During my recent research into the world of sensory interfaces, I had at least a dozen discussions, maybe more, about what the word intuitive means. I can’t remotely claim to have cracked this: on the contrary, it seems to me that people are still at the stage of figuring out the right questions to ask. It’s true that human-machine interfaces have been well studied and there’s vast literature on the subject. However, though sensory interfaces that allow you to interact with the real world (rather than a computer world) will certainly have many things in common with virtual displays, I think there will be some differences too.
Anyway, the first part of my definition is that the more intuitive something is, the less training it should require to be understood. Obvious, yes, but sometimes stating the obvious can be useful…
So, if we are looking for an interaction that requires as little training as possible, what does that mean? From talking to two people in particular—Paul Bach-y-Rita from the University of Wisconsin at Madison and Terry Sanger from Stanford—complexity came out as an important issue.
Bach-y-rita had been working on early tactile-to-vision systems that involved using a dentists’ chair with an array of pins that could be used to ‘show’ various kinds of pictures to the back of the person sitting in it. In one study, he said, they scrambled the picture order: essentially they shuffled the pixels around. However, they kept the shuffle constant during training, so the picture was scrambled in the same way every time. What they found was that the person could still learn to ‘see’ eventually, but it took a long time to learn to do it.
Sanger’s research is about giving dispraxic kids (children who have difficulty in controlling their movements due to various medical conditions) a means to get physical feedback from their own bodies. Specifically he uses a vibro-tactile device to feed back how a particular muscle is moving: so the faster or stronger the vibration the stronger the muscle movement. This means they can learn to ‘feel’ what it’s like to perform a task well despite the fact the fact that this feedback isn’t coming directly from the muscle. It also means that, unlike with other feedback systems that beep, they don’t get startled (startle response is often a problem for such children).
I’ll probably say more about Terry’s work later, but during our discussions he mentioned that he had been involved with an experiment where the movement of the subject’s four fingers were used to control twenty lines on a screen. Where there was a clear relationship between the finger movement and lines, control was easy. When the relationship was more complicated, only one person could do it at all, even with significant training: and she figured it out mathematically!
The problem is that complexity (in the common usage sense, not the mathematical sense) is a relative concept, something is more or less complicated than something else. In the next post I’ll talk about what the something else might be.