Sensation and Perception PDF

Introduction: As human beings, we perceive our world through our senses. This means that we are constantly performing a complex set of processes by which we take in sensory information, convert it into a form usable by the brain, and have the brain send signals to a relevant part of the bod...

Introduction: As human beings, we perceive our world through our senses. This means that we are constantly performing a complex set of processes by which we take in sensory information, convert it into a form usable by the brain, and have the brain send signals to a relevant part of the body in order to tell it how to respond - all in a matter of milliseconds. In this unit, we will highlight the vision and hearing sensory systems and gain a deeper understanding of how we perceive the world around us. As you proceed in this lesson, take note of the concept that sensation is what comes into our body through our sensory organs and perception is what our brain does with that information. Think about examples of how we might be tricked in the process. SENSATION AND PERCEPTION Sensation is the process by which our senses gather information and send it to the brain. Sensations can be defined as the passive process of bringing information from the outside world into the body and to the brain. The process is passive in the sense that we do not have to be consciously engaging in a "sensing" process. Perception can be defined as the active process of selecting, organizing, and interpreting the information brought to the brain by the senses. Sensation occurs: a) sensory organs absorb energy from a physical stimulus in the environment. b) sensory receptors convert this energy into neural impulses and send them to the brain. Sensory receptors are specialized sensitive cells that respond and detects stimulus. Examples of sensory stimulus would be touch, pressure, pain, light, sound, position in space, and vibration. To elaborate the idea of sensation and perception, let’s try this example… On a Saturday morning, imagine your phone is ringing. You take it out and see that it's an unfamiliar or unknown number. You're wary of telemarketers promoting their products, but you're also procrastinating doing homework, so you pick up the call anyway. You hear a voice says: 'hello'; you perceive that the voice is your friend John. He explains that he's calling from a friend's phone because PSYC 1013- Introduction to Psychology | 1 his phone is left at home, and you make plans to see a movie. Even though you didn't recognize John’s contact number, you heard his voice and recognized it. In this scenario, hearing the voice of John was sensation while recognizing John’s voice was perception. Sensation is passively receiving information through sensory inputs and on the other hand, perception is interpreting this information. SENSATION There are three types of sensory receptors: 1. Exteroceptors- Receive sensory information from outside of the body. For examples: Visual, auditory, tactile, gustatory, and olfactory Image online source: https://courses.lumenlearning.com/boundless-ap/chapter/sensation/ 2. Interoceptors- Receive sensory information from inside the body. Detect internal body sensation. Examples: from the viscera (hollow organs), stomach pain, pinched spinal nerves, and deep skin inflammation. It means to say that interoceptors are sensory receptor which receives stimuli from within the body, especially from the gut and other internal organs. 3. Proprioceptors- In here, the unconscious information received where in the detection of body position in space and movement happens. It means to say that proprioceptors are sensory receptor which receives stimuli from within the body, especially one that responds to position and movement. It is located in the muscles, tendons, and joints inside the body and semicircular canals of the inner ear. Here is an illustration of its function: Image online source: https://www.yourtherapysource.com/blog1/2019/02/25/what-is-proprioception-2/ PSYC 1013- Introduction to Psychology | 2  Other than that we also have: Cutaneous receptors are found at the distal ends of the primary sensory axon; they act as dendrites, in which threshold stimuli lead to the firing of an action potential at the initial segment of the primary sensory axon. It responds to pain, temperature, pressure, vibration, and discriminative touch. Location: Superficial or deep layers of the skin, can be either exteroceptors (superficial) or interoceptors (deep). Here is an illustration: Image online source: http://people.eku.edu/ritchisong/378_senses.htm SENSORY ADAPTATION Sensory adaptation refers to a reduction in sensitivity to a stimulus after constant exposure to it. While sensory adaptation reduces our awareness of a