General Psychology An Introduction Chapter 4 Sensation & Perception

Chapter Sensation Perception Sensation and Perception The topics of sensation and perception are among the oldest and most important in all of psychology . People are equipped with senses such as sight , hearing and taste that help us to take in the world around us . Amazingly , our senses have the ability to convert information into electrical information that can be processed by the brain . The way we interpret this our is what leads to our experiences of the world . In this module , you will learn about the biological processes of sensation and how these can be combined to create perceptions . Learning Objectives Differentiate the processes of sensation and perception . Explain the basic principles of sensation and perception . Describe the function of each of our senses . Outline the anatomy ofthe sense organs and their projections to the nervous system . Apply knowledge of sensation and perception to real world examples . Explain the consequences of multimodal perception . Introduction Once I was hiking at Cape Lookout State Park in , Oregon . After passing through a vibrantly colored , pleasantly scented , temperate rainforest , I arrived at a

Sensation and Perception 80 the Pacific Ocean . I grabbed the cold metal railing near the edge and looked out at the sea . Below me , I could see a pod lions swimming in the deep blue water . All around me I could smell the salt from the sea and the scent of wet , fallen leaves . This description of a single memory highlights the way a person senses are so important to our experience of the world around us . Before discussing each of our extraordinary senses individually , it is necessary to cover some basic concepts that to an of It is probably best to start with one very important distinction that can often be confusing the difference between sensation and perception . The physical process during which our sensory involved with hearing and taste , for to external stimuli is called sensation . Sensation happens when you eat noodles or feel the wind on your face or hear a car horn honking in the distance . During sensation , our sense organs are engaging in transduction , the conversion of one form of energy into another . Physical energy such as light or a sound wave is converted into a form of energy the brain can understand electrical stimulation . After our brain receives the electrical signals , we make sense of all this stimulation and begin to appreciate the complex world around us . This psychological sense of the called perception . It is during this process that you are able to identify a gas leak in your home or a song that reminds you of a specific afternoon spent with friends . Regardless we are talking about sight or any ofthe individual senses , there are a number of basic principles that influence the way our sense organs work . The first of these influences is our ability to detect an external stimulus . Each sense eyes or tongue , for a minimal amount of stimulation needed in order to detect a stimulus . This absolute threshold explains why you do smell the perfume someone is wearing in a classroom unless they are somewhat close to you . The way we measure absolute thresholds is by using a method called signal detection . This process involves presenting stimuli to a research participant in order to determine the level at which he or she can reliably detect stimulation in a given sense . During one type of hearing test , for example , a person listens to increasingly louder tones ( starting

Sensation and Perception 81 from silence ) in an effort to determine the threshold at which he or she begins to hear ( see Additional Resources for a video demonstration of a ringtone that can only be heard by young people ) Correctly indicating that a sound was heard is called a hit failing to do so is called a miss . Additionally , indicating that a sound was heard when one played is called a false alarm , and correctly identifying when a sound was played is a correct rejection . Through these and other studies , we have been able to gain an understanding ofjust how remarkable our senses are . For example , the human eye is capable of detecting candlelight from 30 miles away in the dark . We are also capable the ticking ofa watch in a quiet environment from 20 feet away . If you think that amazing , I encourage you to read more about the extreme sensory capabilities of nonhuman animals many animals possess what we would consider abilities . A similar principle to the absolute threshold discussed above underlies our ability to detect the difference between two stimuli . The differential threshold , orjust noticeable difference ( for each sense has been studied using similar methods to signal detection . To illustrate , find a friend and a few objects of known weight ( you need objects that weigh , 10 and 11 in metric terms and ) Have hold the lightest object ( or ) Then , replace this object with the next heaviest and ask him or herto tell you which one weighs more . Reliably , your friend will say the second object every single time . It extremely easy to tell the difference when something weighs double what another weighs ! However , it is not so easy when the difference is a smaller percentage ofthe overall weight . It will be much harder for your friend to reliably tell the difference between 10 and 11 . or versus ) than it is for and . This is phenomenon is called Law , and it is the idea that bigger stimuli require larger differences to be noticed . Crossing into the world of perception , it is clear that our experience influences how our brain processes things . You have tasted food that you like and food that you do like . There are some bands you enjoy and others you ca stand . However , during the time you first eat something or hear a band , you process those stimuli using processing . This is when we build up to perception from the individual pieces . Sometimes , though , stimuli experienced in our past will influence how we process new ones . This is called processing . The best way to illustrate these two concepts is with our ability to read . Read the following quote out loud Notice anything odd while you were reading the text in the triangle ?

