Edrolo_VCE_Psychology_Units_12_-_Chapter_9.pdf

9 CHAPTER 9 Perceptual distortions LESSONS 9A Errors of sight 9B Errors of taste 9C Perceptual distortions Chapter 9 review Unit 2 AOS 2 review KEY KNOWLEDGE the fall...

9 CHAPTER 9 Perceptual distortions LESSONS 9A Errors of sight 9B Errors of taste 9C Perceptual distortions Chapter 9 review Unit 2 AOS 2 review KEY KNOWLEDGE 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 judgement of flavours distortions of perception of taste and vision in healthy individuals, such as synaesthesia and spatial neglect Image: GoodStudio/Shutterstock.com 445 9A Errors of sight STUDY DESIGN DOT POINT the fallibility of visual perceptual systems, for example, visual illusions and agnosia 9A 9B 9C 2.2.4.1 The fallibility of visual perception 2.2.4.1.1 Visual illusions 2.2.4.1.2 Agnosia We rely on our sight for almost everything in our lives. We use our eyes to help us make FEP decisions, guide us through our environment, choose what to wear, what to eat, and much T O Z LPED more. So what if you were told that your sense of sight is not always reliable? In this lesson, PE C FD we will explore the ways in which our visual perception system is prone to error, such as visual illusions and agnosia. ACTIVITY The fallibility of visual perception 2.2.4.1 Log into your Edrolo Our visual perception, like most of our senses, is subject to error. In this lesson, we will explore account for activities that contexts in which our visual perception may be inaccurate, including the effects of visual support this lesson. illusions and agnosia. Theory details Have you ever been walking down a road and seen a puddle in the distance, only to arrive at KEY TERMS the destination of the puddle and realise it wasn’t there at all? Have you ever seen a shadow Fallibility the quality of in the corner of your room, only to realise it was just your imagination? The fallibility of our being prone to error or visual perception is clear when we notice these kinds of perceptual errors. Fallibility refers experiencing difficulties to the quality of being prone to error or experiencing difficulties in judgement. Further, in judgement these errors in the judgement or interpretation of sensory stimuli are known as perceptual Perceptual distortion distortions. The fallibility of visual perception and the presence of perceptual distortions does an error in the judgement not mean something is wrong, but rather demonstrates that normally functioning brains are or interpretation of susceptible to error. sensory stimuli As you learnt in the previous chapter, in order to recognise sensory stimuli, the processes of sensation and perception must both occur. Sometimes the fallibility of visual perception is not due to our inability to detect sensory information. Instead, it is due to the errors made within our brains in processing this information. To demonstrate these perceptual errors we will explore visual illusions and agnosia. 446 Chapter 9: Perceptual distortions  WANT TO KNOW MORE? In addition to the examples of errors of sight discussed within this lesson, there are other 9A THEORY phenomena that demonstrate the fallibility of visual perception. In each of our eyes, we have an area in which there are no photoreceptors (special neurons that aid in vision), this area is known as a ‘blind spot’ as it does not function in image detection. When we are looking at an object with both eyes open, this blind spot goes unnoticed as the visual information received from each of our eyes overlaps to create a whole image (Kawabata, 1982). Even when we are looking at something using only one eye, we often still do not notice this blind spot as our brains conduct a process known as perceptual filling-in, in which it tries to conceal the blindspot in accordance with what our vision is already showing (Raman & Sarkar, 2016). However, under certain conditions, we can ‘see’ our blind spot. Looking at figure 1, close your right eye and look at the plus sign with your left eye. Move your head towards and then away from the image whilst keeping your focus on the plus sign. You should find a point at which the black dot disappears from your vision – this is your blind spot. This process is just another example of how our perception, including our visual perception, is subject to error. Figure 1 Task to identify the existence of the blindspot Visual illusions 2.2.4.1.1 One way in which we can experience errors in visual perception is through the consideration of visual illusions. A visual illusion is the perception of a visual stimulus that conflicts with Visual illusion how it is in physical reality. It is not entirely understood how all visual illusions occur, but they the perception of a visual can result from a variety of sources (Gregory, 1997). Common sources of visual illusions are stimulus that conflicts with outlined in table 1. how it is in physical reality Table 1 Visual illusions are often caused by environmental, biological, or psychological factors Cause of illusion Explanation Something in our Something in our physical external environment that makes an external environment. image tricky to interpret during perception. For example, you may have noticed that the closer the moon is to the horizon line, the bigger it looks. This is something within our physical environment that gives rise to a perceptual visual illusion. Something physiological. Something physiological that makes an image difficult to interpret. For example, have you ever looked at a bright light and then turned it off? Could you still see the image of the bright light, almost like a bright shadow? This is due to our eyes and brain not keeping up with a changing reality after intense light and giving rise to a perceptual visual illusion. Something psychological. Something psychological. As you know, we may see things in a certain way due to our own application of biased reasoning (as demonstrated by perceptual sets). This can also give rise to perceptual visual illusions. Müller-Lyer illusion One famous visual illusion is the Müller-Lyer illusion, named after the man who first identified it. Take a look at figure 2. Which line is longer? The one on the left or the one on the right? Figure 2 The Müller-Lyer illusion is seen when comparing the length of these two lines 9A Errors of sight 447  When measured, the two lines are the same length, as demonstrated in figure 3. However, it is extremely common for individuals to perceive the right line as being longer. So why does the Müller-Lyer illusion occur? The illusion relies on the influence of the accompanying 9A THEORY arrowheads of each line, specifically whether the line is contained within inverted arrowheads or regular arrowheads. However, the process by which these arrowheads affect our visual perception is debated. As mentioned, the causes of visual illusions are not entirely understood, however there are proposed psychological and social/environmental explanations to explain the Müller-Lyer illusion. These are outlined in table 2. Table 2 Explanations of the Müller-Lyer illusion Figure 3 It’s easy to ‘unsee’ the Müller-Lyer illusion when we look Cause of Müller- Description at it like this Lyer illusion Psychological Some psychological explanations of the Müller-Lyer illusion emphasise the role of our personal learning and memory. This is based on the idea of the ‘carpentered world hypothesis’. Richard Gregory (1968) suggests that when we see the plain two-dimensional lines of the illusion, we automatically apply them to real three-dimensional objects in our world stored in our memory, such as the corners of rooms and Figure 4 The carpentered world buildings (objects made by ‘carpenters’). hypothesis is a theory used to When we apply the line with a regular arrowhead to the world, it forms explain the Müller-Lyer illusion the outward corners and wall of a building (shown on the left side of figure 4). When we apply the line with an inverted arrowhead to the world, it forms the inward corners of a room (right side of figure 4). We tend to perceive the line representing the