What is sensation? The process by which our sensory receptors and nervous system receive stimulus from the environment. Is it magic? You be the judge. Check out the following exercise, guaranteed to raise an eyebrow. There's no trick or surprise. Just follow these instructions, and answer the questions one at a time and as quickly as you can! Again, as quickly as you can, but don't advance until you've done each of them... really. Now, arrow down (but not too fast, you might miss something)......... What is: 1+5 2+4 3+3 4+2 5+1 Now repeat saying the number 6 to yourself as fast as you can for 15 seconds. QUICK!!! THINK OF A VEGETABLE! You're thinking of a carrot, right? If you weren't thinking of a carrot, you're among the 2% of the population whose minds are different enough to think of something else. 98% of people will answer with carrot when given this exercise. Freaky, huh? Try it on people you know and see if they are usual or unusual. name a two digit odd number between one and fifty, no two digits the same' Did you pick 37 35% of the mass of people always choose '37' Transduction is the process of converting physical energy into electrochemical codes. Bottom-up processing: we start with the sensory receptors sand work up to higher levels of processing. Bottom-up processing: we start with the sensory receptors sand work up to higher levels of processing. The human fovea can only focus on a very small area at one time We fixate on one location for a moment and then move on to the next fixation. We take in little at each fixation and it’s through a pattern of saccades that we take in our visual environment. Top-Down Processing The top-down process is driven by prior knowledge and expectations as well as our specific goals of the moment. Suppose though, I asked you to find all the occurrences of the letter “P” in the image? Now as you scan the image the letter “P” should start to stand out a bit more and it’s possible that even the highly visible red letters start to fade into the background. At the very least you likely aren’t noticing the words they spell out. You see more of what you’re looking for and less of what you aren’t. Comics and cartoons provide many examples of top-down processing. Simple cues are used to suggest complex feelings and emotions. Cartoonists have a set of conventions for conveying information about mental and physical states. Tiny popping bubbles, for example, show drunkenness. Movement is shown by lines and little puffs of dust trailing after shoes. Spoken language is shown inside a bubble made out of a continuous line. A silent thought is shown inside a broken line. A sudden idea may be shown as a lightbulb lighting up over a character's head. Beads of sweat flying off a character show anxiety or physical exertion. After one gains some experience reading comics, these cues are processed automatically; one is hardly aware of them. In many situations, however, your knowledge or expectations will influence perception. This is called schema-driven or top-down processing. A schema is a pattern formed earlier in your experience. In the figure Bottom-up processing enables our sensory systems to detect the lines, angles and colors that form the horses, rider and surroundings. Using Top-down Processing we consider the paintings title, notice the apprehensive expressions and then direct our attention to aspects of the painting that will give those observations meaning.; Senses are nature’s gift that suit an organism’s needs. A frog feeds on flying insects; a male silkworm moth is sensitive to female sex-attractant odor; and we as human beings are sensitive to sound frequencies that represent the range of human voice. Life would hurt. So we can only take in a window of what is out there. This is the study of psychophysics. Absolute Threshold Intensity No No No Yes Yes Observer’s Response Detected Tell when you (the observer) detect the light. Difference Threshold minimum difference between two stimuli required for detection 50% of the time Or also called the JND just noticeable difference (JND) Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness. Kurt Scholz/ Superstock Absolute Thresholds for Humans SENSE STIMULUS RECEPTORS THRESHOLD A candle flame viewed from a distance of about 30 miles on a dark night Vision Electromagnetic Energy Rods & Cones in the retina Hearing Sound Waves Hair cells of the inner The ticking of a ear watch from about 20 feet away in a quiet room Smell Chemical substances in the air Receptor cells in the nose About one drop of perfume diffused throughout a small house Taste Chemical substances in saliva Taste buds on the tongue About 1 teaspoon of sugar dissolved in 2 gallons of water Touch Pressure on the skin Nerve endings in the skin The wing of a fly falling on a cheek from a distance of about 0.4 inches The idea that, to perceive a difference between two stimuli, they must differ by a constant percentage; not a constant amount. Predicts how and when we detect the presence of a faint stimulus (signal) amid background noise (other stimulation). SDT assumes that there is no single absolute threshold and detection depends on: Carol Lee/ Tony Stone Images Person’s experience Expectations Motivation Level of fatigue Diminished sensitivity as a consequence of constant stimulation. Put a band aid on your arm and after awhile