Each chapter ends with suggestions for further reading, and the final chapter draws together the material from the previous chapters, summarizing the broad principles described, and outlining some major unresolved issues. Assuming no prior knowledge, this book is an accessible and up-to-date overview of the processes of human sensation and perception. Presented in full color, it is an ideal introduction for pre-undergraduate and first year undergraduate students on courses in psychology, as well as neuroscience and biology.
Everything that we experience depends on sensing and perceiving. Specialized receptors for the five senses - hearing, seeing, smelling, tasting, and touching - capture information from chemical compounds, compressed air, electromagnetic waves, mechanical sensations, and more.
From that information, our brain creates an impression of the world around us. Sensation and Perception focuses on how these systems work, from the mechanics of individual cells to the interactions of thousands of cells in the brain. This book also delves into how our sensory capabilities change with age or damage. Readers of this new title from the acclaimed Gray Matter series will learn to understand how sensation and perception prove crucial to interpreting our surroundings, enjoying them, and even surviving in them.
Do you wonder how movies sequences of static frames appear to move, or why 3-D films look different from traditional movies? Why does ventriloquism work, and why can airliner flights make you feel disoriented? The answers to these and other questions about the human senses can be found within the pages of Foundations of Sensation and Perception. This third edition maintains the standard for clarity and accessibility combined with rigor which was set in previous editions, making it suitable for a wide range of students.
As in the previous editions, the early chapters allow students to grasp fundamental principles in relation to the relatively simple sensory systems smell, taste, touch and balance before moving on to more complex material in hearing and vision.
The text has been extensively updated, and this new edition includes: a new chapter devoted to attention and perception over new references over 30 new figures and improved, more colorful, visual presentation a new companion website with a range of resources for students and lecturers The book contains a range of pedagogical features, including tutorial sections at the end of each chapter. This distinctive feature introduces areas of the subject which are rarely included in student texts, but are crucial for establishing a firm foundation of knowledge.
Some tutorials are devoted to more advanced and technical topics optics, light measurement, Bayesian inference , but treated in an accessible manner, while others cover topics a little outside of the mainstream music perception, consciousness, visual art. Foundations of Sensation and Perception will enable the reader to achieve a firm grasp of current knowledge concerning the processes that underlie our perception of the world and will be an invaluable resource for those studying psychology, neuroscience, and related disciplines.
This book combines sensation and perception with all biological-sensory aspects of perception with all biological-sensory aspects of perception covered from an evolutionary point of view.
It raises the key question: How do the senses gather and secure information about the outside world? This basic question is addressed by explaining how the physical world interacts with and stimulates the senses, and, in turn, how the sense and the nervous system transform, integrate, and process the stimulation. Can my dog hear the same things I hear? Maintaining the strong pedagogy, abundant student-friendly examples, and engaging conversational style of the previous editions, the sixth edition of this introductory textbook makes technical scientific information accessible to those who are beginning to specialize in cognitive psychology.
Sensation and Perception, Sixth Edition is newly available in a more affordable paperback version, making it ideal for undergraduate students.
The sixth edition retains the clear organization of previous versions, covering a wide range of core topics, from skin senses such as touch to chemical senses such as taste and smell, to our complex visual and auditory sensory systems.
This book is essential reading for undergraduates and postgraduates studying courses on sensation and perception. In this new edition Bates has built on Foley and Matlin's core text to add updates focusing on multisensory integration, neural plasticity, and cognitive neuroscience, as well as real-world examples and practical applications of psychological phenomena.
The highly accessible Sensation and Perception presents a current and accurate account of modern sensation and perception from both a cognitive and neurocognitive perspective. To show students the relevance of the material to their everyday lives and future careers, authors Bennett L. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment.
Sensation and Perception 10 Edition — eBook pdf. Add a review. Sensation and Perception 10 Edition — eBook pdf quantity. The h ou. The car and ho u se a re separa te. None of thei r lines toudl. C learly we must have processes that s uccessfull y combin e features into objects. That is one of the tBsks that defines middle or mldlevel vision as opposed to low-level vision, whidl was the topic of Chapters 2 and 3. The next part of this cha pter looks at sorne of the processes of middle vision.
