Biases An Example Nonaccidental properties Properties that appear
Biases: An Example Non-accidental properties: Properties that appear in an image that are very unlikely to have been produced by chance, and therefore are likely to reflect properties of the 3 -D world. view-point invariant properties straight lines parallel lines
mental representation of objects book cat key tree etc. . view-point invariant ? mental representation of bars of light view-point dependent
mental representation of objects book cat key tree etc. . view-point invariant 1) Direct models mental representation of bars of light view-point dependent
mental representation of objects book cat 1) Direct models: Lades et al Model Poggio & Edelman Model mental representation of bars of light key tree etc. . view-point invariant • Input layer like representation in V 1 (called “Gabor Jets”) • Inputs on that layer are matched to inputs in a memory layer • The object is identified based on the match with least distortion • Input layer like representation in V 1 • 3 -layer network is trained to rotate all views of an image to one view. • The hidden units are seen as a way of rotating images to match memory images (“radial basis functions”) view-point dependent
mental representation of objects book cat 1) Direct models: Lades et al Model Poggio & Edelman Model mental representation of bars of light key tree etc. . view-point invariant • Input layer like representation in V 1 (called “Gabor Jets”) • Inputs on that layer are matched to inputs in a memory layer • The object is identified based on the match with least distortion • Input layer like representation in V 1 • 3 -layer network is trained to rotate all views of an image to one view. • The hidden units are seen as a way of rotating images to match memory images (“radial basis functions”) view-point dependent
mental representation of objects book cat key tree etc. . view-point invariant 2) View-point invariant mental representation of non-accidental properties of an image Lowe’s SCERPO Model Ullman’s Model mental representation of bars of light view-point invariant • Input layer takes information represented as it is in V 1 • view-point invarient information is extracted • this allows the input image to be rotated in order to fit an image stored in memory view-point dependent
The problem with all of these theories: The representation of objects in memory is stored as a two-dimensional image, which visual images are rotated, distorted, and matched to. But in actuality, objects are three dimensional things in the world. So lets make a model which has the basic units that make up mental representations of objects being three-dimensional solids, rather than lines and edges.
mental representation of objects mental representation of geons book cat key tree etc. . view-point invariant mental representation of non-accidental properties of an image view-point invariant mental representation of bars of light view-point dependent
straight, parallel Geons curved, parallel corner Y intersections
mental representation of objects mental representation of geons book cat key tree etc. . view-point invariant mental representation of non-accidental properties of an image view-point invariant mental representation of bars of light view-point dependent
mental representation of objects book cat key briefcase etc. . mental representation of geons view-point invariant what processing rectangle unit cylinder unit cone unit tube unit view-point invariant where processing above unit below unit left of unit righ of unit temporal binding
Evidence for geons? Experiment 1: Visual Priming Reaction Time: 900 ms. (response) time (response)
Evidence for geons? Experiment 1: Visual Priming Reaction Time: 700 ms. (response) time
Evidence for geons? Experiment 1: Visual Priming Reaction Time: 800 ms. (response) time
Evidence For Geons: Priming Studies First Second Shared? Lines Edges Geons Basic Cat. Response Yes Yes No No Time 700 ms 900 ms
Evidence For Geons: Priming Studies First Second Shared? Lines Edges Geons Spec. Cat. Basic Cat. Resp. Yes Yes Yes Time 700 ms No No Yes Yes 800 ms No No No Yes 800 ms
Objects, Faces and Rotation: Objects
Face Recognition Recognizing faces is an entirely different problem (computationally) from recognizing objects? Objects • “M” shaped function Faces • Shape of rotation function?
Face Recognition Experiment
Objects, Faces and Rotation: Faces
Face Recognition Recognizing faces is an entirely different problem (computationally) from recognizing objects? Objects Faces • “M” shaped function • Less affected by illumination • Shape of rotation function? • More affected by illumination Recognition by components (Geon Theory) Recognition by coordinates (Templates) different processes?
Double Dissociation Patient Studies • Prosopagnosia: Objects can be recognized, Faces can not. Processes responsible for object recognition: Processes responsible for face recognition:
Double Dissociation Patient Studies • Prosopagnosia: Objects can be recognized, Faces can not. • (Patient CK): Faces can be recognized, Objects can not Processes responsible for object recognition: Processes responsible for face recognition:
Double Dissociation Patient Studies • Prosopagnosia: Objects can be recognized, Faces can not. • (Patient CK): Faces can be recognized, Objects can not Neuroimaging Studies • Faces activate the FFA area of the temporal lobe • Objects activate the PPA area of the temporal lobe
Double Dissociation General Form IF: The ability to perform some task X is affected by or correlated with some factor A (damage to an area, activity in a part of the brain, or performing some other task) but not factor B (damage to a different area, activity in a different part, or some other task), AND: The ability to perform some task Y is affected by or correlated with some factor B but not factor A, THEN: There is a double dissociation between X and Y, and the mechanisms required to perform them are functionally independent.
Dissociation What and Where Pathways Some patients Cannot identify objects by shape Say where objects are Cannot navigate the world Damage Parietal lobe Dorsal visual stream X
Dissociation What and Where Pathways Some patients Cannot Can identify objects by shape Say where objects are Cannot navigate the world Damage Temporal lobe Ventral visual stream X
Dissociation What and Where Pathways Patient D. F. Cannot Can Explicitly line up a line with a line Task: Take an envelope and line it up with this line Use motor system (part of “where” pathway) to do same task just failed at Task: Take this envelope and “mail the letter” pretending that this line is a mailbox
Dissociation Two face recognition systems • Recognize faces normal way “ Hey I know you” • Recognize by change in skin conductance for familiar faces
Dissociation Two face recognition systems • Person A can recognize normal way but no change in skin conductance • Person B cannot recognize in normal way but does have change in skin conductance
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