Myers PSYCHOLOGY 6 th Ed Chapter 5 Sensation

Myers’ PSYCHOLOGY (6 th Ed) Chapter 5 Sensation James A. Mc. Cubbin, Ph. D Clemson University Worth Publishers

Sensation § a process by which our sensory receptors and nervous system receive and represent stimulus (or physical) energy and encode it as neural signals. § Perception § a process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events § Refers to how we select, organize & interpret information. Making sense of raw energy received.

Sensation § Our sensory and perceptual processes work together to help us sort out complex processes

Sensation § Bottom-Up Processing (Chapter 5) § analysis that begins with the sense receptors and works up to the brain’s integration of sensory information § Top-Down Processing (Chapter 6) § information processing guided by higher-level mental processes § as when we construct perceptions drawing on our experience and expectations.

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z We exist in a sea of energy. We are being bombarded all the time with stimulus; but our senses are only open a crack…just allowing a small part in. z Before we can receive information from our senses we must first pay attention to it. The incoming information must be strong enough for us to notice it. z A dim light will not be seen during the day or a soft noise will not be heard in the presence of other sounds.

Sensation- Basic Principles § Psychophysics § study of the relationship between physical characteristics of stimuli and our psychological experience of them. § Vision receives light energy § Hearing receives sound waves/energy § Touch receives mechanical energy § Smell receives airborne chemical energy § Taste receives chemical energy The level of sensory stimulation necessary for stimulation is referred to as:

Sensation- Thresholds § The Absolute Threshold § minimum stimulation needed to detect a particular stimulus 50% of the time. It is the intensity at which we can detect a stimulus half of the time.

z Standard absolute thresholds have been determined for each of our senses. Vision-a candle flame seen at 30 miles on a clear night. Hearing-a tick of a watch under quiet conditions at 20 feet away. Taste-one teaspoon of sugar in 2 gallons of water. Smell-one drop of perfume diffused in a 3 bedroom apartment Touch-a bee’s wing falling on your cheek from 1 centimeter above.

z. Detecting a weak stimulus depends on the signal’s strength as well as our psychological state: that being our experience, expectations, motivation and alertness.

Sensation- Thresholds § Signal Detection Theory § predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise) § assumes that there is no single absolute threshold § Signal detection depends partly on person’s § experience § expectations § motivation § level of fatigue

z It investigates the effects of distractions & interference we experience while perceiving the world. z It tries to predict what we will perceive among competing stimuli. z Examples: exhausted parents of a newborn, does a surgeon see a tumor on a CAT scan or noticing directions on top of a test.

Bellwork: 11/3/15 z. Describe sensory adaptation and explain how we benefit from being unaware of unchanging stimuli.

Sensation and Perception Vocabulary

November 3, 2015 z. Review of last week: Intro to Sensation and Perception: z. Our sensory organs receive stimuli z. What we sense and perceive is influenced by: z. How long we have been exposed to stimuli (sensory adaptation) z. How focused we are on them (sensory habituation)

Sensation- Thresholds 100 Percentage of correct detections § Subliminal Stimulation 75 50 Subliminal stimuli 25 0 Low Absolute threshold Intensity of stimulus Medium § When stimuli are below one’s absolute threshold for conscious awareness

§ To function effectively, we need absolute thresholds low enough to allow us to detect important sights, sounds, smells, tastes & textures. We need to be able to detect small differences among stimuli. Ex: wine taster, musician, voices § Difference Threshold § minimum difference between two stimuli required for detection 50% of the time § just noticeable difference (JND)

Sensation- Thresholds This threshold is computed by: § Weber’s Law- to perceive as different, two stimuli must differ by a constant minimum percentage (named after psychophysicist Ernst Weber. ) § The change needed is proportional to the original intensity of the stimulus. The more intense the stimulus, the more it will need to change before we notice a difference. § Example: chili

§ Sensory adaptation-diminished sensitivity as a consequence of constant stimulation. § It is the gradual loss of attention to unneeded sensory information. § It enables us to focus on important changes in our environment. § What we sense is determined by the attention or what we focus on perceiving. § Example: socks.

Vision § Transduction-the process by which our sensory system converts stimulus energies (such as sights, sounds and smells) into neural messages that our brain can interpret. § It is the conversion of one form of energy to another § Example: as you read this, your eyes capture the light reflected off the page in front of you. Structures in your eyes change this pattern of light into signals that are sent to brain and interpreted as language.

Transduction z The sensation of the symbols on the page and perceiving them as symbols allow you to understand what you are reading. This process is the process of transduction. z These neural impulses first travel to the thalamus, and then to different cortices of the brain. z (Hal and Amos tell them where to go!)

Vision z. Is our most dominant sense. z. Sighted people use vision to gather information about their environment more than any other sense. z. The process of vision involves several steps:

Step One: 1. Gathering Light = light is reflected off of objects and gathered by the eye. Visible light is just a small section of the electromagnetic spectrum. The color we see depends on 2 factors: a. Light intensity-describes how much energy the light contains and how bright the object appears. b. Light wavelength-determines the hue we see.

Properties of Light Waves that are gathered by the eye: § Wavelength § the distance from the peak of one wave to the peak of the next § Hue- Different wavelengths within the visible light spectrum are seen as different colors.

