Controls & Design Flashcards
What are controls?
Controls are the action after a decision is made
What is the speed of action selection influenced by?
the number of
possible alternative actions that could be
selected.
What is the Hick Hyman Law of reaction time?
A logarithmic increase in reaction time (RT) as
the number of possible stimulus response
alternatives (N) increases.
RT = a +
b Log2 N
What is the formula to predict response time?
Reaction Time = a + bH
More uncertainty, more time
a = simple reaction time (just to respond)
b = additional time for every 1 bit increase in
information
What is the most efficient way to deliver a given amount of information?
give a smaller
number of complex decisions rather than a
large number of simple decisions.
What is Response
expectancy?
We perceive rapidly and accurately that
information that we expect.
What are the principles of response selection?
- Decision
complexity - Response
expectancy - Compatibility
- Feedback
5.Speed accuracy trade off
What is Location compatibility?
Mapping
What is movement compatibility?
moving a lever right
should move the display to the right
What are factors affecting reaction time?
- Age
- Intoxication
- Time of day (especially in auditory response)
- Fatigue
- Practice
What is an example of a Positioning Control Device?
Mouse with a cursor to a target
What affects the movement time of positioning control devices?
movement of the hand or fingers to
the control device
movement of the control device in
some direction.
What is the equation for Fitt’s Law?
- *MT =**
- *a + b log 2 (2A/W)**
MT is movement time
A is the distance (or amplitude) of movement from start to
target center
W is the width of the target, which corresponds to “accuracy”
(2A/W) is the index of difficulty
What is the ID of Fitt’s law?
Index of difficulty
log 2 (2A/W)
What are some implications of Fitt’s law
•Big targets at a close distance are acquired faster than small
targets at long range
•ID provides a single combined measure of two main physical
properties of movement tasks
•ID increases by one unit for each doubling of amplitude and
halving of width
•Positive intercept indicates additive factors unrelated to ID. It
can be related to mechanism of movement and/or selection
(mouse, button,etc)
What is Welford’s ID?
MT =
a + b log <u>2</u> (A/W + 0.5)
How is Welford’s law different than Fitt’s law?
- MT is proportional to the index of difficulty
- Better fit to data than Fitts ’ original
- Possible negative ID
What is Shannon’s ID?
MT =
a + b log <u>2</u> (A/W + 1)
How is Shannon’s Law different from Fitt’s law?
- MT is proportional to the index of difficulty
- Best fit to data
- Positive ID
- Follows from Info Theory
What are 3 device characteristics?
- Direct position controls
- Indirect position controls
- Indirect velocity controls
What is an example of a direct position control?
Light pen and
touch screen using
a stylus or finger
on a tablet.
What is an example of an indirect position control?
Mouse, touch pad,
and touch tablet.
- (Changes in the*
- position of the limb*
- directly correspond to*
- changes in the*
- position of the cursor,*
- but on a different*
- surface.)*
What is an example of an indirect velocity control?
Joystick and cursor keys.
What are the 3 types of joysticks?
- Isotonic
- Isometric
- Spring loaded
What is an isotonic joystick?
•Typically, cursor moves as a result of
movement of the joystick handle.
•Handle does not move back to a neutral
position.
What is an Isometric Joystick?
•Cursor moves as a result of the force
applied to the joystick handle.
•Joystick does not move at all.
(In some keyboards it’s the weird dot thing)
What is a spring-loaded joystick?
•Resistance is proportional to the force
applied.
•Displaced, but returns to a neutral
position.
•Offers proprioceptive and kinesthetic
feedback.
What are the two important characteristics of usability?
Feedback and gain
What is gain in usability?
Gain is defined as the change of cursor
position/change of control position.
What is control movement?
positional input to control
What is Controlled element?
aspect of system ultimately
affected by control movements
What is the target?
displayed parameter to be matched
What is Forcing function?
disturbances to target
sidenotes: in UX: forcing functions create barriers to divert people away from danger and towards desired outcomes
What is pursuit tracking?
See both controlled element & target
What is compensatory tracking?
Only error (difference desired/actual)
Target & control movements confounded
How does pointing differ from tracking?
In pointing:
Stationary target
No lag
Gain is only control system parameter
What does Control Order
mean?
What the control controls.
What does it mean if a control is zero-order?
the cursor controls the position of the
target
What does it mean if a control is first-order?
order means it controls the velocity of the
target.
What does it mean if a control is second-order?
a change in the position of the cursor changes the acceleration
of the target.
What is instability in controls?
caused by lag somewhere in the total control loop
What are Open loop controls?
no feedback used by
experienced operators
What are closed loop controls?
feedback is valuable in
learning or fine tuning a mental
model.
What is response expectancy?
We perceive rapidly and accurately the information that we expect.
What is decision complexity?
The speed with which an action can be selected is strongly influenced by the number of possible alternative actions that could be selected.
What is the Hick Hyman Law of reaction time?
RT = a + b Log2 N
logarithmic increase in reaction time (RT) as the number of possible stimulus response alternatives (N) increases.
What are direct position controls?
Light pen and touch screen
What are Indirect position controls?
Mouse, touch pad, and touch tablet.
What are indirect velocity controls?
Joystick and cursor keys
