UX might be a relatively new discipline, but it’s informed by decades of research within the field of Human Computer Interaction (HCI). In this second article in the Comprehensive Guide to UX Design, I’ll discuss UX laws.

As I noted in an earlier article Universal Principles of User Experience Design, we are above all designing for humans, and humans broadly share similar characteristics that we should factor in when we make our design decisions. HCI offers us numerous principles that we can apply to the field of user experience design.

Many of these principles have been distilled down in the form of ‘laws’ that we can draw from, for example:

  • Hick’s Law, which stresses the need to minimise choices to ease cognitive burden and help drive decision-making;
  • Fitt’s Law, which provides valuable advice on how we can ease interactions through the careful sizing and positioning of interface elements; and
  • Miller’s Law, which emphasises the benefits of ‘chunking’ to ease complex tasks.

These are principles that can be applied at the both the macro- and micro- level and to improve as a designer they are well worth exploring in depth. I’ll explore three – Hick’s Law, Fitt’s Law and Miller’s Law – but there are many more.

Jon Yablonski’s excellent site Laws of UX is a helpful collection of principles, which is well worth bookmarking. Not only is a lovely piece of design in and of itself, it also provides a good overview of each principle accompanied by links to further reading.

Hick’s Law

Hick’s Law (or, in full, the Hick-Hyman Law) states: The time it takes to make a decision increases with the number and complexity of choices. Named after William Edmund Hick and Ray Hyman, a pair of psychologists, the law stresses the importance of reducing the number of choices you present a user with.

You might think you’re helping your user by offering an endless series of choices, but in reality you’re adding to their cognitive burden. The more choices a user is confronted with, the more likely they are to walk away, crippled by ‘decision paralysis’. This can be particularly problematic in an ecommerce context, where users walking away leads to a direct impact on the bottom line.

 Graphic showing books under category of Recent Releases
Rather than list every single book on its home page, A Book Apart features just recent releases, reducing the number of choices and alleviating decision paralysis. The entire library is just a click away for those looking for a particular book.

We can apply Hick’s Law to UX design in a variety of ways:

  • When creating navigation instead of providing an endless list of choices, focus on just a few. Your users will thank you.
  • In an ecommerce context, instead of listing every single product, reduce the number of choices and focus. Do this and you’ll offset decision paralysis leading to higher conversion rate.
  • Distinguish essential content from secondary content. By enabling users to find a path through fewer choices you’ll reduce their cognitive burden.

We’re often guilty of equating ‘more’ with ‘better’, but Hick’s Law tells us to think otherwise. The greater the number of options, the longer it takes our users to reach a decision (and sometimes leads them to making no decision). Focus is what matters, not least in a world increasingly overwhelmed with choice.

Fitt’s Law

Fitt’s Law states: The time it takes to acquire a target is a function of the distance to and size of the target. Translated that means: The farther away a target is – a button on a screen, for example – the larger it needs to be for a user to be able to reach it easily.

Fitt’s Law is particularly important when it comes to designing buttons and other clickable onscreen elements. Different contexts require different approaches and will inform your design approach.

Webpage with call-to-action for Start your Free Trial and entry box to enter email
On its home page, Intercom ensures that call to action buttons are large and eye-catching so that they’re both easy to see and navigate to.

In a desktop context a user will be using a mouse and – on a large screen – traversing potentially large distances. In this context it’s important to ensure your call to action (CTA) buttons are reasonably sized, easy to see and to click.

In a mobile context it’s critical to consider tap targets when designing interfaces. When designing for touchscreens, our fingers are lower fidelity than mouse pointers, so we need to increase our tap target sizes. (Of course, larger tap targets in desktop environments can help, too!)

We can apply Fitt’s Law to UX design in a variety of ways:

  • When designing for mobile, consider your tap targets. With less screen real estate reduce the number of clickable elements and increase their size.
  • It might sound obvious, but if you have a large button on screen, ensure it’s the primary call to action otherwise you run the risk of users clicking it inadvertently.
  • When designing dropdown menus or other forms of nested navigation, ensure your target sizes are large enough for users to acquire.

Generally speaking, the further away something is the larger it needs to be in order for a user to hit it. When planning out your design at a high level consider important calls to action and ensure you’ve taken on board Fitt’s Law when designing these. Tiny buttons might look neat and tidy, but if they frustrate your user, your design needs work.

Miller’s Law

Miller’s Law states: The average person can only keep seven (plus or minus two) items in their working memory.  In short: there’s only so much we can hold in our heads in a short space of time.

Miller’s law is particularly important when we consider how we organise and group information, and is where chunking can come in useful. Consider the formatting of the following two phone numbers (both the same, fictional number):

  • 07700984964 – or – 07700 984 964

As a string of digits without spacing, an eleven digit number is difficult for a user to hold in working memory. Add some spacing, however, and your users’ task is considerably eased. By chunking the information your user can retain the three groups of numbers in working memory, enabling them to complete their task.

 Web page to enter credit card payment details
When entering your credit card details at Gumroad spaces are added, chunking your credit card digits into groups of four. This helps users when they’re entering their card number and checking they have entered the correct card details.

Miller’s Law goes further than easing micro-interactions like this, it can also be used at a more macro scale. For example, when designing forms, focus on chunking information into logically organised groups: name, address and contact details; account details, like usernames and passwords; bank details; and other groupings.

We can apply Miller’s Law to UX design in a variety of ways:

  • When listing telephone numbers chunk the information so that it can be held easily in working memory
  • When designing payment forms that feature credit card information, a credit card number will be easier to parse by users if it’s broken into four chunks of four.
  • Reduce cognitive load by limiting the number of choices on offer.

As designers we often have to present complex information. Miller’s Law is useful to keep in mind in this context. Where possible look for groups of information that can be broken down and chunked, enabling them to be held more easily in users’ working memory.

Continue reading part three of Comprehensive Guide to UX Design: Communicating Visual Design.