If you want to know if your user interface is intuitive, localise it to German.

It doesn't have to be German. Any language you don't speak will do.

Suddenly, you can't read anything. If, like most developers, you're used to plugging your mind into a firehose of information and soaking it all up, this is incredibly frustrating. You're forced to flail vaguely in the direction of something that looks like it might do the right thing.

And after a while you get so frustrated that you don't care about the details any more.

It's fascinating. I really believe that this is how most people use computers and the web, even in their native language. Either they don't read (why should they?), or even in their native language the text makes no sense to them.

I had this experience while rebuilding a Windows 7 machine for my girlfriend's parents. I've actually never used Windows 7 - I stopped doing PC support five glorious years ago - and the only install disc available defaulted to German. English was only available right at the end of the installation cycle, after several reboots and a manual update. Even with the OS localised, most of the other programs I needed to install weren't. The German keyboard slowed me to a crawl (backslash is RightAlt+?, forward slash is Shift+7, the Y and Z keys are reversed, and I still don't know what Strg does). Reading most text, if forced to, was a matter of painstakingly retyping it into Google Translate, so I tried to avoid it.

Suddenly, colours, placement, icons and defaults really mattered.

It was very like being a novice computer user, and that's exactly the point.