outward corners of a building as extending toward us and therefore being closer to us, whereas we perceive the line representing the inward corners of a room as being further away because the corners extend outwards and away from us. This can be considered as a misapplication of depth cues. Some explanations suggest that this is due to the misapplication of linear perspective to the lines of the arrowheads: each arrowhead is made up of two ‘parallel’ lines and the point at which they meet creates a ‘corner’ of a room or building. For the regular arrowhead, the lines converge at the top point of the arrowhead and separate out downwards. Therefore, they reflect the outside corners of a building because the point at which these arrowhead lines converge emulates the pointed outside corner of a building that extends toward us. On the other hand, the inverted arrowhead shows two ‘parallel’ lines which begin converging and then separate upward. Where the inverted arrowhead lines are converged is therefore the inside corner of a room that extends away from us. Environmental/ Environmental or social explanations for the illusion have also been social proposed. The Müller-Lyer illusion has been found to be environmentally influenced (Ahluwalia, 1978). A study investigating the applicability of the carpentered world hypothesis showed participants in Zambia the illusion. It found that people who lived in cities were more susceptible to the illusion than people that lived in more rural, ‘un-carpentered’ areas. This suggests that those with more exposure to ‘carpentered’ settings are perhaps more likely to see the illusion. The Ames Room illusion Another well-known visual illusion is the Ames Room illusion which is depicted in figure 5. This illusion occurs when a person views two people in a special Ames Room through a peephole using only one eye. As you can see, the person on the left of the room looks to be much tinier than the person on the right. However, in reality, both people are normal-sized humans. Primarily, the illusion occurs because the shape of the room has been constructed in a specific way in Image: Artazum/Shutterstock.com order to ‘trick’ our visual perceptual systems. Figure 5 The Ames Room 448 Chapter 9: Perceptual distortions As you can see in figure 6, the back wall of an Ames Room is not straight and square. The left Actual position of person A side of the back wall extends away from the peephole, allowing the person in the left corner to stand much further away from the viewer than the person in the right corner. Furthermore, ‘Back’ wall 9A THEORY the ceiling of the room is not parallel to the floor, being twice as high on the left side of the Actual and apparent position of person B room compared to the right. Both of these design manipulations allow the person on the left Apparent position of person A to look much smaller than the person on the right. Importantly, the room’s design purposefully manipulates certain visual cues in order to impair a viewer’s ability to correctly apply visual constancies (the ability to perceive an object as staying physically the same, even when projecting different images onto our eyes). These are outlined in table 3. Table 3 Manipulation of visual cues in the Ames room Visual cue Description Judging the size of objects A person standing on the left actually looks to be shrinking as (size constancy) they get further away. Normally, our brain would allow us to see a change in size like this as a change in distance, and therefore it Apparent shape Viewing would not affect our perception of a person’s true size compared of the room peephole to the image of them cast onto our eyes. However, because the Figure 6 Even though from room is deceptively designed, we are unable to see their change front-on the Ames Room appears in distance and are therefore unable to apply size constancy. to be the shape of a normal rectangular room, it is actually Judging the shape of the We are also likely to misinterpret the shape of the room. trapezoid in shape room (shape constancy) We see the room as maintaining a constant rectangular shape when viewed through the peephole because we are unaware that the room is a trapezoid. Agnosia 2.2.4.1.2 Imagine if you woke up one day and went to go and brush your teeth and you left your toothbrush Agnosia a disorder in the same spot that you always do. However, when you go to reach for it, you cannot find it involving the loss or no matter how hard you try. Now, what if it turned out that in this situation, your toothbrush impairment of the ability was in fact in the exact same place as it always is. This is an example of what it may feel like to to recognise familiar experience visual agnosia. Agnosia is a disorder involving the loss or impairment of the ability to stimuli through the use recognise familiar stimuli through the use of one or more senses, despite the senses functioning of one or more senses, normally otherwise. Simply, this means that individuals suffering from agnosia have difficulty despite the senses identifying sensory information, such as objects in their environment. functioning normally otherwise Agnosia usually occurs as the result of a brain lesion (Kumar & Wroten, 2022). An agnosia- causing brain lesion may be incurred as a result of a stroke, dementia, brain injury, brain tumour, or overexposure to a toxin. Visual agnosia, for example, is commonly associated with brain lesions that occur in the parietal lobe, temporal lobe, and occipital lobe, as these areas LESSON LINK of the brain are associated with processing visual information. However, different forms of In lesson 4A Approaches agnosia are associated with different areas of damage. The two main subtypes of visual agnosia to understanding the are outlined in table 4. brain, we learnt that brain lesions are points Table 4 Types of visual agnosia of damage to the brain Type What it involves that can be surgically induced or be acquired Apperceptive visual agnosia Difficulty in perceiving visual information through illness or injury. Intact mental understanding of what objects look like We learnt that brain Inability to identify objects is caused by a difficulty lesions can be used to in perceiving the form or visual elements of an object determine what functional Otherwise normally functioning vision. difficulties a patient has acquired based on where Associative visual agnosia Difficulty in identifying what object is being viewed this damage occurred. No difficulty in perception; individuals are able to identify Similarly, depending on the individual visual elements of objects the type of agnosia a Identification difficulties stem from being unable to link patient is experiencing, prior experience to the object they are viewing professionals will likely be Otherwise normally functioning vision. able to determine what area of the brain a lesion has occurred. 9A Errors of sight 449  It is important to note that these forms of visual agnosia do not suggest that the sufferers have malfunctioning senses. An individual who experiences visual agnosia may still have perfect vision. Instead, it is their processing of this sensory information that leads to errors in perception. 