constant stimulus, it helps free up our attention and resources to attend to other stimuli in the environment around us. All five of our senses are constantly adjusting to what's around us, as well as to us individually and what we are experiencing, such as aging or disease. For example, imagine yourself walking into a house where fried fish and head cheese were prepared for dinner. You would probably pass out at the door, yet people who had been in the house for some time wouldn't be aware of the food odors. Similarly, smokers often don't get how much nonsmokers are bothered by the smell of tobacco smoke. Why? Because sensory receptors respond less to unchanging stimuli, a process called sensory adaptation. Image online source: https://www.discovermagazine.com/mind/the-sense-of-smell-in-humans-is-more-powerful-than-we-think PSYC 1013- Introduction to Psychology | 3  SIGHT/VISION Image online source: https://www.bionicsightllc.com/ The eye is the organ of vision. It has a complex structure consisting of a transparent lens that focuses light on the retina. The retina is covered with two basic types of light-sensitive cells- rods and cones. The cone cells or cones, are photoreceptor cells in the retinas of vertebrate eyes including the human eye. They respond differently to light of different wavelengths, and are thus responsible for color vision, and function best in relatively bright light, as opposed to rod cells, which work better in dim light. They are sensitive to color and are located in the part of the retina called the fovea, where the light is focused by the lens The rod cells are type of photoreceptor cells in the eye found in the concentrated at the outer edges of the retina. They are responsible for vision in low light conditions. They are also not sensitive to color, but have greater sensitivity to light than the cone cells. These cells are located around the fovea and are responsible for peripheral vision and night vision. The eye is connected to the brain through the optic nerve. Experiments have shown that the back of the brain maps the visual input from the eyes. The visual system works on sensing and perceiving light waves. Light waves vary in their length and amplitude: a.) Wave length (also referred to as frequency, since the longer a wave, the less often/quickly it occurs) - affects color perception b.) Wave amplitude (this is the size/height of the wave) - affects brightness perception. Image online source: https://www.abpischools.org.uk/topic/nervoussystem/8 PSYC 1013- Introduction to Psychology | 4  Image online source: https://www.thoughtco.com/how-the-human-eye-works-4155646 A. Cornea - the round, transparent area that allows light to pass into the eye. B. Lens - the transparent structure that focuses light onto the retina. C. Retina - inner membrane of the eye that receives information about light using rods and cones. The functioning of the retina is similar to the spinal cord - both act as a highway for information to travel on. D. Pupil - opening at the center of the iris which controls the amount of light entering the eye. Dilates and Constricts. E. Rods & Cones - many more rods (approximately 120 million) than cones (approx 6.4 million). Cones - visual receptor cells that are important in daylight vision and color vision. The cones work well in daylight, but not in dim lighting. This is why it is more difficult to see colors in low light. Rods – visual receptor cells that are important in nighttime vision. Can only detect shades of gray. Fovea- which is a tiny spot in the center, area of the clearest vision. FACTS ABOUT SENSE OF SIGHT “We see when visible light is processed by the eye’s components and translated into neural impulses that are processed by the brain.” Image online source: https://www.management-issues.com/opinion/6853/seeing-the-world-through-the-eyes-of-your-employees/ People blink 15 times per minute on average. Everything would appear two-dimensional to a person with only one eye. Human eyes are made of over two million working parts. Newborn babies see everything upside down until the brain learns to process everything right side up. Dolphins sleep with one eye open. Creepy? Or super smart? The eyes are made up of over 2 million moving parts and the eye muscles are the most active muscle in the human body. Most people blink every 2-10 seconds and when we do blink we shut our eyes for around 0.3 seconds. There are 3 types of color-blindness: total color blindness, an inability to see one colour and an impairment, not loss, of normal color vision. Color blindness is also more common in males. At birth your eyes are about 70% of their adult size, but your nose and ears never stop growing. The older we are the less tears we produce. Your eyes begin to develop after 2 weeks