When designing software don't forget Fitts and Hick

In technology, ideas and innovation drive successful companies. As new markets arise they quickly become crowded with competitors. Questions such as "How can we differentiate ourselves?" arise. The minimal start-up cost for software and internet companies magnify this question. Excellent user design and interaction can be a differentiating factor.  Although it does not drive immediate customers in the same manner as new features, it should not be ignored. Once a user passes their frustration limit, their advocacy is lost. The following sections describe two design principles at the core of design and interaction.

Fitts' Law
Fitts' Law is defined as follows: "The time required to rapidly move to a target area is a function of the distance to the target and the size of the target." In simpler terms, the bigger or closer an element is, the faster a user can move to it. The starting position is based on the current location of the cursor. When moving to an element, the initial movement is fast. As a user approaches the destination, the speed decelerates to avoid missing the target. Figure 1 (below) outlines this process. Based on this knowledge of distance, aren't the edges of a screen bad? No, users treat the edges of a screen as having unlimited height and width. This works in favor of Fitts' Law and turns the corners into prime real estate.

Figure 1

Fitts' Law is key in the placement and size of features in a design. Although right-click menus are not intuitive they conform to the law by providing functionality with minimal movement. Mobile devices have continued this technique through the holding down of a finger to quickly access options such as copy and paste. Fitts' Law may lead some to believe that increasing the size of all buttons aids the user. It is important to note that the size of buttons are on a logarithmic scale of usability to size. Figure 2 (below) shows the impact of usability on smaller items versus larger items.

Figure 2

Hick's Law
Hick's Law is defined as "the time it takes for a person to make a decision as a result of the possible choices he or she has." In simpler terms, a user's reaction time will decrease in proportion to the number of choices presented. After reviewing the definition most would agree that this law seems obvious. That might be true, but most designs lack implementation. Only highly proficient, seasoned users can handle complex interfaces due to the high cognitive load required. An average user expects and requires a simple interface. When a screen has too many fields, a wizard should be considered. If button farms form on a screen they should be reduced to key features.  Lists such as multi-select boxes, radio buttons, navigation menus, and tree views should have a limit on their length. Figure 3 (below) provides two options for combating this issue. A designer can shorten the viewable list or reducing the total number of options.

Figure 3

This law commonly evokes the question "What's the maximum number of items?" from developers. This leads to the unsavory answer of "It depends." Although that is true, developers are not fond of that answer. Psychologists have determined a person can hold between 5 and 9 thoughts in short-term memory; therefore, a safe guideline is a maximum of 5. This ensures a wide acceptance rate. It is important to clarify this is only a guideline, not a rule. Hick's law is an excellent advocate of the KISS philosophy (Keep It Simple, Stupid).

Final Thoughts
Unfortunately, too many developers limit themselves by ignoring user design. They make excuses such as "I make it functional, not pretty" and "I'm a programmer, not a web designer." These are frustrating statements to hear.  Although it is clear that some have a better feel for design than others, the principles discussed above are not about colors and gradients. They focus on how a user interacts with an application or a website. The concepts are easy to understand, remember, and follow. Adding them to a developer's tool-belt can have an immediate impact.