9A THEORY In essence, individuals with visual agnosia can see clearly, but cannot necessarily identify what they are seeing. Another example of visual agnosia can be seen in the case study of ‘C.K.’, who suffered from associative visual agnosia (Behrmann, et al. 1994). Associative visual agnosia causes individuals to be unable to form a mental representation of the world in their brains as they are only able to perceive elements of a whole and not the whole itself. Like other forms of visual agnosia, sufferers are also unable to categorise or give meaning to objects. For example, when shown an image of a dog, patient C.K. would be able to correctly answer questions such as ‘does it have a long or short tail?’ and ‘what colour is its fur?’, but when asked to identify what the animal is, he would not be able to. PSYCHOLOGY EXPLORATION Oliver Sacks, a famous physician, published a book in 1985 called ‘The man who mistook his wife for a hat’. The book contained stories of many patients he had treated, but was named after Dr. P, a distinguished music professor who was suffering from agnosia. Dr. P reported that ‘people seem to think there’s something wrong with my eyes’ and when asked if he recognised any issues with his sight, he stated, ‘No, not directly, but I occasionally make mistakes’. This demonstrates that, for individuals with agnosia, vision is not an issue. Rather the issue is within their processing of visual information. Sacks detailed many seemingly strange behaviours demonstrated by Dr. P, including: being unable to recognise the faces of his students, yet knowing them by the sound of their voices seeing faces in objects that did not have one mistaking inanimate objects, such as fire hydrants, for children and most famously, he mistook his wife for a hat! In addition, just like patient C.K., Dr. P was able to recognise the individual parts of an object but not the object itself. For example, when presented with a rose, he described it as a red form with a green tube attached to it. (Sacks, 1985) Theory summary In this lesson, you learnt that visual perception is fallible, in that it is prone to error. You explored examples of this fallibility by looking at visual illusions, including theories as to why these illusions occur, and you looked at the experience of individuals with agnosia. Visual perception can be considered as fallible as individuals make mistakes in processing visual information Fallibility of visual perception can be demonstrated through Individuals with Visual illusions visual agnosia Müller-Lyer Illusion Ames room Apperceptive Associative Figure 7 The fallibility of sight and its related examples 450 Chapter 9: Perceptual distortions 9A Questions 9A QUESTIONS Theory review Question 1 Visual perception is always a reliable and accurate representation of the world. A. True. B. False. Question 2 Errors in sight are most commonly attributed to A. an error in processing visual information. B. blindness of the eye. C. an inability to receive visual information. Question 3 Visual illusions and agnosia demonstrate A. that visual perception should never be trusted. B. that visual perception is reliable in all contexts. C. the fallibility of visual perception. Question 4 Which of the following are explanations for why visual illusions occur? (Select all that apply) I. We do not receive images correctly with our eyes. II. Something in our physical environment makes the interpretation process of visual perception difficult. III. Something biological within our eyes or brain makes the perceptual process difficult. IV. Something psychological means that the way we uniquely perceive and interpret an image makes it appear different from reality. Question 5 People who suffer from agnosia have difficulty in seeing objects which leads to difficulty in identifying said objects. A. True. B. False. Assessment skills Perfect your phrasing Question 6 Which of the following sentences is most correct? A. Fallibility is the quality of being prone to bias or experiencing errors in judgement. B. Fallibility is the quality of being prone to error or experiencing difficulties in judgement. Question 7 Which of the following sentences is most correct? A. Visual illusions occur when an individual’s perception of a visual stimulus is experienced in a way that conflicts with how it is in physical reality. B. Visual illusions occur when an individual’s perspective of a visual stimulus is experienced in a way that challenges how it is in physical reality. 9A Errors of sight 451  Question 8 Which of the following sentences is most correct? 9A QUESTIONS A. Agnosia is a disorder involving the loss or impairment of the ability to recognise or identify familiar stimuli through the use of one or more senses, despite the senses functioning normally otherwise. B. Agnosia is a disorder involving the loss or impairment of the ability to recognise or identify similar stimuli through the use of one or more senses, despite the senses functioning regularly otherwise. Text analysis The following assessment skills type reflects the study design assessment type: analysis and evaluation of an experiment or case study. Use the following information to answer questions 9–12. Agnosia is a complex condition, therefore researchers often undertake case study research to understand the perspectives of those who experience it. One case study of visual agnosia is that of patient JPM. JPM is a well-educated and successful man, however, he was diagnosed with associative visual agnosia following a heart attack which caused parts of his brain to be deprived of oxygen. Examinations by researchers showed that his neurological functioning, visual field, perceptual processing, and brain magnetic resonance imaging (MRI) were all normal. During an assessment of JPM’s ability to recognise objects, researchers found that this skill was severely impaired. JPM was only able to recognise 7/48 photographs of inanimate objects. JPM was also assessed using an object decision task, in which he was asked to decide whether an image portrayed a real object or a ‘non-object’. During this task he scored at ‘chance level’, meaning that he scored similarly to someone who was just guessing. (Charnallet, et al. 2008) Question 9 What are the two main criteria that JPM demonstrated to be diagnosed with visual agnosia? A. He had normal intelligence levels and he had difficulty in identifying visual stimuli. B. He had normal intelligence levels and he had normal visual functioning. C. He had otherwise normal visual functioning and he had difficulty in identifying visual stimuli. Question 10 It is likely that JPM would still be able to perceive individual elements of objects, such as their colour or size. A. True. B. False. Question 11 What would not be an appropriate task to test JPM’s agnosia? A. Asking him to identify a specific object from a list of photographs. B. Asking him to identify an object that he has never encountered before. C. Asking him to name an object being presented to him. Question 12 What ethical consideration is being adhered to by hiding JPM’s real name? A. Voluntary participation. B. Withdrawal rights. C. Confidentiality. 452 Chapter 9: Perceptual distortions Exam-style 9A QUESTIONS Remember and understand Question 13 (1 MARK) A visual illusion is A. the misunderstanding of an image due to the way visual information is received at the eye during sensation. B. the misunderstanding of an image due to the way visual information is transmitted during sensation. C. a perceptual distortion of an image due to the way visual information is understood during perception, caused by environmental, biological, or psychological factors. D. a perceptual distortion of an image due to the way the image actually is in physical reality, caused by environmental, biological, or psychological factors. Question 14 (1 MARK) Fallibility in relation to sight involves A. being prone to error during the process of perception. B. the eyes being unreliable. C. errors in the processing of visual sensation. D. individuals being aware that they are making errors in visual sensation and perception. Question 15 (1 MARK) Which of the following statements regarding agnosia is not correct? A. Patients with agnosia have otherwise normally functioning senses. B. Agnosia is the loss or impairment of the ability to recognise or identify familiar stimuli through the use of sight. C. Agnosia is commonly the result of a brain lesion. D. Patients with visual agnosia can see clearly but have difficulty identifying what they are seeing. Question 16 (3 MARKS) Identify and describe one visual illusion and provide one explanation for why it occurs. You may use a diagram in your response. Apply and analyse Question 17 (1 MARK) When in a car at night, Priya watches the moon and notes that it looks like the moon is following her car. This visual illusion is likely a result of A. something in Priya’s physical external environment that makes the image tricky to interpret during perception. B. something biological within Priya that makes the image difficult to interpret. C. something psychological in Priya that causes her to be biased about the moon’s location. D. an issue with Priya’s vision. Question 18 (1 MARK) Noel has spent his whole life on a small island and has never visited or seen images of built-up areas, such as a city. When viewing the Müller-Lyer illusion, compared to someone who lives in Melbourne’s central business district (CBD), Noel is A. more likely to be susceptible to the illusion as demonstrated by the carpentered world hypothesis. B. less likely to be susceptible to the illusion as demonstrated by the carpentered world hypothesis. C. more likely to be susceptible to the illusion due to issues with his sight. D. less likely to be susceptible to the illusion due to issues with his sight. 