of conception PSYC 1013- Introduction to Psychology | 5 Visual defects - impairment of the sense of sight. vision defect, visual disorder, visual impairment. amaurosis - partial or total loss of sight without pathology of the eye; caused by disease of optic nerve or retina or brain. Nearsightedness- (myopia) is a common vision condition in which you can see objects near to you clearly, but objects farther away are blurry. It occurs when the shape of your eye causes light rays to bend (refract) incorrectly, focusing images in front of your retina instead of on your retina. It means to say that this is the inability to see far objects. Farsightedness- (hyperopia) is a common vision condition in which you can see distant objects clearly, but objects nearby may be blurry. The degree of your farsightedness influences your focusing ability. It means to say that this is the inability to see near objects clearly. Presbyopia or old sightedness- physiological insufficiency of accommodation associated with the aging of the eye that results in progressively worsening ability to focus clearly on close objects. Symptoms include difficulty reading small print, having to hold reading material farther away, headaches, and eyestrain. It is a condition where in a person is unable to focus clearly on near objects. AUDITION/HEARING Image online source: https://slideplayer.com/slide/13367103/ The ear is the organ of hearing. It is the transduction of sound waves into a neural signal that is made possible by the structures of the ear. Soundwaves are vibrations in the air that are processed by the auditory system. Sound is a mechanical wave that results from the back and forth vibration of the particles of the medium through which the sound wave is moving. Sound wave is measured by: first, amplitude or the decibel. Secondly is the pitch by means of high/lowness of a sound determined by frequency measured by HERTZ where it is used commonly to measure wave frequencies, such as sound waves, light waves, and radio waves. As to fast or high; slow or low. Lastly the timbre or the complexity of sound/ PSYC 1013- Introduction to Psychology | 6  THE HUMAN EAR Image online source: https://www.webmd.com/cold-and-flu/ear-infection/picture-of-the-ear#1 Knowing the basic structure of the ear is essential to understanding how hearing works. Three basic parts of the ear: Internal/inner ear - Liquid-filled cavity hollowed out of the temporal bone that transforms sound vibrations into nerve influxes to be interpreted by the brain. Middle ear - Air-filled cavity hollowed out of the temporal bone; it receives sounds from the external ear, amplifies them through the auricles and transmits them to the internal ear. External/outer ear - Visible portion of the ear enabling sounds to be collected and directed to the middle ear through the acoustic meatus Hearing loss can be categorized by which part of the auditory system is damaged. There are three basic types of hearing loss: Conductive hearing loss is typically the result of obstructions in the outer or middle ear, perhaps due to fluid, tumors, earwax or even ear formation. This obstruction prevents sound from getting to the inner ear. Conductive hearing loss can often be treated surgically or with medicine. It occurs when sound is not conducted efficiently through the outer ear canal to the eardrum and the tiny bones (ossicles) of the middle ear. Conductive hearing loss usually involves a reduction in sound level or the ability to hear faint sounds. Sensorineural hearing loss (SNHL) is the most common type of hearing loss. It occurs when the inner ear nerves and hair cells are damaged, perhaps due to age, noise damage or something else. Sensorineural hearing loss impacts the pathways from your inner ear to your brain. Most times, sensorineural hearing loss cannot be corrected medically or surgically, but can be treated and helped with the use of hearing aids. It occurs when there is damage to the inner ear (cochlea), or to the nerve pathways from the inner ear to the brain. Most of the time, SNHL cannot be medically or surgically corrected. This is the most common type of permanent hearing loss. Mixed hearing loss is just a combination of sensorineural and conductive hearing loss. As with any medical condition, it’s best to know what you “have” before deciding what to do about it. A consultation with a hearing professional can help determine the type, cause and degree of your hearing loss. PSYC 1013- Introduction to Psychology | 7  FACTS ABOUT HEARING Image online source: https://www.hearingaids.com/hearing-loss-tinnitus/10-facts-about-hearing/ The eardrum moves less than a billionth of an inch in response to sound. In World War I parrots were kept on the Eiffel Tower in Paris because of their remarkable sense