Did you notice the second the ?

If not , it likely because you were reading this from a approach . Having a second the does make sense . We know this . Our brain knows this and does Sensation and Perception 82 Figure . An example of stimuli processing . to be a second one , so we have a tendency to skip right over it . In other words , your past experience has changed the way you perceive the writing in the triangle ! A beginning reader who is using a approach by carefully attending to each be less likely to make this error . Finally , it should be noted that when we experience a sensory stimulus that does change , we stop paying attention to it . This is why we do feel the weight of our clothing , hear the hum of a projector in a lecture hall , or see all the tiny scratches on the lenses of our glasses . When a stimulus is constant and unchanging , we experience sensory adaptation . During this process we become less sensitive to that stimulus . A great example of this occurs when we leave the radio on in our car after we park it at home for the night . When we listen to the radio on the way home from work the volume seems reasonable . However , the next morning when we start the car , we might be startled by how loud the radio is . We do remember it being that loud last night . What happened ?

What happened is that we adapted to the constant stimulus ofthe radio volume over the course ofthe previous day . This required us to continue to turn up the volume of the radio to combat the constantly decreasing sensitivity . However , after a number of hours away from that constant stimulus , the volume that was once reasonable is entirely too loud . We are no longer adapted to that stimulus ! Now that we have introduced some basic sensory principles , let us take on each one of our fascinating senses individually . Vision How vision works

Sensation and Perception 83 Vision is a tricky matter . When we see a pizza , a feather , or a hammer , we are actually seeing light bounce off that object and into our eye . Light enters the eye through the pupil , a tiny opening behind the cornea . The pupil regulates the amount of light entering the eye by contracting ( getting smaller ) in bright light and dilating ( getting larger ) in dimmer light . Once past the pupil , light passes through the lens , which focuses an image on a thin layer of cells in the back of the eye , called the retina . Because we have two eyes in different locations , the image focused on each retina is from a slightly different angle ( binocular disparity ) providing us with our perception of space ( binocular vision ) You can appreciate this by holding a pen in your hand , extending your arm in front of your face , and looking at the pen while closing each eye in turn . Pay attention to the apparent position of the pen relative to objects in the background . Depending on which eye is open , the pen appears back and forth ! This is how video game manufacturers create the perception special glasses two images are presented on top of one another . Anterior chamber ( aqueous humor ) Posterior chamber Zonular Ciliary muscle Suspensory Retin . ligament choroid Vitreous Sclera Hyaloid canal Optic disc Optic nerve blood vessels Figure . Diagram of the human eye . Notice the Retina , labeled here this is the location of the Cones and Rods in the eye commons .

Sensation and Perception 84 It is in the retina that light is , or converted into electrical signals , by specialized cells called . The retina contains two main kinds of rods and cones . Rods are primarily responsible for our ability to see in dim light conditions , such as during the night . Cones , on the other hand , provide us with the ability to see color and fine detail when the light is brighter . Rods and cones differ in their distribution across the retina , with the highest concentration of cones found in the fovea ( the central region of focus ) and rods dominating the periphery ( see Figure ) The difference in distribution can explain why looking directly at a dim star in the sky makes it seem to disappear there are enough rods to process the dim light ! Next , the electrical signal is sent through a layer of cells in the retina , eventually traveling down the optic nerve . After the thalamus , this signal makes it to the primary visual cortex , where information about light orientation and movement begin to come together ( Information is then sent to a variety of different areas of the cortex for more complex processing . Some of these cortical regions are fairly example , for processing faces ( fusiform face area ) and body parts ( body area ) Damage to these areas ofthe cortex can potentially result in a specific kind , whereby a person loses the ability to perceive visual stimuli . A great example ofthis is illustrated in the writing neurologist Oliver Sacks he experienced , the inability to recognize faces . These specialized regions for visual recognition comprise the ventral pathway ( also called the what pathway ) Other areas involved in processing location and movement make up the dorsal pathway ( also called the where pathway ) Together , these pathways process a large amount stimuli ( Phenomena we often refer to as optical illusions provide misleading information to these higher areas processing ( see Additional Resources for websites containing amazing optical illusions ) Dark and light adaptation Humans have the ability to adapt to changes in light conditions . As mentioned before , rods are primarily involved in our ability to see in dim light . Theyare the responsible for allowing us to see in a dark room . You might notice that this night vision ability takes around 10 minutes to turn on , a process called dark adaptation . This is because our rods become bleached in normal light conditions and require time to recover . We experience the opposite effect when we leave a dark movie theatre and head out into the afternoon sun . During light adaptation , a large number of rods and cones are bleached at once , causing us to be blinded for a few seconds . Light adaptation happens almost instantly compared with dark adaptation . Interestingly , some people think pirates wore a patch over one eye in order

