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About Sensation and Perception PowerPoint Presentation

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Description : Check out this medical PowerPoint presentation titled "Sensation & Perception”.

This medical PowerPoint presentation is about sensation and perception.

Sensation refers to the process of detecting and receiving information from the environment through our sensory organs, such as our eyes, ears, nose, tongue, and skin. This information is then transmitted to the brain, where it is processed and interpreted.

Perception, on the other hand, refers to the way we interpret and make sense of the sensory information that we receive. It involves a complex process of organizing and interpreting the information received from our senses to form a meaningful understanding of the world around us.

Sensation and perception are closely related and are often used interchangeably. However, while sensation refers to the initial process of receiving information from the environment, perception involves higher-level processing and interpretation of that information. Together, sensation and perception allow us to experience and make sense of the world around us.

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Published on : Jun 20, 2023 | Views : 987 | Downloads : 5

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Slide 1-

Sensation & Perception Psychology 201
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Sensation & Perception Sensation is the detection and encoding of the changes in physical energy (e.g., light waves, sound waves, pressure, kinetic energy, etc.) caused by environmental or internal events.
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Sensation & Perception Our sense receptors, located in the sense organs (eyes, ears, tongue, nose, and skin) convert the physical energy into brain energy (i.e., electrochemical energy) in a process called transduction.
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Sensation & Perception But sensations alone do not tell us much about the world until we perceive them. Sensations are just meaningless energy (e.g. light waves and sound waves) until we organize them into meaningful information (sights and sounds).
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Sensation & Perception
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Sensation & Perception
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Sensation & Perception If a tree falls in the forest and no one is around, does it make a sound? Why?
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Senses How many senses are there? What are they?
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Sensation & Perception 1. sight 2. sound 3. taste 4. smell 5. touch
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More senses 6. heat 7. cold 8. pressure 9. pain (Would any of you like to live a life without any pain?) 10. itching 11. balance 12. nausea 13. proprioception 14. pheromones 15. thirst 16. hunger 17. chemical pain (red hot peppers) 18. infrared (snakes) 19. electrical (sharks and platypuses) 20. sonar (bats) 21. magnetic north (birds and moles)
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Reality What is reality? What is real? Do we accurately perceive our world? Demonstration #1 Demonstration #2
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Reality
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Do we accurately perceive the world?
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Our brains alter incoming signals
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Our senses are amazingly sensitive. It is commonly cited that a normal individual can: 1. see a candle, on a clear, and dark night from a distance of 30 miles 2. hear a watch ticking in a perfectly quiet room from 20 feet (if they don’t have tinnitus) 3. taste a teaspoon of sugar diluted in two gallons of water 4. smell a single drop of perfume diffused throughout a three bedroom apartment 5. fell the wing of a bee fall on their skin from a height of 1 centimeter
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Light is Color
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Objects absorb and reflect light
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How many colors can we perceive? We can discriminate among 200 steps in the visible spectrum. We can distinguish among 500 levels of brightness. We can discriminate among 20 levels of saturation (i.e., how little white light is reflected) 200 X 500 X 20 = 2 million colors!
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Color is determined by the property of the object
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Maple leaf before (a) and after (b) it changes color in the fall
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Why do things look different in artificial light?
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Light energy is transduced into neuronal energy
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Transduction takes place in the retina.
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120 Million Rods and 5 Million Cones per Eye
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Nocturnal vision is, in part, achieved by higher concentrations of rods.
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Light is color and light affects the brain and mind. Light causes melatonin secretion to stop and thereby regulates our circadian rhythms. Newly discovered photosensitive ganglion cell affects melatonin secretion.
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Newly discovered intrinsically photosensitive ganglion cell
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http://www.brown.edu/Administration/News_Bureau/2001-02/01-080.html
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Light is color and light affects the brain and mind. Light affects mood (e.g., seasonal affective disorder). Disruptions of light cause jet-lag and have been associated with cognitive impairment. The characteristics of light and the architecture of our brain cause us to perceive color.
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Neural Processing
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Colorful illusions in your mind You will see a green, black, and yellow flag. Stare at the circle in the middle for 30 seconds. Then, when the screen changes, blink once or twice and enjoy your color illusion.
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Theories of Color Vision Opponent-Process Theory suggests that color perception depends on receptors that make antagonistic responses to three pairs of colors. After-images
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Theories of Color Vision Trichromatic Theory suggests that humans have three types of receptors with differing sensitivities to different wavelengths. You can make any color by mixing red, green, and blue light
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Theories of Color Vision Trichromatic Theory suggests that humans have three types of receptors with differing sensitivities to different wavelengths. We appear to have three types of cones
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Theories of Color Vision Opponent Process Theory Trichromatic Theory Which theory is correct?
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Genetics affect color perception and color deficiency (not color blindness) Color deficiency affects either blue/yellow or red/green perception. Color deficiency is much more common in men, especially men with European ancestry (8%) (men with Asian ancestry 5%, men with African ancestry 3%). Monochromatism or true colorblindness occurs in 1 out every 100,000 people.
Slide 42-

