Human Behavior and the User Experience

By Ken Mohnkern, Interaction Designer on Nov. 22, 2016 View Comments

shutterstock_517795534.jpgWhile navigating a well-designed user experience feels organic and natural, the science behind that end result is very much a deliberate effort. Assumptions and whims make User Experience (UX) Designers squirm. Instead, we prefer making design decisions based on evidence and data, but when we can’t perform our own research by observing the behaviors of users, we can still avoid “guessing” what users want by following basic UX principles as we design digital systems. Many of those principles are based on well-documented studies, but some of the studies are misunderstood and misapplied to digital design.

Let’s visit the research behind three foundational UX principles and how they can be applied properly to enhance the user experience.

Fitt's Law

The speed to point at something depends on the distance to the thing and its size.

If you intend to make certain links on a webpage easy to access (say, important calls to action), make it easy for a user to point at them and click. Give them large, clickable areas, and maybe you can assume the cursor is at the location of the last link clicked (on the prior page) and place the primary call to action nearby.

There are many ways to implement this:

  1. On a tabbed interface, make the entire tab clickable. Not just its text label.
  2. On a grid of items consisting of multiple elements (i.e. an image, a name, a description, a “read more” link), make as much of each item as clickable as possible. Don’t make users click again and again, trying to figure out which part of the item is the link to the detailed page.
  3. When showing a modal-style pane over a webpage, make the “x” button big enough to easily find and click. In fact, consider making a click on the entire background close the modal.

Conversely, pop-up ads on webpages and mobile apps often have tiny “x” buttons that are hard to click.

You can confirm Fitts’ Law for yourself here.

Hick’s Law

The time it takes to select an item from a group of things increases as the group gets larger.

A user presented with more choices will take longer to find what he or she is looking for than one presented with fewer choices. The effect follows a log formula, so the difference in response time gets smaller as the group size increases.

Some designers mistakenly apply Hick’s Law to the time it takes to make decisions among multiple options. But Hick’s experiments involved no decision making. In them, one bulb in a curved line of lights illuminated and the subject tapped a switch that corresponded to the light’s position along the line. Further, the subjects were Hick himself and a “research worker,” so he wasn’t testing novice/expert effects.

Instead, Hick’s Law is about response times, given that the subject knows exactly what they’re looking for. For example, the experiment’s participants might have thought, “The sixth light is on, so I have to tap the sixth switch.” The equivalent situation for digital designers is when a user knows they need the “Contact Us” page and looks for it in the header among the other links there. That link will be quicker to find among five other links than if it’s among fifteen other links.

Miller’s Law

Short-term memory holds seven chunks of information (plus or minus two, so five to nine).

Some designers apply the 7±2 rule in inappropriate situations, stating that navigation bars and drop-down menus should contain only 5-9 items. Miller’s Law doesn’t support those decisions (though limiting the number of items in a section is a good idea). Items on the page are available for reference there, and don’t need to be stored in short-term memory for reference.

The most common application of Miller’s Law is to never require users to remember anything from page to page. (Short-term memory is affected by interruptions and distractions, so it’s likely, in practice, that people can recall much fewer than five items.) Every page should display all of the information necessary to a user at the time they need it. Product “Compare” features on e-commerce sites allow users to select a few items from a list and see their information all together on another page. Shopping Carts often show all of the information they’ve collected so far in the process at each further step.

Fitts’, Hick’s, and Miller’s research on human behavior has a lot to contribute to UX and usability, but we have to ensure that these ideas aren’t applied to situations where they don’t really fit. Instead, use the research as a guide to ensure that users are getting the information they need easily and frequently, and that the information you want them to see is quickly identifiable. By applying these UX principles, your first round of testing will be closer to that organic, natural experience that users so desire.


Posted in: User Experience Design, UX Design, User Experience