9A Errors of sight 453  Question 19 (2 MARKS) Anika was diagnosed with visual agnosia. To test her abilities, researchers presented her with a drink bottle. 9A QUESTIONS Briefly describe the abilities and difficulties that Anika may demonstrate when viewing the drink bottle. Evaluate Question 20 (3 MARKS) Evaluate whether visual perception should be trusted as a reliable process. Questions from multiple lessons Question 21 (1 MARK) Being susceptible to a visual illusion due to biased reasoning is an example of A. the fallibility of the external environment. B. an error of sensation. C. top-down processing. D. bottom-up processing. Question 22 (2 MARKS) Outline what is meant by a schema and explain how an individual’s schemas may be used to explain the Ames room illusion. 454 Chapter 9: Perceptual distortions 9B Errors of taste STUDY DESIGN DOT POINT the fallibility of gustatory perception, for example, supertasters, exposure to miraculin and the judgment of flavours 9A 9B 9C 2.2.5.1 The fallibility of gustatory perception 2.2.5.1.1 Supertasters 2.2.5.1.2 Exposure to miraculin 2.2.5.1.3 The judgement of flavours If you were blindfolded and asked to identify different foods by taste, would you be confident in your answers? When humans were hunter-gatherers, an accurate sense of taste may have saved lives by preventing individuals from eating rotten or poisonous foods. However, today this is prevented by laws and food manufacturers. Both during hunter-gatherer times and in the modern day, taste perception can be regarded as error-prone. Despite this, we often overestimate how much we can depend on our senses, such as taste. The fallibility of gustatory perception 2.2.5.1 In this lesson, we will explore examples of the fallibility of gustatory perception, including supertasters, exposure to miraculin, and factors that influence the judgement of flavours. ACTIVITY Log into your Edrolo Theory details account for activities that support this lesson. Our sense of taste has an impact in many areas of our lives. It can help to determine the foods that we eat, our favourite restaurants, and it can protect us from foods that are poisonous or contaminated. As taste is so central to our lives, it should be relatively accurate, shouldn’t it? Like all of our senses, our gustatory perception is also prone to error, meaning it is fallible. In the previous lesson, we learnt about the fallibility of sight; our sense of taste experiences this fallibility in a similar way. In lesson 8D Gustatory perception, we learnt about the process of gustatory perception, and its biopsychosocial influences. In this lesson, you will learn about the situations in which our gustatory or taste perception may be prone to error, including: supertasters, exposure to miraculin, and factors that influence the judgement of flavours. Supertasters 2.2.5.1.1 Taste is a significantly important factor in our perception of food. As you learnt in the previous chapter, human taste is facilitated through receptors found in taste buds within the papillae, which are found in the mouth and tongue. Some aspects of taste perception are genetically determined (Shepherd, 2012), hence why some people love the fragrant flavour of coriander but others are convinced that it tastes like soap. 9B Errors of taste 455  American university professor, Linda Bartoshuck (1994), established a very interesting finding KEY TERMS while researching the genetic differences in taste perception. She measured people’s ability to Supertasters individuals detect a common bitter-tasting chemical known as ‘PROP’, and found that 25% of people were 9B THEORY who have significantly low extremely sensitive to its taste. Bartoshuck (1994) found that those same people who were thresholds for taste stimuli extremely sensitive to PROP also had many more taste buds, and therefore more taste receptors and an unusually high than the average person. These individuals are called supertasters, which refer to individuals number of taste buds who have significantly low thresholds for taste stimuli and an unusually high number of taste buds. The difference in taste buds for supertasters as compared to normal individuals is depicted in figure 1. Supertaster Non-supertaster Figure 1 Supertasters have a significantly higher number of papillae than the average person To some, a heightened tasting experience may sound exciting. In reality, however, a supertaster’s sensitivity to bitter foods can lead to many impacts on one’s day-to-day life. They may be more likely to withhold from alcohol use and smoking which is positive for health. However, supertasters also often experience difficulty eating vegetables that contain essential nutrients, and are frequently labelled as ‘picky eaters’. In addition, they often consume excess salt, as salt can counteract the perceived bitterness in their food. This consumption of excess salt can lead to negative health impacts over a prolonged period of time. It is important not to confuse the experience of supertasters with a perceptual distortion, as their perception is actually accurate. Their difference in perceiving taste is due to the biological difference of an increased number of papillae, affecting their reception of taste stimuli. Exposure to miraculin 2.2.5.1.2 What if there was a magical pill that you could take to make all of your least favourite foods Miraculin a type of taste amazing? Well, there is! Miraculin is a type of protein extracted from the ‘miracle protein extracted from berry’ which alters taste perception in humans. Although it may not make a salad taste like the ‘miracle berry’ which a cheeseburger, it does have the ability to make sour foods taste sweet. alters taste perception in humans WANT TO KNOW MORE? From an evolutionary perspective, how has the human utilisation of such a berry persisted across time? Although the discovery of the miracle berry was first documented in the 1700s by European explorers, its properties were utilised by the West African natives long before this. The natives would chew on the berry before eating, making any acidic foods they consumed more palatable. It is not likely that the berry was used simply because the natives loved the taste of sugar. Instead, some researchers suggest that the natives may have incorporated the berry into their diets Figure 2 Miraculin can come as a way to consume larger quantities of fermented foods, which though sour, benefit gut health and in pill form or can be consumed by eating the ‘miracle berry’ preserve food’s longevity. (Lipatova, 2016). You may be wondering how this ‘miracle berry’ actually works. Miraculin is an example of how our senses can be purposefully manipulated to alter perception. When a sour food enters the mouth, the acidity of the food activates gustatory receptors on the tongue that are responsible for detecting sour flavours. In the same way, when a sweet food enters the mouth, the taste receptors on the tongue that are responsible for detecting sweet flavours are activated. Interestingly, miraculin does not cause physiological changes to the functioning of these sour taste buds. Instead, miraculin binds to the taste buds that are responsible for detecting sweet flavours and activates them when an acidic environment is created in the mouth (Koizumi, et al. 2011). 