you don’t sense it. The focusing of conscious awareness on a particular stimulus. Cocktail Party Effect: ability to listen to one voice among many…to pay attention despite distractions. Kittens raised without exposure to horizontal lines later had difficulty perceiving horizontal bars. Pick any number, 1 to 9. Multiply by 9. Add the 2 digits together. If you still have two digits, add them again Take away 5. If A=1, B=2, C=3, assign a letter to your number. Name a country starting with D Pick the second letter in your country Name an animal starting with that letter Tell me the color of that animal Gray Mass Psychology Pick any number, 1 to 9. Multiply by 9. Add the 2 digits together. If you still have two digits, add them again (it'll always give 9). Take away 5. (4) If A=1, B=2, C=3, assign a letter to your number. Name a country starting with D (options: Denmark, Djibouti, Dominica, Dominican Republic), and seeing as it'll probably take a while to figure out a country, people will pick the first one they think of (Denmark) Pick the second letter in your country (E) Name an animal starting with E (Elephant is most obvious) Tell me the colour of that animal (Gray). Perception a process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events Stare at the black dot in the middle. You should see the outer edges of the circle fade away! Although it seems the brain interacts directly with the outside world, it does not. The brain senses the world indirectly because the sense organs convert stimulation into the language of the nervous system: neural messages. In short, the brain never receives stimulation directly from the outside world. In all the sense organs, it is the job of sensory receptors to convert incoming stimuli information into electrochemical signals—neural activity. Transduction: The sensory process that converts energy, such as light or sound waves, into the form of neural messages. Transduction with Hearing Sensation and Perception Focusing conscious awareness on a particular stimulus to the exclusion of others The ability to focus on one stimulus at a time Allows a person to function in a world filled with many stimuli People with ADD have trouble doing this. Cocktail Part Effect: ability to listen to one voice among many. Change blindness is a form of inattentional blindness in which two-thirds of individuals giving directions failed to notice a change in the individual asking for directions. © 1998 Psychonomic Society Inc. Image provided courtesy of Daniel J. Simmons. 58 Two Major Theories Three types of cones: Red Blue Green These three types of cones can make millions of combinations of colors. Does not explain afterimages or color blindness well. Opponent-Process Theory- opposing retinal processes enable color vision “ON” “OFF” red green green red blue yellow yellow blue black white white black The sensory receptors come in pairs. Red/Green Yellow/Blue Black/white If one color is stimulated, the other is inhibited. Opponent Processing Theory Does this make your eyes all weird out?? Opponent processing theory: we see in pairs Afterimage is where you see the image afterwards. Psychology, 4/e by Saul Kassin ©2004 Prentice Hall Stare at the eye of the red parrot while you count slowly to 20, then look immediately at one spot in the empty bird cage. The faint, ghostly image of a blue green bird will appear in the cage. Try the same thing with the green cardinal. A faint magenta bird will appear in the cage. The ghostly birds you see here are called afterimages. An afterimage is an image that stays with you even after you have stopped looking at an object. The back of your eye is lined with light sensitive cells, called cones, which are sensitive to certain colors of light. When you stare at the red bird, your red-sensitive cones adapt to the light and lose their sensitivity. When you shift your gaze to the white background of the bird cage, you see white (minus red) where the red-sensitive cells have become adapted. White light minus red light is blue-green light. That's why the afterimage you see is blue-green and in the shape of a parrot. The same thing happens when you stare at the green bird, but this time it's the green-sensitive cones that adapt. White minus green light is magenta light, so you see the afterimage as a magenta cardinal. http://www.michaelbach.de/ot/col_lilacChaser/index.html Perception is essentially an interpretation and elaboration of sensation. Therefore, sensation refers to the initial steps in the processing of a stimulus. These pictures should look similar The True Picture Let us try something out: You are about to witness the perpetrator of a crime! Describe what you saw. Keep in mind, that this is a police investigation and that your testimony can be used in a court of law. 1 . P a s t e x p e rie n c e s “ S t a r s p a n g le d _ _ _ _ _ _ _ _ _ _ _ _ _ _ ” 2 . M o o d s , A t t it u d e s , a n d V a lu e s H a v i n g a b a d d a y a n d “ th in g s ” s e e m t o s n o w b a ll 3. Needs I f y o u ’ r e h u n g r y , y o u t h in k a b o u t… 4. What the group believes W e h a v e a t e n d e n c y t o , “ g o a lo n g w i t h th e c r o w d .” S E E IN G – H E A R IN G – T O U C H IN G – T A S T IN G – S M E L L I N G Perceptual Set is a tendency to perceive or notice some aspects of the available sensory data and ignore