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Principles of user centric design

Making products usable and easy to understand requires an approach that puts the user at the centre of all design decisions. This applies as much to apps and websites as it does to any physical object we use.

Good user centred design should:

  1. Make it easy to determine what actions are possible at any moment
  2. Make things visible, including the conceptual model of the system, alternative actions and the results of actions
  3. Make it easy to evaluate the current state of the system
  4. Follow natural mappings between intentions and actions and their results

In The Design of Everyday Things, Donald Norman identifies 7 design principles for transforming difficult tasks into simple ones:

1. Use both knowledge in the head and knowledge in the world

This means combining experience of using a product, or a similar product, with cues in the design of the product.

The order of keys on a computer keyboard is knowledge in the head. The bumps on the the F and J keys are knowledge in the world and used by typists to locate the correct keys without looking.

You see this principle with ecommerce websites. The checkout will be familiar so it is easy to complete your order.

2. Simplify the structure of tasks

There’s a limit to how much a new user can remember or is willing to learn. There are 4 different approaches that can help simplify the structure of a task:

  1. Keep the task the same but provide mental aids
  2. Improve feedback and the ability to keep control
  3. Automate but keep the task much the same
  4. Change the nature of the task

In web design, this can mean storing and retrieving data so the user doesn’t have to re-enter it later or only showing form fields that are relevant depending on answers given earlier.

3. Make things visible

Designers can bridge the gap between execution and evaluation by providing feedback and making the outcome of actions as obvious as possible.

As an example, if a website has a personalisation option to customise content, consider where to show that option. It could be placed next to the content that will be changed by selecting it so the consequence is clear.

4. Get the mappings right

Make sure the user can understand the relationship between:

  • Intentions and outcomes
  • Actions and their effects
  • The actual system state and the system state perceived by sight, sound and touch

One of my first roles as a graduate was designing icons for software. There was no need to reinvent icons representing common functions like save or copy. Icons that represent real world objects map the intentions and outcomes e.g. the shopping basket for ecommerce, document icons for files.

5. Exploit the power of constraints

Designers can use constraints so the user feels there is only one possible action. Constraints can effortlessly guide the user through a system.

We often see this online in sales funnels and landing pages. If you want users to complete the checkout, don’t encourage them to leave by having a menu on these pages.

6. Design for error

Assume that every error that could be made, will be made. It’s not that users are deliberately being stupid. Every error is an attempt to correctly complete a task. Allow users to recover from errors, show them what has gone wrong and how to reverse it.

I can recall a project that took 12 months of real use and ironing out user issues before it was truly bug free because we underestimated the variations of data that customers would enter.

7. When all else fails, standardise

The easiest design principle to remember: don’t re-invent the wheel. Something only has to be learnt once to be effective.

When designing an online form, we proposed the method of providing a feedback score was a circle. The user would drag the end from point 1 round to point 5 to close the circle and submit the score. It looked great but was unusable – a simple drop-down option was much easier.

Easy looking is not necessarily easy to use.

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