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General Psychology Unit 2

by: Brooke Hughes

General Psychology Unit 2 PSY 1410-004

Brooke Hughes

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Chapter 3: Sensations and Perceptions
General Psychology
Davis, T
Class Notes
general, Psychology, senses, Sound, light
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This 7 page Class Notes was uploaded by Brooke Hughes on Friday February 26, 2016. The Class Notes belongs to PSY 1410-004 at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months taught by Davis, T in Winter 2016. Since its upload, it has received 27 views. For similar materials see General Psychology in Psychlogy at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months.


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Date Created: 02/26/16
Chapter 3: Sensation and Perception  (lecture & textbook notes) Sensing and Perceiving the World:  What is the difference between sensation and  perception?  A sense is system that translates data from the outside the nervous system into neural  activity.   A sensation is a detection of a physical stimulus such as light.  A perception the process through which people take raw sensations from the  environment and give them meaning using knowledge, experience, and understanding  of the world. o in other words: is the organization and interpretation of sensory input. o Ex: When you look out into a field and you see a cow, your brain can recognize  that it is a cow from prior knowledge, experiences, and understanding the world. Sensory Systems:  How does information from my eyes and ears get to my brain?  Intro: Your senses gather information about the world by detecting various forms of  energy. Eyes detect light energy, ears detect the energy of sound, and skin detects  energy of heat and pressu All senses detect information about stimuli, encode it into  neural activity, and then sends that encoded info to the brain.  The process: 5. Cerebral 3. Sensory cortex Energy 1. 2. Receptor nerves 4. receives contains Accessory transduces transfer Thalamus input and information structure energy into the coded processes produces activity to and relays aboou the modifies neural the central the neural the world engery. response. nervous repsonse. senation system. and perception. (clip art here)  The 1st step: accessory structures which are structures that modifies an incoming  stimulus.  o Ex: the flexible outer part of your ear that extends to the outside of your head is  an accessory structure that collects the sound.  The 2nd step: transduction, which is the process of converting incoming energy into  neural activity  o Ex: When your cell phone rings, its because your phone receives  electromagnetic energy and tranduces it into sound.   o Ex: The same way your ear receives sound energy and tranduces it into neural  activity that you recognize as voices and music.  Transduction occurs the 3rd step of the process in a structure called neural receptors.  These are cells that are specialized to detect certain types of energy and convert it into  neural activity.  These receptors respond to incoming energy by firing an action potential  and releasing neurotransmitters that send signals to near by cells.  Sensory adaptation is the decreasing responsiveness to an unchanging stimulus. o Ex: Then you put on a wristwatch you eventually don’t realize it is still on.  Encoding translates the physical properties of a stimulus, such as its shape and  intensity, into a pattern of neural activity that tells us what those physical properties are. o Your brain organizes these neural patterns, and make sense of the stimulus, and that is how you know you are looking at white car, a black shirt, or a tall person. Absolute Thresholds: Is Something Out There?  Scientists discovered thresholds by exploring psychophysics, the relationship  between physical energy in the environment and your psychological experience  of that energy.  Absolute threshold is the smallest amount of energy that can be detected 50  percent of the time.  Noise is the spontaneous random firing of nerve cells that occur because the  nervous system is always active.  Response Bias (Response Criteria) the internal rule a person uses to decide  whether or not to report a stimulus.  o This will depend on a person’s motivation (wants and needs) as well as  expectations.  Signal Detection Theory is a mathematical model of what determines a  person’s report of a near threshold stimulus. Judging Differences between Stimuli  When our bodies are detecting stimuli, sometimes it isn’t important to detect a  faint stimulus. It is more important to notice small changes in a stimulus or to  decide whether two stimuli are the same or different. o Ex: when you repair a wall, you have to judge whether or not the new  paint matches the old wall color. o Ex: when you are cooking, you have to decide whether you soup tastes  any spicier after adding spices.  It also depends on the strength of the stimuli. The smaller it is, the easier it is to  detect differences. o Ex: If you have an orange in each hand, and one is bigger by even a  fraction of an ounce, you will be able to tell that difference.  However if  you have two 50­pound boxes in each hand, you may not notice the  difference.  Weber’s Law is a law that states that the smallest detectable difference in  stimulus energy (just­noticeable difference) is a constant fraction of the intensity  of the stimulus. Sensory Energy  Sensory energies of light and sound vibrate as waves pass through space. This  happens because of change in air pressure or reflected light.  