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OBJECTIVES:

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. Sensation and Perception: The Distinction.

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OBJECTIVES:

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  1. 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

  2. Sensation and Perception: The Distinction • Sensation : stimulation of sense organs • Perception: selection, organization, and interpretation of sensory input • Sensation begins with a detectable stimulus

  3. 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.

  4. Concepts - continued • 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%

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. Figure 4.7 The human eye

  11. 3 4 2 1 5 6 8 7 Figure 4.7 The human eye

  12. 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

  13. Review: • List 3 terms or concepts that you learned today.

  14. Figure 4.19 Additive versus subtractive color mixing

  15. Visual Information Processing • Trichromatic (three color) Theory • Young and Helmholtz • three different retinal color receptors • red • green • blue

  16. 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

  17. 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

  18. 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

  19. 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

  20. Stability in the Perceptual World: Perceptual Constancies • Perceptual constancies – stable perceptions amid changing stimuli • Size • Shape • Brightness • Hue • Location in space

  21. Emphasis on linear perspective during the Western Renaissance

  22. 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

  23. 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 • Wavelengthdescribed in terms of frequency: measured in cycles per second (Hz) • Frequency increase = pitch increase

  24. 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

  25. Figure 4.49 The human ear

  26. Figure 4.50 The basilar membrane

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