H ow ca n we do that? For exam ple, how d o we knmv that all of the images in Figures4. Witho ut having seen these exact objects before, how d o we go about placing them in the "house" category? Furthermore, h ow d o we know tha t Figu re 4. Middle Vision The goa l of middle vision is to orgartlze the elernents of a visual scene into groups that we can then recognize as objects. Let's begin with the. Finding the edge,s of this object w ill be a good starting place on the road to recogn izin g the object.
We al ready established that '"'e can' t just g roup a ll the edges tha t touch each other into an object.
Because objects a but and overlap other objects, simple connected ness will n o t work. Worse yet, before we can concern ourselves with grouping edges, we n eed to worry about the quality of the raw edge in fo rma tion.
It is easy to see th at arrow. Notice, h owever, that in som e places the object is lighter than the background, while in other places it is darker. In other words, a t these points the shape has n o edge a t all. In o th. If the c hanges an:i oontinuous, it follows that th9f9 must b9 plac9S 'Wher9 the edge of this shape simply disappears, even if you see 9dgee as continuous. Lnterestingly, this oo:asional lack of an edge d oesn' t seem to bother our visual. Asking sirnpl e computer grnphics sofhvare to find the edges in Figure 4.
Fig ures 4. In Figure The human visual system , however, is d oing some thing quite In the early s tages of processing, it is figuring out w hich ed ges m ark the bound aries of objects a nd w h ich represent s urfa ce fea hues like cracks on the rock faces.
All these differen t bits of information are then combin ed to ma ke the syste m's best g uess about the presence of a contour. Here it is still e1sy to see the arrow outline, even th ough the vast majority of the shape's lines are m issing'! Check-it yourself. There really is n o border between the white fig u re and the white background. These edges, called Illusory contours, are perceived because they are the best guess abou t w hat is happening in the world a t that loca tion.
It rea lly does seem likely that a con tom is present, even if there is no physica. I evidem:. TI1is tendency of the visua l system to make inferential leaps was problenrnti. Even though the contour is doo11y visible , there is no piys1ca1 differsnce betw. In the structuralist view, perception is built up of local sensa tio ns the way a crysta l might be built up of an arrny of atoms.
A n i1lusory conto ur challe nges th is view because an extend ed edge is seen brid g ing a gap wh ere no local atom of "edgen ess" can be fo1. Over time, it became clear that there are many examples w here the s tructuralist a rgmnent seems to fail. Gestalt theory he ld tha t the perceptual w hole is more than the s urn of its sensory parts.
Perhaps the most enduring contributio n of this school was to begin the description o f a set of organizin g principles some times known as Gestalt grouping rules tha t d escribe the visual syste m 's interpretation of the raw retin al image. In the next sections, we will d escribe some of those rules. More than the specific rules, it is important to remember the overarching goal. The vis ual syste m is trying to make sense of the vast and often a mbiguous and noisy inputs from the early st.
These rules are useful parts of that effort beca u se they reflect regula. The " rule,'' cartooned in Fig ure 4. Field, Hayes, and Hess, Pola t and Sagi 19Q3 measured how pieces of a contour s upport each o ther. The effect w ill be hard to see in print, but the fainter lines in the a 99 Gestalt In German.
In refe re nce to perception, a schocil of thought stressing that the percep- tual whole could be greate r than the apparent sum of the parts.
The origh1al list was assembled by members o f the Gestatt school of thought. Getsler and J. Part c aftQf Polat and Sagi. Geisler and P'1fty. If a set of lines fo rms a closed s hape like the roughlycircu1u con tom in Figure4,13n, then the sh ort segments support ead1 o ther even m ore s tron gly Kovacs and Julesz, Geisler and Perry d ocumented the regtJ arity in the world that s uppo rts the rule shmvn in Figure 4.
They labeled many, man y contours in na hmd scenes. Then they examined pairs of contour pieces and asked , 11 What is the cha nce th at tliis piece lrere at this orienta ti on is o f the sam e contour as that piece tire re at thaf orienk1tion?
