The trouble is, if it didn't start good,
it might not end up very good at the end, despite iteration.
And the reason for that is a phenomenon that's called *local maxima*.
So, what I've got here is a picture.
You can imagine this is a sort of terrain somewhere.
And one way to get somewhere high – if you're dumped in the middle of a mountainous place –
if you just keep walking uphill, you'll end up somewhere high.
I mean, actually, you can do the opposite as well – if you're stuck in the mountains and you want to get down,
the obvious thing is to walk downhill.
And sometimes that works, and sometimes you get stuck in a gully somewhere.
So, imagine we're starting at this position over on the left.
You start to walk uphill and you walk uphill and you walk uphill.
And eventually you get onto the top of that little knoll there.
It wasn't very high.
Now, of course, if you'd started on the right of this picture,
near the *big* mountain, and you go uphill
and go uphill and you go uphill and you get uphill,
you eventually end up at the top of the big mountain.
Now, that's true of mountains. That's fairly obvious.
It's also true of user interfaces.
If you start off with a really dreadful design
and you fix the obvious errors,
then you end up with something that's probably still pretty dreadful.
If you start off with something that's in the right area to start with,
you do better.
The Malverns are a set of hills in the middle of the U.K.
– somewhere to the southwest of Birmingham.
And the highest point in these hills is about 900 feet.
But there's nothing higher than that
for miles and miles and miles and miles.
So, it's the highest point, but it's not *the* highest point,
certainly in Britain, let alone the world.
If you want to go really high, you want to go to Switzerland and climb the Matterhorn
or to Tibet
and go up Mount Everest
up in the Himalayas.
You'll start somewhere better, right?
So, if you start
– or on the island I live, on Tiree,
the highest point is 120 meters.
So, if you start on Tiree and keep on walking upwards,
you don't get very high.
You need to start in the *right* sort of area.
And similarly with a user interface, you need to start with the right kind of system.
So, there's two things you need for an iterative process:
You need a *very good* starting point.
It doesn't have to be the best interface to start with.
But it has to be in the right area. It has to be something that when you improve it,
it will get really good.
And also – and this is sort of obvious,
but actually is easy to get wrong:
You need to understand *what's wrong*.
So, when you evaluate something, you really need to understand the problem.
Otherwise, what you do is you just try something to fix the obvious problem
and ending up maybe not even fixing the problem,
but certainly potentially breaking other things, as well, making it worse.
So, just like if you're sort of trying to climb mountains,
you need to start off in a good area.
Start off in the Himalayas, not on Tiree.
You also need to know which direction is up.
If you just walk in random directions, you won't end up in a very high place.
If you keep walking uphill, you will.
So, you need to understand where to start
and understand which way is up.
For prototyping your user interface,
you need a really rich understanding of your users,
of the nature of design,
of the nature of the technology you're using
in order to start in a good place.
Then,
when you evaluate things with people,
you need to try and *really deeply* understand what's going on with them
in order to actually make things better
and possibly even to get to a point
where you stand back and think, "Actually, all these little changes I'm making,
I'm not making really a sufficient difference at all.
I'm going around in circles.
Sometimes, you have to stand right back
and make a radical change to your design.
That's a bit like – I mean,
climbing up the mountain and I've suddenly realized that I've got stuck up a little peak,
and I look out over there – and there's a bigger place.
And I might have to go *downhill*
and start again somewhere else.