Sensation and PerceptionChapter 3

Sensation

• Sensation - the activation of receptors in the various sense organs.

• Sensory receptors - specialized forms of neurons.

• Sense organs:• eyes• ears• nose• skin• taste buds

LO 3.1 Sensation and the central nervous system

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Eye Sensory Receptors

Ear Sensory Receptors

Nose Sensory Receptors

Skin Sensory Receptors

Sensation and Perception

Stimulus energy•Heat•Light

Sensory receptor •Eyes•Nose•Skin

Neural impulse

Brain•Visual •Olfactory

Sensation Perception

Sensory Thresholds• Absolute threshold - smallest amount of energy needed

for a person to consciously detect a stimulus (50% of time)

• Just noticeable difference smallest difference between two stimuli that is detectable (50% of time)

• http://www.google.com/search?hl=en&source=hp&q=van+morrison+into+the+mystic+&aq=f&aqi=g10&aql=&oq=&gs_rfai=COBXm3nlkTOXrIouEhQSl6PCFBgAAAKoEBU_Q0NSM

LO 3.1 Sensation and the central nervous system

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Habituation and Sensory Adaptation

• Habituation - tendency of the brain to stop attending to constant, unchanging information.

• Sensory adaptation - tendency of sensory receptor cells to become less responsive to a stimulus that is unchanging.

LO 3.1 Sensation and the central nervous system

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Light Amplitude

Wavelength

Psychological Aspects to Light• Brightness - amplitude

of the wave; higher waves brighter; lower waves dimmer.

• Color - length of the wave; long wavelengths red; short waves blue

• Saturation - purity of the color people see

LO 3.2 What is light

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Brightness

ColorSaturation

Structure of the EyeLO 3.3 How eyes see and see color

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• Cornea – clear membrane that covers surface of eye; protects eye and focuses most of light coming into eye.

• Pupil – hole through which light from the visual image enters eye. Pupil

Cornea

Structure of the EyeLO 3.3 How eyes see and see color

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• Iris - round muscle; can change the size of the pupil, letting more or less light into the eye; helps focus the image.

• Lens – suspended by muscles; finishes the focusing process begun by the cornea.

Lens

Iris

Retina, Rods, and ConesLO 3.3 How eyes see and see color

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• Photoreceptors that respond to various light waves

• Rods – receptors responsible for non-color vision and sensitivity to dim light.

• Cones – receptors responsible for color vision and sharpness of vision.

Optic nerve

Retina

Rod

Cone

Visual Field of left eye Visual field of right eye

Optic nerve Optic chasm

Primary visual area

Color Vision

• Trichromatic theory - theory of color vision that proposes three types of cones: red, blue, and green.

• Opponent-process theory - theory of color vision that proposes four primary colors with cones arranged in pairs: red and green, blue and yellow

LO 3.3 How eyes see and see color

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Or

Or

Color Blindness

• Monochrome colorblindess - either have no cones or have cones that are not working at all.

• Red-green colorblindess - either the red or the green cones are not working.

LO 3.3 How eyes see and see color

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Sound• Amplitude –volume

(how soft or loud a sound is).

• Wavelength –frequency or pitch

• Purity –timbre (a richness in the tone of the sound).

• http://www.youtube.com/watch?v=2RkaD9nAv34

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LO 3.4 What is sound

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Amplitude

Wavelength

Quieter Louder

Deeper pitch Higher pitch

Structure of the Ear

• Auditory canal - short tunnel that runs from the pinna to the eardrum

• Eardrum - thin section of skin that tightly covers the opening into the middle part of the ear

LO 3.4 What is sound

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Auditory canal

Eardrum

Structure of the Ear

Hammer

Anvil

Stirrup

• When sound waves hit the eardrum, it vibrates and causes three tiny bones in the middle ear to vibrate.

• Hammer• Anvil• Stirrup

Hammer

Structure of the Ear• Cochlea - snail-shaped structure of the inner ear that

is filled with fluid.

• Organ of Corti – rests in the basilar membrane; contains receptor cells for sense of hearing.

