The essential characteristic of an ergonomically designed object, system or environment is that it enables people to do the things they need to do. This sounds obvious until you remember all the times that this hasn't worked for you:

• The mobile phone which buries the 'add new name' entry somewhere down amongst the menus.
• The can-opener which won't fit neatly in the cutlery drawer.
• The new DVD player which doesn't work in quite the same way as the old one.
• The call centre which asks you to phone a separate number to get the information you thought they could give you.
• The website whose help pages never quite give you the information you need (mentioning no names...).

The key to these problems is to identify what people want to do and how they want to do it — then design around that. This identification of human needs is central to ergonomics and is supported by a loose set of techniques under the heading task analysis.

Task analysis consists of documenting users' goals and the sequences of tasks and subtasks they perform to achieve them. These sequences may also include alternate ways of doing things, how mistakes are corrected and how to cope with unexpected events. Task analysis can deal with both physical activities (eg, selecting an item on a computer screen) and cognitive (eg, deciding what to select). It also addresses not only the use of the designed object itself, but also tasks in the wider context.

The general aim of task analysis is to provide a way of looking at a design from the end-users' viewpoint. To put it crudely, if an engineer or designer looks after the what of a product, the ergonomist can use task analysis to look after the why.