Sensation and Perception Year 11 Psychology PDF

Chapter 8 Sensation and Perception Year 11 Psychology Attention Attention Attention refers to actively focusing on particular information whilst simultaneously ignoring other information. There are two types of information sources that we can pay attention to: × Internal stimuli × Ext...

Chapter 8 Sensation and Perception Year 11 Psychology Attention Attention Attention refers to actively focusing on particular information whilst simultaneously ignoring other information. There are two types of information sources that we can pay attention to: × Internal stimuli × External stimuli  Attention - Information Sources Internal Stimuli External Stimuli Information or sensations that Information or sensations that originate from within the body. originate from outside the body. E.g. E.g. feeling hungry or tired, conversations with others, having a fever, tasks you are completing, being hot or cold, something you are reading, experiencing pain other events that you having an idea. experience with your five senses.  Types of Attention There are three main types of attention: × Sustained attention × Divided attention × Selective attention  Sustained Attention Sustained attention refers to focusing on one stimulus or task across a prolonged, continuous period of time. Sustained attention makes it possible for us to concentrate in order to complete a task or attend to something Many of our daily activities require sustained attention: × Watching a video from start to finish × Completing a simple maths question × Holding a conversation for a few minutes How long can we sustain attention? Attention is a limited resource. If attention is sustained for too long individuals tend to experience fatigue. Research shows a lack of consensus about the average attention span of humans, however sustained attention is typically more difficult in intellectually easy or boring situations than in more challenging or interesting ones. For example, spending 30 minutes writing a paragraph in English class is going to be easier to sustain attention than watching grass grow for the same amount of time.  The effect of distraction Distractions are internal or external stimuli that draw attention away from the current task. Distractions can mean that we are constantly having to refocus our attention on a task. Sustained attention involves the maintenance of attention even in the presence of distractions. This is typically easier when the task is more engaging and the individual is less fatigued.  Divided Attention Divided attention refers to splitting attention across two or more stimuli at one time. This type of attention involves multitasking - the act of working on multiple tasks at one time. Humans are not as good at multitasking as we’d like to think. Switching tasks can make individuals more prone to distraction and reduce their understanding of the task, decreasing performance.  Divided Attention - Multitasking Multitasking is inevitable, particularly in situations where: × We feel we must complete two tasks at a time. E.g. waitstaff taking an order whilst remembering that another table needed more water × We are juggling a boring task with an interesting task. E.g. listening to a podcast whilst on a long drive × We are actively learning. E.g. writing notes from the whiteboard whilst listening to the teacher  Divided Attention - Multitasking As multitasking requires us to divide our attention, it prevents us from giving our full potential to one task. This can have negative implications for our performance when: × We have to stop a task that is not easy to resume. E.g. pausing writing your essay to sing along to the song playing in the background × The tasks are less related, or are completed using two different platforms. E.g. online shopping whilst holding a conversation with someone × When the tasks are more effortful or complex, therefore ideally require our full attention. E.g. performing a difficult dance routine whilst reciting the countries of the world  Selective Attention Selective attention involves exclusively focusing on a specific stimulus or task while ignoring all other stimuli or tasks. Selective attention requires an individual to filter out external stimuli, such as noise. However, it also requires the filtering out of internal stimuli, such as thoughts or emotions. For example, at a crowded party, you tune your attention into the conversation you are having with someone, despite many other things going on around you. Attention: Theory Summary Sensation and Perception Thank you, Alyssa N 11PSY-2 (2022) What do you hear?  Sensation vs Perception Sensation is the process by which our sense organs and receptors detect and receive sensory information that stimulates them. The information is meaningless until it is sent to the relevant sensory area in the brain for processing. Sensation vs Perception Perception refers to the process by which the brain selects, organises and interprets sensory information. Our sensory systems ‘translate’ the sensations into information that is meaningful and useful.  