Sensation and Perception PDF

Mindoro State University – Calapan City Campus PSY 311 Cognitive Psychology How’s your Senses? Cognitive Psychology This is a gender sensitive instructional...

Mindoro State University – Calapan City Campus PSY 311 Cognitive Psychology How’s your Senses? Cognitive Psychology This is a gender sensitive instructional material.  An Introduction Have you ever been told that you can’t see something that’s right under your nose? How about that you can’t see the forest for the trees? Have you ever listened to your favorite song over and over, trying to decipher the lyrics? In each of these situations, we call on the complex construct of perception. Perception is the set of processes by which we recognize, organize, and make sense od the sensations we receive from environmental stimuli (Goodale, 2000a, 2000b; Koslyn and Osherson, 1995; Marr, 1982; Pomerants, 2003). When you look at an image in this book, sensory receptors in the retina are being stimulated and your sensation is transmitted to the brain through nerve impulses. Your brain interprets and organizes these sensations and turns them into a perception of coherent image. Perception encompasses many psychological phenomena. Learning Outcomes At the end of the unit, you will be able to: 1. How can we perceive an object, such as chair, as having a stable form given that the image of the chair on our retina changes as we look at it from different directions? 2. What are the two fundamental approaches to explaining perception? 3. What happens when people with normal visual sensations cannot perceive visual stimuli? Pretest Identification Directions: Page 1 of 20  From Sensation to Perception We do not perceive the world exactly as our eyes see it. Instead our brain actively tries to make sense of the many stimuli that enter our eyes and fall on our retina. In recent years, researchers have tried to teach computers to “see”. Although computers still lag behind humans in object recognition, the research showed how difficult it is to interpret visual stimuli, or what we see. This section focuses on the processes of visual perception and the processes we use to make sense of the visual stimuli that are focused on our retina. We start our exploration by familiarizing ourselves with some basic concepts. To illustrate the intricacies of perception, look at some optical illusion and learn how the eye receives impressions of stimuli and sends signals to the brain. Page 2 of 20  Some Basic Concepts of Perception James Gibson provided a useful framework for studying perception in his influential work. He introduced the concepts of distal (external) object, informational medium, proximal stimulation, and perceptual object. The distal (far) object is the object in the external world. A tree falling creates a patterns on an informational medium. The informational medium could be sound waves, as in the sound of the falling tree or reflected light, chemical molecules, or tactile information coming from the environment. When the information from the light waves comes into contact with the appropriate sensory receptors of the eyes, (proximal (near) stimulation occurs. Perception occurs when a perceptual object is created in you that reflects the properties of the external world. That is, an image of a falling tree is created on your retina that reflects the falling tree that is in front of you. So, if a tree falls in the forest and no one is around to hear it, does it make a sound? It makes no perceived sound. But it does make a sound by creating sound waves. So the answer is yes or no, depending on how you look at the question. The answer will be yes if the belief is that the existence of sound waves is all that is needed to confirm the existence of a sound, but the answer is no if the belief that the sounds needs to be perceived (for the sound waves to have landed on the receptors in someone’s ears). For the questions, “where does perception end and cognition begin” and “where does sensation end and perception begin” answers to both questions are debatable. These processes must be viewed as part of a continuum, since information flows through the system. Questions of sensation focus on qualities of stimulation. Is that shade of red brighter than the red of a Red Delicious apple? Is the sound of that falling tree louder than the sound of thunder? Perception questions, typically relate to identity and form, pattern, and movement. Is that red thing an apple? Did I just hear a tree falling? Cognition occurs when this information is used to determine further goals. Is that apple edible? Should I get out of the forest? We can never see, hear, taste, smell or feel the same exact set of stimulus properties we experienced before. Given the nature of the sensory receptors, variation is necessary for perception. In sensory adaptation, receptor cells adapt to constant stimulation by not firing until there is a change in stimulation. Through sensory adaptation, detecting the presence of a stimulus is prevented. Scientist use stabilized image in studying visual perception. Stabilized