Sensation and Perception Chapter 3 LO 3.1 Sensation and the central nervous system 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 Menu Eye Sensory Receptors Ear Sensory Receptors Nose Sensory Receptors Skin Sensory Receptors Sensation and Perception Stimulus energy •Heat •Light Sensory receptor •Eyes •Nose •Skin Sensation Neural impulse Brain •Visual •Olfactory Perception LO 3.1 Sensation and the central nervous system 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 Menu LO 3.1 Sensation and the central nervous system 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. Menu Light Amplitude Wavelength LO 3.2 What is light Psychological Aspects to Light • Brightness - amplitude of the wave; higher waves brighter; lower waves dimmer. Saturation Color • Color - length of the wave; long wavelengths red; short waves blue • Saturation - purity of the color people see Brightness Menu LO 3.3 How eyes see and see color Structure of the Eye Cornea Pupil • 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. Menu LO 3.3 How eyes see and see color Structure of the Eye • 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 Menu LO 3.3 How eyes see and see color Retina, Rods, and Cones • Photoreceptors that respond to various light waves Retina • Rods – receptors responsible for noncolor vision and sensitivity to dim light. • Cones – receptors responsible for color vision and sharpness of vision. Cone Optic nerve Rod Menu Visual Field of left eye Optic nerve Visual field of right eye Optic chasm Primary visual area LO 3.3 How eyes see and see color 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 Or Or Menu LO 3.3 How eyes see and see color 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. Menu LO 3.4 Sound • Amplitude –volume (how soft or loud a sound is). • Wavelength – frequency or pitch • Purity –timbre (a richness in the tone of the sound). • What is sound Amplitude Wavelength Quieter Louder http://www.youtube.com/watch ?v=2RkaD9nAv34. Deeper pitch Higher pitch Menu LO 3.4 What is sound 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 Eardrum the middle part of the Auditory canal ear Menu Structure of the Ear • When sound waves hit the eardrum, it vibrates and causes three tiny bones in the middle ear to vibrate. • Hammer • Anvil • Stirrup Hammer Hammer Stirrup Anvil LO 3.4 What is sound 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. Organ of Corti Menu Structure of the Ear http://www.youtube.com/watch?v= 7a2aoZeZhZ8&feature=related http://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. Auditory nerve LO 3.4 What is sound 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. Menu LO 3.4 What is sound Theories of Pitch • Frequency theory - states that pitch is related to the speed of vibrations in the basilar membrane. Menu LO 3.6 Senses of taste and smell 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” Menu LO 3.6 Senses of taste and smell Taste Bitter Taste pore Receptor cell Sour Salty Sweet Nerve fiber Menu LO 3.6 Senses of taste and smell Smell • Olfaction (olfactory sense) – sense of smell. • Olfactory bulbs areas of the brain that receive information from the olfactory receptor cells. Receptor Olfactory bulb Menu LO 3.7 Touch, pain, motion and balance 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. Menu LO 3.7 Touch, pain, motion and balance 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. Menu LO 3.8 Perception and perceptual constancies 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 Menu 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. LO 3.9 Gestalt principles of perception Gestalt Principles • Figure–ground - the tendency to perceive objects as existing on a background. Menu Gestalt Principals • Reversible figures - visual illusions in which the figure and ground can be reversed. Gestalt Principals LO 3.9 Gestalt principles of perception Gestalt Principles Similarity Proximity Continuity Closure Menu LO 3.10 Perceiving the world in three dimensions Development of Perception • Depth perception - the ability to perceive the world in three dimensions Menu LO 3.10 Perceiving the world in three dimensions Monocular Cues • Monocular cues (pictorial depth cues) – cues for perceiving depth based on one eye only. Menu LO 3.10 Perceiving the world in three dimensions Monocular cues Linear Perspective Texture gradient Areal perspective 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. Focal point Left Right Far Near 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 LO 3.11 Visual illusions and other factors influencing perception 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.