Psychology 368 001 Perceptual Processing

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Psychology 368 (001) - Perceptual Processing

• students must take Psyc 367 before taking this
  course

Dr. Debbie Giaschi (pronounced Jawski)
www.giaschilab.ca/psyc368main.html
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Object Perception
subjective contours
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Object Perception
reversible vase
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Object Perception
wife/mother-in-law picture
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Colour Vision
colour contrast
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Colour Vision
x
x
colour adaptation
complementary afterimages
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Depth Perception
Magic Eye picture
relax or cross your eyes to see some of the
penguins pop out
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Depth Perception
Magic Eye picture
What object pops out of the blue -patterned sky?
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Size Constancy Illusions
Ponzo illusion
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Size Constancy Illusions
Muller-Lyer illusion
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Attention and Scene Perception
change blindness
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Motion Perception
biological motion
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Teaching Assistants
Marita Partanen Thursdays 930 - 1030
John Secen Wednesdays 1030 - 1130
Psyc 367 final exams and research reports may be
viewed Jan 6 - 21
e-mail psyc368ubc_at_gmail.com
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Textbook
Sensation Perception, 2nd edition (2009) by
Jeremy Wolfe et al.
Grades
Midterm exam 35 Final exam 45 Research
projects 20
Psych Subject Pool
http//hsp.psych.ubc.ca
up to 3 bonus marks
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Research projects
sign up for a topic in class on Jan 19 (or send
Dr G. a list of group members e-mail addresses
with 3 topic choices in advance)
purchase Insight lab manual with CD
collect data on yourself (follow instructions for
your group in course syllabus Insight manual)
before Feb 9
bring data a relevant reference to class on Feb
9 work in groups for data analysis and
presentation
group presentations March 16 - April 8
individual reports due April 13 at beginning of
class
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INSTRUCTIONAL OBJECTIVES

• By the end of the class, you will be able to
• 1. Describe the 3-stage model of object
  perception and give 3 pieces of
  neuropsychological evidence that support this
  model.
• Use the concept of lateral inhibition and
  ganglion cells with centre/surround receptive
  fields to explain both aspects of the Hermann
  grid illusion.

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low-level vision
Intro to object perception
individual cells in V1 respond to local features
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Intro to object perception
3-stage model
low-level vision
Stage 1
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Intro to object perception
neuropsychological evidence for 3-stage model
scotoma total loss of vision due to striate
cortex damage
Coren et al. (2004)
damage to a region of V1 results in a region of
blindness in the corresponding part of the visual
field
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Intro to object perception
caused by carbon monoxide poisoning (Zeki, 1995)
cant match shapes
cant copy letters, numbers or shapes
apperceptive agnosia selective loss in shape
perception due to extrastriate visual cortex
damage
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Intro to object perception
caused by a stroke to extrastriate cortex (Zeki,
1995)
can copy photo but cant recognize or identify
St. Pauls Cathedral in the drawing
associative agnosia selective loss in object
recognition/identification due to extrastriate
visual cortex damage
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Intro to object perception
Hermann grid illusion
Why do we see grey spots at the intersections?
Why do the spots disappear when we fixate them?
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Intro to object perception
classical explanation retinal ganglion cell
centre/surround receptive fields
Goldstein (1980)
lateral inhibition stimulation of inhibitory
surround of neurons receptive field reduces
response of neuron
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Intro to object perception
Why do we see grey spots at the intersections?
large response
small response

more lateral inhibition in neuron at intersection
if perceived brightness is proportional to
response size, intersections must look less bright
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Intro to object perception
Why do the spots disappear when we fixate them?
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small response
small response
- - - - - -
smaller receptive fields in fovea equal lateral
inhibition at intersection and along stripe
no perceived brightness difference because no
difference in response size
recent explanation lateral inhibition in V1
simple cells