Ishihara Test
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Ishihara Test
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“Color blindness…” Why is the term color blindness a poor term?
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Color Perception varies among Animals Insects and ultraviolet Snakes and infrared Nocturnal animals have more rods
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Color Perception varies among Species Bees can detect three colors: ultraviolet, blue, and yellow, but not red. The ability to see red is rare for insects. The butterfly is an exception; they can perceive the widest range of visual wavelengths (310 nm to 700 nm) From: http://landsat.gsfc.nasa.gov/education/compositor/ http://www.robijns.nl/prod-info/julbo_zonnebrillen.php
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Color Perception Varies among Humans Newborns do not possess cones and therefore can’t perceive color or detail.
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The lack of cones also affects visual acuity
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Color Perception Disorders Color deficiency (retinal) Color blindness (cortical) Synesthesia Brain Damage
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Cortical Color Blindness or Cerebral Achromatopsia Mr. I was in an automobile accident and experienced brain damage. He wrote Dr. Oliver Sacks and said “My brown dog is dark gray. Tomato soup is black. Color TV is a hodge-podge…” Mr. I had been a successful painter.
Slide 51-

Cerebral Achromatopsia
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Cerebral Achromatopsia
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Cerebral Achromatopsia
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Cerebral Achromatopsia
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More Brain Damage
Slide 56-

Visual Motion Blindness or Akinetopsia From: http://www.undergrad.ahs.uwaterloo.ca/~tbolton/Dorsal%20Disorders.htm
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Questions What color is the sound of a fog-horn? What color is the sound an old-fashioned bicycle horn makes? What color is a siren?
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Synesthesia Some people see sounds, feel sights, taste words, or see emotions. Synesthesia is experienced when stimulating one sensory modality leads to a perceptual experience in another. Color-word synesthesia may be most common and vowel sounds may be most common triggering stimuli (e.g., a = blue or red; e = yellow or white; o = yellow, red, white, or black; u = blue or black). http://web.mit.edu/synesthesia/www/karen.html
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Synesthesia Pitch (Hz) Loudness (dB) Visual Experience 30 100 a strip 12-15 cm. in length and the color of old, tarnished silver 50 100 a brown strip against a dark background with red- tongue-like edges 100 86 a strip with a reddish-orange hue in the center and it gradually faded towards the edges until it ended in pink 250(alto sax =196) 64 a velvet cord with fiber jutting out on all sides 500 (violin=440) 100 a streak of lighting splitting the heavens in two 500 74 dense orange color that which made him feel as though a needle had been thrust into his spin 2000 113 "It looks something like fireworks tinged with a pink- red hue. The strip of color feels rough and unpleasant and has an ugly taste- -rather like a briny pickle…you could hurt your hand on this one”
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Does color exist in the external world or only in our minds? What makes a tomato red? Why do long wavelengths (usually) look red? Support for color existing in our minds: Animals’ color perception Color deficiency or blindness Cortical color blindness Synesthesia Illusions
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Monocular versus binocular depth cues How do we know how far away an object is by simply looking at it?
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Overview of Questions How can we see far into the distance based on the flat image of the retina? Why do we see depth better with two eyes than with one eye? Why don’t people appear to shrink in size when they walk away?
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Binocular Depth Cues Oculomotor - cues based on sensing the position of the eyes and muscle tension Convergence - inward movement of the eyes when we focus on nearby objects Accommodation - change in the shape of the lens when we focus on objects at different distances
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Figure 8.2 (a) Convergence of the eyes occurs when a person looks at something that is very close. (b) The eyes look straight ahead when the person observes something that is far away.
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Monocular Depth Cues Monocular - cues that come from one eye Pictorial cues - sources of depth information that come from 2-D images, such as pictures Interposition - when one object partially covers another Relative height - objects that are higher in the field of vision are more distant
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Monocular Depth Cues Relative size - when objects are equal size, the closer one will take up more of your visual field Perspective convergence - parallel lines appear to come together in the distance Familiar size - distance information based on our knowledge of object size
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Figure 8.3 A scene in Tucson, Arizona containing a number of depth cues: occlusion (the cactus occludes the hill, which occludes the mountain); perspective convergence (the sides of the road converge in the distance); relative size (the far motorcycle is smaller than the near one); and relative height (the far motorcycle is higher in the field of view; the far cloud is lower).
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Monocular Depth Cues Atmospheric perspective - distance objects are fuzzy and have a blue tint Texture gradient - equally spaced elements are more closely packed as distance increases Shadows - indicate where objects are located
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Figure 8.5 A scene along the coast of California that illustrates atmospheric perspective.
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Figure 8.6 A texture gradient in Death Valley, California.
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Monocular Depth Cues Motion parallax - close objects in direction of movement glide rapidly past but objects in the distance appear to move slowly Deletion and accretion - objects are covered or uncovered as we move relative to them Also called occlusion-in-motion
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Binocular Depth Perception Binocular (or retinal) disparity - difference in images between the two eyes Difference can be described by examining corresponding points on the retina that connect to same places in the cortex
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Figure 8.16 The two images of a stereoscopic photograph. The difference between the two images, such as the distances between the front cactus and the window in the two views, creates retinal disparity. This creates a perception of depth when (a) the left image is viewed by the left eye and (b) the right image is viewed by the right eye.
Slide 75-