Sharp turns are much rarer. There are many other p ossible orga nizations Figtue 4. TI1e 1' all else being equar' phrase is imp ortant. These seem to operate according to a sort of committee model Everyone gets together and voices o pinions about how the s timulus ou gh t to be unders tood.
Fo r example, look a t Figme 4. Now, the sam e intersecting lin es are interpreted differently. In this case clos ure is stronger than goo d. The illusory disk in c aris4:ls when the v isuru system combines a whole collec tion of guasses about the line rninations. So, returning to the Kanizs. TI1e answer tha t the visual syste m seems to come up v.. Note that we also interpret the notches as places where one object is occluding another.
Rgure 4. II eadl black line genera ted weak illusory contours at right an gles to its e ndpoint, then this figure would contain a set of ro ughly coli. By the way, illusory con tom s li ke this rnake exce llent doodles when you would rathe r be d oing informal p erception exp erim e nts than paying attention. Texture Segmentation and Grouping Connecting s hort line segments w ill get u s only so far in di";ding the raw image into objects. On the left in Figure4.
An edge detector like the one described. Here, ra thel' th. How do we distinguish the two halves o fth9 11gure? How do we Si9gment out the smaller regions inside each halt? On the bottom, hO'W might we know that the large area is stone, surrounding a smaller area of 'Water?
The red lines arie vertical ori average and the blue lines, horizontal. That would be quite a coincidence. Another committee consid ers all the possibilities a nd d eval ues any tha t involve accidental vievvpoin ts,. And so we p roceed htrther and further into the visual system, until a si ngle, gen erally correct interpre tation emerges. It Is llkay that the surroo1ded regbn Is the figure.
Armed with this understanding of the g r The edge- and region-finding medrnnism s, discussed earlier, would divide Flgure 4. But how s h ould those regions be und erstood? The ba:sic idea of a template is rather like a lock a nd key. For instance, look at the "shape--pattem " theory o f olfaction in Chapter Figures 4. Figure A letter A stimulus falls on an array of spot d etectors.
If the A falls on the filled d etectors and not the empty on es, it is identified as an A. Therefore, the array of detectors serves as an A template. The difficulty w ith a nalve template m odel is that too many templates a re required.. All of the objects in Figure 4. A11d just think about the p roblem of building a Jennifer Aniston rep resentation i n th is way. One way out of this problem is to no tice tha t all the As--a t least all the capitalAs--share abasics tmcture.
Cnstead of ma tching each p oint in the image to 3 point in a te mplate, perhaps we perform 3 more concephMl match. Just be described by the relationship of its three lin es: the about any capital A two flankin g lines me-et, and the third line spans the a ngle cre. A key component of each theory is how object parts are re presented in the s tructum l descripti ons. Marr and Nishihara used "generalized cylind ers'' that could be scaled longer,.
Bied errnan proposed a set of geons "geometr ic ions'' ; Figure 4. Geans are specified as collections o f n onacddenta l feah. Geons are fea h. In the brain. Each geion is s hown in three orientatb n s, Illustrating the fact that thgy are. Just as the finite set of le tters in the a lphabet ca n be combin ed in vari ous ways to produce an infinite nmn. Attaching a noodle to the side of a cylinder gives us a coffee mug Figure 4. Moving the noodle to the top of the cy linder produces d pail Figure 4.
Changi ng the cylinder to a brick gives us an a ttache case Figure 4. Because geonsa nd relationships s uch as'' A is beside B" are designed to be eJect recogni tion. In response to these questions about structurc1l-description models, researchers s uch as lvlich ael Tarr1 Heinrich BUJ.
For e.. During tralning, the objects were always s hown in the upright orientation. The mme the object was rotated, the longer the observel's took to name it. This result s u ggests tha t the subjects may have s tored a te mplate-like representation of the object during the training phase, and then recognized.
Objects that can be identified on the basis of their geons can stlll sh ow a dependence on vie,,.. Ga uthier e t al. Fran Gauthi9,r 9t al. S: Viewpoint Effects lets you test yourself in a s hort experiment us ing s uch objects.
