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Jef Raskin – Humane Interface

1. chapter 3
1. modes
1. different modes can be a significant cause of error, confusion, complexity
2. complexity comes from the same gesture (action) having different results in different modes.
1. habitual actions of experts will have different effects
2. beginners might assume that the same actions will have the same effect because they don't know the system well enough.
3. “A human-machine interface is MODAL with respect to a given gesture when (1) the current state of the interface is not the user's locus of attention and (2) the interface will execute one among several different possible responses to the gesture, depending on the system's current state.”
4. example aircraft control (unmanned)
2. preference settings
1. preference settings are actually different modes that a computer can run in.
2. users run into problems when they don't remember changing preferences or don't remember how to change things back
3. users are not generally expert interface designers, so choices are not always optimal
4. expert users don't need more control over their interface, they need a stable interface that let's them do what they want to do with minimal errors.
5. “an interface that optimizes productivity is not always an interface that optimizes subjective ratings”
3. modes vs quasimodes
1. if the caps lock key is a mode, then the shift key is a quasimode.
2. quasimodes have been shown to not have the same errors as modes do.
3. rule of thumb: “quasimodes re reserved for control functions. operations you perform when no qusimode is engaged create content”
4. noun-verb > verb-noun construction.
5. visibility and affordances
1. visibility refers to being detectable by the human sense, often but not always sight
2. affordance refers to the types of interactions that are natural for an object.
1. a flat surface just below waist hight affords sitting. a flat surface affords putting things on. a ball affords throwing and bouncing.
6. monotony in this paper refers to a one-to-one correspondence actions in an interface and the inputs to create those actions.
1. argument is that it is not good to have multiple ways to do the same thing. a beginner and expert route to the same task is argued to be unnecessary and indicative of bad design.
2. chapter 4
1. quantification
1. GOMS
1. “goals, objects, methods, and selection rules”
2. “the aim of exact science is to reduce the problems of nature to the determination of quantities of operations with numbers”
3. can find times of user interactions within about 5%
1. this allows ranking and comparison of various interfaces without the need for extensive user studies
4. efficiency
1. information needed divided by information supplied by user
2. information is measured in a similar way to the actions in the timing measurment in GOMS
2. Fitt's Law and Hick's Law
1. fitt's law gives the average time to get a cursor to a button
1. S is size along direction of movement, D is distance from starting point
2. Time = a + b ( log2 ( D/S + 1) ),
3. a and b determined experimentally. roughly a = 50, b = 150
2. hicks law states the time to choose between n equally likely choices
1. time = a + b ( log2 ( n+1) ),
2. faster to have 8 options all at once that 4 options two times

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