Sensory Register
Response Selection
Response Execution
Attention Resources
Thought/Decision Making
Working Memory (aka Short Term Memory)
Long Term Memory
Simple Reaction Time
No choice reaction, takes at least 100 ms
  • ex. hear bell run immediately
  • Doesn't take long to respond
  • At least 100 ms with mean of 200 ms
Process of interpreting and giving meaning.
Short Term Memory
7+/- 2 Chunks
approx. 20 seconds
  • Duration as a function of memory load
3 Components
1. Verbal - phonological
2. Spacial - Visual/Pictures
3. Executive
 - Timing
 - Sequence
 - Controlling
Mental Rotation
  • Mentally Rotate/Spacial
  • Concrete Evidence
  • Experiment by Stanford Prof
Types of Long Term Memory
Semantic Memory
Meaning Oriented
Event Memory
About something happening
Memory of Past Events
Memory of events that will/should happen
Failure of this memory is  one of the major causes of doctor failure
Basic Mechanisms
  • Item strength
  • Association Strength
  • Exponential Decay: Practicing HW  an hour after class
  • Interference - can confuse you
Distortions of Spacial Memory
  • Filled distance effect in distance estimation
  • Rectilinear normalization 
    - Fit image to rectangular sides
  • Canonical Orientation
    - North
    - East
    - West
    - South
Mental Models
An understanding about the real world that is residing in your mind 
  • If mental model matches the designer model then you will understand how to operate the design, otherwise failure.
  • Ex. Elevator button: You keep pushing the button thinking the elevator will come faster. 
Sensory Memory Characteristics
  • Lasts about 200 ms
  • Iconic: Like old movies, fast frames, story is continuous
  • Hearing: Music is continuous
Choice Reaction Time
Hick-Hymen Law (Fig 9.1)
  • Not a linear function
    RT = a + b*
  • RT = Reaction Time
  • a,b = coefficients to be determined (need to solve for a and b)
  • N = # of choices you have
Possible Exceptions to Hick-Hyman
Opportunities for designers to improve designs
Response Expectancy
You can time yourself because you expect something to happen
Stimulus Response Compatibility
The degree to which the relationship between stimulus and response meet our expectations
Location Compatibility
  • Relationship between location of stimulus and response should meet our expectations
Movement Compatibility
  • Stimulus response based on movement
Conceptual Compatibility
Warrick's Rule
Intuition: movement of stimulus and expected movement of response
The direction of movement of the POINTER should be the same as the direction of movement of the nearest point on the CONTROL
4. Multiple Resources
Recognize Competing Resources. 
  • 4 Dimensions to define resources
  • At least 8 resources
  • Shouldn't use more than 2 resources at the same time. 
Speed-Accuracy Tradeoff
Accuracy VS TIME
- the longer the time it takes, the more accurate you will be. 
Fitt's Law
Movement Time as a function of distance of movement and width of target. Very robust.

MT = a + b*log2(2A/W)
     = a + b*ID

MT = Movement Time
a, b = constants
A = distance of movement from start to target's center
W = width of target (accuracy)
Factors affecting attention and time sharing:
1. Controlled vs. Automatic Processes
ex. Walking/Driving starts very controlled, then becomes automatic.
5. Task Management and Interruptions
When to start/stop
3. Similarity-Induced Confusion
Confusing familiar things with similar things
2. Time-Sharing Skill
Split time doing one thing vs another
4 Dimensions
Many resources
Each dimension has at least 2 levels (min 16 resources)
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