456 Chapter 9: Perceptual distortions  WANT TO KNOW MORE? If you want to see miraculin in action you can search for ‘Kids Try Miracle Berries | Kids Try | HiHo 9B THEORY Kids’ (HiHo Kids, 2017) on YouTube and watch the five-minute and 32-second video to observe how children react to miracle berry tablets. The judgement of flavours 2.2.5.1.3 Our perception of flavour involves information integrated from other sensory systems, including vision, touch, and smell. Perceptual distortions or difficulties when judging flavour often occur due to external and internal influences on taste, often from these other sensory systems. Although information from our other senses like vision, or faculties like our memory, can help us to judge flavours, they can also ‘fool’ us into believing we are tasting something different from what is objectively there. Our perceptual set, the intensity of the food’s colour, and the food’s texture can all influence the way we judge flavour. Influence of perceptual set As you have learnt, a perceptual set is a predisposition to perceive certain sensory stimulus features and ignore other features of the stimulus deemed irrelevant. Our perceptual set can cause perceptual distortions when they cause us to interpret flavours differently, or cause LESSON LINK us to taste something more or less intensely than it truly is in our food. For example, the appearance of food and its packaging can give us certain expectations that can influence the In lesson 8D Gustatory flavours we perceive. If we eat food with packaging that represents a popular brand, we may perception, you learnt that be predisposed to expect a high-quality taste and therefore actually believe we are tasting an individual’s perceptual better food. This example is depicted in figure 3. set is influenced by factors such as past experiences, motivations, values, beliefs, and culture. A perceptual set can influence taste perception through factors, such as your past experience with a brand or belief about a type of food. Images (left to right): Audio und werbung, BigMouse/Shutterstock.com Figure 3 A food’s packaging and appearance can influence our taste perception through perceptual sets Influence of colour intensity Would you rather eat a bright red strawberry, or a slightly pink strawberry? The intensity of the colour of the food we eat can lead to perceptual distortions in flavour judgement. As a general rule, food that is more intensely coloured leads us to perceive it to have a stronger flavour, even Figure 4 The colour of food can when this is not the case. This information exists within our perceptual set, as past experience influence our perception and has predisposed us to expect that a brighter colour means something is more ripe or intensely expectations of its taste flavoured. Several studies have found, for example, that the intensity of a beverage’s colour correlates to the intensity of sweetness perceived (Johnson et al., 1982; Roth et al., 1988). LESSON LINK This association can often encourage food brands to artificially dye their products, especially confectionery. Consider figure 4 and think about which strawberry you would rather eat. In lesson 8D Gustatory perception, you learnt Influence of texture about the biological, How would you feel if you were given a mushy apple? Or a crunchy and gritty banana? psychological and social How a food feels in the mouth, or its ‘texture’, can affect our experience and judgement factors that can influence of a food’s flavour. Two ways that texture can affect our judgement of flavour are that: our gustatory perception. The factors that influence 1. It can change the intensity of the flavour we experience. our judgement of flavours This is because the texture of food determines how much of it actually is received by our can also be attributed to this biopsychosocial gustatory receptors and how long it stays in the mouth. For example, orange juice is generally approach. For example, more flavourful than an orange. In liquid form, more of the ‘orange’ flavours are able to be colour intensity can act as received by our gustatory receptors, whereas when we chew an orange less of it comes into direct a social or a psychological contact with them. Creamier foods also tend to stay in our mouth longer than thinner, more influence on flavour liquidy foods, and so we are able to taste them more. This is not a perceptual distortion because perception. we are physically able to taste more or less of the food we are consuming depending on its form. 9B Errors of taste 457  2. It can also change how much we enjoy the flavour we perceive. Whether we judge food to be tasty is also dependent on its texture. This is often informed by our expectations of how a food should feel and our past experiences with specific food items. 9B THEORY If you were given soft crackers, would you still enjoy them? Our enjoyment of flavour according to texture is not necessarily a perceptual distortion either. Additionally, preferences for the kinds of textures that are more enjoyable in different foods may vary between individuals. WANT TO KNOW MORE? Have you ever been so hungry, that when you finally ate a meal it was the best-tasting meal you had ever had? Later, when you ate it again while you were less hungry, it may not have tasted anywhere near as delicious. Many people claim that the hungrier you are, the better food tastes, and it seems that research actually does support this notion. A study by Zverev (2004) found that when people were deprived of food for a short period of time, their sensitivity to the taste of sweet and salty flavours was heightened as compared to when they had not been deprived of food. Similarly, recent research by Fu et al. (2019) found that when mice were deprived of food, they demonstrated a preference for sweet tastes and demonstrated a decreased sensitivity to bitter tastes. This study suggested that this change was due to the activation of specific neurons in the hypothalamus, which influences taste preferences during times of fasting in order to increase food consumption and therefore survival. This phenomena is just another example of the fallibility of taste and how biological changes can alter the way in which food and flavours are experienced, even in the absence of perceptual distortions. Theory summary In this lesson, we learnt about the ways in which our sense of taste is fallible, meaning that it is prone to error and individual differences or distortions. This fallibility includes: genetic variations in taste, such as supertasters purposeful manipulation of our senses, such as intentional exposure to miraculin unconscious influences on our judgement of flavours, such as perceptual set, colour intensity, and texture. 9B Questions Theory review Question 1 Gustatory perception is completely reliable as it receives sensory information from physiological structures, such as papillae. A. True. B. False. Question 2 Supertasters are categorised by A. a decreased sensitivity to taste sensation. B. a high threshold for taste sensation. C. a low threshold for taste sensation. Question 3 Miraculin is known for A. making sweet foods taste sour. B. making sour foods taste sweet. C. heightening taste sensitivity. 