The three processes of sensation Stage of sensation What it involves Reception Sensory information is received Transduction The information is converted into a neural impulse Transmission The information is sent to the brain for processing  The three processes of perception Stage of What it involves perception Selection The process of attending to certain sensory stimuli, or features of certain stimuli, and excluding others. Organisation The process of regrouping selected features of sensory stimuli in order for them to be cohesively arranged. Interpretation The process of understanding and assigning meaning to sensory information in order to understand it. Types of Perceptual Processing  Bottom-Up Processing During bottom-up processing , perception is determined by incoming sensory information, moving from specific stimulus information to general knowledge. Perceptual interpretations are entirely based on the way that information is organised. Typically used when information is unfamiliar or highly complex. Entry-level sensory data is processed in real time and moves up to the brain to be perceived and understood Bottom-Up Processing Watch this video to see bottom-up processing in action.  Bottom-Up Processing For example when learning a new language: 1. First we would interpret each letter that makes up a word 2. Then, we can combine words to make a sentence 3. This enables us to be able to read a whole piece of writing Another example: When you look at your computer, you are able to recognise that it is a computer… But before you could do this, your brain needed to process the different parts of the computer  Top-Down Processing During top-down processing , perception is driven by prior knowledge and expectations, moving from general knowledge to specific stimulus information. This type of processing is typically used when what is being perceived is relatively familiar and less complex. If we expect something to appear in a specific way or mean something in particular, it is more likely to be perceived in alignment with this expectation. We use schemas for this! Top-Down Processing  Top-Down Processing For example: Imagine Judy spills water on her favourite childhood novel and the ink smears several pages… Despite the words being smudged, Judy can still interpret the sentences and storyline because the novel’s familiarity informs her expectations of what is being said. Bottom-Up vs Top-Down Bottom-Up vs Top-Down: Example! Visual Perception  Visual Perception Visual perception is the process of becoming consciously aware of visual stimuli as a result of the interactions between the visual sensory system and the individual’s internal and external environment. The visual sensory system refers to the network that is involved in the sensation and perception of visual stimuli, including the eyes, brain, and the neural pathways connecting them. The structure of the eye (We will cover this more in depth later!) Sensation & Perception in Vision  Stages of Visual Perception - Selection × We receive many visual signals, but only some are selected for processing × The visual selection process is performed by feature detectors - specialised cells along the neural pathway that connect to and are found within the primary visual cortex × Feature detectors select and filter visual signals according to perceptually important features. E.g. certain colours, shapes × This filtering helps to reduce how much the brain actually needs to process  Stages of Visual Perception - Organisation × Once selected, visual signals are regrouped and organised to reflect an image of reality × We use certain guiding principles to help us group these fragmented signals together again, including our visual perception principles  Stages of Visual Perception - Interpretation × The Primary Visual Cortex works with other areas of the brain to interpret and make sense of the visual stimuli × Our interpretation of images is influenced by many things, such as our motives or beliefs, and our perceptual set Gustatory Perception  Gustatory Perception The sensory activity responsible for our ability to taste is gustatory perception. Gustatory perception is the process of becoming consciously aware of flavour.  Sensations in Taste The primary sensory organ for detecting gustatory information is our tongue. Before sensation begins, when chewing, our saliva breaks down our food into tastants. Tastants are the sensory stimuli received in the form of chemical molecules that can be tasted.  Sensations in Taste Tastants are received by our gustatory receptors located within our taste buds. Taste buds are clusters of gustatory receptors. × have about 100 gustatory receptors in each taste bud. Tastants are then converted into a neural impulse and sent to the brain. The primary gustatory cortex in the parietal lobe processes information about the type and intensity of flavour.  