Usability: Rules and Principles

Usability is a term used to denote the ease with which people can employ a particular tool or other human-made object in order to achieve a particular goal.

  • 7 +/- 2 Principle:

    human brain has some limits on its capacity for processing information. Argument for limiting the number of options in navigation menus;

  • 2-Second-Rule:

    user shouldn't need to wait more than 2 seconds for certain types of system response;

  • 3-Click-Rule:

    users stop using the site if they aren't able to find the information or access the site feature within 3 mouse clicks;

  • 80/20 Rule (Pareto principle):

    80% of the effects comes from 20% of the causes ("80% of your sales comes from 20% of your clients");

  • Fitts' Law:

    predicts the time required to rapidly move to a target area, as a function of the distance to the target and the size of the target;

    [Office 2007's Mini Toolbar]

  • Inverted Pyramid:

    the summary of the article is presented in the beginning of the article;

  • Satisficing:

    Web users don't prefer optimal ways to find the information they're looking for. Instead they permanently scan for quick'n'dirty-solutions which are "good enough";

  • Baby-Duck-Syndrome:

    the tendency for visitors to stick to the first design they learn and judge other designs by their similarity to that first design;

  • Banner-Blindness:

    Web users tend to ignore everything that looks like advertisement. they focus only on the parts of the page where they would assume the relevant information could be, i.e. small text and hyperlinks.

    Eye tracking is the process of measuring either the point of gaze ("where we are looking") or the motion of an eye relative to the head.

    Heatmaps from eyetracking studies: The areas where users looked the most are colored red; the yellow areas indicate fewer views, followed by the least-viewed blue areas. Gray areas didn't attract any fixations;

    [Times Original, Times Eyetracked, Google, Test]

  • Cliffhanger-Effect

    (Zeigarnik-Effect): based upon the fact that human beings can't stand uncertainty (movies, articles with an abrupt ending, often leaving with a sudden shock revelation or difficult situation). This often tend to force them to read the ad, click on the banner or follow a link;

  • Gestalt principles of form perception [example]:
    • The law of proximity: posits that when we perceive a collection of objects, we will see objects close to each other as forming a group;
    • The law of similarity: captures the idea that elements will be grouped perceptually if they are similar to each other.;
    • The Law of Prägnanz: captures the idea that in perceiving a visual field, some objects take a prominent role while others recede into the background [Macintosh OS Logo];
    • The law of symmetry: captures the idea that when we perceive objects we tend to perceive them as symmetrical shapes that form around their centre;
    • The law of closure: posits that we perceptually close up, or complete, objects that are not, in fact, complete;
  • The Self-Reference Effect:

    things that are connected to our personal concept are remembered better than those which aren't directly connected to us;

  • Visual-syntactic text formatting:

    transforms block-shaped text into cascading patterns that help readers identify grammatical structure. [Live Ink]

    Normal Text
    Visual-syntactic text formatting
Visual Representations

Visualize Information - Representing information in spatial or visual relationships can make complex data sets clear and understandable:

Visualize Calendar
  • Calendar Entry 1
  • Calendar Entry 2
  • Calendar Entry 3
  • Calendar Entry 4
  • Calendar Entry 5
  • Realizaţi în format vectorial reprezentarea unui instrument care permite citirea timpului (ceas).
  • Se va aprecia intuitivitatea (uşurinţa de a afla ora curentă) şi creativitatea.
  • Se va utiliza un editor grafic de genul Inkscape.
  • Se va realiza o arhivă (.tgz) ce va conţine sursele (.svg, .psd, .cdr etc.) şi o vizualizare (.png). Arhiva va fi trimisă prin mail (conform protocolului de contact) până Vineri, 2 Noiembrie 2007, ora 18:00.
  • In cazul în care dimensiunea fişierelor este foarte mare, se recomandă precizarea locaţiilor (links) acestor fişiere (.psd + .png).