458 Chapter 9: Perceptual distortions Question 4 An individual’s judgement of flavour is influenced by 9B QUESTIONS A. perceptual set, colour intensity, and texture. B. previous experience, texture, and sweetness. C. perceptual set, time of day, and colour intensity. Question 5 Biology, purposeful manipulation of the senses, and perceptual set can all lead to errors in gustatory perception. A. True. B. False. Assessment skills Data analysis The following assessment skills type reflects the study design assessment type: a data analysis of generated primary and/or collated secondary data Use the following information to answer questions 6–9. Bellizzi and Martin (1982) conducted a study in order to compare the effects that branding, specifically name-brands and generic brands, had on taste perception. The researchers set up a booth at a university fair and presented each participant with two identical sized jars of grape jelly. One was labelled with a name brand, and one was labelled with a generic brand. In one trial, both jars contained the same name-brand jelly, and in another trial, both jars contained the same generic brand jelly. The participants’ taste perception of the jellys was measured using a 5-point rating system, starting from ‘this jelly has an excellent taste’ (1) to ‘this jelly has an extremely bad taste’ (5). This means that the lower a jelly was scored, the higher that its taste was rated by participants. The results of the participants’ ratings of what they perceived to be the name-brand and generic jellys are depicted in the graph below. The researchers were interested in the data that demonstrated the participant’s taste perceptions based on the labelling of the jars across both trials. Mean ratings of jelly products Mean rating out of 5 2.5 2.0 1.5 Key 1.0 0.5 Male 0 Female Labelled as name-brand Labelled as generic-brand Brand type The difference in ratings between the name-brand and generic-brand jars were found to be significant. Note: The researchers purposely used an inverse scoring method, so that a higher score means a worse taste rating. Question 6 Which type of jelly was rated as tasting better? A. Name-brand. B. Generic brand. C. This conclusion cannot be made with the information provided. 9B Errors of taste 459  Question 7 A taste rating of 5 would indicate that 9B QUESTIONS A. the jelly has a perfect taste score. B. the participants are biased. C. the jelly is rated poorly. Question 8 The mean rating that females gave the name-brand jelly was 1.7, this means that A. all females who particiapted rated the name-brand jelly as 1.7. B. when all of the female’s ratings of the name-brand jelly were added up, it equated to 1.7. C. to work out the male’s mean rating of the name-brand jelly, 1.7 should be subtracted from the total score of 5. D. some females may have rated the name-brand jelly higher than 1.7 and some females may have rated the name-brand jelly lower than 1.7. Question 9 The type of brand the jelly is labelled as, is not related to what type of influence on flavour judgement? A. Perceptual set. B. Colour intensity. C. Prior experience. D. Beliefs about a brand. Exam-style Remember and understand Question 10 (1 MARK) A defining biological characteristic of a supertaster is A. increased levels of the bitter-chemical ‘PROP’ in their bloodstream. B. a larger sized tongue. C. reduced smoking levels. D. a significantly greater amount of taste buds. Question 11 (1 MARK) How does miraculin affect gustatory perception? A. It binds to the taste buds that detect sweet flavours and activates them in an acidic environment. B. It causes temporary physiological changes to the functioning of taste buds responsible for detecting sour flavours. C. It binds to the taste buds that detect sweet flavours and instantaneously activates them. D. It alters the brain during the process of perception. Question 12 (1 MARK) When judging flavour, what influence does the texture of food have? A. It causes individuals to experience perceptual distortions when it conflicts with past experiences. B. It can change the intensity and enjoyment of flavours. C. It causes individuals to experience perceptual distortions as it can determine how much of a food’s taste is received by gustatory receptors. D. All of the above. Question 13 (2 MARKS) Using an example, explain how colour intensity can influence flavour perception. 460 Chapter 9: Perceptual distortions Apply and analyse 9B QUESTIONS Question 14 (1 MARK) Jona hates eating whole pieces of fruit, but loves blending fruit to make smoothies as he claims that they taste much better. Jona’s preference for smoothies is an example of A. food being more enjoyable when it can be consumed faster. B. a supertaster, as Jona is sensitive to the flavour of fruit. C. a perceptual distortion, as both food items consist of the same things. D. the texture of food influencing the intensity of flavour as liquid foods are more easily received by gustatory receptors. Question 15 (1 MARK) Ahmed had been recommended by a friend to visit a popular Italian restaurant in his town. His friend tirelessly emphasised how amazing the food was and how much he loved it. Ahmed decided to visit the restaurant with his parents, who had never heard of it. Ahmed and his parents decided to share multiple dishes so that they could all experience the food together. When the meal was over, Ahmed could not believe how amazing the food was, whereas his parents were rather unimpressed. What is the most likely possible explanation for the difference in opinion between Ahmed and his parents? A. Ahmed has a lower threshold for taste than his parents. B. Ahmed was influenced by his perceptual set due to being exposed to his friend’s opinions, whereas his parents were not. C. Ahmed lied about the food being good so he did not upset his friend. D. Ahmed and his parents have a different amount of pappilae. Question 16 (3 MARKS) Describe the concept of a perceptual set and explain how it can lead to perceptual distortions in taste, using an example. Question 17 (3 MARKS) Is the experience of supertasters a perceptual distortion? Justify your response. Questions from multiple lessons Question 18 (1 MARK) In the processing of sensory stimuli, during what stage does the difference in taste for supertasters occur? A. Sensation. B. Organisation. C. Interpretation. D. Saliency. Question 19 (1 MARK) An individual’s judgement of flavour being influenced by past experiences is an example of A. a perceptual distortion. B. top-down processing. C. bottom-up processing. D. organisation. Question 20 (2 MARKS) With reference to nature and nurture, compare the difference between supertasters and individuals who are influenced by their perceptual set when tasting food. 9B Errors of taste 461 9C Perceptual distortions STUDY DESIGN DOT POINT distortions of perception of taste and vision in healthy individuals, such as synaesthesia and spatial neglect 9A 9B 9C 2.2.6.1 Distortions of taste and visual perception 2.2.6.1.1 Synaesthesia 2.2.6.1.2 Spatial neglect Throughout this chapter we have learnt about the ways in which our brains can make errors when processing sensory information. So, what does this mean about us and our level of functioning? How do we fix this? The experience of distortions in our perception of the world is normal, expected, and often not harmful. Our brains are not perfect computers and our perceptual experience is individual and dynamic. In this lesson, you will learn about synaesthesia and spatial neglect, which are conditions that demonstrate that otherwise healthy people can experience perceptual distortions. ACTIVITY Distortions of taste and visual perceptions 2.2.6.1 Log into your Edrolo In this lesson, we will explore the ways in which healthy individuals may experience account for activities that distortions within their visual and taste perceptions. Specifically, we will explore the support this lesson. experiences of individuals with synaesthesia and spatial neglect. Theory details Imagine that you had a distorted mirror. Every time you looked at yourself your face was warped and your body didn’t look like your own. You may be inclined to think of this mirror as malfunctioning, broken, and want to replace it. However, not everything that produces distortions has something inherently wrong with it. Our brains, and in turn our perceptual processing systems, are prone to distortions, such as distortions of taste and visual perception. At the beginning of this chapter, we learnt that perceptual distortions are errors in the judgement or interpretation of sensory stimuli. However, it is important to note that these distortions occur in most healthy brains and provide no indication of something being ‘wrong’. In this lesson, we will explore examples of how individuals with otherwise normally functioning brains may experience perceptual