others. What is seen in the center figures depends on the order in which one looks at the figures: If scanned from the left, a man’s face is seen. If scanned from the right, a woman’s figure is seen. Psychology, 4/e by Saul Kassin ©2004 Prentice Hall Perceptual Set is a tendency to perceive or notice some aspects of the available sensory data and ignore others. Perceptual Set is a tendency to perceive or notice some aspects of the available sensory data and ignore others. Bruner & Minturn, 1955 illustrated how expectation could influence set by showing participants an ambiguous figure '13' set in the context of letters or numbers e.g. The physical stimulus '13' is the same in each case but is perceived differently because of the influence of the context in which it appears. We EXPECT to see a letter in the context of other letters of the alphabet, whereas we EXPECT to see numbers in the context of other numbers. If the sounds do not work click here for link. Illusions provide good examples in understanding how perception is organized. Studying faulty perception is as important as studying other perceptual phenomena. Line AB is longer than line BC. The images are exactly the same except for the thick black area in the right image (an example of the Poggendorff illusion (1860)). In the figure on the right, there appear to be two continuous diagonal lines: a red and a blue line. What occurs in your visual system that could account for the appearance of the continuous diagonal lines? Reprinted with kind permission of Elsevier Science-NL. Adapted from Hoffman, D. & Richards, W. Parts of recognition. Cognition, 63, 29-78 It takes a great deal of effort to perceive this figure in two dimensions. When vision competes with our other senses, vision usually wins – a phenomena called visual capture. How do we form meaningful perceptions from sensory information? We organize it. Gestalt psychologists showed that a figure formed a “whole” different than its surroundings. A specially-built room that makes people seem to change size as they move around in it The room is not a rectangle, as viewers assume it is. A single peephole prevents using binocular depth cues. Psychology, 4/e by Saul Kassin ©2004 Prentice Hall The image above is constructed from about 7,000 randomly placed dots. In a sequence of frames, the dots in a square were randomized again, such that each of the subsequent frames has a different randomization pattern in a selected square area. The squares selected for randomization were constructed from 1/10 of the X and Y values progressively from the lower left to the upper right along the diagonal of the matrix. Dots change randomly within the succession of squares, but no dots move along the diagonal, despite the appearance that they do. Perceptual Adaptation (vision) ability to adjust to an artificially displaced visual field prism glasses Perceptual Set a mental predisposition to perceive one thing and not another What you see in the center is influenced by perceptual set Life would hurt. So we can only take in a window of what is out there. This is the study of psychophysics: relationship between physical stimuli and our psychological experiences to them. Flying Saucers or Clouds? We need both of our eyes to use these cues. Retinal Disparity (as an object comes closer to us, the differences in images between our eyes becomes greater. Convergence (as an object comes closer our eyes have to come together to keep focused on the object). Organization of the visual field into objects (figures) that stand out from their surroundings (ground). Time Savings Suggestion, © 2003 Roger Sheperd. Perceptual Organization Gestalt Laws of Grouping Proximity Seeing 3 pair of lines in A Similarity Seeing columns of orange and red dots in B Continuity Seeing lines that connect 1 to 2 and 3 to 4 in C Closure Seeing a horse in D Psychology, 4/e by Saul Kassin ©2004 Prentice Hall 1. Closure 2. Proximity 3. Continuity 4. similarity Proximity Gestalt grouping principles are at work here. Do you see triangles? Gestalt grouping principles are at work here. Although grouping principles usually help us construct reality, they may occasionally lead us astray. Both photos by Walter Wick. Reprinted from GAMES Magazine. .© 1983 PCS Games Limited Partnership The General's Family There are 9 people in this picture, called The Generals Family, which is a work by the Mexican artist Octavio Ocampo. There are nine different faces in this picture combining to make up the face of the General and to tell the story and the secrets of his life. Although perceived as a distinguished gentleman of solid stock, the images of his past betray his emergence from a peasant family and his impoverished beginnings. We see his mother and father, his wife and other members of his family, even his dog (masquerading as his hand) and as you study the painting you see behind the facade and read the story of a remarkable life... Innervisions Depth perception enables us to judge distances. Gibson and Walk (1960) suggested that human infants (crawling age) have depth perception. Even newborn animals show depth perception. Visual Cliff Retinal disparity: Images from the two eyes differ. Try looking at your two index fingers when pointing them towards each other half an inch apart and about 5 inches directly in front of your