Design Principles for Usability

Flexibility-Usability Tradeoff

As the flexibility of a system increases, its usability decreases. (design simplicity)

Hick's Law

The time it takes to make a decision increases as the number of alternatives increases. (design simplicity)

80/20 Rule

A high percentage of effects in any large system are caused by a low percentage of variables. (design simplicity)

Ockham's Razor

Given a choice between functionally equivalent designs, the simplest design should be selected. (design simplicity)

Affordance

A property in which the physical characteristics of an object environment influence its function (teaching through design)

Mapping

A good relationship between controls and their movements or effects. (teaching through design)

Recognition over Recall

Memory for recognizing things is better than memory for recalling things. (teaching through design)

Shaping

A technique used to teach a desired behavior by reinforcing increasingly accurate approximations of the behavior. (teaching through design)

Aesthetic-Usability Effect

Aesthetic designs are perceived as easier to use than less-aesthetic designs. (aiding perception)

Gutenberg Diagram

A diagram that describes the general pattern followed by the eye when looking at evenly distributed, homogeneous information.(aiding perception)

Form follows Function

Beauty in design results from purity of function.(aiding perception)

Picture Superiority Effect

Pictures are remembered better than words.(aiding perception)

Figure-Ground Relationship

Elements are perceived as either figures (objects of focus) or ground (the rest of the perceptual field) (aesthetic communication)

Common Fate

Elements that move in the same direction are perceived to be more related than elements that move in different directions or are stationary. (aesthetic communication)

Similarity

Elements that are similar are perceived to be more related than elements that are dissimilar. (aesthetic communication)

Orientation Sensitivity

A phenomenon of visual processing in which certain line orientations are more quickly and easily processed and discriminated than other line orientations. (aesthetic communication)

Fitts Law

The time required to move a target is a function of the target size and distance to the target. (Ease of use)

Preference vs. Performance

The designs that help people perform optimally are often not the same as the designs that people find most desirable. (Ease of use)

Control

The level of control provided by a system should be related to the proficiency and experience levels of the people using the system. (Ease of use)

Visibility

The usability of a system is improved when its status and methods of use are clearly visible. (Ease of use)

Five Hat Racks

information is categorized by: Category, Time, Location, Alphabet, and Continuum (Information Communication)

Three-Dimensional Layering

Layering is the process of organizing info into related groupings in order to manage complexity and reinforce relationships in info. (Information Communication)

Progressive Disclosure

A strategy for managing information complexity in which only necessary or requested information is displayed at any given time. (Information Communication)

Comparison

A method for illustrating relationships and patterns in system behaviors by representing two or more system variables in a controlled way. (Information Communication)