images do not move across the retina because they follow the eye movement. This technique confirms the hypothesis that constant stimulation of the cells of the retina gives the impression that the image disappears. When your eyes are exposed to a uniform field of stimulation, you will stop perceiving that stimulus after a few minutes and see just a gray field instead. This is because the eyes have adapted to the stimulus. This uniform visual field is called Ganzfeld, which is German for “complete field” also known as “Ganzfeld effect” Sensory adaptation ensures that the sensory information is changing constantly. Because of the dulling effect of sensory adaptation in the retina (the receptor surface of the eye), our eyes constantly are making tiny rapid movements. These movements create constant changes in the location of the projected image inside the eye. Thus, stimulus variation is an essential attribute for perception. Seeing Things that Aren’t There or Are They? (Lifted from Sternberg, 2017) To expand our knowledge of perception, psychologists often study situations that pose problems in making sense of our sensations. Consider the image on the right. To most people, the figure initially looks like a blur of meaningless shadings. This figure of a cow is hidden within the continuous gradations of shading that constitute the picture. Before recognizing the cow, you correctly sensed all aspects of the figure. But then you had not yet organized those sensations to form a mental percept – a mental representation of a stimulus that is perceived. Without such a percept of the cow, you could not meaningfully grasp what you previously had sensed. Page 3 of 20  Another example shows that sometimes we cannot perceive things that exist. At other times, however, we perceive things that do not exist. Just like in the figure with blue and while triangle. Both triangles are optical illusions. They involve the perception of visual information not physically present in the visual sensory stimulus. The existence of perceptual illusions suggests that what we sense (in our sensory organs) is not necessarily what we perceive (in our minds). Our minds must take the available sensory information and manipulate that information to create mental representations of objects, properties and spatial relationships within our environments. The way we represent these objects will depend in part on our viewpoint in perceiving the objects. So sometimes we perceive what is not there. Other times, we do not perceive what is there. And at still other times, we perceive what cannot be there. How Does Our Visual System Work? The precondition for vision is the existence of Light. Light is electromagnetic radiation that can be describes in terms of wavelength. Humans can perceive only a small range of the wavelengths that exist; the visible wavelengths are from 380 to 750 nanometers. Vision begins when light passes through the protective covering of the eye. This covering, the cornea is a clear dome that protects the eye. The light then passes, through the pupil, the opening in the center of the iris. It continues through the crystalline lens and vitreous humor (which is a gel-like substance that makes up the majority of the eye). Eventually, the light focuses on the retina where electromagnetic light energy is transduced – that is, converted – into neural electrochemical impulses. Vision is most acute in the fovea, which is a small, thin region of the retina, the size of the head of a pin. When you look straight at an object, your eyes rotate so that the image falls directly into the fovea. The retina contains the photoreceptors, which convert light energy into electrochemical energy that is transmitted by neurons to the brain. There are two kinds of photoreceptors – rods (roughly 120 million in each eye) and the cones (about 8 million). Within the rods and cones are photo pigments, chemical substances that react to light and transform physical electromagnetic energy into an electrochemical neural impulse that can be understood by the brain. Page 4 of 20  The rods are long and thin photoreceptors highly concentrated in the periphery of the retina and are responsible for night vision and are sensitive to light and dark stimuli. The cones are short and thick and allow for the perception of color highly concentrated in the foveal region. Both are connected to the brain and the neurochemical messages processed travel via the bipolar cells to the ganglion cells. The axons of the ganglion cells in the eye collectively form the optic nerve for that eye. This optic nerves join at the base of the brain to form the optic chiasma and about 90% of the ganglion cells fo to the thalamus. Then messages are carried to the primary visual cortex which contains several processing areas for intensity and quality, including color, location, depth, pattern, and form. Pathways to Perceive the What and the Were A pathway in general is the path the visual information takes from its entering the human perceptual system through the eyes to its being completely processed. Generally, researchers