Lec 5- object recognition

Lec 5- object recognition - Lecture 5 Object recognition...

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Lecture 5- Object recognition and Lecture 8- Visual search Notes from chapter 5 (p145) of Goldstein. Questions: 1. Why do some perceptual psychologists say “the whole is greater than the sum of its parts”? 2. How do we use “rules-of-thumb” to aid us in arriving at a perception of the environment? 3. What makes it possible to distinguish an object from its background? 4. Why haven’t we been able to program a computer to see objects as well as people can? These notes will look as the psychophysical level of analysis. It will describe research that has looked at the relationship between stimuli and perception. You can understand a lot without the need for brain scans etc and detailed physiology of the perceptual processes. When perception is studied at the psychophysical level this is what occurs: INDIVIDUAL FEATURES GROUPS OF FEATURES OBJECTS SCENES The Gestalt approach to perceptual organisation WILHELM WUNDT started the first laboratory of scientific psychology in 1879 . STRUCTURALISM- behaviour is created by adding elementary elements. Perceptions are created by combining elements called SENSATIONS . For example dotted drawings of a face, add up to create our perception of a face. MAX WERTHEIMER- was important in Gestalt psychology. Saw a STROBOSCOPE which caused an illusion of movement and wondered how Wundt's idea of sensations could explain this. It two stimuli are in slightly different positions and are flashed, movement is perceived between the two, this is an illusion called APPARENT MOVEMENT . Wertheimer wondered how this could be caused by sensations, and so set up a laboratory of what he called Gestalt psychology and published numerous papers that posed serious problems for the structuralist idea that perceptions are created by sensations. ILLUSORY CONTOURS- for example a 3-d cube without complete lines, but you perceive the lines that represent the lines even though they don’t actually exist (Cube by )
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Structuralists would have a hard time explaining illusory contours because they would not be able to identify and sensations along the contours that could lead to our perception of the contour. It is also possible to make these illusions disappear by imagining it differently, for example the black things as holes, structuralism would have difficulty in explaining a perception that is present one moment and gone the next in terms of sensations, especially as the exact same stimulus is projected onto the retina. Gestalt psychologists thus held that THE WHOLE IS GREATER THAN THE SUM OF ITS PARTS . This emphasis on the ‘wholes’ led the gestalt psychologists to focus on determining principles to explain PERCEPTUAL ORGANISATION- how small elements become grouped into larger objects. For example the picture of black and white shapes that can be perceptually organised into the image of a Dalmatian. The Gestalt approach to perceptual organization was to propose a number of rules that
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Lec 5- object recognition - Lecture 5 Object recognition...

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