eyes. You will see a “finger sausage” as shown in the inset. Convergence: Neuromuscular cues. When two eyes move inward (towards the nose) to see near objects and outward (away from the nose) to see faraway objects. Relative Size: If two objects are similar in size, we perceive the one that casts a smaller retinal image to be farther away. Interposition: Objects that occlude (block) other objects tend to be perceived as closer. Rene Magritte, The Blank Signature, oil on canvas, National Gallery of Art, Washington. Collection of Mr. and Mrs. Paul Mellon. Photo by Richard Carafelli. Relative Clarity: Because light from distant objects passes through more light than closer objects, we perceive hazy objects to be farther away than those objects that appear sharp and clear. Texture Gradient: Indistinct (fine) texture signals an increasing distance. © Eric Lessing/ Art Resource, NY Relative Height: We perceive objects that are higher in our field of vision to be farther away than those that are lower. Image courtesy of Shaun P. Vecera, Ph. D., adapted from stimuli that appered in Vecrera et al., 2002 Relative motion: Objects closer to a fixation point move faster and in opposing direction to those objects that are farther away from a fixation point, moving slower and in the same direction. Linear Perspective: Parallel lines, such as railroad tracks, appear to converge in the distance. The more the lines converge, the greater their perceived distance. © The New Yorker Collection, 2002, Jack Ziegler from cartoonbank.com. All rights reserved. Light and Shadow: Nearby objects reflect more light into our eyes than more distant objects. Given two identical objects, the dimmer one appears to be farther away. From “Perceiving Shape From Shading” by Vilayaur S. Ramachandran. © 1988 by Scientific American, Inc. All rights reserved. The distant monster (below, left) and the top red bar (below, right) appear bigger because of distance cues. Alan Choisnet/ The Image Bank From Shepard, 1990 Perceptual Constancies Shape Constancy Have you ever noticed, for example, when you approach the dinner table that the shapes of the plates do not change? When you look at them from some distance away from the table, the shapes of the round plates are elliptical on your retina. The only time that the image of a round plate is approximately round on your retina is when you look at it straight on. If you are not sure what I mean, look at the dinner plate demo. Psychology, 4/e by Saul Kassin ©2004 Prentice Hall Perceiving objects as unchanging even as illumination and retinal images change. Perceptual constancies include constancies of shape and size. Shape Constancy Kittens raised without exposure to horizontal lines later had difficulty perceiving horizontal bars. Blakemore & Cooper (1970) Courtesy of Hubert Dolezal Visual ability to adjust to an artificially displaced visual field, e.g., prism glasses. Face schemas are accentuated by specific features on the face. Kieran Lee/ FaceLab, Department of Psychology, University of Western Australia Students recognized a caricature of Arnold Schwarzenegger faster than his actual photo. Eyes and mouth play a dominant role in face recognition. Courtesy of Christopher Tyler Portrait artists understood the importance of this recognition and therefore centered an eye in their paintings. Context instilled by culture also alters perception. To an East African, the woman sitting is balancing a metal box on her head, while the family is sitting under a tree. Understanding human factors enables us to design equipment to prevent disasters. Two-thirds of airline crashes caused by human error are largely due to errors of perception. Extrasensory Perception controversial claim that perception can occur apart from sensory input telepathy clairvoyance precognition Parapsychology the study of paranormal phenomena ESP psychokinesis Telepathy: Mind-to-mind communication. One person sending thoughts and the other receiving them. 2. Clairvoyance: Perception of remote events, such as sensing a friend’s house on fire. 3. Precognition: Perceiving future events, such as a political leader’s death. 1. Can psychics see the future? Can psychics aid police in identifying locations of dead bodies? What about psychic predictions of the famous Nostradamus? The answers to these questions are NO! Nostradamus’ predictions are “retrofitted” to events that took place after his predictions. In an experiment with 28,000 individuals, Wiseman attempted to prove whether or not one can psychically influence or predict a coin toss. People were able to correctly influence or predict a coin toss 49.8% of the time. Below one’s absolute threshold for conscious awareness. Show clip Does this work? Yes and No •Slide studies showed some emotional react (called priming a response). •The effects are subtle and fleeting. Stimuli below our absolute threshold. Backmasking 25th frame Do Subliminal Messages work? Probably a placebo effect 1) The Pepsi Cool Can In 1990, Pepsi actually withdrew one of its “Cool Can” designs after someone protested that Pepsi was subliminally manipulating people by designing the cans such that when six-packs were stacked at grocery stores, the word SEX would emerge from the seemingly random design. Critics alleged that the red and blue lines on the “Cool Can” design were far from random <27>.