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Chapter 3.2 Notes

by: Christina Ha

Chapter 3.2 Notes PSYC 1101

Christina Ha

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About this Document

In this section, we learn how sensation and perception are related to behavior.
Elementary Psychology
Kara A. Dyckman
Class Notes
Psychology, light, color, Vision
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This 7 page Class Notes was uploaded by Christina Ha on Sunday September 4, 2016. The Class Notes belongs to PSYC 1101 at University of Georgia taught by Kara A. Dyckman in Fall 2016. Since its upload, it has received 108 views. For similar materials see Elementary Psychology in Psychology (PSYC) at University of Georgia.


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Date Created: 09/04/16
9/2/2016   What do we see?  Light: electromagnetic energy wave  o Fluctuating electric and magnetic fields o Light is fast o No light, no sight  Wavelength: the distance between two waves o Different wavelengths correspond to different colors that we  perceive o All that is out there in the physical world are different  wavelengths of light o As humans, we can only see the “visible light” band o What we see as purple and blue are shorter wavelengths (400  nm)  Gamma rays have short wavelengths because they’re on  the far left of the spectrum.  o What we see as red and orange are longer wavelengths (700  nm)  Radio waves have long wavelengths. Features of color  Hue: color o Determined by wavelength of light it reflects o Ex: blue, red, green  Brightness: intensity of color o Depends on wave height (amplitude: distance from midpoint to  peak)  o Higher amplitude = higher brightness o Ex: bright blue, duller blue  Saturation: how pure the color is o Determined by how constant the wavelength is o Ex: Think of the color red. What color red are you thinking  about? There are many different shades of red, which have  different wavelengths of light in them. A number of different  wavelengths are all combined to create a color. How many  different wavelengths are making up this stimulus that you can  see? The Human Eye  Cornea: clear outer layer over the colored portion of the eye o Shields the eye from damage by dust, bacteria, poking o Focuses incoming light waves o Imperfections in its shape can often lead to blurred vision o LASIK eye surgery: uses a laser to reshape the cornea, leading it to focus the light properly  Iris: a muscle that opens and closes, or changes the size of, the pupil  Pupil: the black hole in the center of the iris o Ex: When it’s dark in the room: your iris muscles relax, causing  your pupil to get bigger/wider. Your pupil getting bigger allows  more light to get inside your eye.  o Ex: When you’re outside in the bright sun: the iris muscles  squeeze, which causes your pupil to constrict.   Lens: similar to the cornea, it focuses incoming light  Also, the lens changes its shape so it can see images that are near  and far (accommodation) o The lens is behind the pupil o Lens is the one that bends the light. It affects how clear your  image is. o If you are nearsighted or farsighted, that means your lens is not bending the light properly. Your lens should bend the light so  you get a nice image on the other side. Retina  Retina: it lines the back of your eye o No retina = no vision o Light waves move through the jellylike filling of the eyes after  getting past the cornea, pupil, and lens o Retinopathy of prematurity (ROP): a condition in which blood  vessels in the retina grow incorrectly  Ex of ROP: Think back to the triplets (Emma, Zoe, and  Sophie from chapter 3). Because they were born  prematurely, their blood vessels started to branch in an  unusual way. In the end, it pulled the retina from the back  of the eye. o Retina is responsible for transduction: sensing light, relaying  messages to the brain  Photoreceptors: absorb light energy and turn it into chemical and  electrical signals for the brain to process o After light goes through your entire eye and hits the very back  of your eye (your retina), you will reach your photoreceptors o Photoreceptors allow you to take information from the physical  world and transmit it o Two types of photoreceptors: Cones and rods (easy to  remember because they are shaped like their names)  Rods: useful for night vision because it is responsible for  sight when the light level is low; not sensitive to color  If we only had rods, we would only be able to see  black and white  Cones: provides color vision and allows us to see fine  details (ex: small print on back of a shampoo bottle) o When the light hits them, it transduces this light signal into a  neural system and fires an action potential. They synapse into  bipolar cells, which synapse onto the ganglion cells. o The collection of axons of the ganglion cells becomes your  optic nerve.  o Fovea is the place you are looking right now. (precise detail) If  you move your eyes, something else is going to be your fovea.   Lacks rods and cones are most densely packed here. TRY THIS  How do you find your blind spot?  Close your left eye. Hold your left thumb out at arm’s length. Put your  right thumb next to your right thumb so that they’re touching each  other. Keep looking at your left thumb and move your right thumb to  the right so that it’s not in your field of view anymore (about six inches to the right?)  Side note: Saccades get the object that we want to see in that area  on our retina that has really good visual acuity. Your eye movements  change fast so that they can jump from one place to another. Coding for objects in our environment  Simple stimuli  o Feature detectors are actual neurons that code for specific  simple stimuli; like the orientation of a line o Ex: If you present a vertical line, there are certain neurons in  your brain that will fire very quickly. However, they may not fire  a lot for horizontal lines. This is experience dependent.  When you’re a baby (which is a critical period to learn  types of visual input), you need to be exposed to all these different types of lines in order for your brain to develop  these types of neurons to code  If you are deprived of some orientation of lines, you will  behave differently.  Ex: An experiment was done with kittens who were    raised with vertical stripes. Because they were only raised with vertical lines, the researchers studied that they could  not see or process horizontal lines  Complex stimuli (Imagine Oprah Winfrey) o Patterns of activation of different neurons o They allow you to recognize Oprah’s face. You don’t have one  neuron in your brain that allows you to recognize your best  friend or a famous celebrity. Feature detectors activate your  neurons and allows you to perceive different objects or different people in your environment. Color Vision  How do wavelengths translate into perception of color? o I call an object red and I have an idea of what this red is. You  and I have both been taught to call this color red, but my  perception could be different than yours. o Here is where the trichromatic theory and the opponent­ process theory explain human color vision.  Trichromatic theory has three types of cones that correspond to  different wavelengths of light: o Red: long wavelength of light; 620­700 nanometers (come into  your eye, go all the way back to your photoreceptors, and  signal the red cones) o Green: medium wavelength of light; 500­575 nm o Blue: get excited by short wavelengths of light; 450­490 nm o When red, blue, and green light wavelengths are combined in  equal proportions, they create a white light. o Any other wavelength of light is a combination of red, green,  and/or blue of what color you see.  Color deficiency (or color blindness): loss/ damage to one or more of  the cone types o Ex: Ishihara Test  o Red­green color defects: 8% of men and less than 1% of  women have some degree of color blindness  o Afterimage: “an image that appears to linger in your visual field  after its stimulus, or source, is gone”  Opponent­process theory: a special group of neurons that respond to  opponent colors (blue/yellow, red/green, and black/white) o One neuron fires by the color red, but is inactive when you see  green. The other neuron gets excited when you look at green,  but is turned off when you look at red.  We need both the trichromatic and opponent­process theories in  order to make the different aspects of color vision clear. Color  perception takes place in the light­sensing cones in the retina and in  the opponent cells serving the brain


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