The Five Basic Tastes Taste Examples Sweet Cherries, sugar Salty Chips, popcorn Sour Lemons, limes Bitter Coffee, rocket, kale Umami Meat, tomatoes, soy sauce  Myths about Taste A common misconception about taste is that we have different areas of the tongue that are responsible for tasting different tastes. These ‘tongue maps’ are largely inaccurate! Our taste buds are dispersed all throughout our mouth, and some are more sensitive to certain tastes than others.  Perception in Taste Taste is very complex! Our olfactory cortex (smell) and primary somatosensor y cortex also play a role in taste Taste - sensation Taste - perception Theory Summary  Visual Perception (eye structure and depth cues)  Factors influencing visual perception The process of visual perception can be understood as being largely influenced by biological, psychological and/or social factors. The visual sensory system is inherently biological through its use of physiological components. However, visual perception also interacts with psychological and social processes.  Biological Factors Biological factors are internal genetic and/or physiologically based factors. As such, we must consider the biological factors that influence the way we perceive visual stimuli. Biological factors include: - The eye - Colour blindness - Short-sightedness - Depth cues  The Eye The eye is a sensory organ responsible for receiving light to enable vision. Light first enters the eye through the pupil, and is focused through the lens onto the retina (at the back of the eye). The retina contains photoreceptors , the sensory receptors of the eye which receive light and convert this sensory information into a form that can be sent to the brain.  The Human Eye Where would the blind spot be?  Photoreceptors in the Eye There are two types of photoreceptors located in the retina: × Rods : which are photoreceptors that allow someone to see in low levels of light × Cones : which are photoreceptors that allow someone to see colour and fine details in well-lit conditions. Humans have 3 distinct colour-sensing cones; blue light, red light and green light. Photoreceptors in the Eye  Colour Blindness Our photoreceptors heavily influence how we perceive visual stimuli. Colour blindness is a result of defective photoreceptors (cones) , usually from a genetic cause. There are three main types of colour blindness: - Red-green colour blindness - Blue-yellow colour blindness - Complete colour blindness Did you know? All dogs and cats are born technically color blind, with the inability to see red and green colors. They are biologically limited to seeing the world in blue, yellow, brown and grey due to the limited number of cones in their eyes, compared to humans.  Short-sightedness The eye naturally bends or ‘refracts’ to focus light on the retina. Abnormalities in the shape of the cornea (and lens) can lead to refractory errors , which are defects in the eye causing it to not bend light as it is supposed to, resulting in reduced visual acuity. Myopia : short-sightedness due to the focal point of one or both eyes being located in front of, instead of on, the retina. - Far away objects appear blurry, but up close objects are clear.  Depth Cues Depth cues are visual clues that allow someone to perceive the world in three dimensions and judge the distance and position of objects in their environment. Monocular depth cues Depth cues are categorised into: Binocular depth cues  Monocular Depth Cues - Accommodation - Motion parallax - Pictorial cues - Linear Perspective - Interposition - Texture gradient Mono - one - Relative size Ocular - eye - Height in the visual field  Monocular depth cues Accommodation involves the automatic adjustment of the shape of the lens to focus an object in response to changes in how far away the object is. This change is monitored/registered by the brain.  Motion Parallax Motion parallax uses our perception of movement to help us gauge how far away things are. This phenomenon helps us to measure depth. The less objects in our visual field move, the further away they are from us.  Pictorial cues Pictorial cues are so named because artists use them to create depth and distance on two-dimensional surfaces such as paper and canvas. Linear perspective is the apparent convergence of parallel lines as they recede (‘go back’) into the distance.  Pictorial cues Interposition occurs when one object partially blocks or covers another, and the partially blocked object is perceived as further away than the object that obscures it (and vice versa).  Pictorial cues Texture gradient refers to the gradual reduction of detail that occurs in a surface as it recedes into the distance, compared with a surface that is close and perceived in fine detail. We perceive objects for which fine detail is clear as being closer and those that lack detail , as being further away. Pictorial cues Relative size refers to the tendency to visually perceive the object that produces the largest image on the retina as being closer, and the object that produces the smallest image on the retina as being further away. However, the objects being perceived must be expected to be about the same size in real life. Pictorial cues Height in the visual field refers to the location of objects in our field of vision, whereby objects that are located closer to the horizon are perceived as being more distant than objects located further from the horizon. Binocular Depth Cues Bi - two - Convergence Ocular - eye - Retinal Disparity Binocular Depth Cues Convergence involves the brain detecting and interpreting depth or distance from changes in tension in the eye muscles that occur when the two eyes turn inwards to focus on objects that are close. Greater muscle tension =closer the object Less muscle tension = object is further away. Convergence is only useful when the object is within 6 meters.  