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Write the first thing you think of when you hear the following.

Sensation: detecting and encoding physical energy as neural signals
Sensation: detecting and encoding physical energy as neural signals
aka: what you hear/see/touch/smell/taste
Perception: selection, organization, and interpretation of our sensations;
aka: what it all MEANS
We transform sensations into perceptions

Bottom-Up Processing: analysis of information incoming from sense receptors
Bottom-Up Processing: analysis of information incoming from sense receptors
“Bottom” = Stimulus
Top-Down Processing: Drawing meaning from experience and expectations
“Top” = mental set in the brain

Absolute threshold: minimum stimulation needed to detect a stimulus 50% of the time
Absolute threshold: minimum stimulation needed to detect a stimulus 50% of the time
Difference threshold: minimum difference detected between 2 stimuli 50% of the time
Aka: Just Noticeable Difference (JND)

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Weber’s Law: to be perceived differently, stimulus must differ by a constant minimum percentage
Weber’s Law: to be perceived differently, stimulus must differ by a constant minimum percentage
Fechner’s Law: actual magnitude vs. perceived magnitude
Steven’s Power Law: estimation of magnitude

All senses require CHANGE to FUNCTION
All senses require CHANGE to FUNCTION
Sensory Adaptation: diminished sensitivity resulting from constant stimulation
Heightens sensitivity to important information
“We perceive the world not exactly as it is, but as it is useful for us to perceive it.”

VISION: Light Energy
Eyes see pulses of electromagnetic energy

VISION: Light Energy

VISION: Parts of the Eye

VISION: The Retina

VISION: Blind Spot

The Other Senses: Hearing

How do we hear?

Physical Properties of Waves

How is sound measured?

How safe is your iPod?

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The Other Senses: Touch
Essential to development
Attachment, Harlow’s monkeys
Mixture of 4 elements
Pressure, warmth, cold, pain
Only pressure has identifiable sense receptors
Why can’t you tickle yourself??

The Other Senses: Pain
Pain tells you something is wrong
NO brain, NO pain!
Melzack & Wall – Gate Control Theory
theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain
“gate” opened by the activity of pain signals traveling up small nerve fibers
“gate” closed by activity in larger fibers or by information coming from the brain

The Other Senses: Taste
200 + tastebuds
Receptors for: sweet, sour, salty, & bitter
Taste receptors reproduce every 1-2 weeks
Decrease in taste sensitivity as age increases
Smoking and alcohol speed up process
Smell & Taste coexist
Sensory interaction: one sense influences another
Smell+Texture+Taste=Flavor

The Other Senses: Smell
Olfaction: sense of smell
20,000 breaths a day
10-20 million olfactory receptors
Odors can evoke memory & emotion
Anosmia: Inability to smell

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Module 13:
Sensations become Perceptions
Gestalt Psychology: study human tendency to organize pieces of information into meaningful wholes

Form Perception
Figure-Ground: perceive an object (figure) as distinct from its surroundings (ground)

Grouping

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Depth Perception: A 3-D World

How does 2-D become 3-D?
Binocular Cues
Retinal Disparity: the greater difference between objects viewed, the closer it is

How does 2-D become 3-D?
Monocular Cues
Relative Size
Interposition: object blocking the view of another perceived as closer
Relative Height
Relative Motion (motion parallax)
Linear Perspective
Light & Shadow

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Perceptual Constancy
Perceiving objects as unchanging, even though our sensations of them have changed
Shape
Size
Distance
Lightness

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The Nature/Nurture of Perception
Does experience influence our perception of the world around us?
The blind have problems perceiving objects once their vision is restored due to lack of experience and neural connections
Critical Period: optimal time for sensory and perceptual development

Can our perceptions change?
Perceptual adaptation: ability to adjust to changing perceptual conditions
Ex: Looking at the world upside down

Do Assumptions Effect Perception?
Perceptual set: mental predisposition influencing what we perceive
         Mary had a
         a little lamb
         
         Paris in the
         the Springtime

Looking in Context
Perception different between individuals due to differing schemas and context
“Dye” vs. “die”; “attacks” vs. “a tax”

The Human Factor
Human Factor Psychologists: design technology & environments to fit our perceptions
Mind the “curse of knowledge”
User-test products