agree that there are two pathways. The information from the primary visual cortex in the occipital lobe is forwarded through two fasciculi or fiber bundles: one ascends towards the parietal lobe (along the dorsal pathway) and one descends to the temporal lobe (along the ventral pathway). The dorsal pathway is also called the where pathway and is responsible for processing location and motion information. The ventral pathway is called the what pathway because it is mainly responsible for processing the color, shape, and identity of visual stimuli. Approaches to Perception: How Do We Make Sense Of What We See? There are different views on hoe we perceive the world. These views can be summarized as bottom-up theories and top- down theories. Bottom-up theories describe approaches in which perception starts with the stimuli whose appearance you take in through your eye. They are data-driven theories. Many theorists prefer top-down theories, according to which perception is driven by high level cognitive processes, existing knowledge, and the prior expectations that influence perception. These theories then work their way down to considering the sensory data, such as the perceptual stimulus. Bottom-Up Theories The four main bottom-up theories of form and pattern perception are direct perception, template theories, feature theories, and recognition-by-components theory. Page 5 of 20  Gibson’s Theory of Direct Perception. According to this theory, the information in our sensory receptors, including the sensory context, is all we need to perceive anything. As the environment supplies us with all the information we need for perception, this view is sometimes also called ecological perception. Gibson believed that, in the real world, sufficient contextual information usually exists to make perceptual judgements. We do not need to appeal to higher-level intelligent processes to explain perception but rather use contextual information directly. We use texture gradients as cues for depth and distance, which aid us to perceive directly the relative proximity or distance of objects and parts of objects. Neuroscience also indicates that direct perception may be involved in person perception. About 30 to 100 milliseconds after a visual stimulus, mirror neurons start firing. Mirror neurons are active both when a person acts and when he or she observes that same act performed by somebody else. Furthermore, studies indicate that separate neural pathways (what pathways) in the lateral occipital area process form, color, and texture in objects. Template Theories. This theory suggest that our minds store myriad sets of templates. Templates are highly detailed models for patterns we might recognize. We recognize a pattern by comparing it with our set of templates. We then choose the exact template that perfectly matches what we observe. Template matching theories belong to the group of chunk-based theories; these theories suggest that expertise is attained by acquiring chunks of knowledge in long-term memory that can be later accessed for fast recognition. The goal is to find one perfect match and disregard imperfect matches. However, this theory fail to explain some aspects of the perceptions of letters. Letters of the alphabet are simpler than faces and other complex stimuli. Experiments suggest that there is a difference between perceiving a letter and digits. It was found out there is an area that is activated significantly more when a person is presented with letters than with digits. Feature Matching Theories. According to these theories, we attempt to match a whole pattern to a template or a prototype. One such feature-matching model has been called Pandemonium (“pandemonium” refers to a noisy, chaotic place and hell). In this model, metaphorical “demons” with specific duties receive and analyze the features of a stimulus. Conceived by Oliver Selfridge, there are four kinds of demons: image demons, feature demons, cognitive demons, and decision demons. The “image demons” receive a retinal image and pass Page 6 of 20 it on to “feature demons”. Each feature demons calls out when matches are made between the stimulus and the given feature. These matches are yelled out at “cognitive (thinking) demons”. The cognitive demons in turn shout out possible patterns stored in memory that conform to one or more of the features noticed by the feature demons. A “decision demon” listens to the pandemonium of the cognitive demons. It decided on what has been seen, based on which cognitive demon is shouting the most frequently. Some support for feature theories comes from neurological and physiological research. Researchers used single-cell techniques with animals. They carefully measured the responses of individual neurons to visual stimuli in the visual cortex. Then they mapped those neurons to corresponding visual stimuli for particular locations in the visual field. Their research showed that the visual cortex contains specific neurons that respond only to a particular kind of stimulus, and only if that stimulus fell into a specific region of the retina. Each