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Letters are crucial features that the visual system attempts to detect during the process of word recognition – became too hard to identify so many letters in just 200msec if the contrast energy was too lowoLetters with low contrast energy are weak signals that the visual system will ‘squelch’Squelching= tendency of the nervous system to inhibit the processing of unclear featuresPrevents us from just guessing, otherwise we would see many false features Recognition by Components-What are the fundamental elements / size of these features we put together, i.e. for complex 3D objects such as people/cars-Biederman: Recognition by components (RBC) theory= theory that we recognize objects by breaking them down into their fundamental geometric shapes -Geons = the set of 36 basic 3D shapes from which all real-world objects can be constructed oObjects broken into geons, which are then compared with existing geon configurations stored in memory – match input and memory to recognize the object -Tf if objects are parsed into geons, recognition should be a function of the number of geons available to perceive -Experiment – varied number of geons used to depict a given object oMore complex objects (penguin) needed more geons than less complex (flashlight)oObjects were flashed for 100msec then covered to interrupt perceptual processing-FINDINGS:oPeople were good at recognizing objects represented by only 2-3 geons, and recognition improved when more geons were added to add detailoTf accuracy increased for more detailed penguins than lessoAlso – more complex objects (penguin) were recognized more efficiently than less complex (flashlight)o***would have thought more complex require more processing time-Conclusion: complexity and detail lead to more geons and more geons lead to better recognition-Deconstructing objects into geons is a critical component of object recognition
Context and Knowledge -Context in which features appear is important-Context effects = influence of proximate stimuli and the situation on the perceptual experience of the stimulusoI.e. you see a hand Tf likely on wrist is a bracelet / watch not an elephant -Interesting example of context: Moon illusion= tendency for the moon to appear different in size depending on where it is in the sky Letters in Context -Profound example of the effect of context on letter/word perception:-Jumbled word effect= ability to read words in sentences despite having mixed-up letters in the middle of some of the words. oExpectations regarding what the words will be help you determine what the wordsactually are -Word superiority effect= its easier to identify a letter if it appears in the word than if it appears alone (e.g. P versus WARP)oCan more efficiently map strings of tentatively identified letters to real words-Context effects can be modelled using connectionist approaches-Parallel distributed processing (PDP)= model of perception according to which different features are processed at the same time by different ‘units’ (simple processing