Binocular Depth Cues Retinal disparity refers to the very slight difference (‘disparity’) in the location of the visual images on the retinas (due to their slightly different angles of view), which enables us to make judgments about the depth or distance of an object.  Psychological Factors Psychological factors are internal factors pertaining to an individual’s mental processes, including their cognition, affect, thoughts, beliefs and attitudes. Psychological factors include: - Visual perception principles - Gestalt principles - Visual constancies - Perceptual set  Visual Perception Principles Visual perception principles are guiding rules that apply to incoming visual signals and determine how they are organised and interpreted. They help make sense of our reality by combining visual signals in a systematic way. There are two types of visual perception principles: - Gestalt principles - Visual constancies VISUAL PERCEPTION PRINCIPLES Gestalt Principles  Gestalt Principles Gestalt Principles refer to the ways in Similarity which we organise the Proximity features of a visual scene by grouping them Closure to perceive a whole, Figure-ground complete form.  Gestalt Principles Similarity involves the tendency to perceive parts of a visual image that have similar features as belonging together in a unit , group or whole. This similarities can include size , shape , texture or colour.  Gestalt Principles Proximity (also called nearness) is the tendency to perceive parts of a visual image which are positioned close together as belonging in a group.  Gestalt Principles Closure is the perceptual tendency to mentally ‘close up’, fill in or ignore gaps in a visual image and to perceive objects as complete.  Gestalt Principles Figure-ground is the organization of visual information by perceptually dividing a visual scene into a ‘figure’ which stands out from the ‘ground’ which is the surroundings.  Gestalt Principles Figure-ground organisation is generally achieved when we separate the figure from the ground using a contour. A contour is a line or boundary between the figure and the ground and is always perceived as  What happens if the contour line cannot easily be distinguished? Figure-ground Figure-ground camouflage: reversible If the contour line cannot be figure: identified, the figure disappears into Depending on what the background part of the image you perceive the contour line belonging to, the same image can be perceived in multiple ways  How might we use figure-ground and proximity to understand written language?  Figure ground is Proximity is also used used when you read this when we group sentence - The words individual letters into printed in black (figure ) words simply because stand out from the they are physically whiteboard (ground ). close together. Writtenlanguageishardwithoutusingproximitytodifferentiate wordsinasentence. VISUAL PERCEPTION PRINCIPLES Visual Constancies  Visual Constancies Visual Constancies refer to our ability to perceive visual objects as staying the same, even if they may appear to change or do change in our sensation Three of the perceptual constancies involve: size, shape & brightness  Perceptual Constancies Size Constancy Involves recognising that an object’s actual size remains the same, even though the size of the image it casts on the retina changes. Perceptual Constancies  Perceptual Constancies Shape Constancy Is the tendency to perceive an object as maintaining its shape despite any change in the shape of the image of the object on the retina. We perceive the object to be a rectangular door opening but, if we drew this out, it is made up of varying shapes  Perceptual Constancies Brightness Constancy Is the tendency to perceive an object as maintaining its level of brightness in relation to its surroundings, despite changes in the amount of light being reflected from the object to the retina. Example : A sheet of white paper seen in the bright sunlight reflects a very different amount of light than the same sheet of paper seen later that night in a softly lighted room. Yet we perceive the paper as having the same whiteness in each case. “ Perceptual Set  Perceptual Set Perceptual set is the predisposition to perceive certain features of sensory stimuli and ignore other features that are deemed irrelevant. Our expectations of what an object or event will be make us more likely to interpret the object or event in the predetermined way. Our perceptual set includes the many schemas that we have, to form a holistic way of perceiving the world that is specific to the individual.  