individual cortical neuron, therefore, can be mapped to a specific receptive field on the retina. Recognition-by-Components Theory. Irving Biederman (1987) suggested that we recognize 3-D objects by manipulating simple geometric shapes called geons (geometrical ions). These shapes include objects such as bricks, cylinders, wedges, cones, and their curve axis counterparts. According to Biederman’s recognition-by-components (RBC) theory, we quickly recognize objects by observing the edges of them and then decomposing the objects into geons. The geons also may be recomposed into alternative arrangements. The objects constructed from geons thus are recognized easily from many perspectives, despite visual noise. The RBC theory parsimoniously explains how we recognize the general classification for multitudinous objects quickly, automatically accurately. This recognition occurs despite changes in viewpoint. The RBC theory explains how we may recognize general instances of chairs, lamps, and faces, but it does not adequately explain how we recognize particular chairs or particular faces. He recognized that aspects of his theory require further work, such as how the relations among the parts of an object can be described. Geons are viewpoint-invariant, so studies should show that neurons exist that react to properties of an object that stay the same, no matter whether you look at them from the front or the side. Studies have found neurons that are sensitive to just those viewpoint-invariant properties. Many neurons, however, respond primarily to one view of an object and decrease their response gradually the more the object is rotated. This finding contradicts the notion of Biederman’s theory that we recognize objects by means of viewpoint-invariant geons. Page 7 of 20 Top-Down Theories In constructive perception, the perceiver builds (constructs) a cognitive understanding (perception) of a stimulus. The concepts of the perceiver and his or her cognitive processes influence what he or she sees. The perceiver uses sensory information as the foundation for the structure but also uses other sources of sensory information to build the perception. This viewpoint is known as intelligent perception because it states that higher-order thinking plays an important role in perception. An interesting feature of the theory of constructive perception is that it links human intelligence even to fairly basic processes of perception. According to this theory, perception includes not merely a low-level set of cognitive processes but actually a sophisticated set of processes that interact with and are guided by human intelligence. For example, picture yourself driving down a road you have never traveled before. As you approach a blind intersection, you see an octagonal red sign with white lettering. It bears the letters ST_P. an overgrown vine cuts between the T and the P. Chances are you will construct from your sensations a perception of a stop sign. You thus will respond appropriately. According to constructivists, during perception, we quickly form and test various hypotheses regarding percepts. The percepts are based on the following:  What we sense (the sensory data)  What we know (knowledge stored in memory  What we can infer (using high-level cognitive processes) Further, for constructivists we usually make the correct attributions regarding our visual sensations. The reason is that we perform unconscious inference, the process by which we unconsciously assimilate information form a number of sources to create perception. In other words, using more than one source of information, we make judgments that we are not aware of making. One reason for favoring the constructive approach is that bottom-up (data driven) theories of perception do not fully explain context effects. Context effects are the influences of the surrounding environment on perception. Perhaps even more striking is a context effect known as the configural-superiority effect, by which objects presented in certain configurations are easier to recognize than the objects presented in isolation, even if the objects in the configurations are more complex than those in isolation, (see figure below) Similarly there is an object-superiority effect, in which a target line that forms a part of a drawing of 3-D objects is identified more accurately than a target that forms a part of a of a disconnected 2-D pattern. These findings parallel findings of letter and word recognition: The word-superiority effect indicates that when people are presented with strings of letters, it is easier for them to identify a single letter is the string makes sense and forms a word instead of being just a nonsense sequel of letter. For example it is easier to recognize the letter o in the word house than in the word huseo. Page 8 of 20  The viewpoint of constructive or intelligent perception shows the central relation between perception and intelligence. According to this viewpoint, intelligence is an integral part of our perceptual processing. We do not perceive simply in terms of what is “out there in the