If we want to design effectively for humans working with computers, clearly we need to understand humans. So let's talk a little bit about the nature of humans, the way we operate from our senses through to our actions. And one way to think about this is almost like a computational analogy. If you think about the computer, there's inputs to the computer, the things that you type at it;
the presses you do on its surface. It does some work and it produces outputs. And one of the models for human psychology is to think like that about the human. So on the one side, you've got perception, you've got our senses, our sight, our sound and things like that that feed in. Then you've got your brain in the middle that does lots of chuntering and processing. And then it creates outputs, so physical actions but also speech, and anything else that we're using – facial expressions.
So that's a model of the human, which is the input-output engine model. That can be quite powerful. You can look at those parts individually, and a lot of psychology is about focusing on one part or another part at a time and trying to make sense of what's going on there. However, that doesn't give you, shall we say, a rounded picture of the human. Because we don't just act as an output; we act in order to live our lives.
There's actually a loop that goes on – a complete picture – so we might perceive something... So I might spot something I'm interested in. I might then think, "Oh, I'll go and look at it." And then perhaps I start to move off in that direction to go and have a look at the thing. If you're dealing with a computer, of course, the thing you act on typically is a computer. So maybe I'll look at my computer. I see something. I think, "Ah, I want to read my mail". I reach out and,
you know, if it's a phone, I might tap the icon. If it's on my computer, I might use my touchpad and move the mouse and click the icon. And then, of course, when I click the icon, something happens. There the computer does something back. If it's the world, if I pick something up, if I throw a stone, the stone moves through the world, and I perceive the impact of my actions on the world. I might perceive that by seeing it; I might perceive it by feeling it.
So there's this complete loop that goes from action through to the world, through to perception, to cognition, back to action. And when I drew it as an input/output loop, we started off with perception as if perceptions drove things. However, there's also a good argument to think starting with action. Actions might arise because of perceptions. But actually, what are we about as humans and as any animal? We're there to do things. We're there to do things,
to get food for ourselves, to help us keep comfortable. So it's about *doing things in the world*. And so there's one way to perceive, to look at this picture as *input to output*, but another is to actually focus on that action, about really achieving the things that we want to achieve. Now that's true of our physical existence in the world, but also crucially, that's true when we design digital interactions.