Perceptual Set Context refers to the setting or environment in which a perception is made. When organising and interpreting visual information, we take account of the setting and pay more attention to those aspects of the setting that are immediately relevant.  Context For example, consider the different interpretations that could be made of a fast-moving bright light in the sky that has a tail streaking behind it. How would you interpret this visual stimulus if you observed it in the sky over: 1. outback central Australia? 2. a war zone? 3. a NASA launch site in the USA? 4. Melbourne’s Yarra River on New Year’s Eve? 5. a ship at sea?  Perceptual Set Motivation refers to internal processes which activate behaviour that we direct towards achieving a particular goal. Motives can be influenced by psychological factors (such as interests, ambitions and desires) or biological factors (such as bodily processes associated with hunger or thirst).  Perceptual Set Emotional state can also influence the way in which we perceive visual information. Different emotions can ‘set’ us to perceive information in a particular way which is consistent with the emotion being experienced.  Perceptual Set Past experience refers to our unique combination of personal events that lead to many individual differences in perception. Such experiences also predispose, or ‘set’, us to perceive information in a particular way. When shown these two images (one image to each eye, simultaneously) people who had police training had a 52% chance of focusing on the violent scene compared to 22% for a group of university students.  Social Factors Social factors are external factors relating to an individual’s interactions with others and their external environment, including their relationships and community involvement. Social factors include: - Culture - Cultural norms  Culture Culture Experience with or in a particular culture, can influence the way we process and interpret visual information. Culture outlines the customs, behaviour, and values of a particular group in society. It is a key influence on who we are.  Cultural Norms Cultural norms Cultural norms are standards or values that outline appropriate behaviours or experiences within a culture. Common cultural norms may involve language, food, style or education, religion, clothing, or social dynamics specific to a culture.  Example When visually perceiving a scene, research has shown that people from collectivist cultures are more likely to attend to the broad scene, and are more consciously aware of relationships and changes. Whereas, people from individualistic cultures tend to attend to a specific or salient object in the scene, usually one that is big and/or colourful, and analyse this object’s individual attributes. Theory Summary Gustatory Perception  Factors influencing gustatory perception The process of gustatory perception can be understood as being largely influenced by biological, psychological and/or social factors. Our experience of taste is subjective and influenced by these three factors. Whilst these factors can be explored separately, they are interconnected with our other senses, such as smell, to construct the overall experience of gustatory perception.  Biological Factors Gustatory perception is dependent on the parts of the body that detect and process flavours. Differences in an individual’s physical ability to taste are considered biological factors. Biological factors include: - Age - Genetics  Age The ability to taste many substances is already well-developed at birth. But this changes as we get older… Ageing is speculated to affect our taste due to: - A decline in taste buds, therefore gustatory receptors, as we get older - The papillae on our tongue become less sensitive - Poorer chewing leads to decreased oral health, as well as decreased saliva production - Decline in other senses that assist with taste  Genetics Our genes can influence how sensitive we are to bitterness, sweetness or any other tastes. For example, variants of a certain gene have been found to influence how strongly an individual will be able to detect bitter tastes, which may explain why some people refuse to eat broccoli, Brussels sprouts and similar dark green, leafy vegetables.  Genetics About 25% of people inherit a gene that makes them a “supertaster” - and develop an unusually high number (double to triple the number!) of taste receptors. These people experience flavours more intensely, and are particularly sensitive to bitter tastes. About 25% of people are “non-tasters” - with an unusually low number of taste receptors. The rest of the population fall somewhere between these extremes. We call these people ‘medium-tasters’.  Psychological Factors Similarly to our biological factors, our psychological factors can impact the way in which we experience taste. Psychological factors include: - Perceptual set (influenced by): - Appearance - Food packaging Perceptual set and appearance The taste we experience is shaped by our perceptual set. This means that we often taste what we expect to taste. Although taste perception is dependent on the various sensory properties of food, the process often begins with the eyes (appearance of the food).  