world”. Rather, we perceive in terms of the expectations and other cognitions we bring to our interaction with the world. In this view, intelligence and perceptual processes interact in the formation of our beliefs about what it is that we are encountering in our everyday contacts with the world at large. Recent work suggests that whereas the first stage of the visual pathways represents only what is in the retinal image of an object, very soon, color, orientation, motion, depth, spatial frequency, and temporal frequency are represented. Later stage representations emphasize the viewer’s current interest or attention. In other words, later-stage representations are not independent of our attentional focus. On the contrary, they are directly affected by it. Moreover vision for different things can take different forms. Visual control of action is mediated by cortical pathways that are different from those involved in visual control of perception. In other words, when we merely see an object, such as a cell phone, we process it differently than if we intend also to pick up the object. In general, according to Ganel and Goodale (2003), we perceive them more analytically so that we can act in an effective way. Activity Page 9 of 20  Perception of Objects and Forms Viewer –Centered versus Object-Centered Perception One position, viewer-centered representation, is that the individual stores the way the object looks to him or her. Thus, what matters is the appearance of the object to the viewer (in this case, the appearance of the computer to the author), not the actual structure of the object. The shape of the object changes, depending on the angle from which we look at it. A number of views of the object are stored, and when we try to recognize an object, we have to rotate that object in our mind until it fits one of the stored images. The second position, object-centered representation, is that the individual stores a representation of the object, independent of its appearance to the viewer. In this case, the shape of the object will stay stable across different orientations. This ability can be achieved by establishing the major and minor axes of the object, which then serve as a basis for defining further properties of the object. Both positions can account for how the author represents a given object and its parts. The key difference is in whether he represents a given object and its parts. The key difference is in whether he represents the object and its parts in relation to him (viewer-centered) or in relation to the entirety of the object itself, independent of his own position (object-centered). A third orientation in representation is landmark-centered. This representation is where the information is characterized by its relation to a well-known or prominent item. Imagine visiting a new city. Each day you leave your hotel and go on short trips. It’s easy to imagine that you would represent the area you explore in relation to your hotel. Evidence indicates that, in laboratory, participants can switch among these three strategies. There are however, differences in brain activation among these strategies (Committeri et. Al. 2004). The Perception of Groups – Gestalt Laws The Gestalt approach to form perception that was developed in Germany in the early twentieth century is particularly useful for understanding how we perceive groups of objects or even parts of objects to form integral wholes. This approach was founded by Kurt Koffka (1886-1941), Wolfgang Köhler (1887-1968), and Max Wertheimer (1880-1943) and was based on the notion that the whole differed from the sum of its individual parts. The Law of Prägnanz explains, that we tend to perceive any given visual array in a way that most simply organizes the different elements into a stable and coherent form. Thus we do not merely experience a jumble of unintelligible, disorganized sensations. The figure-ground perception tells that we tend to perceive a focal figure and other sensations as forming a background for the figure on which we focus. Other Gestalt principle include proximity, similarity, continuity, closure and symmetry. We see groupings of nearby objects (proximity) or of like objects (similarity). We also perceive objects as complete even though we may only see a part of them (closure), continuous line rather than broken ones (continuity), and symmetrical patterns rather than asymmetrical ones. Page 10 of 20  The Gestalt principles provide valuable descriptive insights into form and pattern perception. But they offer few or no explanations of these phenomena. To understand how or why we perceives forms and patterns, we need to consider explanatory theories. Two Different Pattern Recognition Systems Humans have two systems for recognizing pattern, according to Martha Farah. The first system specializes in recognizing parts of objects and in assembling those parts into distinctive wholes (feature analysis system). The second system (configurational system) specializes in recognizing larger configurations, not analyzing the parts of the object or the construction of the