Sensation and Perception 85 to keep it adapted to the dark while the other was adapted to the light . Ifyou want to turn on a light without losing your night vision , do worry about wearing an eye patch , just use a red light this wavelength does bleach your rods . Color vision Our cones allow us to see details in normal light conditions , as well as color . We have cones that respond preferentially , not exclusively , for red , green and blue ( not new it dates back to the early century ( Young , 1802 Von ' however , does not explain the odd effect that occurs when we look at a white wall after staring at a picture for around 30 seconds . Try this stare at the image of the flag in Figure for 30 seconds and then immediately look at a sheet ofwhite paper or a wall . According to the trichromatic theory of color vision , you should see white when you do that . Is that what you experienced ?

As you can see , the trichromatic theory does explain the afterimage witnessed . This is where the theory comes in ( This theory states that our cones send information to retinal ganglion cells that respond to pairs of colors ( These specialized cells take information from the cones and compute the difference between the two process that explains why we can not see or , as well as why we see . Color blindness can result from issues with the cones or retinal ganglion cells involved in color vision . Figure . State at the center of the Canadian flag for fifteen seconds . Then , shift your eyes away to a white wall or blank piece of paper . You should see an after image in a different color scheme . Hearing ( Audition ) Some of the most celebrities and top earners in the world are musicians . Our worship of musicians may seem silly when you consider that all they are doing is vibrating the air a certain way to create sound waves , the physical stimulus for audition . People are capable of getting a large amount of information from the basic qualities of sound waves . The amplitude ( or intensity ) of a sound wave codes for the loudness of a stimulus

Sensation and Perception 86 higher amplitude sound waves result in louder sounds . The pitch ofa stimulus is coded in the frequency ofa sound wave higher frequency sounds are higher pitched . We can also gauge the quality , or timbre , ofa sound by the complexity of the sound wave . This allows us to tell the difference between bright and dull sounds as well as natural and synthesized instruments ( 1996 ) Canals Vestibule Saccule Temporal Bone Auditory Nerve Cochlea Outer Ear Middle Ear Inner Ear Figure . Diagram of the human ear . Notice the Cochlea labeled here it is the location of the auditory Hair Cells that are organized . In order for us to sense sound waves from our environment they must reach our inner ear . Lucky for us , we have evolved tools that allow those waves to be funneled and amplified during . Initially , sound waves are funneled by your pinna ( the external part of your ear that you can actually see ) into your auditory canal ( the hole you stick into despite the box advising against it ) During , sound waves eventually reach a thin , stretched membrane called the tympanic membrane ( eardrum ) which vibrates against the three smallest bones in the malleus ( hammer ) the incus ( anvil ) and the stapes ( stirrup ) called the . Both the tympanic membrane and the amplify the sound waves before they enter the cochlea , a bone structure containing auditory hair cells arranged on the basilar membrane ( see Figure ) according to the frequency they respond to ( called organization ) Depending on age , humans can normally detect sounds between 20 and 20 . It is inside the cochlea

Sensation and Perception 87 that sound waves are converted into an electrical message . Because we have an ear on each side of our head , we are capable of localizing sound in space pretty well ( in the same way that having two eyes produces vision ) Have you ever dropped something on the floor without seeing where it went ?