Vision § Intensity § amount of energy in a wave is determined by amplitude § Brightness § loudness (in sound waves)

The spectrum of electromagnetic energy

Vision- Physical Properties of Waves Short wavelength=high frequency (bluish colors, high-pitched sounds) Great amplitude (bright colors, loud sounds) Long wavelength=low frequency (reddish colors, low-pitched sounds) Small amplitude (dull colors, soft sounds)

Vision Step Two: Within the Eye a. The reflected light first enters the cornea, which is a protective covering that helps to focus the light. b. The light then goes through the pupil. The pupil works like the shutter of a camera.

Within the Eye con’t c. The muscles that control the pupil are called the iris, and they dilate it or open it to let in more light and make it smaller to let in less light. d. As the light passes through the lens, the image is flipped upside down and inverted.

Vision § Pupil- adjustable opening in the center of the eye § Iris- a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil opening § Lens- transparent structure behind pupil that changes shape to focus images on the retina

Vision § Accommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retina § Retina- the light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information

Retina The focused inverted image projects on to the retina, which is like a screen on the back of your eye.

Retina’s Reaction to Light Receptors § Rods § peripheral retina § detect black, white and gray § twilight or low light § Cones § near center of retina § fine detail and color vision § daylight or well-lit conditions

Perceiving Color in your peripheral vision: z. One Volunteer! z. Focus on thermostat. z. Tell us what object you see in your periphery z. What color is it?

Reaction: z. How did this activity exemplify the placement of rods and cones on our retinas? z. Knowing what you know about the eye so far, how might you explain cats’ awesome night vision?

Vision

Vision- Receptors in the Human Eye Cones Rods Number 6 million 120 million Location in retina Center Periphery Sensitivity in dim light Low High Color sensitive? Yes No

Sending the signal to your brain. z. Once rods and cones are activated by particles of light, chemical changes generate neural signals. z. The neural signals travel to the bipolar cells and then to the ganglion cells. z. The axons of the ganglion cells make up the Optic Nerve which sends the signal to your brain to be perceived.

Rods and Cones Sensitivity z�Close your eyes and look to your left z. Carefully press your finger against your right eyelid. z. What do you see? Where do you see it? z. How might you explain this?

Vision § Acuity- the sharpness of vision § Nearsightedness- condition in which nearby objects are seen more clearly than distant objects because distant objects focus in front of retina § Farsightedness- condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind retina

Vision § Far -sighted Vision Nearsighted Vision Normal Vision

Retina’s Reaction Light to § Optic nerve- nerve that carries neural impulses from the eye to the brain § Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there § Fovea- central point in the retina, around which the eye’s cones cluster

Blind Spot Activity z. Cover one eye z. Stare at the dot but also note the cross that is on your paper. z. Slowly move your paper away from your nose, continuing to stare at the dot. z. Where did the cross go? z. What color did you see in it’s place? z. Can you predict what you would see if the color of the paper was bright pink?

Pathways from the Eyes to the Visual Cortex

Vision- Stabilized Images on the Retina

Bellwork: Nov. 4, 2015 z. Create a Venn diagram to compare and contrast the two types of light receptors in the retina. z. Describe the retina’s reaction to light

Visual Information Processing § Feature Detectors § nerve cells in the Cell’s responses brain that respond to specific. Stimulus features § shape § angle § movement

Feature detection cells pass simple info to other areas of the cortex where cells respond only to more complex patterns

How the Brain Perceives z As you stare at the Necker cube, providing fairly constant stimulation to your retina, your perception, and the accompanying neural activity in your brain, will change every couple seconds

Illusory Contours

Visual Information Processing § Parallel Processing § simultaneous processing of several aspects of an object such as color, motion, depth etc.

Parallel Processing z. Studies of patients with brain damage suggest that the brain delegates the work of processing color, motion, form and depth to different areas. z. Destroy one of these workstations of the cortex and something peculiar happens: z. Mrs. M- People moving about a room were “suddenly here or there but I have not seen them moving. ”

Parallel Processing: Facial Recognition 1) Retina projects information to different areas of the visual cortex 2) The brain integrates the info from these areas 3) Compares this information to stored information 4) Recognition occurs

Blindsight z. Loss of one portion of the visual cortex, the patient experiences blindness in part of their field of vision. z. Examples: znot recognizing the size of an object but correctly being able to grab it z. Not recognizing an angle that is flashed, but correctly “guessing” it.

Two Visual Systems z. One that gives our conscious perceptions z. Another that guides our actions

Visual Information Processing § Trichromatic (three color) Theory § Young and Helmholtz § There are three different retinal color receptors: § red § green § blue *When both the red and the green cones are activated, we see yellow.

Color-Deficient Vision § People who suffer red-green blindness have trouble perceiving the number within the design § The cones that detect red or green lack proper functioning

But, how do color blind people see yellow? z. If colorblind people have non-functioning red and/or green cones, and the two images combine to make yellow; how is it that they still see yellow? z. Enter: The Opponent-Process Theory! zhttps: //storify. com/Maria. Vita 1/opponentprocess-theory

Visual Information Processing Opponent-Process Theory- opposing retinal processes enable color vision. In the ganglion cells and in the thalamus, some neurons are turned on by one color, such as red and turned off by green (these are opposing colors) “ON” “OFF” red green blue yellow black white green red yellow blue white black

Afterimages z. After staring at one color for a long time, the receptor for that color gets tired and stops firing, but it’s opponent color continues to fire. z. Stare at a green object, look at a white page-the green receptor neurons are no longer firing from the white color, but the red ones are; therefore, we see a red

Opponent Process. Afterimage Effect

Visual Information Processing § Color Constancy § Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

Recap: Parallel processing is another way of saying that we are really good at _________ when it comes to our vision. How do Trichromatic Theory and Opponent. Processing Theory compliment each other?