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Sensation and Perception Essay

Memory – knowing the past
Thinking – knowing the future
Cognition = the influence of perception, memory, and thinking Aug 29th, 2012
Basic principles of perception

1.Stimulation
-Many kinds of energy implode on the body
Electromagnetic energy (light)
Mechanical energy
-Pressure waves in air
Pressure on skin
Body movement
Thermal energy (heat)
Chemical energy (molecules in air, food)
-Energy changes detected by receptors

2.Information

a.Our sensory systems evolved to pick up information (not just stimulation)

b.In general, information is provided by change

c.Change can occur over time, or over space

3.Transduction
-The process of converting stimulus energy into nerve impulses -Generally, stimulus energy causes a change in a receptor cell’s electrical potential (voltage) -If change is enough, it will trigger “nerve impulses”

4.Transmission
-For perception to occur, sensory organs (containing receptors) must transmit nerve impulses to the brain -Perception occurs in the brain, not in the sensory organs

5.Mediation
-Our perception of the world is mediated by various processes between transduction and our conscious awareness -These processes alter the neural information
-What we consciously perceive may not be an accurate reflection of the original stimulation

6.Interpretation
-Sensory information is ambiguous (there are ALWAYS multiple possible interpretations)

7.Construction
-Sensory information is “sketchy”; the brain “fills in” missing information

8.Modularity
-Your brain consists of independent “modules”. These modules may construct different, possibly conflicting, interpretations of the world. -You “see” one interpretation of an ambiguous
**Missed Class…locked out of room**
Sept 5th, 2012
Signal Detection Theory
(Slides and appendix in book)
Sept 7th, 2012
The Eye
Light
-Light is electromagnetic radiation varying in:
Wavelength
Intensity
Radiance – intensity of light as it leaves the light source Illuminance – intensity of light as it is absorbed by object (white objects higher in illuminance than black objects) Luminance – amount of light that is reflected by object

100 illuminance omits 40 luminants; albedo = 40/100= .4

Retinal Illuminance – light that reaches your eye
Brightness – perception of radiance, illuminance, or luminance Lightness – perception of the reflectance (albedo)
Brightness is a perception of the light; lightness is a perception of the object surface Myopia = nearsighted = focal length is shorter than distance to retina Hyperopia = farsighted = focal length is longer than distance to retina Presbyopia = aged vision, lens can’t adjust because of age (reading glasses for old people)

Sept 10th, 2012
The Retina
Fovea is the part of eye where visual acuity is highest
Vision involves “rods” and “cones” in the back of the retina
Photopic = conesScotopic = rods
Purkinje Shift – as illumination decreases, red objects lose brightness more quickly than green, blue; red goes to black whereas green and blue pass through shades of gray **2 Missed Classes – Canada**

Sept 19th, 2012
Gestalt Psychology
-Brief history of behaviorism, psychoanalysis
-The laws of perceptual grouping

October 1st, 2012
Distance Perception
Why is depth perception important?
-Effective action (e.g. grasping) requires correct perception of distance -Correct perception of size and shape requires correct perception of distance Size and shape consistency
Just as an infinite number of object sizes and shapes can cast the exact same image on the retina, a single object can cast an infinite number of sizes and shapes of retinal image

Size Consistency = we (usually) perceive the size of an object as constant, despite changes in the size of the retinal image

Shape Consistency = we (usually) perceive

The farther away something is from your eye, the less the retinal disparity will be

Stereopsis
-Retinal Disparity = the mismatch between the left and right eyes’ retinal images -Stereopsis = the ability to use retinal disparity as a depth cue Motion parallax
Interposition = idea that an object in front of another object will block that object out Aerial Perspective
-Refers to effects of the air on distance perception
Clarity = as light passes through more air, light is scattered and so the image gets blurrier oBlueness = as light passes through more air, long wavelengths are filtered out and so the image gets bluer

