UX Psychology

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. 

Summary

Fitts' Law

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.

Taken from

“The information capacity of the human motor system in controlling the amplitude
of movement”, published 1954

Creator

Paul Morris Fitts Jr. (May 6, 1912 – May 2, 1965), a psychologist at Ohio State University and University of Michigan. He developed a model of human movement, Fitts’s law, based on rapid, aimed movement, which became a well studied mathematical model of human motion.

UX learnings

Create larger targets and minimize cursor movement, avoid muscular tension, exploit the fastes pixels

Example by Anastasios Karafillis, Smashing Magazine

Radial Menu, Wikipedia

Criticism

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.

Summary

Miller's Law

The number of objects an average person can hold in working memory is about seven (+/- 2)

Taken from

“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.

Creator

George Armitage Miller (Feb 3, 1920 – July 22, 2012), American cognitive  psychologist, Harvard University‘s Dtm. of Psychology. Founders of cognitive psychology, and more broadly, of cognitive science

UX learnings

Chunking  groups related items into units with less items, making all easier to process

Criticism

There is justifiable concern that the magical seven was only an allegory

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.

Summary

Hicks Law (Hick–Hyman law)

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.

Taken from

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

Creator

William Edmund Hick (1. Aug. 1912 – 20 Dec. 1974),  British psychologist, pioneer in the new sciences of experimental psychology and ergonomics in the mid-20th century.

Ray Hyman (born June 23, 1928) is a Professor Emeritus of Psychology at the University of Oregon in Eugene, Oregon,

UX learnings

Reduce options, especially when response times are critical.

One-click purchase function reduces steps in a purchase process

Criticism

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

Have you applied these laws to your UX work?

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