Did you notice that you were somewhat capable of locating this object based on the sound it made when it hit the ground ?

We can reliably locate something based on which ear receives the sound first . What about the height of a sound ?

If both ears receive a sound at the same time , how are we capable of localizing sound vertically ?

Research in cats ( Populin Yin , 1998 ) and humans ( positioning . After being processed by auditory hair cells , electrical signals are sent through the cochlear nerve ( a division of the nerve ) to the thalamus , and then the primary auditory cortex ofthe temporal lobe . Interestingly , the organization of the cochlea is maintained in this area ofthe cortex ( Knight , Roth , 1975 , The inner ear is only involved in hearing it also associated with our ability to balance and detect where we are in space . The vestibular system is comprised ofthree semicircular canals bone structures containing cells that respond to changes in the head orientation in space . Information from the vestibular system is sent through the vestibular nerve ( the other division of the nerve ) to muscles involved in the movement of our eyes , neck , and other parts of our body . This information allows us to maintain our gaze on an object while we are in motion . Disturbances in the vestibular system can result in issues with balance , including vertigo . Touch Who does love the softness of an old or the smoothness of a clean shave ?

Who actually enjoys having sand in their swimsuit ?

Our skin , the body largest organ , provides us with all sorts of information , such as whether something is smooth or bumpy , hot or cold , or even if it painful . includes our ability to sense touch , temperature and physical stimuli , such as fuzzy velvet or scalding water , into electrical potentials that can be processed by the brain .

Sensation and Perception 88 Tactile sensation Tactile that are associated with by special receptors in the skin called like in the eye and auditory hair cells in the ear , these allow for the conversion of one kind of energy into a form the brain can understand . Homunculus Somatosensory Map Figure . The Homunculus ( Latin little man ) on the left you see a human body drawn to demonstrate the areas that possess the most sensitivity lips , hands , genitals and feet . On the right you see the drawing of the somatosensory cortex in the brain and the areas in the human body that correspond to it they are also drawn in proportion to the most sensitive or the most parts of the body . After tactile stimuli are converted by , information is sent through the thalamus to the primary somatosensory cortex for further processing . This region of the cortex is organized in a map where different regions are sized based on the sensitivity of specific parts on the opposite side of the body ( 1950 )

Sensation and Perception 89 Put simply , various areas ofthe skin , such as lips and fingertips , are more sensitive than others , such as shoulders or ankles . This sensitivity can be represented with a homunculus ( small human ) shown in Figure . Pain Most people , if asked , would love to get rid of pain ( because the sensation is very unpleasant and does appear to have obvious value . But the perception of pain is our body way of sending us a signal that something is wrong and needs our attention . Without pain , how would we know when we are accidentally touching a hot stove , or that we should rest a strained arm after a hard workout ?

Phantom limbs Records of people experiencing phantom limbs after amputations have been around for centuries ( As the name suggests , people with a phantom limb have the sensations such as itching seemingly coming from their missing limb . A phantom limb can also involve phantom limb pain , sometimes described as the muscles of the missing limb uncomfortably clenching . While the mechanisms underlying these phenomena are not fully understood , there is evidence to support that the damaged nerves from the amputation site are still sending information to the brain ( 1998 ) and that the brain is reacting to this ( 19 , There is treatment for the alleviation of phantom limb pain that works by tricking the brain , using a special mirror box to create a visual representation ofthe missing limb . The technique allows the patient to manipulate this representation into a more comfortable position ( 1996 ) Smell and Taste The Chemical Senses The two most underappreciated senses can be lumped into the broad category of chemical senses . Both olfaction ( smell ) and gustation ( taste ) require the transduction of chemical stimuli into electrical potentials . I senses are underappreciated because most people would give up either one of these if they were forced to give up a sense . While this may not shock a lot of readers , take into consideration how much money people spend on the perfume industry annually ( 29 billion US Dollars ) Many of us pay a lot more for a favorite brand of food because we prefer the taste . Clearly , we humans care about our chemical senses .