Perceptual set - continued When we actually taste the food and it meets our taste expectation, the experience reinforces our perceptual set of its taste. Similarly, when we believe that food is unsafe to eat, we usually expect that it will have a bitter or sour taste, which are in themselves biologically determined signs to avoid such food.  Perceptual set - continued The shape of our food can also influence our perception of taste. Research has shown that round shapes tend to be associated with sweet flavours, whereas more angular and cornered shapes are associated with bitter and savoury flavours.  Perceptual set - continued Packaging, labelling and branding also influence our perception of taste. For example, research participants report that Coca-Cola™ and peanut butter taste worse when consumed from a plain, unlabelled container than from one marked with a familiar brand. Children report that an apple tastes better if it comes from a bag with the McDonald’s logo. What’s the difference between these two chocolates?  Social Factors As with our visual perception, social factors play a role in our gustatory perception too. Social factors include: - Culture  Culture Diets in Asian cultures include many more sour and bitter tastes than Western diets. We are exposed to these cultural differences from birth and they are reflected in our perceptual judgments of what tastes good and what tastes bad. The values we were exposed to when growing up also influence our gustatory perception. For example, if you grew up in a culture that emphasises health and wellbeing, you may have a greater liking for the taste of fruits and vegetables than someone who grew up with different values. Theory Summary  Chapter 9 Perceptual Distortions Year 11 Psychology  9A Errors of Sight  VCAA Dot Point Distortions of perception the fallibility of visual perceptual systems, for example, visual illusions and agnosia the fallibility of gustatory perception, for example, supertasters, exposure to miraculin and the judgment of flavours distortions of perception of taste and vision in healthy individuals, such as synaesthesia and spatial neglect  Fallibility of visual perception Fallibility refers to the tendency to make mistakes or be wrong: These errors in the judgement or interpretation of sensory stimuli are known as perceptual distortions. Fallibility of perception and perceptual distortions do not mean something is wrong! Our brains are naturally susceptible to error!  Distortions of perception A perceptual distortion is an error in the judgement or interpretation of sensory stimuli  Distortions of perception A visual illusion is the perception of a visual stimulus that conflicts with how it is in physical reality. It is an experience in which there is a mismatch between our perception and what we understand as physical reality.  What causes visual illusions? Visual illusions can result from a variety of sources: Something in our external environment E.g. The moon appearing bigger when it is close to the horizon E.g. The colours or brightness of the image E.g. The angle you view the image from  What causes visual illusions? Something physiological E.g. Afterimages are the result of the photoreceptors in your eye remaining activated for a short period of time after being activated for a long period of time  What causes visual illusions? Something psychological E.g. The part of the image you pay attention to E.g. biased reasoning or perception due to past experiences, culture There is a tribe that perceives colour differently to how we do due to their cultural language…  Distortions of perception The Ames room illusion involves people appearing smaller or larger, depending on where they are standing. It involves a trapezium - shaped room that is longer and higher on one side than the other. When viewed through a peephole at the front of the room using only one eye, the room appears rectangular. The room’s unusual shape and being restricted to the use of monocular vision to view it provides the basis for the illusion.  The Ames room illusion As a result of the optical illusion, a person standing in one corner appears to the observer to be very large (because they’re close to the observer ), while a person standing in the other corner appears to be very small (because they’re further from the observer ). The illusion is so convincing that a person walking back and forth from the left corner to the right corner appears to grow or shrink.  The Ames room illusion - size constancy The Ames room illusion illustrates our inability to maintain size constancy when our use of depth cues is restricted, or the depth cues are misleading. Size constancy fails because the retinal information - the changing sizes of the people as they cross the floor - cannot be corrected due to the lack of accurate depth information. You know that people cannot change size just by walking - but this illusion causes you to perceive a person growing or shrinking.  