of hearing. When the parrots heard enemy aircraft, they warned every one of the approaching danger long before any human ear would hear it. Sometimes if you have damage to your ears, your perception of taste may be off because the nerves (called the Chorda Tympani) run through the ear and connect the taste buds on the front of your tongue to your brain. Sometimes people who have had ear surgery experience a change in their sense of taste. It does not mean that hearing loss directly correlates to an inability to taste. Ear infections are more common in children because of their developing immune systems and differences between their Eustachian tubes (at more of a horizontal angle) than those of adults. Earwax has been useful to anthropologists for studying mankind’s early migratory patterns. Sitting close to loudspeakers at concerts (which can reach about 120 decibels) can damage your hearing in just 7.5 minutes! At the age of 65, one in three adults has some hearing loss; however, a majority of the people who suffer from hearing loss are under age 65. Hearing loss is the third most common health problem in the United States. Excessive noise exposure is the #1 cause of hearing loss. The bones in the middle ear (malleus, incus, and stapes) are the body’s smallest bones. All three can fit together on the surface area of a penny. 37% of children with hearing loss fail at least one grade. The outer ear never stops growing throughout one’s lifetime. The middle ear is about the size of an M&M. The inner ear is no larger than a pencil eraser in circumference. Not all living creatures hear with ears. Snakes use jawbones, fish respond to pressure changes, and male mosquitoes use antennae. PSYC 1013- Introduction to Psychology | 8  SMELL/ OLFACTION Image online source: https://www.medicaldaily.com/our-perception-odor-can-change-depending-its-description-do-you- smell-fresh-flowers-or-cheap-perfume The olfactory system, or sense of smell, is the sensory system used for smelling (olfaction). Olfaction is one of the special senses, that have directly associated specific organs. Most mammals and reptiles have a main olfactory system and an accessory olfactory system. It is a chemical sense that occurs when chemicals in the air reach receptor cells in the nasal cavities. FACTS ABOUT SENSE OF SMELL Image online source: https://theconversation.com/can-you-pass-this-smell-test-82681 1. People can detect at least one trillion distinct scents. 2. Women have a better sense of smell than men. 3. Humans have 7 primary odours that help them determine objects and if your nose is at its best you can tell the difference between a staggering 4,000 – 10,000 smells. 4. Humans can tell the difference between 10,000 different odors. But often it is difficult to name the odors. 5. Each human has their own distinct odor. 6. Scent cells are renewed every 30 to 60 days. 7. You can smell fear and disgust. 8. Age-related loss of smell is linked to race. 9. Loss of smell may signal future illnesses. 10. As you get older your smell gets worse, so children are more likely to have a better sense of smell 11. Everyone has a unique smell except for identical twin. 12. Taste is about 75% smell. 13. Dogs have nearly 44 times more scent cells than humans. 14. Dogs can be 10,000 times more sensitive to odors than humans. Yet, a individual human olfactory receptor is no less sensitive than a dog's. 15. Decline in smell may predict death within five years. PSYC 1013- Introduction to Psychology | 9  Image online source: https://slideplayer.com/slide/5947979/ Olfactory Receptors ü Smell (olfactory) receptors and taste receptors are chemoreceptors, which means that chemicals dissolved in liquids stimulate them. Smell and taste function closely together and aid in food selection because we usually smell food at the same time we taste it. This figure shows the lateral wall of the nasal cavity (cut in sagittal section) showing the olfactory recess and olfactory bulb. People who have a smell disorders either have a decrease in their ability to smell or changes in the way they perceive odors. Here are some of the smell disorders: ü Hyposmia or microsmia is a reduced ability to detect odors. It is a reduced ability to smell and to detect odors. Some of the causes of olfaction problems are allergies, nasal polyps, viral infections and head trauma. ü Anosmia or smell blindness is the inability to detect odors. In rare cases, someone may be born without a sense of smell, a condition called congenital anosmia. It is the loss of the ability to detect one or more smells. Anosmia may be temporary or permanent. It differs from hyposmia, which is a decreased sensitivity to some or all smells. ü Parosmia is a change in the normal perception of odors, such as when the smell of something