human factor engineering (mental processes)

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PHYSIOLOGYChapter: 2

PowerPoint SlidesHuman Factor Engineering-490220

Lect : 04Dept of Aero & Astro

Institute of Space Technology

Thursday, March 19, 2015Human Factor Engineering 490220

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MENTAL PROCESSES

OUTLINE

1. Attention2. Perception3. Sensation – Vision, Hearing, Taste, Smell & Balance.4. Memory 5. Emotions, motivation6. Thinking and intelligence


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Human capabilities and limitations Eureka!

We will change the human!

MANTAL PROCESSES


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1. Attention and perception –

How methodical should you be?

Do you notice the small things?

Are you being constantly distracted by the actions of other people, whether for your interpretation of something or just to supply some extra grunt on a difficult task?

MANTAL PROCESSES


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How readily can you pick up the thread of your thoughts from before the disturbance?

Do you keep mental or written notes of the stages of work carried out to aid you?

How have you interpreted the maintenance procedure from the manual?

Attention and Perception


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• Sensation– The processes by which our sense organs receive information

from the environment. • Transduction

– The process by which physical energy is converted into sensory neural impulses.

• Perception• The processes by which people select, organize, and

interpret sensations ie., conscious awareness

• Cerebral cortex function

Sensation and Perception

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Perceptual Organization Form Perception Depth Perception Motion Perception Perceptual Constancy


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Perceptual Interpretation Sensory Deprivation and

Restored Vision Perceptual Adaptation Perceptual Set Perception and the Human

Factor


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Sensation & Perception

How do we construct our representations of the external world?

To represent the world, we must detect physical energy (a stimulus) from the

environment and convert it into neural signals. This is a process called sensation.

When we select, organize, and interpret our sensations, the process is called perception.Thursday, March 19, 2015

Human Factor Engineering 490220Lect : 05


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Sensation and Perception


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Our sensory and perceptual processes work together to help us sort out complex processes

“The Forest Has Eyes,” Bev Doolittle

Sensation

Bottom-Up Processing analysis that begins with the sense receptors and

works up to the brain’s integration of sensory information

Top-Down Processing information processing guided by higher-level

mental processes as when we construct perceptions drawing on our

experience and expectations

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Bottom-up Processing

Analysis of the stimulus begins with the sense receptors and works up to the level of

the brain and mind.

Letter “A” is really a black blotch broken down into features by the brain that we perceive as an

“A.”Thursday, March 19, 2015


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Top-Down Processing

Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience

and expectations.

THE CHTThursday, March 19, 2015


Sensation- Basic Principles

Psychophysics study of the relationship between physical

characteristics of stimuli and our psychological experience of them

Light- brightness Sound- volume Pressure- weight Taste- sweetness

Sensation- Thresholds

Absolute Threshold minimum stimulation needed to detect a

particular stimulus 50% of the time Difference Threshold

minimum difference between two stimuli required for detection 50% of the time

just noticeable difference (JND)

Sensation- Thresholds

Signal Detection Theory predicts how and when we detect the presence of a

faint stimulus (signal) amid background stimulation (noise)

assumes that there is no single absolute threshold detection depends partly on person’s

experience expectations motivation level of fatigue

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Our sensory and perceptual processes work together to help us sort out complex

images.

Making Sense of Complexity

“The Forest Has Eyes,” Bev Doolittle


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Sensing the World

Senses are nature’s gift that suit an organism’s needs.

A frog feeds on flying insects; a male silkworm moth is sensitive to female attractant odor; and we as human beings are sensitive to sound frequencies that represent the range of human voice.


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Exploring the Senses

What stimuli cross our threshold for conscious awareness?


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Human Factor Engineering 490220 Lect : 05

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Psychophysics

A study of the relationship between physical characteristics of stimuli and

our psychological experience with them.

Physical WorldPsychological

World

Light Brightness

Sound Volume

Pressure Weight

Sugar Sweet

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Thresholds

Absolute Threshold: Minimum stimulation needed to detect a particular stimulus 50%

of the time.

Pro

port

ion

of

“Yes”

Resp

on

ses

0.0

0

0

.50

1.0

0

0 5 10 15 20 25 Stimulus Intensity (lumens)Thursday, March 19, 2015



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Subliminal Threshold

Subliminal Threshold: When stimuli are below one’s absolute threshold

for conscious awareness.

Kurt Scholz/ Superstock

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Weber’s Law

Two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as

different. Weber fraction: k = dI/I.

Stimulus Constant (k)

Light 8%

Weight 2%

Tone 3%Thursday, March 19, 2015

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Sensory Adaptation

Diminished sensitivity as a consequence of constant stimulation.

Put a band aid on your arm and after awhileyou don’t sense it.


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Now you see, now you don’t


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Key Takeaways• Sensation is the process of receiving information

from the environment through our sensory organs. Perception is the process of interpreting and organizing the incoming information in order that we can understand it and react accordingly.

• Although our experiences of the world are rich and complex, humans - like all species - have their own adapted sensory strengths and sensory limitations.


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• Sensation and perception work together in a fluid, continuous process.

• Our judgments in detection tasks are influenced by both the absolute threshold of the signal as well as our current motivations and experiences. Signal detection analysis is used to differentiate sensitivity from response biases.


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Key Takeaways

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• The difference threshold, or just noticeable difference, is the ability to detect the smallest change in a stimulus about 50% of the time. According to Weber's law, the just noticeable difference increases in proportion to the total intensity of the stimulus.

• Research has found that stimuli can influence behavior even when they are presented below the absolute threshold (i.e., subliminally). The effectiveness of subliminal advertising, however, has not been shown to be of large magnitude.


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Key Takeaways

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Assignment No: 2 Exercises and Critical Thinking

• The accidental shooting of one's own soldiers (friendly fire) frequently occurs in wars. Based on what you have learned about sensation, perception, and psychophysics, why do you think soldiers might mistakenly fire on their own soldiers?

• If we pick up two letters, one that weighs 1 ounce and one that weighs 2 ounces, we can notice the difference. But if we pick up two packages, one that weighs 3 pounds 1 ounce and one that weighs 3 pounds 2 ounces, we can't tell the difference. Why?

• Take a moment and lie down quietly in your bedroom. Notice the variety and levels of what you can see, hear, and feel. Does this experience help you understand the idea of the absolute threshold?

• Submit on 31st March 2015 to CR Mr Zeeshan.


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human factor engineering (mental processes)

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