Chapter 2
Transduction and receptive fields

Signal Detection Theory
-Always noise (random activity)
Eye Movements
EXAM 2 MATERIAL OCT 12TH 2012
Perceptual Ambiguity (Lecture 9)
States of form perception
1.Feature extraction
2.Perceptual grouping
3.Figure-ground differentiation
4.Figural resolution
5.Pattern recognition
Ambiguity – multiple possible interpretations – can occur at any level (2-5) Figure-ground differentiation
-Some perceptual groups are treated as “figure”, other groups are treated as “ground” Yates Thesis
-Yates. J (1985). The content of awareness is a model of the world. Psychological Review, 92, 249-284 -Visual images are inherently ambiguous (allow multiple interpretations) -Coherent action requires selection of one interpretation

-We tend to represent in awareness the simplest interpretation of the most sensory data Figural Resolution
-After “figure” has been differentiated from “ground”, it may still be necessary to resolve the structure of the figure -Figural resolution influenced by…
Bottom up vs. top-down
October 15th, 2012
Lecture 10 Pattern Recognition
Pattern Recognition – knowing what figures in the visual field ARE. Requires interaction of sensation/perception with memory (pre-existing knowledge)

Template Matching
-Match of whole pattern to a stored pattern
-Problems
onfinite variation of problems
No access to feature differences
Can’t recognize…

Feature Analysis
-Patterns are recognized by detection of particular “critical features” -Accounts for recognition of partially obscured patterns
-Predicts that objects with more features in common are more confusable

Problem:
Not ALWAYS true
Some confusions are predicted better by the whole shape
New “configural properties” (or emergent features) arise from the combination of features •Impossible to define complex objects entirely by simple features

Template Matching vs. Feature Analysis

-Template matching emphasizes the whole, fails to account for importance of parts -Feature analysis emphasizes the parts, fails to account for importance of the whole

-Possible solutions:
Maybe more than one brain mechanism for pattern recognition oA “hybrid” approach that encompasses both the whole AND the parts

Structural Theories of Pattern Recognition
Objects are recognized by their “structural description”, how their parts are organized into the whole •DO NOT CONFUSE WITH STRUCTURALISM! (Structuralism assumed that the “structure” can be decomposed into elemental parts”

Yates Thesis

-We tend to represent in awareness the simplest explanation for the most sensory data Oct 17th, 2012
Three kinds of brain damage
1.Agnosia = “loss of knowledge”
a.Prosopagnosia – loss of ability to recognize faces
b.Object agnosia – loss of ability to recognize objects
c.Word agnosia (alexia) – loss of ability to recognize written words

2.Object agnosia never occurs without either word agnosia or prosopagnosia Oct 24th, 2012
Light
Light is electromagnetic radiation varying in:
Wavelength
Intensity
Amplitude, if considered as a wave
Number of photons, if considered as particulate
Color is all in your head!

“Hue” does not exist in the physical world – wavelength is a simple quantitative continuum, like intensity, or frequency of sound, or length, or weight •You brain CONSTRUCTS categories of perception, resulting in qualitative differences in the perception

Dimensions of Color

-HUE – the perception of wavelength, or (in a mixture) dominant wavelength

-SATURATION – the perception of purity (proportion of the dominant wavelength in a mixture)

-BRIGHTNESS – perceived intensity

Subtractive Color Mixture

-A paint pigment absorbs certain wavelengths, reflects others

-When two pigments are mixed, each subtracts out certain wavelengths

-You see what’s left over

Exam 2:
Perceptual ambiguity
Pattern recognition
Color vision
Sound & Music
The Ear
Ear to Brain
Visual Illusions
Inner ear- cochlea, organ of corti,
Moon Illusion – moon looks larger when at horizon than when it is over-head Perceived size = retinal image size x perceived distance

EXAM 3 MATERIAL(FINAL EXAM)NOV 9TH, 2012
Final Exam – Friday Dec 14th, 3:30-5:30
66 questions, appx. 2/3 material last 3rd of class
Study 1st 2 exams for remaining 1/3
Don’t need to know every single experiment, just the general results Medial and lateral superior olives
-Loudness in 2 ears and time of arrival in 2 ears


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