familiar is distorted, or when something that normally smells pleasant now smells foul. Parosmia is a term used to describe health conditions that distort your sense of smell. If you have parosmia, you may experience a loss of scent intensity, meaning you can't detect the full range of the scents around you. ü Phantosmia is the medical word used by doctors when a person smells something that is not actually there. It is also called a phantom smell or an olfactory hallucination. The smells vary from person to person but are usually unpleasant, such as burnt toast, metallic, or chemical smells. GUSTATION/TASTE Image online source: https://www.scarymommy.com/4-popular-diets-i-killed-with-delicious-food/ PSYC 1013- Introduction to Psychology | 10 Taste, or gustation, is a sense that develops through the interaction of dissolved molecules with taste buds. Currently five sub-modalities (tastes) are recognized, including sweet, salty, bitter, sour, and umami (savory taste or the taste of protein). Taste, or gustation, happens when chemicals stimulate receptors in the tongue and throat, on the inside of the cheeks, and on the roof of the mouth. These receptors are inside taste buds, which in turn are inside little bumps on the skin called papillae. Taste receptors have a short life span and are replaced about every ten days. Recently, researchers have suggested the presence of a fifth taste called umami. The spice monosodium glutamate (MSG) has an umami taste, as do many protein-rich foods. Sweet, sour, salty, bitter and savory tastes can actually be sensed by all parts of the tongue. Only the sides of the tongue are more sensitive than the middle overall. This is true of all tastes – with one exception: the back of our tongue is very sensitive to bitter tastes. This is apparently to protect us so that we can spit out poisonous or spoiled foods or substances before they enter the throat and are swallowed. Taste disorders ü Hypogeusia - is a reduced ability to taste things (to taste sweet, sour, bitter, or salty substances). The complete lack of taste is referred to as ageusia. Causes of hypogeusia include the chemotherapy drug bleomycin, an antitumor antibiotic as well as zinc deficiency. PSYC 1013- Introduction to Psychology | 11 ü Dysgeusia - a persistent taste, usually unpleasant. It is also known as parageusia which is a distortion of the sense of taste. It is also often associated with ageusia, which is the complete lack of taste, and hypogeusia, which is a decrease in taste sensitivity. The sensation of something as “hot” or “spicy” is quite often described as a taste. Technically, this is just a pain signal sent by the nerves that transmit touch and temperature sensations. The substance “capsaicin” in foods seasoned with chili causes a sensation of pain and heat – and this does not happen through the sensory cells specialized for taste. FACTS ABOUT TASTE Image online source: https://www.brainfacts.org/thinking-sensing-and-behaving/taste/2018/do-different-parts-of-the-tongue-taste- different-things-010319 1. Everyone has a different number of taste BUDS and We have over 10.000 taste buds in our mouth that get replaced every 2 weeks 2. You can’t taste well the food if you can’t smell. 3. Some of your taste preferences are genetic. 4. Sugar cravings have a biological basis. 5. In general girls have more taste buds than boys. 6. Taste buds are more sensitive after a night’s sleep, but caffeine, spicy food, smoking and alcohol dulls the senses and it generally takes 24 hours for them to re-cleanse. 7. Eating sweet foods helps form a memory of a meal. 8. Cats have a weak sense of taste. They have only 473 taste buds, humans have 10,000. 9. The role of olfactory senses is clearly stated in physiology of taste. Onion and Strawberry taste the same way if the eyes and nose are tightly closed TACTILE/TOUCH Image online source: https://www.spectrumnews.org/features/deep-dive/social-touch-shapes-autism-traits/ PSYC 1013- Introduction to Psychology | 12 Our skin acts as the protective barrier between our internal body systems and the outside world. It’s not only the body’s largest sensory organ, but it’s also the largest organ–period. The skins “sense of touch” is what gives our brains a wealth of information about the natural environment, including temperature, humidity, and air pressure. Most importantly, this sense of touch lets us feel physical pain–a necessity for avoiding injury, disease, and danger. It is truly amazing how much information we receive about the world through our sense of touch, and although we still don’t know all the ins and outs of how the skin perceives touch, what we do know is interesting. The sense of touch is really a collection of several senses, encompassing pressure, pain, cold, and warmth. The