The Laws of HXD
As the art of Human Experience Design evolves some basic "laws" have developed to help guide our early assumptions and keep the phycology of the individual front and center. This is a few of the laws I have come to trust.
Hick's Law
The time it takes to make a decision increases with the number and complexity of choices.
Hick’s Law (or the Hick-Hyman Law) is named after British psychologist William Edmund Hick and American psychologist Ray Hyman. In 1952, this pair set out to examine the relationship between the number of stimuli present and an individual’s reaction time to any given stimulus. As you would expect, the more stimuli to choose from, the longer it takes the person to make a decision on what to choose. People given an abundance of choices have to take time to interpret and decide, giving them work they don’t want.
Doherty Threshold
Productivity soars when a computer and its users interact at a pace (<400ms) that ensures that neither has to wait on the other.
In 1982 Walter J. Doherty and Ahrvind J. Thadani published, in the IBM Systems Journal, a research paper that set the requirement for computer response time to be 400 milliseconds, not 2,000 (2 seconds) which had been the previous standard. When a human being’s command was executed and returned an answer In under 400 milliseconds, it was deemed to exceed the Doherty threshold, and use of such applications were deemed to be “addicting” to users.
Fitt's Law
The time to acquire a target is a function of the distance to and size of the target.
In 1954, psychologist Paul Fitts, examining the human motor system, showed that the time required to move to a target depends on the distance to it, yet relates inversely to its size. By his law, fast movements and small targets result in greater error rates, due to the speed-accuracy trade-off. Although multiple variants of Fitts’ law exist, all encompass this idea. Fitts’ law is widely applied in user experience (UX) and user interface (UI) design. For example, this law influenced the convention of making interactive buttons large (especially on finger-operated mobile devices)—smaller buttons are more difficult (and time-consuming) to click. Likewise, the distance between a user’s task/attention area and the task-related button should be kept as short as possible.
Law of Common Region
Elements tend to be perceived into groups if they are sharing an area with a clearly defined boundary.
The principles of grouping (or Gestalt laws of grouping) are a set of principles in psychology, first proposed by Gestalt psychologists to account for the observation that humans naturally perceive objects as organized patterns and objects, a principle known as Prägnanz. Gestalt psychologists argued that these principles exist because the mind has an innate disposition to perceive patterns in the stimulus based on certain rules. These principles are organized into five categories: Proximity, Similarity, Continuity, Closure, and Connectedness.
Miller's Law
The average person can only keep 7 (plus or minus 2) items in their working memory
In 1956, George Miller asserted that the span of immediate memory and absolute judgment were both limited to around 7 pieces of information. The main unit of information is the bit, the amount of data necessary to make a choice between two equally likely alternatives. Likewise, 4 bits of information is a decision between 16 binary alternatives (4 successive binary decisions). The point where confusion creates an incorrect judgment is the channel capacity. In other words, the quantity of bits which can be transmitted reliably through a channel, within a certain amount of time.