LO 3.4 What is sound

MenuOrgan of Corti

Structure of the Ear

Auditory nerve

http://www.youtube.com/watch?v=7a2aoZeZhZ8&feature=relatedhttp://www.youtube.com/watch?v=8wgfowbbTz0&feature=related

Auditory nerve - bundle of axons from the hair cells in the inner ear; receives neural message from the organ of Corti.

Theories of Pitch• Pitch - frequency of the sound waves; higher

frequencies are perceived as higher pitches.

• Place theory - states that different pitches are experienced by the stimulation of hair cells in different locations on the organ of Corti.

LO 3.4 What is sound

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Theories of Pitch

• Frequency theory - states that pitch is related to the speed of vibrations in the basilar membrane.

LO 3.4 What is sound

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Taste• Taste buds – taste receptor cells in mouth;

responsible for sense of taste

• Gustation - the sensation of a taste.

• Five Basic Tastes:• Sweet• Sour• Salty• Bitter• “Brothy”

LO 3.6 Senses of taste and smell

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LO 3.6 Senses of taste and smell

Taste

Nerve fiber

Receptor cell

Taste poreSour

Sweet

Salty

Bitter

Smell• Olfaction (olfactory

sense) – sense of smell.

• Olfactory bulbs - areas of the brain that receive information from the olfactory receptor cells.

LO 3.6 Senses of taste and smell

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Receptor

Olfactory bulb

Somesthetic Senses• Somesthetic senses - the skin

senses, the kinesthetic sense, and the vestibular senses.

1. Skin senses - the sensations of touch, pressure, temperature, and pain.

1. Kinesthetic sense - sense of the location of body parts in relation to the ground and each other.

LO 3.7 Touch, pain, motion and balance

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Somesthetic Senses

3. Vestibular senses - the sensations of movement, balance• Sensory conflict

theory in which the information from the eyes conflicts with the information from the vestibular senses resulting in dizziness.

LO 3.7 Touch, pain, motion and balance

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Perception and Constancies

• Perception - the method by which the sensations experienced at any given moment are interpreted and organized in some meaningful fashion.

• http://www.youtube.com/watch?v=L3AgO6H0H98

LO 3.8 Perception and perceptual constancies

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Constancy

• Size constancy - the tendency to interpret an object as always being the same actual size, regardless of its distance.

Constancy

• Shape constancy - the tendency to interpret the shape of an object as being constant, even when its shape changes on the retina.

Constancy

• Brightness constancy – the tendency to perceive the apparent brightness of an object as the same even when the light conditions change.

Gestalt Principles• Figure–ground - the tendency to perceive

objects as existing on a background.

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LO 3.9 Gestalt principles of perception

Gestalt Principals

• Reversible figures - visual illusions in which the figure and ground can be reversed.

Gestalt Principals

Gestalt PrinciplesLO 3.9 Gestalt principles of perception

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Similarity Proximity Continuity Closure

Development of Perception• Depth perception - the ability to perceive the world in

three dimensions

LO 3.10 Perceiving the world in three dimensions

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Monocular Cues• Monocular cues (pictorial depth cues) – cues for

perceiving depth based on one eye only.

LO 3.10 Perceiving the world in three dimensions

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LO 3.10 Perceiving the world in three dimensions

Monocular cues

Linear Perspective

Areal perspective Texture gradient Relative size

Binocular Cues• Binocular cues - cues for

perceiving depth based on both eyes.

1.Convergence - the rotation of the two eyes to focus on a single object, resulting in greater convergence for closer objects and lesser convergence if objects are distant.

Far

Near

Focal point

Left Right

Binocular Cues

• Binocular disparity - the difference in images between the two eyes, which is greater for objects that are close and smaller for distant objects.

LO 3.11 Visual illusions

Perceptual Illusions

Müller-Lyer illusion

LO 3.11 Visual illusions

Perceptual Illusions

Moon Illusion

Perceptual Illusions• Illusions of Motion:

• Stroboscopic motion - seen in motion pictures, in which a rapid series of still pictures will appear to be in motion.

LO 3.11 Visual illusions and other factors influencing perception

Factors that Influence Perception• Perceptual expectancy- the tendency to perceive

things a certain way because previous experiences or expectations influence those perceptions.

LO 3.11 Visual illusions and other factors influencing perception