senses of itch and tickle are related to pressure, and burn injuries are related to pain. Touch receptors are stimulated by mechanical, chemical, and thermal energy. Here is a photo that illustrate the Human Skin: Image online source: https://www.stanfordchildrens.org/en/topic/default?id=anatomy-of-the-skin-85-P01336 Here are the receptors that involves in the sense of touch: ü Hairbulbs- the bulbous expansion at the base of a hair from which the hair shaft develops. It is responsible of why we feel different “Pressures” ü Free nerve endings- is an unspecialized, afferent nerve fiber sending its signal to a sensory neuron. Afferent in this case means bringing information from the body's periphery toward the brain. It is responsible of why we feel “Pain” ü Ruffini cylinders- A cutaneous nerve ending suspected as the mediator of warmth. It is responsible of why we feel “warmth” ü Krause end bulbs- this is a erve terminals in skin, mouth, and other parts, consisting of a laminated capsule of connective tissue enclosing the terminal, branched, convoluted ending of an afferent nerve fiber; generally believed to be sensitive to cold. This is why we experience and feel “cold’. FACTS ABOUT SENSE OF TOUCH Image online source: https://www.plt.org/family-activity/get-in-touch-with-trees/ 1. Our brain pays wildly disproportionate attention to touch on different parts of your body 2. The skin is the largest organ in the body and detects touch via receptors for pain, pressure, movement, cold and heat. PSYC 1013- Introduction to Psychology | 13  3. Our sense of touch gets worse as you ageWe have more pain nerve endings than any other type and we have over 100 touch receptors in each fingertip and sex organs 4. Touch is the first sense to develop in humans, and may be the last to fade. 5. The least sensitive part of our body is the middle back and the most sensitive parts are lips, neck, face, hands, tongue and feet. 6. A touch of any kind can reduce the heart rate and lower blood pressure. 7. Touch is mysteriously crucial for a baby's development 8. Touch shapes first impressions of people in weird ways PERCEPTION What is Perception? Perception is the ability to capture, process, and actively make sense of the information that our senses receive. It is the cognitive process that makes it possible to interpret our surroundings with the stimuli that we receive throughout sensory organs. This important cognitive ability is essential to our daily lives because it makes it possible to understand our surroundings. Perception includes the five senses; touch, sight, sound, smell, and taste. It also includes what is known as proprioception, a set of senses involving the ability to detect changes in body positions and movements. It also involves the cognitive processes required to process information, such as recognizing the face of a friend or detecting a familiar scent. Image online source: https://courses.lumenlearning.com/wmopen-psychology/chapter/outcome-sensation-and-perception/ Based on the meaning of perception, it means that there are five types of perception based on our senses: 1. Visual or visual perception: This refers to the ability to see and interpret light information within the visible spectrum that arrives to our eyes. The area of the brain responsible for visual perception is the occipital lobe. PSYC 1013- Introduction to Psychology | 14  2. Hearing or auditory perception: This refers to the ability to receive and interpret information that arrives to our ears by audible frequency waves through the air or another mean (sound). The area of the brain in charge of the basic stage of auditory perception is the temporal lobe. Touch, touch perception, somatosensory or haptic perception: The capacity to interpret information of pressure and vibration received on the surface of our skin. The parietal lobe is the area of the brain responsible for the basic stages in haptic perception. Haptic refers to the communication via sense of touch. 3. Smell or olfactory perception: The ability to interpret information of chemical substances dissolved in the air (smell). 