distortions, including through the experiences of synaesthesia and spatial neglect. Synaesthesia 2.2.6.1.1 KEY TERMS What if you could see sounds? Or taste images? Imagine that each letter in the alphabet had its own colour. These kinds of perceptual experiences really do occur for some people who Synaesthesia experience a phenomenon called ‘synaesthesia’. Synaesthesia is a perceptual phenomenon a perceptual phenomenon characterised by the experience of unusual perceptions in one sensory system after another characterised by the sensory system has been activated. Importantly, even though synaesthesia involves perceptual experience of unusual perceptions in one sensory distortions, it is not a mental health disorder and can occur in people who have healthy, system after another intact brains. sensory system has been activated 462 Chapter 9: Perceptual distortions Synaesthesia is a phenomenon of perception that occurs when two sensory systems cross over in an abnormal and involuntary manner. More specifically, when one sensory system is activated, another sensory system also involuntarily experiences unusual or unexpected 9C THEORY perceptions. For example, some synaesthetes (people who experience synaesthesia) see a colour when they hear a specific music note (e.g. they see the colour green when they hear the note F#). There are some consistent characteristics of synaesthesia, outlined in table 1. Table 1 Characteristics of synaesthesia Characteristic Description Synaesthesia is automatic and The perceptual experiences elicited in the secondary sense feel very vivid and real. Further, cannot be controlled if an individual sees the colour green when looking at the number 4, the perception is out of the individual’s control and cannot be prevented. Synaesthesia is generally A person who sees the colour green when looking at the number 4 will not see the number 4 experienced as a one-way when looking at the colour green. process Synaesthesia is usually A person who sees the number 4 as green will usually always see it as green and not as consistent another colour. The way that synaesthesia is If one person sees the number 4 as green, this does not mean that a person with the same kind experienced is unique to the of synaesthesia will also see a 4 as green. They might, for example, see 4 as red. individual Synaesthesia is relatively There are a wide range of estimates regarding its prevalence, and some forms are far more common common than others. However, estimates can range from as high as one in 100 people to as low as one in 2000 people (Neckar et al., 2014). As discussed, synaesthesia does not exclusively impact one sense and can occur in a range of different combinations between individuals. Therefore, there are many recognised forms of synaesthesia, the most common, involving visual and gustatory perceptual systems, are outlined in table 2. Table 2 Common forms of synaesthesia Form of synaesthesia Description Grapheme-colour Grapheme-colour synaesthesia occurs when a person sees colours when looking at ordinary symbols, such as numbers and letters (Lunke et al., 2019). For example, an individual may perceive the letter ‘A’ to be blue. Sound-colour Sound-colour synaesthesia occurs when sounds cause the secondary perception of colours. For example, an individual may see the colour red when they hear a car horn. Lexical-gustatory In lexical-gustatory synesthesia, when a person sees a word (a ‘lexeme’), a taste is triggered (Simner et al., 2009). For example, an individual may taste garlic when reading the word ‘train’. We know that our senses work together to make sense of sensory information; for example, flavour perception makes use of both taste and smell areas of the brain as they integrate different information that has come from their sensations of food. However, this is not what occurs in synaesthesia. In synaesthesia, a secondary sensory system, which has not been stimulated by any sensation, experiences and integrates unusual perceptions. An example of this process is depicted in figure 1. ‘A’ smells like a banana Looks like letter ‘A’ Sensation Perception Figure 1 An individual with synaesthesia, when viewing the letter ‘A’, may begin to smell the scent of a banana due to their sense of smell activating involuntarily when their sense of sight detects sensation 9C Perceptual distortions 463  This process can be further broken down into two distinct steps, as follows: 1. A sensory stimulus is detected by one sensory system. 2. During perception, information from another secondary area of the brain is integrated 9C THEORY and combined within the cerebral cortex as though it belongs to the same true sensory experience. This process supports the notion that the brain is in fact in charge of our perception, and for synaesthetes, the brain is responsible for their unique perceptual distortions. In addition to this, the phenomenon of synaesthesia also demonstrates that sensation and perception are two distinct processes, with perception being highly subjective. Many synaesthetes are, at least at first, unaware that they are experiencing unusual perceptions. However, this ultimately demonstrates that two individuals who are perceiving the same stimuli can experience vastly different things. USEFUL TIP The experience of synaesthesia can be thought of as ‘getting our wires crossed’, or accidentally turning on the wrong switch. For example, when we see a word, we want to turn on the ‘switch’ for visual perception; however, a person who experiences synaesthesia might automatically turn on their ‘switch’ for taste perception as well. This is depicted in figure 2. Visual perception Taste perception ON ON Visual sensation OFF OFF Figure 2 Synaesthesia ‘turns on’ the switch for a secondary sensory system’s perception even though it has not experienced any sensations People with synaesthesia are often born with it, however, it can also develop in some people as a result of substance use or brain injury. WANT TO KNOW MORE? The phenomenon of synaesthesia leaves many people wondering why it might occur. Theories behind why synaesthesia occurs are still largely unclear and controversial, however, there are a range of proposed explanations for synaesthesia which are explored in table 3. Table 3 Proposed explanations for synaesthesia Sensitivity to neural Synaesthetes are highly sensitive to the associations that a sensory stimulus triggers. In childhood associations development, unusually strong networks between a sensory stimulus and its associations are formed through learning. For example, lexical-gustatory synaesthetes may have learnt in childhood to associate the word ‘pear’ with the taste of ‘pear’, so much so that the taste perception is now experienced when the word pear is seen (Simner et al., 2009). However, less obvious associations can also be formed, such as tasting spice when reading the word ‘pear’. Structurally unique The brain networks of synaesthetes are structurally unique. The connections between different brains areas of the brain may result in the activation of one area, automatically triggering the activation of another, such as the sense of taste being activated when the sense of sight detects sensory information (Neckar et al., 2014). Synaptic pruning It has been suggested that synaesthetes undergo less synaptic pruning than non-synaesthetes. Synaptic pruning involves the elimination of underused synapses. Therefore synaptic connections between neurons are eliminated during development in order to create room for essential neural connections in the brain, and make brain functioning more efficient. Instead of undergoing this typical developmental process, synaesthetes may maintain synaptic connections that would have otherwise been pruned, leading to connections being activated in an unusual way. 464 Chapter 9: Perceptual distortions Spatial neglect 2.2.6.1.2 While synaesthesia is a perceptual distortion that can be experienced within any of the five senses, there are also perceptual phenomena that are related primarily to one sense. Spatial Spatial neglect 9C THEORY