H owever, view-based m odels have thei r mvn problem. Multiple Recognition Committees? Indeed, recognition may not be a sing le act. We can recognize a n object in multiple ways, perhaps simulta neous ly. As an example, Figure 4. But these objects are also quite clearly different At a s ubordinate level -a m ore specific level ben ea th the e ntry level-Figure 4. Recognizing the objects in Figure 4A5a--c as animals seem s like qui te a different act.
Even more imp ressively, studies looking at brain recordings provide strong evidence tha t different parts of the bram are more active w hen people are engaged in s ubordinate-level recognition than w hen they are recognizing objects a t the entry level Pa lmeri and Gauthier, ; Rich. There a! For exa mple, wh en s hown an a typical member of a category, s uch as the bird in Figure4. And when people becom e experts at recognizing a certain class of objects, s ubordinltelevel recognition becomes as fas t as or fas ter than en try-level recognition or, looking at this a nother wny, we might say that the entry level shifts d ow n one level when one becomes an exper t.
Take, for exam ple, the images in Figure 4. As you will see, both faces look fine do"A'n, but o ne of them looks quite strikingty" when turned right side up. After Thompson, 1QBO. An lnablllty to rec- double dissociation The phencm - errn In which one of two! Jice versa. The p rocesses that recognize a face asa face care little about inversion, and they don' t seern to be d isturbed bpd,jStortio,n of the face.
See Web Activity 4. Damage to specific areas in the temporal lobe o f the brain can p roduce prosopagnosla, a d isorder in w hich the cannot identify faces. See Web Essay 4. Though she m ay be abl e to recognize an object as a face, s he will not know w ho the person might be. A neu ropsych ological mark of truly separa te brain mo dules is double dissociation.
Thus, you can be blind a nd s till hear or you can be deaf and s till see. How could you recognize a foc-e as yom m other without recogn izing it as a face? Interestingly, it is possible to be born with a specific impairment in the ability to recognize faces.
The exis tence o f this congenital prosopagnosla is a good in d ication that there is a specific neural mo du le fo r fa ce recogni ti on Beh rma nn and Avidan, You may think you're suffering from this disorder w hen you fail to m atch a name to a face. However, tha t is a much more cornm on failure of memory. You can recognize the focei you just can't remember the na me tha t goes wi th it. The Pathway Runs in Both Directions: Feedback and Reentrant Processing We've been discussing object recognition as a progression of steps down th e what from Vl into the temporal lobe, an d as mentioned earlier, it d oes seem to be the case that you can perform some acts of object categorization in this feed-fonvMd m anner Serre, Oliva, and Poggio, Most of th e routine acts of object recogni tion that you perform w ill in volve information flowin g up and d ow n these pathways.
All of the connections in Figure 4. Consider that receptive fields get bigger and bigger as you ascend the what pathway.
TI1e cells care less and less about where an object is in the visual field or how it is oriented.. They become increasingly interested in the object's identity as, perh aps, the Eiffel Tower. However, you know that the Eiffel Tower is right there and it has that red light in thnt s pot. This precision is p robably achieved by going back do,,.. Theoct of object recogniti on should be seen as a con ve rsation am ong many pieces of the brain r. There is good eviden ce that atfention to an object is critical in recogniti on of that object.
If so, tha t piece of the brain probably requires a single face as its i. Fo r example, a receptive field might change its size to wrap itself around a n a tte nded object Moran a nd Desim one, This makes it pa rt of the nehvork processing tha t object. The same ne uron may be involved in the processing of a different object w hen attention shifts a m ornent later.
Many of the brain s truch ues critical for the deployment of attention seem to lie in the o ther m ain path coming o ut of the primary visual cortex-the on e tha t goes toward the pa rie tal lobe. This p ath way, a nd th e general topic of a ttentio n , is taken up in C ha pte r 7. Summary 1. A series of ex trastriate visual areas continue the work of visual processing. Emerging from Vl primary visuaJ cor tex are h.
