Prof. Greg Francis1PSY 310: Sensory and Perceptual ProcessesPurdue UniversityGestalt PsychologyPSY 310Greg FrancisLecture 14This is a real object!Purdue UniversityWilhelm Wundt Established the first true psychology laboratory in 1879 University of Leipzig (Germany) Tried to identify basic elements ofperception Structuralism Similar to approaches in chemistry/physics Find basic elements of matter (molecules) Find basic elements of molecules (atoms) Find basic elements of atoms (protons, electrons) Find basic elements of…. Along the way you learn about how the basic elementscombine to have different propertiesPurdue UniversityStructuralism The basic idea is the perception is based onsensations Look at the title of your textbook and this class! Sensations are supposed to be simpler responsesto stimuli Sensations are identified by introspection “Looking” inward to identify the basic elements of theexperiencePurdue UniversityStructuralism If you take a bite of an apple, you might describe its basicsensations as Cold, sweet, crisp It would be a mistake to refer to it as applePurdue UniversityStructuralism If you could do this for lots of people and lots of stimuli, youmight identify the basic sensory elements of many differentperceptual experiences Scientific reductionism It never really worked out Different people report different basic sensory elements No set of basic sensory elements seemed to cover lots ofdifferent perceptual experiences The goal of reduction is still a strong part of perception, butnot along these linesPurdue UniversityOther problems Some percepts seem problematic for thestructuralist approach In structuralism, percepts are built of up sensations So sensations must be necessary to produce percept What about a stimulus like this? What sensation contributesto the perception of theillusory contour?Prof. Greg Francis2PSY 310: Sensory and Perceptual ProcessesPurdue UniversityOther problems Likewise, there are stimuli where presumablysensations are being gathered, but they do not giverise to a percept Motion Induced Blindness movie For that matter, one seems to get entirely new kindsof perceptual experiences from some stimuli Apparent motion (demo)Purdue UniversityAmbiguous stimuli There are thousands of stimuli that can be interpreted indifferent ways Presumably they produce the same sensations, but differentperceptsPurdue UniversityAmbiguous stimuli There are thousands of stimuli that can be interpreted indifferent ways Presumably they produce the same sensations, but differentpercepts Find the man playing the flutePurdue UniversityAmbiguous stimuli There are thousands ofstimuli that can beinterpreted in different ways Presumably they producethe same sensations, butdifferent percepts Find the Dutch girlPurdue UniversityAmbiguous stimuli There are thousands of stimuli that can be interpreted indifferent ways Presumably they produce the same sensations, but differentpercepts It’s not just clever drawings Much of perception involves ambiguity More than you realize Motion noWobbleGlobe.movPurdue UniversityGestalt Psychology The structuralists recognized these kinds of problems fortheir approach, but they thought one could eventually dealwith them Other people advocated an entirely different approach German scientists (Wertheimer, Koffka, Kohler) Gestalt is a German word that roughly means “whole” Gestalt psychologists suggested that understandingperception could not be done by breaking it down into parts,but by considering the whole experienceThe whole is different than the sum of its parts. One task of perception is to identify how to organize different partsof a visual scene How to identify objects?Prof. Greg Francis3PSY 310: Sensory and Perceptual ProcessesPurdue UniversityPerceptual organization What about the image or the visual system allows you to correctlygroup different parts of the scene into objects? Similarity: color, texture, orientation Position Familiarity Gestalt “laws” of perceptual organizationPurdue UniversitySimilarity Can isolate effectsPurdue UniversityPosition Can isolate the effectPurdue UniversityFamiliarity Having seen this image before, your perceptual organization isdifferent than the first timePurdue UniversityGood continuation Object have boundaries Generally the boundaries run smoothlyPurdue UniversityGood continuation Object have boundaries Generally the boundaries run smoothlyProf. Greg Francis4PSY 310: Sensory and Perceptual ProcessesPurdue UniversityGood continuation Object have boundaries Generally the boundaries run smoothlyPurdue UniversityCommon fate Motion in a common direction is one example Can be more complicated than just direction Biomot.movPurdue UniversityPragnanz “Good figure” Law of simplicity The percept you see should be the simplestinterpretation of the scenePurdue UniversityGestalt Laws They are not really laws, but suggestions aboutwhat the visual system might be doing Most people do not really believe them in thesame way we believe the laws of physics or thelaw of natural selection In fact, it is fairly easy to show that the Gestaltlaws are not anywhere near a completedescription of perceptual organizationPurdue UniversityImpossible figures What is the percept of this image? Is this “good figure”?Purdue UniversityImpossible figures This is aphotograph ofa real object Do you see itin the“simplest” waypossible?Prof. Greg Francis5PSY 310: Sensory and Perceptual ProcessesPurdue UniversityImpossible figures This is aphotograph of areal object Do you see it inthe “simplest”way possible?Purdue UniversityConclusions Structural psychology Gestalt psychology Rules of perceptual organization Impossible figuresPurdue UniversityNext time Perceiving objects Figure-ground