Sensation and Perception 90 Olfaction ( smell ) Unlike any of the other senses discussed so far , the receptors involved in our perception of both smell and taste bind directly with the stimuli they . in our environment , very often mixtures ofthem , bind with olfactory receptors found in the olfactory epithelium . The binding of to receptors is thought to be similar to how a lock and key operates , with different binding to different specialized receptors based on their shape . However , the shape theory of olfaction is universally accepted and alternative theories exist , including one that argues that the vibrations of odorant molecules correspond to their subjective smells ( 67 ) Regardless of how bind with receptors , the result is a pattern of neural activity . It is thought that our memories ofthese patterns underlie our subjective experience ( Interestingly , because olfactory receptors send projections to the brain through the cribriform plate ofthe skull , head trauma has the potential to cause anosmia , due to the severing ofthese connections . lfyou are in a line ofwork where you constantly experience head trauma ( professional boxer ) and you develop anosmia , do sense of smell will probably come back ( Sumner , 1964 ) Gustation ( taste ) Taste works in a similar fashion to smell , only with receptors found in the taste buds of the tongue , called taste receptor cells . To clarify a common misconception , taste buds are not the bumps on ( located in small divots around these bumps . These receptors also respond to chemicals from the outside environment , except these chemicals , called , are contained in the foods we eat . The binding of these chemicals with taste receptor cells results in our perception of the five basic tastes sweet , sour , bitter , salty and umami ( savory ) some scientists argue that there are more ( Researchers used to think these tastes formed the basis for a ' organization of the tongue there was even a clever rationale for the concept , about how the back ofthe Ghost Pepper , also known as is one of the hottest , hotter , tongue sensed bitter so we would know to spit out Sauce What , do you think happen to your poisons , and the front of the tongue sensed sweet taste so we could identify foods . However , we guy ?

Sally Sensation and Perception 91 now know that all areas of the tongue with taste receptor cells are capable of responding to Wei ) taste ( During the process of eating we are not limited to our sense of taste alone . While we are chewing , food are forced back up to areas that contain olfactory receptors . This combination of taste and smell gives us the perception of flavor . If you have doubts about the interaction between these two senses , I encourage you to think back to consider how the flavors of your favorite foods are impacted when you have a cold everything is pretty bland and boring , right ?

Putting it all Together Multimodal Perception Though we have spent the majority of this module covering the senses individually , our world experience is most often multimodal , involving combinations of our senses into one perceptual experience . This should be clear after reading the description of walking through the forest at the beginning of the module it was the combination of senses that allowed for that experience . It should shock you to find out that at some point information from each ofour senses becomes integrated . Information from one sense has the potential to influence how we perceive information from another , a process called multimodal perception . Interestingly , we actually respond more strongly to multimodal stimuli compared to the sum of each single modality together , an effect called the effect of integration . This can explain how you still able to understand what friends are saying to you at a loud concert , as long as you are able to get visual cues from watching them speak . If you were havinga quiet conversation at a , you likely would need these additional cues . In fact , the principle of inverse effectiveness states that you are less likely to benefit from additional cues from other ifthe initial unimodal stimulus is strong enough ( Because we are able to process multimodal sensory stimuli , and the results ofthose processes are qualitatively different from those of unimodal stimuli , it a fair assumption that the brain is doing something qualitatively different when they being processed . There has been a growing body of evidence since the on the neural correlates of multimodal perception . For example , neurons that respond to both visual and auditory stimuli have been identified in the superior temporal sulcus ( Additionally , multimodal what and where pathways have been proposed for auditory and tactile stimuli ( et , 2009 ) We are limited to reading about these regions of the brain and what they do we can experience them with a few interesting examples ( see

Sensation and Perception 92 Additional Resources for the Effect , the Double Flash Illusion , and the Rubber Hand Illusion ) Conclusion Our impressive allow usto and most miserable experiences , as well as everything in between . Our eyes , ears , nose , tongue and skin provide an interface for the brain to interact with the world around us . While there is simplicity in covering each sensory modality independently , we are organisms that have evolved the ability to process multiple as a unified experience .