TI1is chapter follows that pathway. The parietal where pa thway v. After early visual processes extract basic features from the visual input, it is the job of middle vision to organize these features intb the regions, s urfaces, and objects that ca n, in tum, serve as input to object recognition and sceneunders tanding processes. Pen::eptual "rommlttees" serve as an important metaphor in this chapter. Different processes may come to different conclusio ns about the presence of an edge or the relationship be hveen tv.
Under most circumstances, we see the single conclusion that the committees settle upon. Bayesian models are one way to formalize this process of finding the most likely explanation for input. Multiple processes seek to carve the input into regions and to define the edges of those regions, and many rnles are involved in this parsing of the image.
For example, image e lements are likely to group together if they are similar in color or s hape, if tile ' are near E'f'"h other! Many of these grouping principles we re fi rst articu lated by members of the Gestalt school. Other, reL. These rules of grouping and figure-ground assignment are driven by an implicit understanding of the physics of the world. Thus, events that are very unlikely to happen by chance e.
The proce Among these are the fad that parts of otJ;ec ts may be hidden behind other objects occlusion and the fuct that objects themselves have a structure. Is your nose an object or a part of a larger whole? In addition to perceiving the shape of objects and their parts, we are also very adept at categorizing the material that an o bject seems to be made An evaluation version of novaPDF was used to create this PDF file.
Refer to 1he Sensation and Perception C. Ompanlon Website sltes. We use material perception to estimate physical properties. Can it be grasped like a bottle or would it s lip through o ur fingers like sand?
Template models of object recognition hold that an object in the world is recognized when its image fits a particular representation in the brain in the. It has ah,.
Structural models propose tha t objects are recognized by the relationship of parts. In their pure form, such models are vi5vpoint independent. Object recognition, however, is often viewpoint-dependent, su ggesting that the cor-rect model lies behveen lhe extremes of naYve template matching and pure s tructural description.
Faces are an interesting special case in which viewpoint is very important. Upright face. Moreover, some regions o f the brain seem to be specifically interes ted in faces.
They lie neilr regions in the tem poral lobes the eyes Fig Jn addition, s uppose that the lig ht that looks red produces 40 units of activity in the M-cones a nd 80 in the L-cones.
If we assume that we c. TI1e ab. What is hnportant is these hvo ligh ts, mixed together, produce a mixture that excites the L- and M. Pass that absorbs Shorter to the result. O ther particles occlude each other, a nd w. Color boundaries are sharper than yo u might think. If you have to remember a 12olor, as in the task s hoW11 in Figure 5. Rosch found tha t the Dani's perfonnance on s uch tasks reflected the same color bounda ries, even when their language did not recognize the distinction be tween the hvo colors a Dani might call all the colors in Figure 5.
Ii but would still do be tte r vvith the task in Figure 5. This finding leads to th e conclusio n tha t color perception is not especially influenced by cu lture an d language; blue a nd green are seen as ca tegorically different, even if o ne's language does not e mploy color ternlS to express this difference. In the late s, Debi Roberson went up the Sepik River in New G uinea to study the Berinmo, whose lang uage, like the Dani 's, has a limited set o f basic color terms.
Unlike previously s tudi ed g ro ups, the Berinmo have terms tha t for m novel botmdaries in color space. Eng lis h speakers sh m,. For example, supposa you had to H. And even m ore recen tly, evid ence has eme rged tha t lea rning new color s ubca tegories produces increases in gray m a tter in parts of the bra in impli cated in color vision V. Kwok et al. So, can language or culture influence color perception? For many years, we thought the answer was "no.
Let's think a little rnore abou t the blue and green patches in Figure 5. Looking across the bottom four disks, you can categorize them as blue, blue, blue, and green. At the sa me time, you can tell tha t the first and second blues are not the sarne.
When Bird e t al. Under most circmns tances, if you d eclare two lights to be m etamerically matched, those arotmd yo u w ill generally agree, even if we can' t make definitive s tatements about their qualia. There will be some varia tion between individuals.
