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Midterm 2 is March 11th and 12th Read Land article for March 5th. Illusions related to depth perception. Misperceptions of size Misperceptions of location. Muller - Lyer Illusion. Muller-Lyer Illusion. What theory does Gregory take up?. Muller-Lyer Illusion.
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Midterm 2 is March 11th and 12th Read Land article for March 5th
Illusions related to depth perception • Misperceptions of size • Misperceptions of location
Muller-Lyer Illusion What theory does Gregory take up?
Muller-Lyer Illusion What theory does Gregory take up? Thiery / Woodworth : Muller-Lyer figure “suggests perspective”
Muller-Lyer Illusion What theory does Gregory take up? Thiery / Woodworth : Muller-Lyer figure “suggests perspective” Is there something about the presence of pictorial depth cues in an image that distorts size?
Depth Cues and Size Distortion The Ponzo Illusion:
Depth Cues and Size Distortion The Ponzo Illusion:
Depth Cues and Size Distortion The illusion of depth in an image seems to distort the perception of size in the image This is due to misapplication of Size - Constancy
Pictures are Weird What does Gregory find paradoxical about pictures?
Pictures are Weird What does Gregory find paradoxical about pictures? Pictures convey depth yet also appear flat Why?
The Apparatus When you view a picture there are some depth cues telling you to perceive depth, but other cues telling you that the image is on a flat surface …the surface matters!
Pictorial Depth Cues • Retinal image size
Pictorial Depth Cues • Retinal image size
The Apparatus What does he do to remove the paradox so that the Muller-Lyer figure no longer looks flat? Remove the background surface
Removing the Background With background removed, Muller-Lyer figure actually looks 3D What prediction can you make about how the perceived size and the perceived distance of the center line are related?
Removing the Background With background removed, Muller-Lyer figure actually looks 3D What prediction can you make about how the perceived size and the perceived distance of the center line are related? When the centre line appears close,it should also appear small When the centre line appears far, it should also appear large
Removing the Background How did Gregory test that?
Removing the Background Perceived size and perceived distance are tightly related inward arrowheads make line look closer/ outward arrowheads make line look farther
Misperception of Depth Drives Other Illusions • Ames Room view from above
Stereograms Divider Left Eye Right Eye • Right eye sees face to the left; left eye sees face to the right therefore: • faces present crossed disparity to the brain • Face appears in front of square
Autostereograms • Optically separate images aren’t needed
Autostereograms • Optically separate images aren’t needed • WARNING! Tricky stuff coming in the next slides
Autostereograms • Optically separate images aren’t needed • WARNING! Tricky stuff coming in the next slides • Keep the definitions of convergence and disparity separate.
Autostereograms What would happen if you remove the divider of a stereoscope? • Convergence is on a point at the same distance as the images • Boxes and faces are on the horopter • How many boxes would you see? boxes and faces are on the horopter
Autostereograms Now cross your eyes: • right-eye line of sight crosses left-eye line of sight in front of image (crossed convergence) • each retina is now pointed at the opposite box • How many boxes would you see? • What would happen to the face? crossed convergence
Autostereograms • There would be three boxes • middle box: right eye sees face shifted to right; left eye sees face shifted to left therefore: • uncrossed disparity • Face in the middle box appears behind square crossed convergence
Autostereograms • What would happen if you moved the faces within the box? • What would happen if you viewed this with uncrossed convergence?