Presentation on theme: "Table of Contents OBJECTIVES: EXPLAIN THE DIFFERENCE BETWEEN SENSATION AND PERCEPTION COMPARE AND CONTRAST THE JND AND WEBERS LAW; AND THE ABSOLUTE THRESHOLD."— Presentation transcript:
Table of Contents OBJECTIVES: EXPLAIN THE DIFFERENCE BETWEEN SENSATION AND PERCEPTION COMPARE AND CONTRAST THE JND AND WEBERS LAW; AND THE ABSOLUTE THRESHOLD AND THE SIGNAL DETECTION THEORY IDENTIFY AND EXPLAIN THE PARTS OF THE EYE AND THEIR FUNCTION
Table of Contents Sensation and Perception: The Distinction Sensation : stimulation of sense organs Perception: selection, organization, and interpretation of sensory input Sensation begins with a detectable stimulus
Table of Contents 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.
Table of Contents Just noticeable difference (JND): smallest difference detectable - ex. 5 lb dumbell and 5.1 lb dumbell Webers 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
Table of Contents 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 persons 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.
Table of Contents REVIEW: What is the difference between the JND and Webers law? –JND is the smallest difference detectable between to similar stimuli. Webers 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.
Table of Contents 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.
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
Table of Contents 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
Table of Contents 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
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
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
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
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
Table of Contents Stability in the Perceptual World: Perceptual Constancies Perceptual constancies – stable perceptions amid changing stimuli –Size –Shape –Brightness –Hue –Location in space
Emphasis on linear perspective during the Western Renaissance
Table of Contents 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 http://www.michaelbach.de/ot/
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
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
Table of Contents Figure 4.50 The basilar membrane
Table of Contents 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)
Table of Contents 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.
Table of Contents 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
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.
Table of Contents Figure 4.54 The olfactory system
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
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