4. Taste or taste perception: The ability to interpret information from chemical substances dissolved in saliva (taste). Two Functions of Perception: Localization and Recognition LOCALIZATION: In order to localize objects, it is necessary to separate them first and then organize them into groups. One way for separation of objects will be figure and ground wherein stimulus with two or more distinct regions, usually see part as figure (contains objects of interest) and rest as ground (or background) Image online source: https://www.slideshare.net/AHS_student/chapter5perceptiondranna Some illusions cause you to perceive what is not there and others will lead you to perceive what cannot be and it is called Perceptual Illusions. Here are some of the Cues in perception: PSYC 1013- Introduction to Psychology | 15 RECOGNITION: Recognizing object requires that the features of an object are correctly bound together The binding problem: pre-attentive & attentive processes – Feature integration theory – information about primitive features of an object acquired via pre-attentive processes, and then integrated in subsequent attentive processing stage. When you read these words, you probably have no difficulty differentiating the A from the H. Look more closely at each of these two letters. PSYC 1013- Introduction to Psychology | 16 Determining what an object: Shape plays critical role in determining what object is. One of them is Visual processing which refers to early stages use information on the retina to create description, later stages use comparison with visual memory to select best match. THE CONSTRUCTIVIST Constructivist theories are all based on the idea that we do not perceive the world directly, that we process any image we see before it is consciously recognized. (There are many different types of constructivist theory, perhaps the best known is Gestalt theory. This has quite a few, far reaching, implications. For instance, one consequence of the constructivist approach is that a child must learn some base amount of knowledge before it can ‘see’ (as we understand the term ‘see’). To illustrate their point, the constructivists show how the mind uses contextual information and world knowledge to affect what we see. By using optical illusions, we are challenged to question if what our eye detects is really what we “see.” A Theory – Contextual Information 1 2 13 1 4 What do you see? Is the middle symbol a “B” or a “13”? The context in which we see C a symbol has a huge influence over how we “see” it. What about this two words? The symbol in the middle of each word is clearly identical, yet we are able to “see” it differently in each context. We can read this as “THE CAT”, because our brain was able to use information about the context in which a symbol appears. It can use the contextual information to disambiguate the symbol, so that we “see” complete and meaningful words. Application - Contextual information Contextual perception obviously has applications in interface design. Interfaces aim to go a step further providing improved orientation on information spaces and leading to more explorative interaction strategies as to this ‘check box’ illustration. For instance, an icon design which means one thing in one part of the interface, might mean something completely different in another place. A good example of this is the check box. It denotes agree or yes as context by means of check box symbol. One group of symbols which have different meanings are arrows. For instance, the back arrow can mean “scroll left” or “Undo” or “Go back to previous Web page” depending on context, as well as the “right arrow” depicts next page depending on the context. This icons or symbols has its own meaning depending on how you use it as a PSYC 1013- Introduction to Psychology | 17 context. Actions tend to be more ambiguous than nouns as nouns refer to concrete static objects whilst actions describe transformations to nouns which happen over time, this could be solved by providing animated icons. Why context important when designing an interface? In a bigger picture, it is imply because context gives meaning to a symbol. Without context, symbols such as the box with a cross in it can be ambiguous. Context can remove that ambiguity. For example, context to symbols are very important, because this will give us good understanding in our daily life situation. A better example of this is when we are driving, there are a lot of symbols by its context that we should learn for a safe driving. Theory - World Knowledge From childhood, humans develop a huge knowledge about objects and how to recognize them. Our perceptual systems exploit this knowledge, allowing us to recognize objects when parts of that object are hidden. In figure below, we can readily identify the wine glass, even though roughly half the original information is incomplete. The final glass is much harder to identify. Not only is much more information missing, but crucial details (such as the contour of the glass) is not present. Using world knowledge to recognize partial shapes A lot of research has been conducted in to the types of information, our perceptual systems need to identify objects. Edge information and contour information is vital to other information, in particular color, is largely redundant. (Even an object which is heavily reliant on color to identify it, such as a banana, can be as quickly recognized in black and white). PSYC 1013- Introduction