Sensation and Perception 93 Outside Resources Audio Auditory Demonstrations from Richard Warren lab at the University of Wisconsin , Milwaukee Audio Auditory Demonstrations . published by the Acoustical Society ofAmerica ( ASA ) You can listen to the demonstrations here Book , 1990 ) A natural history of the senses . Vintage . Book Sacks , 1998 ) The man who mistook his wife for a hat And other clinical tales . Simon and . Video Acquired knowledge and its impact on our interpretation of the world Street Art Video Acquired knowledge and its impact on our interpretation of the world Anamorphic Illusions Video Acquired knowledge and its impact on our interpretation of the world Optical Illusion Video ?

Video Seeing Sound , Tasting Color ?

Video The Phantom Limb Phenomenon ?

Sensation and Perception 94 Web A regularly updated website covering some of the amazing sensory capabilities of animals . Web A special ringtone that is only audible to younger people . Web Amazing library with visual phenomena and optical illusions , explained Web An article on the discoveries in the use of sound in locating people and things Web An optical illusion demonstration the theory of color vision . Web Anatomy of the eye Web Animation showing organization of the basilar membrane . Web Best Illusion of the Year Contest website Web Demonstration of contrast gain adaptation Web Demonstration of illusory contours and lateral inhibition . Mach bands Web Demonstration of illusory contrast and lateral inhibition . The Hermann grid Web Demonstrations and illustrations of cochlear mechanics can be found here

Sensation and Perception 95 Web Double Flash Illusion Web Further information regarding what and pathways Web Great website with a large collection of optical illusions Web Effect Video ?

Web More demonstrations and illustrations of cochlear mechanics Web Scientific American Frontiers Web The Genetics of Taste ?

Web The Chemical Sense Center website Web The Rubber Hand Illusion ?

Web The Tongue Map Tasteless Myth Debunked Discussion Questions . There are a number of myths that exist sensory capabilities . How would you design a study to determine what the true sensory capabilities of infants are ?

A phenomenon experienced by millennials is the phantom vibration of a cell phone when no actual text message has been received . How can we use signal detection theory to explain this ?

Sensation and Perception 96 . What physical features would an organism need in order to be really good at localizing sound in space ?

Are there any organisms that currently excel in localizing sound ?

What features allow them to do this ?

What issues would exist with visual recognition ofan object if a research participant had corpus callosum severed ?

What would you need to do in order to observe these deficits ?

Sensation and Perception 97 Vocabulary Absolute threshold The smallest amount of stimulation needed for detection by a sense . Agnosia Loss of the ability to perceive stimuli . Anosmia Loss of the ability to smell . Audition Ability to process auditory stimuli . Also called hearing . Auditory canal Tube running from the outer ear to the middle ear . Auditory hair cells Receptors in the cochlea that sound into electrical potentials . Binocular disparity Difference is images processed by the left and right eyes . Binocular vision Our ability to perceive and depth because ofthe difference between the images on each of our retinas . processing Building up to perceptual experience from individual pieces . Chemical senses Our ability to process the environmental stimuli of smell and taste . Cochlea Spiral bone structure in the inner ear containing auditory hair cells . Cones of the retina sensitive to color . Located primarily in the fovea .

Sensation and Perception 98 Dark adaptation Adjustment of eye to low levels of light . Differential threshold The smallest difference needed in order to differentiate two stimuli . See lust Noticeable Difference ( Dorsal pathway Pathway of visual processing . The where pathway . Flavor The combination of smell and taste . Gustation Ability to process gustatory stimuli . Also called taste . Just noticeable difference ( The smallest difference needed in order to differentiate two stimuli . see Differential Threshold ) Light adaptation Adjustment of eye to high levels of light . Mechanical sensory receptors in the skin that response to tactile stimulation . Multimodal perception The effects that concurrent stimulation in more than one sensory modality has on the perception of events and objects in the world . Our ability to sense pain . Chemicals by olfactory receptors . Olfaction Ability to process olfactory stimuli . Also called smell .

