is a little problem.
So, the fact is that, in principle,
every channel that I described as a way to
express quantity can be used to express the idea of order,
because when you want to express the idea of order,
the information that you need is that something comes before or after something else.
But the problem is that,
if we use the channels that I described when I
presented out the information about how to express quantity,
it's very hard to distinguish or it's very hard to perceive
this information without also proceeding at
the same time the idea that there is a quantity attached to these values.
Let me give you a practical example to make this clearer.
So, if I want to express order as the size of
bubbles similar to what I have shown before,
you can't help but perceive the area of this bubbles as communicating to you a quantity.
So, in a way there is a mismatch,
there is a breakdown of the expressiveness principle. What do I mean here?
What I mean is that, if you are
encoding ordinal information with a channel like area size,
you will also be conveying the idea that these elements have a quantity attached,
even if this is not the case.
So, this is a little bit of a problem.
So, what are good channels to express the idea of order without at the same time
giving too much of an impression that
these elements also have a quantity attached to them?
Well, the best way to do that is to use
channels that can in principle express the idea of quantity,
but they are not particularly good at doing that.
Let me give you an example of two channels that can do that pretty well.
The first one is texture or density.
So, see that I have three graphic called elements or patches like this one.
So, I can use a textured like this one,
or one that is higher density like this one,
or another one that is even higher density like this one.
So, now you naturally perceive these three elements as ordered.
In principle you could also attach a quantity or express a quantity with them,
but they are not particularly good at doing that.
Because of that, they are good at expressing
order without necessarily conveying the idea of quantity.
