Core Concept 5-1

• The brain senses the world indirectly because the sense organs convert stimulation into the language of the nervous system: neural messages.

Stimulus• Any physical energy that can be

sensed

• Examples: sound or light waves.

Sensation

Sense organs change physical energy into

pattern of neural impulses that represent a

stimulus

Transduction

• Process of converting physical energy into neural impulses

• Specialized receptor cells in each of the senses are activated by specific forms of energy

• Bundles of neurons then carry information from sense organs to the brain

Sensory Adaptation

• Loss of responsiveness in receptor cells after prolonged, unchanged stimulation

• Sense organs are novelty detectors that notice changes in external world

Absolute Threshold

• Smallest amount of stimulation necessary

for detection

Subliminal Perception

• Responding to stimuli below the absolute threshold

• Advertising• Learning while asleep

Core Concept 5-2

• The senses all operate in much the same way, but each extracts different information and sends it to its own specialized region in the brain.

Five Basic Human SensesSense Stimulus Organ Receptor

Sight Light Waves Eye Retina

Hearing Sound Waves Ear Hair Cells

Touch Pressure Skin Nerve Endings in Skin

Smell Volatile substances

Nose Hair Cells

Taste Soluble substances

Tongue Taste Buds

Electromagnetic Spectrum

Color Blindness

Smell

Taste

Taste buds –

Receptors for taste (primarily on the upper side of the tongue)

Core Concept 5-3

• Perception brings meaning to sensation, so perception produces an interpretation of the world, not a perfect representation of it.

Perception and Philosophy

• Does objective reality exist?

• Or only our subjective interpretation?

Visual Illusion

• Common incorrect experience of a

stimulus pattern

• The mind does not always “see” the same

thing as the eyes.

The Herman Grid

Do you see or ?

Principles of Perception

• Scientific “laws” that guide perception• Explanation for perception

– Learning-based inferences– Gestalt Theory--innate brain factors– Likely an interaction of both– Example: depth perception

Depth Perception• Perception is 3-D

• Even though image on retina is not

• Cues from the eyes

• Cues from the stimulus

Active Processing

• Perception not a passive recording

• Actively constructed by brain

• Impossible Figures

Perceptual Constancy

• Ability to recognize the same object under different conditions

Context

• Perception is influenced by the surrounding conditions

Perceptual Set

Readiness to detect a particular stimulus in a

given context

Culture• Everyday experiences

in different cultures create differences in perception.

• No long roads or railroads in Guam

Figure-Ground• Figure--part of a

pattern that commands

attention

• Ground--part of

pattern that does not

command attention; the

background

Camoflauge

• Designs that break up figure-ground

• Used to avoid detection

Camoflauge

Jungle

Desert

New Multi-Environment

Gestalt Principles of Grouping

Gestalt Law of Pragnanz

• Simplest organization, requiring least effort, will emerge.