Sensation and Perception 99 Olfactory epithelium Organ containing olfactory receptors . theory Theory proposing color vision as influenced by cells responsive to pairs of colors . A collection of three small bones in the middle ear that vibrate against the tympanic membrane . Perception The psychological process of interpreting sensory information . Phantom limb The perception that a missing limb still exists . Phantom limb pain Pain in a limb that no longer exists . Pinna Outermost portion of the ear . Primary auditory cortex Area of the cortex involved in processing auditory stimuli . Primary somatosensory cortex Area of the cortex involved in processing somatosensory stimuli . Primary visual cortex Area of the cortex involved in processing visual stimuli . Principle of inverse effectiveness The finding that , in general , for a multimodal stimulus , if the response to each unimodal component ( on its own ) is weak , then the opportunity for enhancement is very large . However , if one sufficient to evoke a strong response , then the effect on the response gained by simultaneously processing the other components ofthe stimulus will be relatively small . Retina

Sensation and Perception 100 Cell layer in the back of the eye containing . Rods of the retina sensitive to low levels of light . Located around the fovea . Sensation The physical processing of environmental stimuli by the sense organs . Sensory adaptation Decrease in sensitivity of a receptor to a stimulus after constant stimulation . Shape theory of olfaction Theory proposing that of different size and shape correspond to different smells . Signal detection Method for studying the ability to correctly identify sensory stimuli . Ability to sense touch , pain and temperature . map Organization of the primary somatosensory cortex maintaining a representation of the arrangement of the body . Sound waves Changes in air pressure . The physical stimulus for audition . effect of integration The finding that responses to multimodal stimuli are typically greater than the sum of the independent responses to each unimodal component if it were presented on its own . Chemicals by taste receptor cells . Taste receptor cells Receptors that gustatory information . processing Experience influencing the perception of stimuli .

Sensation and Perception 101 Transduction The conversion of one form of energy into another . Trichromatic theory Theory proposing color vision as influenced by three different cones responding preferentially to red , green and blue . Tympanic membrane Thin , stretched membrane in the middle ear that vibrates in response to sound . Also called the eardrum . Ventral pathway Pathway of visual processing . The what pathway . Vestibular system Parts of the inner ear involved in balance . Weber law States thatjust noticeable difference is proportional to the magnitude ofthe initial stimulus .

Sensation and Perception 102 References , Hansen , 2001 ) Detection of integration sites in humans criteria to the BOLD effect . 14 ( Hoon , 2006 ) The receptors and cells for mammalian taste . Nature , 444 ( 7117 ) Milner , 1992 ) Separate visual pathways for perception and action . Trends in , 15 ( 1920 ) der vom . 1962 ) Receptive fields , binocular interaction and functional architecture in the cat visual cortex . 106 . Knight , Roth , 1975 ) Representation of cochlea within primary auditory cortex in the of Neurophysiology , 38 ( Green , 991 ) Sound localization by human Review of Psychology , 42 ( Mitchell , 1871 ) Phantom limbs . Magazine of Popular Literature and Science , 1950 ) The cerebral cortex of man a clinical study of localization . Oxford England Populin , Yin , 1998 ) Behavioral studies of sound localization in the cat . of Neuroscience , 18 ( ran , 2000 ) Phantom limbs and neural plasticity . Archives of Neurology , 57 ( 1996 ) in phantom limbs induced with mirrors . Proceedings of the Royal Society of London Biological Sciences , 263 ( 1369 ) De , 2009 ) integration and stimuli in processing what and where . 29 ( 35 ) 1982 ) organization of the human auditory cortex . Science , 216 ( 4552 ) Shepherd , 2005 ) Outline ofa theory its relevance to humans . Chemical Senses , 30 (

Sensation and Perception 103 Stein , Meredith , A . 1993 ) The merging of the senses . The MIT Press . Stewart , Golding , Clifton , 2010 ) Oral sensitivity to fatty acids , food consumption and in human subjects . of Nutrition , 104 ( Sumner , 1964 ) Post Traumatic Anosmia . Brain , 87 ( 1955 ) Spectral response curves from single cones . Acta . 39 ( 134 ) Turin , 1996 ) A spectroscopic mechanism for primary olfactory reception . Chemical Senses , 21 ( Von , 1867 ) der ( Vol . Voss . 1996 ) Virtual musical sound using physical models . Organised Sound , 02 ) Walker , King , A . 2011 ) and robust representations of sound features in auditory cortex . of Neuroscience , 31 ( 41 ) 1998 ) Phantom limb pain and related disorders . Neurologic Clinics , 16 ( Young , 1802 ) The lecture On the theory of light and colours . Philosophical transactions of the Royal Society of London ,