Binocular Depth Information - continued Stereopsis - depth information provided by binocular disparity Stereoscope uses two pictures from slightly different viewpoints 3-D movies use the same principle and viewers wear glasses to see the effect Random-dot stereogram has two identical patterns with one shifted to the right
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Stereograms http://www.eyetricks.com/3dstereo.htm
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Figure 8.33 Two cylinders resting on a texture gradient. The fact that the bases of both cylinders cover the same number of units on the gradient indicates that the bases of the two cylinders are the same size.
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Size Constancy Perception of an object’s size remains relatively constant This effect remains even if the size of the object on the retina changes
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Demonstration Look at the red circle on the next slide for 30 seconds. Then look at a piece of paper and blink a few times. How many inches across do you perceive the circle after image to be? Then look at the wall…
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Figure 8.31 The principle behind the observation that the size of an afterimage increases as the afterimage is viewed against more distant surfaces.
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Light directly on each coin. Each coin was the same distance from the observer. Which did they think was the farthest away?
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I wondered why the baseball was getting bigger. Then, it hit me.
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Visual Illusions Nonveridical perception occurs during visual illusions Müller-Lyer illusion: Straight lines with inward fins appear shorter than straight lines with outward fins Lines are actually the same length
Slide 87-

Which is larger? Front Monster or back monster?
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Figure 8.34 The Müller-Lyer illusion. Both lines are actually the same length.
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Müller-Lyer Illusion Why does this illusion occur? Misapplied size-constancy scaling: Size constancy scaling that works in 3-D is misapplied for 2-D objects Observers unconsciously perceive the fins as belonging to outside and inside corners Outside corners would be closer and inside would be further away
Slide 90-

Müller-Lyer Illusion - continued Since the retinal images are the same, the lines must be different sizes Problems with this explanation: The “dumbbell” version shows the same perception even though there are no “corners” The illusion also occurs for some 3-D displays
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Figure 8.35 According to Gregory (1973), the Müller-Lyer line on the left corresponds to an outside corner, and the line on the right to an inside corner. Note that the two vertical lines are the same length (measure them!).
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Figure 8.39 The Ponzo (or railroad track) illusion. The two horizontal rectangles are the same length on the page (measure them), but the far one appears larger.
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Fig. 8-40, p. 187
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The Ames Room Two people of equal size appear very different in size in this room The room is constructed so that: Shape looks like normal room when viewed with one eye Actual shape has left corner twice as far away as right corner
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Figure 8.41 The Ames room, showing its true shape. The woman on the left is actually almost twice as far away from the observer as the woman on the right; however, when the room is viewed through the peephole, this difference in distance is not seen. In order for the room to look normal when viewed through the peephole, it is necessary to enlarge the left side of the room.
Slide 96-

Fig. 8-40, p. 187
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The Ames Room - continued Why does the illusion occur? One possible explanation: Observer thinks the room is normal Women would be at same distance One has smaller visual angle (R) Due to the perceived distance (D) being the same Her perceived size (S) is smaller
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The Ames Room - continued Another possible explanation: Perception of size depends on relative size One woman fills the distance between the top and bottom of the room Other woman only fills part of the distance Thus, first woman appears taller
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What is the difference between these two animals?