User experience changes or influences behaviour. Good user experience does so consciously by understanding and working with the curiosities of human nature. In the 50’s it was still assumed that perfect people would operate perfect machines under perfect conditions. When the first mass machine errors started to occur, Fitts and other scientists created a paradigm shift from seeing a human error to seeing a system design error. Cumulating in Steve Jobs’ approach in 1984 to teach computers about people, instead of teaching people about computers. Nowadays most industries are building computer systems around the fleeting, unpredictable ways of the user.
When UX professionals are called in there is usually already a financial crisis as the result of not understanding users. UX people usually grasp the intricacies of our complex nuances intuitively when evaluating UX & UI, because after all, most had terrible childhoods and years of hard-earned training in people-reading. But childhood survival doesn’t explain the gut feeling, so UX psychology provides the scientific training to decode the behavioural phenomenon that is stopping someone from completing a task through an interface.
Here is my checklist of the most important scientific laws on behavioural whys and hows that tell us everything about the faults of a system that we already knew but were unable to articulate professionally. BTW, all scientifically proven laws listed here originated with someone’s gut feeling. This list is continuously being expanded, whenever there is an ounce of time.
The closer and larger a target, the faster it is to click on that target. The speed of controlled movements is limited by information processing capacity of the human nervous system and muscle force.
Sometimes grouping, chunking (Millers Law) or combined actions as in search filters, grouped menu items, dropdowns, swipe & delete, override Fitts Law (moving a target closer to a user’s focal point) for clarity and security reasons. It’s when you shouldn’t use Fitts Law to measure user experience
Infos & Stories
During WW2 US fighter plane controls looked exactly the same and pilots reaching for the landing gear would instead pull the wing flaps, slowing descent and driving the plane into the ground. A young psychologist was called in to investigate the “pilot errors”, and ended up inventing shape coding and later, defined ground usability rules used in every computer today.
Extension to Fitts’ law: the steering law of Accot and Zhai, 1997. Steering a vehicle through a narrow tunnel needs more time than steering it through a wide tunnel. The same is true for steering the mouse through cascading menus.
Fitt’s law and Fitts’s Law: The Importance of Size and Distance in UI Design, two articles by the Interaction Foundation,
Towards a Standard for Pointing Device Evaluation: Perspectives on 27 Years of Fitts’ Law Research in HCI, R. William Soukoreff and I. Scott MacKenzie
Breaking down Fitts law for UX designers, Sourabh Purwar
A lecture on Fitts’ law, Heiko Drewes
The number of objects an average person can hold in working memory is about seven (+/- 2)
“The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information” is a highly cited psychology paper published in 1956 in Psychological Review by the cognitive psychologist George A. Miller It argues that the number of objects an average human can hold in short-term memory is 7 ± 2. This has been referred to as Miller’s law.
Chunking groups related items into units with less items, making all easier to process
Infos & Stories
The more commonly known Miller’s law (also by G. A. Miller): “To understand what another person is saying, you must assume that it is true and try to imagine what it could be true of.” A primal law for any type of communication.
Miller’s Law, Wikipedia
Miller’s Law, Jeremiah Lam
Design Principles for Reducing Cognitive Load, Jon Yablonski
The Most Important Rule in UX Design that Everyone Breaks, Jeff Davidson
The time it takes to make a decision increases with the number and complexity of choices. So if the number of choices increases, the time to make a decision increases logarithmically.
Hick, W.E. (1952). “On the rate of gain of information” Quarterly Journal of Experimental Psychology.
Hyman, R (March 1953). “Stimulus information as a determinant of reaction time”. Journal of Experimental Psychology
At the end of his paper Hick ruefully concluded that, while his information theory statement might be useful for practical applications, the details of the mechanism remained vague and that speculation about neural networks was outside the scope of his work. Choice is pervasive, and anyone concerned with modelling mechanisms still needs to know about Hick’s work.
Infos & Stories
Hick’s Law, Wikipedia
Choice, confusion and consciousness, Philip Barnard
Design principle: Hick’s Law — quick decision making, Anton Nikolov
Hick’s Law: Making the choice easier for users, Interaction Design Foundation
Have you applied these laws to your UX work?