Some of these differences " Pt;due tel fo owlik ag which turns the lens o f the eye yell ow Q. To a flrs t a pproxi mation , however1 your pe rfor man ce on s tandard measures of color vision w ill be the sa me as others,,.
Those dlscrlm! Cone rnonoc hromats are truly color-blind. Fema les have hvo copie. Nagy e t al. See Web Essay 5. TI1ere are a number of different types of color blindness. One de te rmining factor is the type of cone affected. A second factor is the ty pe of d efect; either the photopigment for tha t cone type is anoma lous different from the nom1 o r the cone type is missing a ltogether.
Although we call people w h o a re m issing one cone type "colo r-blind,'' it is a mistake to think tha t this m eans they ca nn ot see colors at a ll. The world "'ill sti ll be seen in color, but you will have a "fl a tter'' color experience, d ifferent from that of people v.
Because M- and L-rone defects are the most common, most color-blind individuals have difficul ty discriminating Lig hts in the middle- to-long-wavelength range. English-speakin g trichromats wou ld labe l the colors of these two ligh ts as ''green'' and " re ddis h ora nge," respectively. Now consi d er a deuteranope. H is photoreceptor output to these hv o ligh ts ""-ill be identical.
A protanope--someone w h o has n o L-cones- w iU il.. Gene tic factors can Color-anomalous individ uals ty pi cally also make people have three cone photopigrnen ts, but two o f them are so si mila r th. TI1ey can compare what they see w ith the color-blind eye to w ha t they see with the n ormal eye, enabling us to reconstruct the appearance of the color-blind world M acleod and Lennie, True co lor blindness does occur but it is very tmusuaL ft is possi ble to be a cone monochromat, with on ly o ne type of cone in the re tina.
Cone monochromats who also have rods li ve in a one-dimensional color s pace, seeing the world only in shad es of gray. Even m ore vis ually impaired are rod monochromats1 w ho are missing cones a ltogether.
Because the rods work well only i:n dim light and are genera lly absen t in the fovea, these individuals no t only fail to discriminate colors; they also have very poor acuity and serious difficulties seein g tmder n om1al d ayl. An achroma top sic ind ividual sees the world as drained of color, even w hile s howing e viden ce that wavelen gth infom1 ation is p rocessed a t ear lier stages in the visu al pa thway. Brain lesion s ca n a lso produce various for ms of color agnosia or a ne mia Ox bury, Oxbury; an d Humphrey, In agnosia, the p a tient can see something but fai ls to know w ha t it is.
Anomia is a n ina bili ty to n a me-in th is case, an ina bility to n ame colors. From the Color of Lights to a World of Color All the work of this chapter1 up t o this point, has concerned the d etection , d iscrimin ati on, and appearance of isola ted lights. Thus, in Figure S. So, in Figure 5. Not only can other colors i. Agnosla is damage. So, in the S9cond column th.
A:ft9r Stcx::krnan and Brainard, Light stimuli produce dark negative afterimages. S are oornplementruy: for example. If red-green and blue-yellow medianlsrns are at their neutral points. The black-white prooess ' ""no neutral point. Tiiot light wi ll look white if seen as an isolated or unrelated color. To be seen as it mus t be seen i. Thus it is a related color.
In isola ti on, a light mi ght look yellow or orange. Lt w ill only to patches. Adaptation and Afterimages Color contrast effects show how the spatial relations between colors can influence color a ppearance. Temporal relations ma tter, too. What you saw before has an influence on the color you see now. You already know this from the discussion of light a dapta tion in Chapter 2. Adapting to a bright light ma kes a moderate light look darker.
Adapting to darkn ess would ma ke that same mo derate li ght appear brighter. Now Jet's extend tha t principle to color. Adaptation can be color-specific, as we see in the phe no1nenon of negattve attertmages. If yo u look a t one color for a few seconds, a subsequently viewed ach romatic region w ill appear to take o n a color opposi te to the original color.
