9.1 Cognitive Ergonomics: Theories

Sensory Register

Theories

Perception

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

Perception

Process of interpreting and giving meaning.

Short Term Memory

Characteristics:

Capacity

7+/- 2 Chunks

Duration

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

Note

Description

Varieties

Types of Long Term Memory

Semantic Memory

Meaning Oriented

Event Memory

About something happening

Episodic

Memory of Past Events

Prospective

Memory of events that will/should happen

Failure of this memory is one of the major causes of doctor failure

Description

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*log₂N
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

Description

Warrick's Rule

Intuition: movement of stimulus and expected movement of response

Functioning:

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.

Note

Description

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

Where
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:

Description

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)