neglect is one of these, which is a perceptual distortion that mainly affects visual perception. an inability to perceive, Spatial neglect refers to an individual’s inability to perceive, report, or orient sensory report, or orient sensory information located within one side of space (Li & Malhotra, 2015). For example, an individual information located within one side of space with spatial neglect will only perceive sensory information from either the left or right side of the environment, as depicted in figure 3. Real sensory information USEFUL TIP Individual without Individual with It can be easy to confuse spatial neglect spatial neglect spatial neglect with the experience of not being able to see out of one eye. If we break down the word, ‘spatial’ can be thought of as our field of vision and ‘neglect’ can be thought Figure 3 Individuals with spatial neglect fail to perceive information in one side of space of as an act of ignoring. Therefore, to understand It is important to understand that individuals who experience spatial neglect do not have the mechanisms behind malfunctioning senses. In fact, most sufferers have otherwise normally functioning vision, with spatial neglect, think the distortion instead occurring during the process of perception. It is an attentional disorder, about it as ignoring one where patients simply ignore one side of their visual field. side of one’s visual field Spatial neglect, unlike synaesthesia, cannot be caused innately and is most often attributed (unintentionally). to a brain lesion resulting from neurodegenerative diseases, trauma, or a hemispheric stroke. The hemisphere of the brain that the lesion occurs in dictates which side of space the individual is unable to attend to, as spatial neglect occurs contralaterally. This means that LESSON LINK if a lesion occurs within the right hemisphere of the brain, the left field of vision will be impacted. While it can occur within either hemisphere, spatial neglect mainly occurs due to In lesson 4A Approaches damage in the brain’s right parietal lobe. Like synaesthesia, the phenomenon of spatial neglect to understanding the is experienced in a consistent way, in that the side of space that cannot be attended to does brain, you learnt about not change. how vision is processed contralaterally and how As we have learnt, often individuals who experience perceptual distortions don’t realise their this information was difference in perception until they are alerted by others, which for some conditions may take utilised by researchers in many years. However, spatial neglect is often very obvious to those surrounding a sufferer due split-brain studies. You to the way in which it can affect behaviour (Sarwar & Emmady, 2022). Some common ways that learnt that contralateral this manifests include that an individual with spatial neglect: visual processing means may consistently gaze in a way that ‘drifts’ toward the side of the brain in which the lesion that stimuli in the left visual field is processed occurred. For example, spatial neglect of the left visual field that has occurred due to a in the right hemisphere of lesion in the right side of the brain may cause an individual to be constantly looking to the the brain and vice versa. right, even when considered inappropriate, such as during conversation. This is also true for the may begin to display difficulties in dressing or grooming themselves as they unintentionally experience of individuals fail to attend to one side of their body. For example, an individual may only shave one side with spatial neglect, hence of their face or put a shoe on only one of their feet. why the incurred lesion will fail to attend to stimuli on one side of their visual field in obvious ways, such as only and subsequent visual eating food off of one side of a plate. deficit is contralateral. If food is presented in this way, the individual will If you were to then move the remaining food only attend to the information on one side of to the side of space which they can attend space and not realise that there is more food in to, they would be able to eat it front of them Figure 4 An example of how spatial neglect may manifest during meal-times Although spatial neglect is commonly recognised by those around the individual with spatial neglect, there are specific tests used by clinicians in order to diagnose the condition (Molenberghs & Sale, 2011). Some of these tests are outlined in table 4. 9C Perceptual distortions 465  Table 4 Examples of clinical tests used to diagnose spatial neglect Test Details 9C THEORY Line bisection task Individuals are provided with a line and are asked to mark where they perceive the middle of the line to be. Individuals with normal perception will be relatively accurate in their marking, whereas an individual with spatial neglect will likely demonstrate a clear bias to one side. Normal perception Spatial neglect Figure 5 Example of differing results in the line bisection task Target cancellation Individuals are presented with a picture of different shapes, with the left task and right side containing an equal number of each shape. They will be asked to ‘cross out’ all of a specific type of shape, such as all of the circles. If an individual only crosses that shape on one side of the image, it is likely they are suffering from spatial neglect. Cross out all of the circles Normal perception Spatial neglect Figure 6 Example of differing results in the target cancellation task Copying tasks Individuals are provided with different images and are asked to draw a copy of the images provided. Individuals who suffer from spatial neglect tend to disregard one side of the images when reproducing them. Original Normal perception Spatial neglect Figure 7 Example of differing results in a copying task WANT TO KNOW MORE? In 1995, Ro and Rafal conducted a study in which they tested whether the Müller-Lyer illusion would work on a patient with spatial neglect. Earlier in this chapter, you learnt about visual illusions including the Müller-Lyer illusion. In order for the Müller-Lyer illusion to work, we know that both arrowheads need to be perceived. It was hypothesised that an individual with spatial neglect would Müller-Lyer illusion not be affected by the Müller-Lyer illusion due to an inability to perceive both arrowheads. A However, when a patient with spatial neglect was asked to view the Müller-Lyer illusion, it was found that the arrowheads affected B her perception of the illusion (similarly to an individual that did not have spatial neglect), even though she was unable to perceive the full illusion. According to the researchers, this provides evidence that spatial neglect is rooted in errors of perceptual processing rather than visual deficits. (Ro & Rafal, 1996) 466 Chapter 9: Perceptual distortions  Theory summary 9C QUESTIONS In this lesson you learnt about different forms of perceptual distortions and how these distortions can affect otherwise healthy individuals. You learnt about the specific examples of synaesthesia and spatial neglect and the impact these can have on individuals’ perceptions. Figure 8 provides a further summary of the lesson. Combination of Synaesthesia multiple senses Perceptual distortions Healthy individuals Spatial neglect Primarily sight Figure 8 Summary of perceptual distortions in healthy individuals 9C Questions Theory review Question 1 Perceptual distortions indicate that there is something wrong with an individual’s brain. A. True. B. False. Question 2 Which of the following is not an example of a perceptual distortion? A. A damaged pupil leading to blindness in one eye. B. Synaesthesia. C. Spatial neglect. Question 3 Synaesthesia occurs when two different sensory systems detect sensation and integrate this information. A. True. B. False. Question 4 Individuals with spatial neglect fail to _ sensory information located within one side of space. Which of the following best fills in the blank? A. perceive B. detect Question 5 Spatial neglect is usually a result of A. an intellectual deficit. B. genetics. C. a brain lesion.