Word: Interaction Cost

Definition: An interaction cost is equal to the physical effort plus the mental effort exuded by the user per a given task.

In a perfect world, the interaction cost would be zero, in that the user would know exactly what she has to do and how she can accomplish her goals, all without any effort or strain. However, we know that this is an impossible standard to attain, so the point is to get close!

Reference: This term comes from the early days of Human Computer Interaction and is used to evaluate a product's usability. Tools such as heuristic evaluations directly influence and ultimately minimize the interaction cost for the user.

Thoughts:  Examples of efforts that can be minimized and ultimately lower the interaction cost are:

• Reading
• Scrolling
• Clicking/tapping
• Typing
• Page loading
• Way-finding

Now let's reduce the abstraction and look at a very basic example! Image you are filling out a form on a mobile app. You are exerting effort every time you read a form field label, click into the field, type a value into that field, and then finally submit the value. When broken down in this manner, that is a lot of effort!

Think about the small things that we can do as UX designers that will help lower this effort. We can automatically display the numerical keyboard on a phone number or zip code fields. We can allow the user to tab from one field to the next without exiting the keyboard display. We can display shortcuts to various form field sections for easy access. The possibilities are endless!

These may seem like small interactions and mundane examples but it is through such details that the larger interaction cost is reduced and the usability of a product ultimately increases.