objects. The second system is most relevant to face recognition although the feature analysis can also be used. Face recognitions occurs, at least in part, in the fusiform gyrus of the temporal lobe. This brain area responds intensely when we look at faces but not when we look at other objects. Page 11 of 20 The Neuroscience of Recognizing Faces and Patterns There is evidence that emotion increases activation within the fusiform gyrus when people are processing faces. There was one study that when shown a face and asked about the name or the expression there was increased activation in the fusiform gyrus. The study of person with autism having impaired emotional recognition showed less activity in the fusiform gyrus as compared to people with no autism. However, there were researches that does not agree that fusiform gyrus is specialized for face recognition. Some believe that there are also action in other areas but not as much face perception and view that areas of the brain are not all-or-none but differently activated depending on what is perceived. According to the expert-individuation hypothesis, the fusiform gyrus is activated when one examines items with which one has visual expertise. If the brain is scanned during the differentiation activity, activation in this area specifically the right one would be seen. This theory is able to account for he activation of the fusiform gyrus when people view faces because, people in effect, are experts in identifying and examining faces. Prosopagnosia is the inability to recognize faces which means there is damage to the configurational system. Someone with this can see the face of another person and even recognize whether that person is happy, sad, or angry. But fails to recognize if that person being observe is a stranger, his friend or his own mother. The ability to recognize faces is influenced by lesions of the right fusiform gyrus, either unilateral or bilateral. Facial memories are affected in particular, when the bilateral lesions include the right anterior temporal lobe. Healthy individuals scan faces with inverted triangle, focusing on the eyes, nose and lips, while people with schizophrenia look at fewer salient features and exhibit fewer long fixations. The Environment Helps You See Perceptual constancies The perceptual system addresses variability by analyzing the objects in the perceptual field. Perceptual constancy occurs when our perception of an object remains the same even our proximal sensation of distal object changes. Because we must be able to deal effectively with the external world, our perceptual system has mechanisms that adjust our perception of the proximal stimulus. Size constancy is the perception that an object maintains the same size despite changes in the size of the proximal stimulus. The size of an image on the retina depends directly on the distance of that object from the eye. The same object at two different distances projects different-size images on the retina. Striking illusions can be achieve when our sensory and perceptual systems are misled by the same information that usually helps us to achieve size constancy. Judging the sizes of objects accurately is something that we largely have to learn because it is not completely inborn. An example of size constancy is the Müller-Lyer illusion. Here two line segments that are of the same length appear to be different lengths. We use shapes and angles from our everyday experience to draw conclusions about the relative sizes of objects. Equivalent image sizes at different depths usually indicate different-size objects. Studies indicate that the right posterior parietal cortex (involved in the manipulation of mental images) and the right temporo- occipital cortex are activated when people are asked to judge the length of the lines in the Müller-Lyer illusion. The strength of the illusion can be changed by adjusting the angles of the arrows that delimit the horizontal line- the sharper the angles, the more Page 12 of 20 pronounced the illusion. The strength of the illusion is associated with the bilateral (on both sides) activation in the lateral (i.e. located on the side of the) occipital cortex and the right superior parietal cortex. As the right intraparietal sulcus (a gap where the surface of a structure is folded) is activated as well, showing the interaction of illusory information and the right parietal cortex that are responsible for visuospatial judgments. Shape constancy is the perception that an object maintains the same shape despite changes in the shape of the proximal stimulus. An object’s perceived shape remains the same despite changes in its orientation and hence in the shape of its retinal image. As the actual shape of the pictured door changes, some parts of the door seem to be changing differentially in their distance from us. It is possible to use neuropsychological imaging to localize parts of the brain that are used in this shape analysis is in the extrastriate cortex. Depth Perception Depth is the distance from a surface, usually using your own body as a reference surface when