Post on 13-Dec-2015
Chapter 3 Sensing & Responding
Human Performance Engineering
Robert W. Bailey, Ph.D.
Third Edition
Responders
Sensors
Figure 4-1 Simplified model of human information processing with the sensors emphasized
Sensing is done by specialized
nerves called receptors.
Ex. Pain receptors- spread throughout
the body
Ex. Eyes- Concentrated in one location
Senses:Vision, Hearing, Smell, Taste, Touch
Cold, warmth, pain, kinesthetic (movement),vestibular (movement through space)
Sensing VS. Perception
Sensing is the capture and transformation
of information required for the
process of perception to take place.
Perception can be enhanced with experience.
Threshold - The point on an intensity scale below which we do not detect the stimulus and above which we do.
Difference threshold - The minimum physical difference that produces a perceptible difference.
Table 4.1 Various Forms of energy and the senses each stimulates
Stimuli SenseElectromagnetic VisionMechanical Hearing
TouchPainVestibularKinesthetic
Thermal ColdWarm
Chemical TasteSmell
(Adapted from Human Behavior: A System Approach. By N. W. Heimstra and V.S. Elingstad. Copyright ©1972 by Wadsworth Publishing Company, Inc. Reprinted by permission of the publisher. Brooks/Cole Publishing Company. Monterey, California.)
Table 4.2 Some Approximate Sensory Thresholds
Sense Detection Threshold
Sight Candle flame seen at 30 miles on a dark clear night
Hearing Tick of a watch under quiet conditions at 20 feet
Taste Teaspoon of sugar in 2 gallons of water
Smell Drop of perfume diffused into the entire volume of a three-room apartment
Touch Wing of a bee falling on your cheek from a distance of 1 centimeter
(Adapted from Galanter, 1962)
What is the most important sense?
Vision
The light that stimulates the eye is a form of electromagnetic radiation. The eye converts the light into a form that can be used by the brain.
The Sensity of the eye depends on:
Size of stimulus, brightness and contrast of the stimulus, size of visual field, region of retina stimulated
Common Visual Defects:
Hyperopic- Eyeball is shorter than normal
Myopic- Abnormally long eye ball
Night Blindness – Vitamin A deficiency
We will discuss only three of several visual deficiencies that could exist and that are correctable if recognized. Two of the most common correctable visual defects, hyperopic and myopia (nearsightedness), are usually due to shape abnormalities in the eyeballs. Figure 4-8 illustrates the structure of normal, hyperopic, and myopic eyes.
Normal: Light Focuses on the retina
Hyperopia: Light focuses in back of the retina for near objects
Myopia: Light focuses in front of the retina for far objects
What are two visual deficiencies not correctable?
Blindness & Color Blindness
(Red, Green, Gray)
8% of Men, 1% of Women
Hearing
19% of working-age Americans have a hearing impairmentFrequency – pitch, intensity – loudness
Sound Pressure Level (d8)
01020
3040
50607080
Threshold of hearing
Whisper
Quiet Office, Household sounds
Normal conversation
Average auto; loud radio
90Truck or bus
100
110
120130140
Subway train
Loud Thunder
Painful sound
Ear damage possible
Figure 4-10 Sound pressure levels for typical sounds
What are cutaneous senses?
Related to the Surface of the Body:
Touch (Pressure)-experienced when a depression is formed on the skin.
Pain- can motivate and deteriorate human performance more than any other stimulus.
Temperature – Cold & Warmth
Skin Temperature – 91.4 F
Taste- Sweet, Sour, Salty, & Bitter
Smell- 6 Qualities:Spicy, Fruity, Burnt, Resinous, Flowery, & Putrid 10,000 times as sensitive as taste
Kinesthetic (muscle sense) 3rd most important sense related to human performance. It provides information on: The position of the limbs,How far they have moved,The posture of the body as a whole.
Vestibular- Provides people with information about their position in a three – dimensional space and their movement through space. Located in the inner ear.
* Sensory adaptation & sensory interaction