Transcript Sensation
Sensation Sensation – Raw data of experiences, including smells, sights, tastes, touch, balance and pain. The process by which stimulation of a sensory receptor produces neural impulses that the brain interprets. The first series of steps in processing of incoming information. How does stimulation become sensation? Sensory Receptors – Converts incoming stimulus information into electrochemical signals – neural activity – the only language the brain understands. Example – Light only reaches the back of your eyes, neurons then carry what your eyes see to your brain. How does stimulation become sensation? Transduction – Transformation of one form of energy into another – especially the transformation of stimulus information into nerve signals by the sense organs. Ripe tomatoes would not appear red without transduction. Sensory Adaptation Sensory Adaptation – Loss of responsiveness in receptor cells after stimulation has remained unchanged for a while. Example – When a swimmer becomes adapted to the temperature of the water. Thus, our sense organs are really just change detectors. Example – Feed lots in Greeley. Thresholds Absolute Threshold – The amount of stimulation necessary for a stimulus to be detected. Varies from one person to another. In practice, this means that the presence or absence of a stimulus is detected correctly half the time over many trials. Example – Dog Whistle, Smell Thresholds Difference Threshold – The smallest amount by which a stimulus can be changed and the difference detected half the time. Example – Turn up the volume on the TV a very small amount and your sister says, “You haven’t turned it up enough.” By “enough,” she is referring to her difference threshold. Example – Frog in hot water. Just Noticeable Difference – Same as the difference threshold. Thresholds Weber’s Law – This concept says that the size of the JND is proportional to the intensity of the stimulus. The JND is large when the stimulus intensity is high and is small when the stimulus intensity is low. Signal Detection Theory Signal Detection Theory – Explains how we detect “signals,” consisting of stimulation affecting our eyes, ears, nose, skin, and other sense organs. Says that sensation is a judgment the sensory system makes about incoming stimulation. Often, it occurs outside of consciousness. In contrast, the older theories from psychophysics, signal detection theory takes observer characteristics into account. Subliminal Sensations Sensations in the outside world that occur outside our conscious awareness. Do they still influence our thinking? Example – Pop and Popcorn at a movie. Example – Words in the clouds at a Disney movie. Vision Vision – Parts of the Eye Cornea – Where light enters the eye Pupil – Opening in the center of the eye Iris – Colored part of the eye Lens – Part of the pupil light passes through Retina – Light sensitive inner lining of the back of the eyeball on which light is focused Retina then contains the receptor cells responsible for vision. Fovea – Center of the Visual field, area where images are sharpest. The Retina Retina – The thin, light- sensitive layer at the back of the eyeball. Contains millions of photoreceptors and other nerve cells. Photoreceptors – Lightsensitive cells (neurons) in the retina that convert light energy to neural impulses. This is as far as light gets into the visual system. Rods & Cones in the Retina Rods – Photoreceptors in the retina that are especially sensitive to dim light but not to colors. Cones – Photoreceptors in the retina that are especially sensitive to colors but not to dim light. Fovea Fovea - The tiny area of sharpest vision in the retina. With movements of our eyeballs, we use the fovea to scan whatever interests us visually. Optic Nerve Optic Nerve – The bundle of neurons that carries visual information from the retina to the brain. Blind Spot Blind Spot – The point where the optic nerve exits the eye and where there are no photoreceptors. Any stimulus that falls on this area cannot be seen. Processing Visual Sensation in the Brain We look with our eyes, but we see with the brain. Visual images are imported through the optic nerve to the visual cortex in our brains, which process the information. Brightness Psychological sensation caused by the intensity of light waves. Color Color – Color is not a property of things in the external world. Rather, it is a psychological sensation created in the brain from information obtained by the eyes from the wavelengths of visible light. Color Electromagnetic spectrum – The entire range of electromagnetic energy, including radio waves, X rays, microwaves, and visible light. Visible Spectrum – The tiny part of the electromagnetic spectrum to which our eyes are sensitive. The visible