The Ames room illusion - shape constancy The Ames room illusion illustrates our inability to maintain shape constancy. We are likely to misinterpret the shape of the room. We perceive the room as maintaining a constant rectangular shape when viewed through the peephole because we are unaware that the room is a trapezoid. The window on the left is physically larger than the window on the right. However, (when people are not sitting in them), we cannot tell.  Ames room illusion Which depth cues would × Therefore, we cannot the observer not be able use retinal disparity to use due to the or convergence to peephole? determine distance BINOCULAR CUES × This causes both corners of the room × The peephole only to appear as the allows you to view same distance the room with one away , even though eye they are not!  Which depth cues do we use in the Ames room illusion? Relative size: × We believe the people are similar size in real life × The person further back casts a smaller image on the retina than the person closest to the peephole × Since we believe both people are the same distance away, the only explanation for the difference in the size of the image is that one person is physically bigger than the other!  The Muller-Lyer Illusion The Muller-Lyer Illusion is a famous visual illusion. The two lines are exactly the same length, but often individuals will perceive the right line as being longer. So why does this occur?  Psychological Explanations Many explanations emphasise the role of our personal learning and memory. - The regular arrowhead forms the outwards corners and wall of a building - The inverted arrowhead forms the inward corners of a room - Misapplying depth cues - Some say it is a misapplication of linear perspective. The way the lines converge distorts our perception  Environmental/Social Explanations The carpentered world hypothesis showed that people who live in cities are more susceptible to the illusion than people who live in more rural, un-carpentered areas Why might this be? Cultural experience with parallel lines and right angles (growing up around buildings) increases susceptibility to the illusion by shaping the assumptions that a person makes when viewing the lines. Complete edrolo 9A Q 1,2,4,6,7, 13, 14, 16-18, 20-22 in your workbook If you have finished, search the internet for interesting visual illusions and see whether you can identify how they work! Agnosia  Agnosia Imagine you go to brush your teeth one morning and you try to pick up your toothbrush from the spot it normally lives but you can’t seem to find it… However, it turns out your toothbrush is in fact in that normal spot. Agnosia is a disorder involving the loss or impairment of the ability to recognise familiar stimuli through the use of one or more senses, despite the senses functioning normally otherwise. Agnosia  Agnosia Simply put, individuals suffering from agnosia may have trouble identifying sensory information, such as objects in their environment. Agnosia usually occurs as a result of a brain lesion. These lesions can occurs through a stroke, dementia, brain injury, brain tumour or overexposure to a toxin. Which areas of the brain might someone with visual agnosia have brain lesions on?  Types of Visual Agnosia Apperceptive visual agnosia Difficulty perceiving visual information Understanding of what objects look like, and functioning of vision is intact (shown by ability to draw from memory) Inability to identify objects is caused by difficulty perceiving shapes, forms or visual elements of an object (shown by inability to copy)  Types of Visual Agnosia Associative visual agnosia Difficulty identifying visual information No difficulty in perception or identifying visual elements of an object (can copy from an image) Inability to link prior experience to present stimuli (cannot name the object they just drew) Otherwise vision is normal.  Prosopagnosia Prosopagnosia is a form of However, they cannot associative agnosia, also associate the face (visual known as ‘face blindness’. stimuli) with the people they Someone with prosopagnosia know (link prior experience), can recognise they are looking therefore they find it hard to at a face (therefore it is not identify who they are looking apperceptive). at, even if they know them very well.  Visual Agnosia It is important to note that visual agnosia does not suggest that sufferers have malfunctioning senses. Instead, it is the processing of sensory information that leads to errors in perception. Visual Agnosia Complete workbook activity 9.5 part A and part C in your booklet Theory Summary  9B Errors of Taste  The fallibility of taste perception Taste perception can be influenced by: 1. Genetics - supertasters 2. Exposure to Miraculin 3. The judgement of flavours: × Perceptual set × Colour intensity × Texture  Supertasters A supertaster is a person who is more sensitive to certain tastes than most others.  