Chapter 02 - Human Limits & Differences

Question 1

Three categories of limits

Answer 1

1 - Sensory limits:

1. 1. Threshold - Least amount of light can be perceived, faintest noise that can be heard
2. 2. Deficiencies
3. Responder limits
4. 1. Reach & Strengh
5. Cognitive Processing Limits
6. 1. Response time
7. 2. Accuracy

Question 2

Response time

Answer 2

The time taken to recognize that a signal for a certain action has occurred and decide on the appropriate movement (reaction time) and the time it takes to move (movement time).

Question 3

Reaction time comparison

Answer 3

Sound - 150 ms
Sight - 200 ms
Smell - 300 ms
Sensing pain - 700 ms

Question 4

Reaction times delays in msec

Answer 4

Sensory receptor 1-38
Neural transmission to brain 2-100
Cognitive-processing delays (brain) 70-300
Neural transmission to muscle 10-20
Muscle latency and activation time 30-70
Total 113-528

Question 5

Top speeds for a variety of communication tasks

Answer 5

words per minute:
≅ 600 Silent reading
≅ 500 Speaking 
≅ 300 Stenotypist
≅ 300 Oral reading (prose)
≅ 225 Oral reading (one-syllable words)
≅ 225 Conversational speaking
≅ 170 Keying (text)
≅ 150 Typing (text)
≅ 100 keying (numerical kboard)
≅ 30 Hanprinting / handwriting

Question 6

Accuracy

Answer 6

Not physiologically limited
More under the person’s control
Certain critical activities - done perfectly
People establish their own accuracy level on a task-by-task basis

Question 7

Difference of overestimate and underestimate

Answer 7

Not involved- over estimate, involved- under
Looking down- over estimate, up- under
Hot- over estimate, cold- under
Bulky- over estimate, compact- under

Individual Differences
			“KNOW THY USER”