spectrum of other creatures may be slightly different from our own. Two Ways of Seeing Colors Trichromatic Theory – The idea that colors are sensed by three different types of cones sensitive to light in the red, blue, and green wavelengths. Opponent-Process Theory – The idea that cells in the visual system process colors in complementary pairs, such as red or green or as yellow or blue. Colors Afterimages – Sensations that linger after the stimulus is removed. Most visual afterimages are negative afterimages, which appear in reversed colors. Colors Color Blindness – Typically a genetic disorder (although sometimes the result of trauma, as in the case of Jonathan) that prevents an individual from discriminating certain colors. The most common form is red-green color blindness. Sound and the Ear The Ear From Coren, Ward, & Enns. Sensation and Perception 6th ed. John Wiley & Sons, Inc. 2004 Outer Ear •Auditory Canal •Eardrum Middle Ear •Hammer, anvil, stirrup Inner Ear •Cochlea Unit IV. Sensaton and Perception Parts of the Ear Tympanic Membrane – The Eardrum. Includes 3 tiny bones. Hammer Anvil Stirrup These bones pass vibrations to the primary organ of hearing, the cochlea. Parts of the Ear Cochlea – The primary organ of hearing. A coiled tube in the inner ear, where sound waves are transduced into nerve messages. Cochlea then focuses vibrations on the basilar membrane. Parts of the Ear The Basilar Membrane – A thin strip of tissue sensitive to vibrations in the cochlea. Contains hair cells connected to Neurons. When a sound wave causes the hairs cells to vibrate, the associated neurons become excited. As a result, the sound waves are converted into nerve activity and carried to the brain (the auditory cortex). Sensations of Sound Pitch – Sensory characteristic of sound produced by the frequency of the sound wave. Loudness – Sensory characteristic of sound produced by the amplitude (intensity) of the sound wave Timbre – The quality of a sound wave that derives from the wave’s complexity. Table 4.3 page 127 Deafness Conduction Deafness – An inability to hear resulting from damage to structures of the middle or inner ear. Deafness Nerve Deafness – An inability to hear linked to a deficit in the body’s ability to transmit impulses from the cochlea to the brain, usually involving the auditory nerve or higher auditory processing centers. Hearing / Parts of the ear Eardrum – Hearing begins when sound waves strike the eardrum and cause it to vibrate. Hammer, Anvil, and Stirrup – Three tiny bones that hit one another, allowing the vibrations of the eardrum to be carried to the inner ear. Vibrations then travel to the Oval Window, Cochlea, and Basilar Membrane before they reach the receptor cells in the Organ of Corti and finally reach the brain. Taste Gustation – The sense of taste – from the same word root as “gusto” – also called the gustatory sense Taste Evolves throughout life Babies – Enjoy bland food Adults – Like novelties (pickles, mustard, ice cream are all acquired tastes). Flavor vs. Taste Flavor – Combination of smell and taste. Taste – Sweet, sour, salty, and bitter. Can still get taste without smell, but can’t get flavor. Taste Taste Buds – Located on the tip, sides, and back of the tongue, they are the receptor cells for the sense of taste. Adults – 10,000 taste buds Number of taste buds decreases with age, explaining why some elderly people lose interest in food. Papillae – Bumps on your tongue that house the taste buds. The Nose and Smell Olfaction – The sense of smell Olfactory Epithelium – Area of the nose that receives airborne molecules high in each nasal cavity. Receptor Cells in O.E. then send smell to Olfactory Bulb. Olfactory Bulb – Receives information from the O.E. and sends it to the temporal lobes of the brain where we then become aware of smells. The Nose and Smell Smell sensitivity is related to gender and age: Women more sensitive to smell than men. Young adults have the most sensitive sense of smell. The older you get the less sensitive you become to smell. Pheromones! Humans??? Vestibular and Kinesthetic Sense Vestibular – The sense of body orientation with respect to gravity. Closely associated with the inner ear and, in fact, is carried to the brain on a branch of the auditory nerve. Kinesthetic – The sense of body position and movement of body parts relative to each other. Skin Senses Sensory systems for processing touch, warmth, cold, texture, and pain. Gate Control Theory – Proposes that we have a neural “gate” that can, at times, block incoming pain signals. Pain Serves as a warning signal, telling us that we have been injured or that something is wrong. Comes from nerve endings No pains / Phantom limb pains Individuals have different thresholds and tolerances for pain.