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Sensation & Perception

n     Sensations are relatively meaningless bits of information that result when the brain processes signals that come from the sense organs.

n     Perceptions are meaningful sensory experiences that result after the brain combines hundreds of sensations.

How do sensations become perceptions?

n    Transduction: sensory receptors convert a physical energy into nerve impulses

Sensory Thresholds

n    Each sensory system has a threshold level of energy that is required to activate that sense

¨  Absolute threshold: 

¨  Difference threshold:

n    Different people can have widely varying sensory thresholds

n    Thresholds can change within a person over time and as a function of hormone status

Some Absolute Thresholds

n     Sight: A candle flame seen at 30 miles on a dark clear night.

n     Hearing: The tick of a watch under quiet conditions at 20 feet.

n     Taste: One teaspoon of sugar in 2 gallons of water.

n     Smell: One drop of perfume diffused into the entire volume of a six-room apartment.

n     Touch: The wing of a fly falling on your cheek from the distance of 1 cm.

Sensory Adaptation

n  

Vision

n   

n   

¨ 

Anatomy of the Eye

Sensory Coding

n   

Photoreceptors

n   Photoreceptors are light-sensitive cells found within the retina

¨ Rods

¨ Cones

Color Perception

n    Humans are able to discriminate 7 million different hues.

n   

n    Trichromatic theory

¨ 

n

n    Opponent-Process theory

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CONE Overuse

Gustation

n  

n  

Olfaction

n   Functions of olfaction

¨

¨ Warn us of potentially dangerous foods

¨

¨ For some animals, functions to locate food, mates, territory

Perception

n    Perceptual processes include

¨  Selection refers to

¨  Organization involves

¨  Interpretation involves

n    Perceptions can be in error

¨  Illusions are visual stimuli that are misinterpreted

Selection

Organizational Rules

n   Form Perception

Gestalt Organizational Principles

Gestalt Example

Perceptual constancy

¨ 

¨  Two cases of perceptual constancies:

n   Size constancy

¨ 

n   Shape constancy

¨ 

Interpretation

n   Perceptual set

¨

Extrasensory Perception???

n    Telepathy:

n    Precognition:

n    Clairvoyance:

n    Psychokinesis: