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OBJECTIVES:

EXPLAIN THE DIFFERENCE BETWEEN SENSATION AND PERCEPTION

COMPARE AND CONTRAST THE JND AND WEBER’S LAW; AND THE ABSOLUTE THRESHOLD AND THE SIGNAL DETECTION THEORY

IDENTIFY AND EXPLAIN THE PARTS OF THE EYE AND THEIR FUNCTION

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Sensation and Perception: The Distinction

Sensation : stimulation of sense organs Perception: selection, organization, and

interpretation of sensory input Sensation begins with a detectable stimulus

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Psychophysics: Basic Concepts

Transduction – the conversion of external physical stimuli to neural impulses the brain can understand. - KNOW WHERE AND HOW THIS HAPPENS FOR VISION, AUDITION, AND SMELL

Absolute threshold: detected 50% of the time. - ex. automatic lights turn on when a threshold is reached.

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Just noticeable difference (JND): smallest difference detectable - ex. 5 lb dumbell and 5.1 lb dumbell

Weber’s law: size of JND proportional to size of initial stimulus so you can use a ratio or percentage - ex. 100 lb dumbell and 102 lb dumbell

light intensity- 8%weight- 2%tone frequency- 0.3%

Concepts - continued

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Psychophysics: Concepts and Issues

Signal-Detection Theory: predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise)detection depends partly on person’s experience, expectations, motivation, level of fatigue

– Ex. Hearing the doorbell ring at a loud, crowded party because you were expecting it to ring at a certain time AND NO ONE ELSE HEARS IT

Sensory Adaptation: Decline in sensitivity to a stimulus after a few minutes

– TAKE 30 SEC TO LIST AS MANY EXAMPLES OF SENSORY ADAPTATION AS YOU CAN.

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REVIEW:

What is the difference between the JND and Weber’s law?– JND is the smallest difference detectable between

to similar stimuli. Weber’s law is the constant proportion of the JND to the initial stimulus.

What is the difference between the absolute threshold and the signal-detection theory?– Absolute threshold is minimum amount of stimulus

detected 50% of the time. Signal-detection theory accounts for experience, expectations, motivation, level of fatigue, etc.

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Vision: The Stimulus

Light = electromagnetic radiation – Amplitude (height): perception of brightness– Wavelength: perception of color– purity: mixing of wavelengths (colors)

• perception of saturation, or richness of colors.

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The Eye: Converting Light into Neural Impulses

The eye: housing and channeling Components:

– Cornea: where light enters the eye – Lens: focuses the light rays on the retina

• Accommodation -

– Iris: colored ring of muscle, constricts or dilates via amount of light

– Pupil: regulates amount of light

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The Retina: An Extension of the CNS

Retina: absorbs light, processes images, and sends information to the brain– Fovea - clearest vision due to highest concentration of

cones Activity - xyz Optic disk (Blind Spot): where the optic nerve

leaves the eye so there are no photoreceptors Activity – color vision Photoreceptor cells:

– Rods: black and white/ low light vision– Cones: color and daylight vision

• Adaptation: becoming more or less sensitive to light as needed

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Figure 4.7 The human eye

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Figure 4.7 The human eye

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The Retina and the Brain: Visual Information Processing

Light -> cornea -> lens -> iris -> pupil -> retina -> rods and cones -> neural signals -> bipolar cells -> optic nerve (blind spot) -> optic chiasm -> opposite half brain ->

HOMEWORK – COME UP WITH A MNEMONIC DEVICE FOR REMEMBERING THE ORDER AND PARTS OF VISION. DUE TOMORROW

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Review:

List 3 terms or concepts that you learned today.

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Table of ContentsFigure 4.19 Additive versus subtractive color mixing

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Visual Information Processing

Trichromatic (three color) Theory Young and Helmholtz three different retinal color receptors

red green blue

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Theories of Color Vision

Trichromatic theory - Young and Helmholtz– Receptors for red, green, blue – color mixing – F 4.21

Opponent-Process theory – Hering– 3 pairs of antagonistic colors – negative afterimages– red/green, blue/yellow, black/white

Current perspective: both theories necessary Trichromatic theory is explained by color blindness Opponent-Process theory is explained by the

afterimage effect

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Perception: Perceiving Forms, Patterns, and Objects

Reversible figures – Perceptual sets – readiness to perceive a stimulus

in a particular way – ambiguous stimuli – effects of motivational factors

Inattentional blindness/change blindness – http://www.youtube.com/watch?v=nkn3wRyb9Bk&feature=related http://www.youtube.com/watch?v=38XO7ac9eSs

Feature detection theory - bottom-up processing. Form perception - top-down processing Subjective contours Gestalt psychologists: the whole is more than the

sum of its parts– Reversible figures and perceptual sets demonstrate that the

same visual stimulus can result in very different perceptions

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Principles of Perception

Gestalt principles of form perception:– figure-ground, proximity, similarity, continuity, closure, and

simplicity

Recent research:– Distal (stimuli outside the body) vs. proximal (stimulus

energies impinging on sensory receptors) stimuli. – Perceptual hypotheses

• Context

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Depth and Distance Perception

Binocular cues – clues from both eyes together – retinal disparity – convergence

Monocular cues – clues from a single eye – motion parallax – accommodation – pictorial depth cues

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Stability in the Perceptual World: Perceptual Constancies

Perceptual constancies – stable perceptions amid changing stimuli – Size– Shape– Brightness– Hue– Location in space

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Emphasis on linear perspective during the Western Renaissance

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Optical Illusions: The Power of Misleading Cues

Optical Illusions - discrepancy between visual appearance and physical reality

Famous optical illusions: Muller-Lyer Illusion, Ponzo Illusion, Poggendorf Illusion, Upside-Down T Illusion, Zollner Illusion, the Ames Room, and Impossible Figures

Cultural differences: Perceptual hypotheses at work http://www.michaelbach.de/ot/ - website with visual

illusions and other visual effects

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Hearing: The Auditory System

Stimulus = sound waves (vibrations of molecules traveling in air)– Amplitude (loudness)– Wavelength (pitch)– Purity (timbre)

• ex. - a violin and a piano playing the same note

Wavelength described in terms of frequency: measured in cycles per second (Hz)– Frequency increase = pitch increase

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The Ear: Three Divisions

External ear (pinna): collects sound. Middle ear: the ossicles (hammer, anvil, stirrup) Inner ear: the cochlea

– a fluid-filled, coiled tunnel – contains the hair cells, the auditory receptors– lined up on the basilar membrane

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Figure 4.49 The human ear

Table of ContentsFigure 4.50 The basilar membrane

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The Auditory Pathway

Sound waves vibrate bones of the middle ear Stirrup hits against the oval window of cochlea Sets the fluid inside in motion Hair cells are stimulated with the movement of the

basilar membrane Physical stimulation converted into neural impulses

– TRANSDUCTION

Sent through the thalamus to the auditory cortex (temporal lobes)

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Theories of Hearing: Place or Frequency?

Hermann von Helmholtz (1863) – Place theory

Other researchers (Rutherford, 1886)– Frequency theory

Georg von Bekesy (1947) – Traveling wave theory - the whole basilar membrane does

move, but the waves peak at particular places, depending on frequency.

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Auditory Localization: Where Did that Sound Come From?

Two cues critical: Intensity (loudness) Timing of sounds arriving at each ear

– Head as “shadow” or partial sound barrier

Timing differences as small as 1/100,000 of a second

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The Chemical Senses: Taste

Taste (gustation) Physical stimulus: soluble chemical substances

– Receptor cells found in taste buds

Pathway: taste buds -> neural impulse -> thalamus -> cortex – Four primary tastes: sweet, sour, bitter, and salty– Taste: learned and social processes

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The Chemical Senses: Smell

Smell (Olfaction) Physical stimuli: substances carried in the air

– dissolved in fluid, the mucus in the nose– Olfactory receptors = olfactory cilia

Pathway: Odor molecule, Nasal Passage, Nasal Cavity, Olfactory cilia (transduction)-> neural impulse ->olfactory nerve (axons pass through ethmoid bone)-> olfactory bulb (brain)->olfactory tract (inside bulb)->olfactory cortex in temporal lobe->limbic system– Does not go through thalamus– Retro-nasal Olfaction -> food in your mouth goes through the

back of your mouth to your nasal cavity where you smell it.

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Figure 4.54 The olfactory system

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Skin Senses: Touch

Physical stimuli = mechanical, thermal, and chemical energy impinging on the skin.

Pathway: Sensory receptors -> the spinal column -> brainstem -> cross to opposite side of brain -> thalamus -> somatosensory (parietal lobe)

Temperature: free nerve endings in the skin Pain receptors: also free nerve endings

– Two pain pathways: fast vs. slow

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Other Senses: Kinesthetic and Vestibular

Kinesthesis - knowing the position of the various parts of the body– Receptors in joints/muscles

Vestibular - equilibrium/balance– Semicircular canals

Synesthesia – “The man who tasted shapes”