There’s much to like in this book, including
- a taxonomy of error types: at the top level this distinguishes slips from mistakes. Slips are unconscious and generally due to dedicating insufficient attention to a task that is well-known and practised. Mistakes are conscious and reflect factors such as bad decision-making, bias, or disregard of evidence.
- discussion of affordances: an affordance is the possibility of an action that something provides, and that is perceived by the user of that thing. An affordance of a chair is that you can stand on it. The chair affords (in some sense is for) supporting, and standing on it utilises that support.
- focus on mappings: the idea that the layout and appearance of the functional elements significantly impacts on how a user relates them to their outcome. For example, light switch panels that mimic the layout of lights in a room are easier to use.
- consideration of the various actors: the role of the designer is to satisfy their client; the client may or may not be the user; the designer may view themselves as a proxy user; the designer is almost never a proxy user; the users are users; there is rarely a single user (type) to be considered.
But the two things I’ve found particularly striking are the parallels with Harry Collins’ thoughts in a couple of areas:
- tacit and explicit knowledge: or knowledge in the head and knowledge in the world, as Norman has it. When you are new to some task, some object, you have only knowledge that is available in the world about it: those things that you can see or otherwise sense. It is on the designer to consider how the affordances suggested by an object affect its usability. This might mean – for example – following convention, e.g. the push side of doors shouldn’t have handles and the plate to push on should be at a point where pushing is efficient.
- action hierarchies: actions can be viewed at various granularities. In Norman’s model they have seven stages and he gives an example of several academics trying to thread an unfamiliar projector. In The Shape of Actions, Collins talks about an experiment attempting to operate a laboratory air pump. Both authors deconstruct the high-level task (operate the apparatus) into sub-tasks, some of which are familiar to some extent – perhaps by analogy, or by theoretical knowledge, or by having seen someone else doing it – and some of which are completely unfamiliar and require explicit experience of that specific task on that specific object.
I love finding connections like this, even if I don’t know quite what they can afford me, just yet.