Human Computer Interaction Concepts
Aimed movements -- pointing at a target-- are a series of micro-movements that "zero in" on the target as visual feedbacks.
Movement time depends on the number of micro-movements , which depend on the target size(S) and distance(D).
Far targets relatively fast
Small targets much slower
This is known as Fitt's Law:
Fitt's law states that the time for aimed movements (such as mouse cursoring) is proportional to the logarithm of the ratio of distance over target size. This means that the time increases when the target gets further away or smaller.
Here is an interesting VIDEO ABOUT FITT'S LAW:
In other words, time depends upon target size(S) and distance(D).
- Far targets relatively fast
- Small targets much slower
Cursor Key vs. The Mouse
When analyzing cursor key vs. the mouse, the cursor key is effective in some cases. For example, for placing the cursor between the two periods.
In accordance with fitt's law, mouse can be more effective in showing things on the screen.
The mouse follows the fitt's law:
Or rather PROPERLY DESIGNED mouse follows the Fitt's law
- Extremely efficient for long moves
- Not much longer to reach the cursor keys
- But small targets can be a problem
Other devices are slower because time governed differently
- E.g. Cursor key linear with total of x and y distance.
- Joysticks can be very different, in some cases quite difficult to learn and to use- depending upon control regime
Mouse is a good way to point, but keyboard are faster if only a few keystrokes needed.
Keyboards
- Hand entry of characters is very slow
- Keyboards are much faster after practice
- Pen-based interfaces are not fast but have other advantages
Output Basics: Human Vision
It is interesting to note that how the output should be displayed is affected by human vision.
Human vision uses two receptor systems:-
- High resolution color system
- Receptors("Cones")
- Requires higher light levels(e.g. normal daylight(official light)
- Receptors from three color ranges : red, blue, green
Sensitive Monochrome Light
Receptors("rods")
Poor resolution - relatively bw reception density
Extremely sensitive but not involved in normal lighting
Basic Principles of Display Design:
What NOT to do: Exclusive focus on appearance
Be concerned only with what the screens look like; screen layouts, color icons, attractiveness
What to do: Present the right information in the right way on the right time
Choose the right information:
- What decisions will the user make at each point in the task?
- What information will the user need to make those decisions?
Pick a good representation of the Information
- Different ways of representing the same abstract information can have huge effects = the "Representation " effect
- Attempt to present all relevant information simultaneously
because : Eye can move in milliseconds from one place to another
This means that:
-> Visual search of even a complex display can be extremely fast compared to bringing up additional screens.
- With good visual layout, displays can deliver much more information than generally delivered.
Icons vs. Words as Display Objects
Misguided Style: Use nifty icons , not boring words
- Icons are fun, decorative BUT NOT usually helpful.
Icons are definitively better mouse targets than words
- Square shape gives more target area
- Words tend to be long and thin ; often provide a small target
Icons are often arbitrary and meaningless as compared to typical words for computer objects
- Icons can be hard to recognize compared to words
especially, if the item concepts are abstract
WHY MAKE USER MEMORIZE MEANINGLESS SYMBOLS?
Throughout his life, the user has used words for information processing
- Words can be better than icons for doing visual search.
- Icons are generally too complex to guide visual search.
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