speaking in terms of depth perception. This use of depth information extends beyond the range of your body’s reach. When you drive, you use depth to assess the distance of an approaching automobile. When you decide to call out a friend walking down the street, you determine how loudly to call. Your decision is based on how far away you perceive your friend to be. Depth Cues Look at the difficult configuration on the left. They are confusing because the depth information is contradictory in the different sections of the picture. Small segments of these impossible figures look reasonable to us because there is no inconsistency in their individual depth cues. It is difficult however to make sense of the figure as a whole. The reason is that the cues providing depth information in various segments of the picture are in conflict. Monocular depth cues can be presented in just two dimensions and observed with just one eye. They include texture gradients, relative size, interposition, linear perspective, aerial perspective, location in the picture plane, and motion parallax. For example try to look at the figure below the Annunciation by Carlo Crivelli. He masterfully illustrated at least five monocular depth cues: (1, 2) Texture gradient and relative size: the floor tiles appear similar both in front of and behind the figures in the forefront of the corridor forefront of the corridor, but the tiles at the front of the corridor are larger and are spread farther and are spread farther apart than the tiles at the rear. (3) Interposition: the peacock partially blocks our view of the frieze on the wall to the right of the corridor. (4) Linear perspective: the sides of the wall seen to converge inward toward the rear of the corridor. (5) Location in the picture plane: the figures art the rear of the corridor are depicted higher in the picture plane than are the figures at the front of the corridor. The motion parallax is not shown in the figure. Motion parallax requires movement. Thus it cannot be used to judge depth within a stationary image, such as a picture. Page 13 of 20  Another means of judging depth involves binocular depth cues, based on the receipt of sensory information in three dimensions from both eyes. Binocular depth cues use the relative positioning of the eyes. The eyes are positioned far enough (about 65 mm) to provide two kinds of information to the brain: binocular disparity and binocular divergence. In binocular disparity, the two eyes send increasingly disparate (differing) images to the brain as objects approach the person. The brain interprets the degree of disparity as an indication of distance from the viewer. In addition, for objects viewed at relatively close location, the depth cues used are based on binocular convergence. In binocular convergence, the two eyes increasingly turn inward as objects approach the viewer. The brain interprets these muscular movements as indication of distance. Depth perception may depend on more than just the distance or depth at which an object located relative to oneself. The perceived distance to a target is influenced by the effort required to walk to the location of the target. People with a heavy backpack perceive the distance to a target location as farther than those not wearing a heavy backpack. In other words, there can be an interaction between the perceptual result and the perceived effort required to reach the object perceived. The more effort one requires to reach something the farther away it is perceived to be. Depth perception is a good example of how cues facilitate perception. When one sees an object that appears small, there is no automatic reason to believe it is farther away. Rather, the brain uses this contextual information to conclude that the smaller objects is farther away. Deficits in Depth Perception People who suffer from an agnosia have trouble perceiving sensory information. Agnosia often are caused by damage to the border of the temporal and occipital lobes or restricted oxygen flow to areas of the brain, sometimes as a result of traumatic brain injury. There are many kinds of agnosia and not all of them are visual. Generally, people with agnosia have normal sensations of what is in front of them. They can perceived the colors and shapes of objects and persons, but they cannot recognize what the objects are. Page 14 of 20 They have a trouble with the what pathway. People who suffer from visual-object agnosia can see all parts of the visual field, but the objects they see do not mean anything to them. Disturbance in the temporal region of the cortex can lead to simultagnosia. A different kind of perceptual deficit is associated with damage to the how pathway. This deficit is optic ataxia. People with this deficit have trouble reaching for things. All have experienced coming home at night and trying to find the key hole in the front door. It’s to dark to see, and have to grope with the key for the keyhole, often taking a while to find it. Someone with optic ataxia has this problem even with a fully lit visual field. The how pathway is impaired. Ataxia results