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Chapter 6

Chapter 6. Object Perception. Recognition: Relates a current percept to something familiar. Identification: Recognition of a specific instance. Categorization: Placing a specific object into a category. Object recognition. 0.1 sec to identify many objects.

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Chapter 6

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  1. Chapter 6 Object Perception

  2. Recognition: Relates a current percept to something familiar. • Identification: Recognition of a specific instance. • Categorization: Placing a specific object into a category.

  3. Object recognition • 0.1 sec to identify many objects. • We typically don’t encounter things tachistoscopically; but we instead scan. • Fixations last typically about .25 sec.

  4. Challenges in object recognition • Occlusion (desk, screen) • Upside down • Picture of a chair vs. chair • Far chair in room vs. toy chair on desk

  5. Two types of theories for object recognition • Recognition by components (Biederman) • View-based recognition (Bülthoff, Tarr, et al.)

  6. Geons: • Distinguishable from almost any perspective. • Recognizable even with occlusions.

  7. Pros and cons of geon theory • Explains why it is hard to recognize objects from unusual angles. • No physiological evidence. • Sometimes recognition is viewpoint dependent. • Doesn’t explain recognition of individuals.

  8. View-based recognition • People have preferred viewing angles for familiar objects. • Less consensus on preferred viewing angles for novel objects. • Recognition is slower the greater the deviance from preferred viewing angle.

  9. Impact of rotation on recognition • James Stone (1998) showed ameboid images.

  10. Impact of rotation on recognition • James Stone (1998) showed ameboid images. • Guy Wallis (1998) five head shots in apparent rotation.

  11. Learning to see • The young woman – old woman illusion • James Elkins experiences with moth hunting • Face - woman illusion • High contrast images

  12. Perceptual learning (p. 203) • Panel A: Orientation discrimination • Panel B: Vernier acuity (The degree to which a pair of fine lines can be aligned to each other.) • Panel C: Orientation of 3-line bars (followed by mask) • Panel D: Face recognition in the presence of noise.

  13. Perceptual learning • Chicken sexing • Perception of high contrast images (p. 232) • Pre-training: 55% for faces; 13% for others. • Post-training: 93% for faces; 87% for others.

  14. Inferotemporal cortex • Single cell recording reveals: • Few neurons that prefer oriented lines. • Neurons with large receptive fields. • Neurons that are sensitive to “diagnostic” features, such as eyes of a face. • Neurons that are occlusion insensitive. • Neurons that are object size invariant.

  15. Dolan: Viewing gray-scale images facilitates interpreting high contrast versions of those images. • Tovee, Rolls, and Ramachandran, (1996). Monkeys shown black & white, then gray-scale, then black & white again. IT cells were more active the second time around.

  16. Kobatake, Wang, & Tanaka, (1998). Monkeys shown a target, then after a delay the target with three other objects. Monkeys improved with practice to be able to perform with longer delays. IT cells changed firing patterns.

  17. Face Recognition • Much worse when contrast is reversed. • Much worse when inverted. • The top half of a face is harder to recognize, when the face is hybridized. • Anger is the most distinctive of the six basic facial expressions (sadness, happiness, anger, fear, surprise, and disgust).

  18. Prosopagnosia • Two types of strategies to cope: • Configural: patients base their judgements on the overall similarity of the faces’ configuration. • Featural processing: patients base their judgements on parts of the face, rather than the whole.

  19. Greebles • http://mail.cog.brown.edu/~tarr/projects/greeble_poster.html • They have symmetric body parts, families, and genders. • Becoming a greeble expert.

  20. Greebles • Expert recognition: As good with general categories as with specific categories. • Bird and black-capped chickadee • Sex, family, and individual identity • People can become greeble experts after thousands of trials.

  21. Become a Greeble expert • The better a person is at greeble recognition, the more than fMRIs look like facial fMRIs. • The ‘face’ area appears to be deployed in the inspection of even novel greebles.

  22. Attention and object recognition • Attention reduces variability in perception. • Prinzmetal, et al., show that distractors increase trial-to-trial variability in color assessments. • Attention changes an object’s appearance • Attention can increase sensitivity of appearances.

  23. Inattentional Blindness

  24. Spotlight versus object attention • Edgly, Driver, and Rafal (1994)

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