Brief review of Information Visualization by Colin Ware. This is a textbook with a great amount of detail on the physics, biology and psychology behind visual perception.
The main purpose of visualization is to help people detect patterns – though the author cautions that people are quite capable of seeing patterns where there are none… The author also cautions against overuse of visual techniques:
Natural language is the most elaborate, complete and widely shared system of symbols that we have available. For this reason alone, it is only when there is a clear advantage that visual techniques are preferred.
Some practical advice extracted from the book.
- Don’t use grayscale values to color categories in a graph.
- Blue areas focus behind red areas, for most people. This can be used to create an illusion of depth. It can also be used to make text unreadable…
- Colors allow an additional three dimensions to be visualized (rgb!)
- Fast movements or sudden appearance of items in the visual periphery attract attention – which may or may not be intended.
- Multi-dimensional, discrete data can be encoded by spatial position of a “glyph”, color, shape, orientation, texture, motion or frequency (e.g. blinking).
- Items can be associated visually by making use of proximity, similarity (see previous point), symmetric or continuous arrangement, or enclosure (e.g. in windows or Venn-diagrams).
- Animation can be useful though “the kinds of animated critters that are starting to crawl and hop over web pages are often unnecessary and distracting. Just as elegance is a virtue in static diagrams, so it is in diagrams that use animation.”
- People are poor at remembering images, but good at recognizing previously seen images.
- Large collections of images can be scanned faster by flashing the images in rapid succession (up to 16 images/s) than by looking through thumbnails (requires refocussing, only 3-4 images/s).
- Display numbers in an object view rather than in tables, if there is a natural or metaphorical mapping to a physical object.
- For displaying 3D surfaces use a single light source that is located above (the brain assumes this!), at an infinite distance. Make shadows soft, and use textures.
- Using three dimensions may increase the maximum complexity in a tree or graph that can be understood.
- Most people get sick in virtual reality simulators when they move their head from side to side while moving.
- Flowcharts are less suitable than natural language or pseudocode for helping people understand processes, because they require the brain to perform an additional translation step.
- Diagrams on the other hand can help people understand relationships.
- Data input always has a speed-accuracy trade off. This means that applications that are tolerant of small errors allow people to work faster.