The illusory color that is seen aften vard is the negati ve afterimage. See We b Ac tivity 5. The principle is i1lus trated in Fig ure 5. Figure 5. Now, s tare at th e black d o t at the cen ter of Pigure 5. The L-cones w ill be more stimulated th an the M- or S-cones. The L-cones wi ll be mo re adap ted tha n M- or S-cones, as w ill the later processes in the retina a nd brain that were more s timulated by the red spot. They respond less vigorous ly than unadapted processes.
The result is a bit like w hat would happen if you he ld a pe ndulum up and released it. The redgreen oppo nent color mecha nis m swi ngs back toward the neutral point, overs hoots th is point, and slides over to the green si de. As a consequence, the gray s pot appears g reenish until the opponen t mechanism settles back to the n eutral point. If you look at the green d ot at the bottom of Figme 5. Other colors '""ill prod uce othe r results, w hich you sho uld n ow be able to predict.
In Figures 5. If you s tare at the black d ot in Figm e5. Notice that we are not attributing negati ve afterimages to just the cones or j11st one set of cone- or color-opponent processes.
Aft91' 10 seconcls or so, shift your fixation t o the black dot In '8. The cird es should n ow look cdored. This is a negative aft9rlmage. Wrry does it happen? Of it didn't hapPQn , try fixating more rigorously. Now try with a real scene. Fixate the black dot In c , and then fl ick your gyes t o the same spot in d. Color Constancy You m ay recall fro m Ch apte r 2 tha t ad aptation is one way of dealing with the vast range of light levels in the e nvironme nt.
Assuming tha t you are readin g this on good old-fashioned p aper, w hen you are inside, you see this black text on a w hite page. If you take this book outside, you still see black on white, even though the illumination is so mudl brigh ter that the black text, viewed outside, reflects more light to th e eye tha n does the w hite paper inside. TI1is is an achromatic example o f the m ore general phe no meno n of colo r constancy, the tendency for the colo rs of objects to appear relatively Wlchanged in spite of s ubs tantial changes in the lighting conditions.
M- , and L-cones c. However, if you a re told that the first number is behveen 9 and 14, you 're saved. The first mm1be r must be 12, and the second, then, mus t be 4.
In a nalogous way, color constan cy must be based on some information o r assumpti ons tha t cons train the possible answers. There are rnany possible assu mptions that could help. Suppose we assumed that, in a complex scene, the brightest region was white Land and McCann, or th at the ave. VVe could scale the other colors relative to these white or gray anch ors. H owever, th is can ' t be entirely right.
Think wha t would happen if you were in a dark romn w ith two spots of light on the wa ll: a red one and a blue one. Under a simple version of a bri ght-is-white theory, the bright"' SJl. Coul19sy o f Tom Elsnar. In a dditi on tosea rchi. Here, too, color plays a central role.
ColorfrJ d isplays-from the dramatic patterns on tropical fish Figure 5. Wha t makes the peacock that has the most colorful tail the most desirable mv;ewer to attribute the distortion to the s lant of the picture surface. In anamorphic projection, the mi es of linear perspective are pushed to an extreme. Now the projection of three dimensions into two dimensions creates a hNo-cHmensiona1 image that is only from an unusual vantage point or sometimes with a ctu ved mirror.
TI1e res ults are k. As an exa mple, there is an odd diagonal s me. Despite its s ua:essful recovery of the shapes in Figure 6. It is just a flat image that looks threedhnenslonal when viewed from the correct position. More on the role of pictorial depth cues in art can be fmmd in Web Essay 6. The first no n pictoits power and rial d epth cue we w ill discuss is motion parallax.
To to und erstand why photograp hs of the forest often don' t come out well , the best thi n g to do is to go outside a nd lie w1der a tree. You w-ill notice that leaves and branches form a rela tively fla t text u re. You can see a U the details, but you may have trouble deciding vvhe the r one little branch lies in front of or behind.
Close the eye, and the volume collapses ag'1in. The geometrtc Information cbtalned fran an f! As you b ok out the window of a moving train , oqects closer to you the flower in this illustration shift position m ore quickly than c:b obj9Cls farth. Qf" away the tr"9 fro m on9 moment a t o th nQXt b.
This r9gularity can b"' explo itf'ld as a depth a.
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