from a processing failure in the posterior parietal cortex, where sensorimotor information is processed. It is assumed that higher=order processes are involved because most patients’ disorders are complex, and they can indeed grasp objects under circumstances. People with ataxia can improve their movements toward a visible aim when they hold off with their movements for a few seconds. Anomalies in Color Perception Color perception deficits are much more common in men then in women, and they are genetically linked. There are several kinds of color deficiency and the least common is rod monochromacy, al also called achromacy. People with this condition have no color vision at all. It is the only true form of pure color-blindness. In this condition the cones are nonfunctional. They see only shades of gray as a function of this vision through the rods. In dichromacy, only two of the mechanisms for color perception work, and one is malfunctioning. The result of this malfunction is one of three types of color-blindness (color-perception deficits). The most common is red-green color blindness. People with this form of color-blindness have difficulty in distinguishing red from green although they may be able to distinguish dark red from light green. The extreme form of red-green blindness is called protanopia. The other types of color blindness are deuteranopia (trouble seeing greens with symptoms similar to protanopia) and tritanopia (confusion of blues and greens, and yellow that disappear or appear as light shades of reds). The figure below shows test plates that are commonly used to detect anomalies in color perception. Page 15 of 20  Activity 2: Depth Cues in Photography Models and actors often use depth cues of perception to their advantage while being photographed. Some of these processes to alter perceptions are so basic that many animals have special adaptations designed to make them appear larger or to disguise their identity from predators. How could you apply perceptual processes to your advantage when having a photo? Discuss how the depth cues altered the perception of your image and made it as your advantage. Assessment: Identifying Depth Cues Look at the figure below. List the depth cues you have observed and explain. Page 16 of 20  References: Birion J C., Austrias, M & De Jesus E. (2013) General Psychology., Mutya Publishing House Inc.. Chance P.,( 2014). Learning and Behavior7th Edition. Cengage Learning Freberg, Laura A. (2014), Discovering Biological Psychology, 2nd Edition, Cengage Learning Kalat, James W. (2019), Biological Psychology, Cengage Learning Inc., USA King L.(2016), Experience Psychology: Third Edition. McGraw-Hill Higher Education Pinel, John P.J., (2011), Biopsychology 8th Ed., Pearson Education Inc., Boston Higgs S., Cooper, A., Lee, J., (2020), Biological Psychology 2nd Ed., SAGE London Wickens, Andrew P. (2021), Introduction to BioPsychology 4th Ed., SAGE Los Angeles, USA Website https://www.ted.com/talks/dan_pink_on_motivation https://www.youtube.com/watch?v=ilA1V7sUXUA Photos Kanisza Triangles copied from https://www.fandom.com/Licensing?rdfrom=https%3A%2F%2Fcommunity.fandom.com%2Fwiki%2FLicensing%3Fredirect%3Dno https://www.opticalillusion.net/optical-illusions/dark-kanizsa/ Electromagnetic Spectrum copied from https://www.researchgate.net/figure/The-electromagnetic-spectrum-3_fig1_258283057 Page 17 of 20 Rubrics for Essay Score 4 Score 3 Score 2 Score 1 Focus and Ideas The writing is about The writing is mostly The writing is not The writing is not one main topic. All of about one main topic. complete dome of the complete. The ideas the ideas are Most of the ideas are ideas are supported are not supported supported with strong supported with strong with details. with details. details. details. Voice The writing sounds Most of the writing Some of the writing The writing does not like how the writer sounds like how the sounds like how the sound like how the thinks and talks. writer thinks and writer thinks and writer thinks and talks. talks. talks. Word Choice The writing includes The writing includes The writing includes The writing includes vivid verbs, strong some vivid verbs, mostly simple nouns only simple nouns adjectives, and strong adjectives, and verbs, and may and verbs, and some specific nouns. and specific nouns. have some of them are incorrect. adjectives. Sentence Fluency The writing uses The writing uses The writing uses The writing uses al different kinds of some different kinds many of the same the same kinds of complete sentences of sentences. They kinds of sentences. sentences. Many that flow together. are mostly complete. Some sentences are sentences are not not complete. complete. Conventions The writing has no The writing has a few The writing has some The writing has many mistakes in spelling mistakes in spelling. mistakes in spelling, mistakes in spelling, The writer used The writer made few capital letters, and capital letters, and capital letters and mistakes with capital punctuation. punctuation. punctuation correctly. letters and punctuation. Page 18 of 20 Page 19 of 20