to Psychology | 18  Gestalt psychology The term gestalt refers to something which has a well-structured form; a form which is often more than the sum of its parts. For instance, four lines arranged in a square form something which we primarily recognize as ‘square’ - not as a collection of four lines arranged in some fashion. Gestalt theory would argue that our perception of the lines is influenced by the knowledge we have about geometric shapes (in this case the square) which causes us to perceive a square and not individual lines. The constructivism described by Gestalt theory, therefore, is the way our mind’s knowledge of different types of form affect our perception. The relationship between the lines in the Muller-Lyer illusion (below) serves as a good example of how our brain constructs something more from the lines than is actually found in the diagram. In this instance, our brain constructs views from the two groups of three lines such that the top horizontal line looks longer than the horizontal line beneath it. In actual fact, there are both the same length. Theory: Figure and Ground One key “form” in the Gestalt theory is the idea of “Figure and Ground.” Organize perceptions by distinguishing between a figure and a background. Look at the figure below. What do you see? Do you see a complete triangle with a circle placed on top of it? Or, do you see a triangle with a circular hole through which you can see the square beneath? In other words, is the circle part of the ‘figure’ or is it part of the ‘ground’? PSYC 1013- Introduction to Psychology | 19 Presenting the distinction between figure and ground is essential if we are to produce pictures and icons which are unambiguous. Consider the following symbols which could be used to represent “exit” Another example is the image below, there are two image can be perceived. The first image can be perceived as two person facing each other. The other one is the cup. This now applies the organization of perceptions by distinguishing between a figure and a background. Too much foreground Another application of figure and ground distinction is increasing the amount of information conveyed without increasing the amount of “ink” used to represent that information. Often, computer graphics can become cluttered and hard to read because the designer is trying to convey a lot of information in a small space. To illustrate the point, consider the graph below. Here the information being presented (as represented by the height of the bars) is drawn in the same color as the contextual information (the lines of the graph). The graph on the right, however, exploits figure and ground to show the information in one color but keep the context information as part of the ground. PSYC 1013- Introduction to Psychology | 20  Theory: Perceptual Organization and grouping laws One of the main contributions of Gestalt theory is in the principles by which objects group themselves in visual perception. There are five different types of grouping: Proximity: These are the elements tend to be grouped together according to their nearness. In the figure below, the dots could be organized in rows or columns. Due to the proximity of dots in the figure below, the dots arrange themselves in columns. Conversely, the dots in the figure below appear in rows. Proximity need not only apply to organized items, then tendency to group by proximity can be seen in random allocations such as in the figure below: PSYC 1013- Introduction to Psychology | 21  Similarity: Objects of similar shape or color will be perceived to be grouped together, as in figure below. Closure: Items are grouped together if they tend to complete a figure. Rather than appearing as three separate lines, the application of closure to perception means that we see a circle and hexagon in this figure below: Continuity: Based on smooth continuity which is preferred to abrupt changes of direction. By using continuity in perception, we tend to see two distinct trails of dots in the following figure. PSYC 1013- Introduction to Psychology | 22  Symmetry: Prefer to perceive objects as mirror images. Areas that are surrounded by symmetrical lines tend to be recognized as shapes, rather than the lines being perceived as shapes in their own right. (see below) Grouping too closely Grouping objects too closely together can play tricks on your perceptual system, causing an illusion called moire movement. Stare at the following image and you should experience the effect. Moire effects arrive from the perception of movement, a shimmering, in lines that are grouped too closely together. Essentially it tells us that we cannot trust our visual perception – patently the page is not moving but yet we see movement. PSYC 1013- Introduction to Psychology | 23