Wavelength is the distance from one peak of the wave to the next.  Wave Frequency is the number of complete waves, or cycles, that pass a given  point in a given amount of time.  Amplitude is the height of the wave from baseline to peak. Seeing:  Why do some people need eyeglasses? Light  Light is a form of energy known as electromagnetic energy. This invisible to the  human eye. o This includes: x­rays, radio waves, TV signals, Wi­Fi, and radar.  Light intensity is how much energy light contains which determines the  brightness of light.  Depending on the Light wavelength is how you decide what color something is. o Ex: 440­nm light appears violet blue, and 700­nm appears orangish­red.   Focusing Light  Your eye transducers light energy into neural activity.  1 :  Light rays enter the eye by passing through the curved, transparent,  protective layer called the cornea.  2 :  The light then passes through the pupil, the opening just behind the cornea.  3 :  The iris (give eye color) adjusts the amount of light allowed in the eye by  constricting to reduce the size of the pupil or delighting it to enlarge it.  4 :  Behind the pupil is the lens. o (both cornea and lens are curved to bend light. Ex: camera lens.) o this bending process focuses light rays coming from various angles into a  sharp image on the inner surface at the back of eye. th  5 :  This surface is called the retina where the lens focuses light rays.  The Ocular Accommodation is the ability of the lens to change its shape and  bend light rays so objects are in focus. Converting Light into Images  A conversion of light energy into neural activity takes place in the retina.  Special cells in the retina called photoreceptors convert light energy into neural  activity.  There are two main types: Rods and Cones. o  Rods  are photoreceptors in the retina that allow sight even in dim light,  BUT cannot distinguish colors.  Located on the edge of the eyes     Cones are photoreceptors in the retina that are less light sensitive than  rods but that can distinguish colors.      Located at the center of the eyes This is related to why when you come inside after being out side in the sun it can  be difficult to see. The chemicals in you rods and cones have to take a minute to  adjust. This is called dark adaptation, which is the increasing ability to see in the dark  as time passes. Cones are concentrated at the center of the eye in an area called fovea. The  fovea is a region that focuses on light.  o Cones are Specialized for daylight o Rods are specialized for night vision. Seeing Color  (NOTE: these color concepts dealing with light are NOT the same as concept with mixing  paint)  Hue is the essential color determined by the dominated wavelength of light. o Black, white, and grey are not considered hues because they don’t have  a dominate wavelength.  Color Saturation is related to the purity of the color. o A color is more saturated or more pure if just 1 wavelength is more  intense and contains more energy than another wavelength.  o A yellow school bus or red stop sign are saturated color, but pastel colors  are desaturated because whiteness is added to it.  Brightness is the overall intensity of the wavelength making up light. Theories of Color Vision: Trichromatic Theory & Opponent­Process Theory  Early 1800s, Thomas Young proved that if you mix pure version of blue, green,  and red light in different ratios could produce any other color.  Hermann von  Helmholtz later confirmed the findings. The Young­Helmholtz theory of color  vision is called Trichromatic Theory. o There are three types of cones (in the retina):  Short­Wavelength is sensitive to the blue range  Medium­Wavelength is sensitive to the green range.  Long­Wavelength is sensitive to the red range.  o Its saying that no single cone by itself can signal color in light. It is saying  that a ratio of those three cones can signal a certain color  Like a TV.  The trichromatic theory doesn’t explain after images. Therefore, Ewald Hering  came up with the opponent­process theory. It states that the visual elements  that are sensitive to color are grouped into red­green, blue­yellow, and black­ white pairs. Hearing:  How would my voice sound on the moon?  Sound is a repeating fluctuation­a rising and falling­in the pressure of a substance, such as air. Sound  Loudness is a psychological dimension of sound that is determined by the amplitude of  a sound wave. o Measured in decibels (DB)  Pitch is how high or low a tone sounds; pitch depends on the frequency of a sound  wave. o The higher the frequency­ the higher the pitch. (shorter) o Humans hear sounds between 20­20,000 HZ  Sounds that are a mixture of many frequencies and amplitudes creates sound’s timbre. o Quality of sound. The Ear  Divided into three sections:     External Ear o Pinna: the sound collecting cone. (The clumped part of the outer ear.) o Ear drum: is the membrane that vibrates as sounds waves hit it.  Sounds conducted through vibrations of air.     Middle Ear o Hammer, Anvil, Stirrup: 3 tiny bones.  Sound conducted through movement of bones.     Inner ear o Cochlea: it is a fluid filled coiled tunnel that contains the receptors for hearing  Looks like a shell o The basilar membrane forms the floor of the fluid­filled duct that runs through  the cochlea.  As sound waves pass through the fluid in the tube, it makes the basilar  membrane rise and fall.  This movement bends the hair cells on the membrane. They make connections with fibers from the acoustic nerve. They are a bundle of axons that go to the brain.


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