Supertasters About 25% of people inherit a About 25% of people gene that makes them a are “non-tasters” - “supertaster” - and develop an with an unusually unusually high (double to low number of taste triple!) the number of taste receptors. receptors. These people The rest of the experience population fall somewhere flavours more between these intensely. extremes.  Supertasters and ‘bitter’ It has been noted that supertasters are extremely sensitive to ‘bitter’ tastes - how might this be advantageous for survival?  Miraculin A type of protein extracted from the ‘miracle berry’ which alters taste perception in humans. Miraculin attaches to taste receptors for sweet and upon interaction with acids from sour foods, changes shape to activate the sweet receptors that are normally set off by sugars. The result is a sweet taste perception that drowns out the sour taste. This effect lasts until the protein is washed away by saliva (Koizumi et al., 2011). Miraculin  How does it work? The mouth must be coated by miraculin extracted from the ‘miracle berry’ either in the form of fruit, or a tablet. When the mouth becomes an acidic environment (due to consumption of a food containing acid), the miraculin molecules bind to the taste receptors responsible for detecting sugars / ‘sweet’ taste. This replicates and enhances the sensation of ‘sweet’, leading the person to believe the food they are tasting is now ‘sweet’ instead of ‘sour’. Miraculin blocks sweetness receptors. Therefore, eating sweet foods will taste less sweet if there is no acid present!  Complete pg 11 in your booklet. Complete any worksheets from earlier in your booklet. If finished, you can do the 9B Edrolo questions from your textbook.  Judgement of flavours Perceptual set Intensity of colour Texture The taste we experience is shaped by our perceptual set. This means that we often taste what we expect to taste. Although taste perception is dependent on the various sensory properties of food, the process often begins with the eyes.  Judgement of Flavours Perceptual Set Appearance Packaging Brand  Judgement of flavours Colour intensity Changing the intensity of a colour can exert a dramatic impact on our expectations, and hence on the taste and flavour experiences. For example, a brighter or richer coloured food item can seem to taste different to a more bland coloured one, even when there is no change in the ingredients that make up the flavour.  Judgement of flavours Texture is the property of food or beverage that is felt in the mouth and contributes to flavour. Texture can affect flavour by determining how much of its surface area comes in contact with the tongue. For example, consider the flavor difference between chewing a solid piece of carrot compared to drinking carrot juice. The length of time food spends in the mouth also affects how strong the flavour seems. 9C - Perceptual Distortions  Synaesthesia Synaesthesia is a perceptual experience in which stimulation of one sense produces additional unusual experiences in another sense. For example, the colour orange may always be associated with the letter A. The note ‘C sharp’ may be associated with the colour blue  Characteristics of synaesthesia Synaesthesia is: Automatic / cannot be controlled A one way process ○ E.g. if you smell donuts everytime you see the colour orange, you won’t necessarily see the colour orange everytime you smell donuts! Consistent ○ E.g. Tasting apples every single time you see the number 4, and never tasting anything else when you see the number 4. Unique to each individual Relatively common ○ Estimated to be experienced by between 1/100 to 1/2000  Explanations of synaesthesia Researchers still know relatively little about synaesthesia and why it is experienced. It is likely that something is occurring in the sensory areas of the brain, but precisely what still remains unclear. The brains of synaesthetes may have abnormal neural pathways or be ‘wired’ differently, so that neighbouring sensory areas in the brain cross-activate one another, thereby triggering additional sensations. Another explanation is that synaesthetes have an excess of neural connections that would usually be pruned as the brain matures. Create a mind map in your booklet about synaesthesia, for example: Definition __________ __________ Prevalence Synaesthesia Brain processes _____________ _____________ Forms of synaesthesia Explanations  Spatial neglect × Spatial neglect is a neurological disorder whereby individuals are unable to notice anything either on one side of space. × They tend to behave as if that one side of their world does not exist. × Caused by damage to the parietal lobe (usually in the right hemisphere resulting in the patient being unable to pay attention to the left side of their world) Spatial neglect  Is it a problem of sensation or perception? The patient’s eyes and visual sensation pathways are undamaged and unaffected This means light information from all sides of space is being detected by photoreceptors. The problem is that the patient is unable to pay attention to the information received from one side of space This causes them to ‘ignore’ it or be unable to perceive it. Complete the Chapter 9 Topic Test