chapter 4 powerpoint : intro and vision
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Chapter 4 Powerpoint : Intro and Vision . Detect. Interpreting. Environment. taste. smell. attention. Vestibular Sense. Sensation and Perception. Sensory Information. Senses. sight. touch. Kinesthesis. processing. Organizing. brain. hearing. Warm up. - PowerPoint PPT PresentationTRANSCRIPT
Chapter 4 Powerpoint: Intro and Vision
Sensation and Perception
Detect
Environment
Organizing
Interpreting
Sensory InformationSenses
Kinesthesis
Vestibular Sense
processing
attention
tastesmell
hearingbrain
touchsight
Warm up
What is sensation? What is perception?
DefinitionsSensation-- the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.
Perception--the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.
Do we process everything our senses take in?
Top-down processingInformation processing guided by higher-level
mental processes, as when we construct perceptions drawing on our experience and expectations.
Analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information.
Bottom- up processing
Top Down vs. Bottom Up Processing
THEORIES OF SELECTIVE ATTENTION
Bottom up Theories
Top Down Theories
Top Down Theories of Attention• These theories say that perception starts from the more complex• Selective Attention/ Attenuation Theory:
• We process everything but everything doesn’t reach the highest centers of processing
• You “pick and choose” what to process the most
• Ex. Cocktail Party Phenomenon
Bottom Up Theories of Attention• This theory says that perception starts with sensation• Because so much information is coming in, some sensory
information is never processed• Filter Theory– We can’t process everything
Example
Selective Attention• the focusing of conscious awareness on a particular
stimulus.• You cannot pay attention to everything, only some things
Psychophysics
The study of the relationship between physical characteristics of stimuli and our psychological experience of them
Light- brightnessSound- volumePressure- weightTaste- sweetness
Sensation- Thresholds
Absolute Threshold minimum stimulation needed to detect a particular stimulus 50% of
the time
Difference Threshold minimum difference between two stimuli required for detection 50%
of the time just noticeable difference (JND)
Selective Attention• List 10 things you saw in the picture…..
Inattentional Blindness
• Change Blindness (failing to notice changes in the environment)
• Choice Blindness• Choice Blindness Blindness
failing to see visible objects when our attention is directed elsewhere.
Sensation- Thresholds
Signal Detection Theory predicts how and when we detect the presence of a faint stimulus
(signal) amid background stimulation (noise) assumes that there is no single absolute threshold detection depends partly on person’s
experience expectations motivation level of fatigue
Primingthe activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or response.
ThresholdsSignal Detection•Signal-detection theory
• Ratio of “hits” to “false alarms”
Signal Detection is not necessarily true…
Subliminal When stimuli are
below one’s absolute threshold for conscious awareness
0
25
50
75
100
Low Absolutethreshold
Medium
Intensity of stimulus
Percentageof correctdetections
Subliminal stimuli
Sensation- Thresholds
Weber’s Law- to perceive as different, two stimuli must differ by a constant minimum percentage light intensity- 8% weight- 2% tone frequency- 0.3%
Sensory adaptation- diminished sensitivity as a consequence of constant stimulation
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Wrap-up
TICKET OUT: What are sensation and perception? How does our perceptual system help us to interpret the world around us? Explain.
Short Video About Sensation and Perception
Warm upHow does the visual system work?
Vision
EYE
Vision Pupil- adjustable opening in the center of the eye Iris- a ring of muscle that forms the colored portion of the eye
around the pupil and controls the size of the pupil opening (dilates in response to changing light intensity)
Lens- transparent structure behind pupil that changes shape to focus images on the retina
Cornea - outer covering of the eye Retina - the light-sensitive inner surface of the eye, containing
the receptor rods and cones plus layers of neurons that begin the processing of visual information.
Blind Spot - the point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there
Fovea - the central focal point in the retina, around which the eye’s cones cluster.
Optic Nerve- the nerve that carries neural impulses from the eye to the brain
How does the eye work?
?
Distal Stimulus– the object in the outside world
Proximal Stimulus– the object as it is projected on the retina (upside down)
This is how we see
Animation of how this works...
TERMS: Distal stimulus, proximal stimulus, fronto-parallel plane, Distal Object, Percept
Pathways from the eyes to the visual cortex
Visual Information ProcessingFeature Detection
•Feature detectors
Visual Information ProcessingParallel Processing
•Parallel processingsimultaneous processing of several aspects of a problem simultaneously
• Blind sight
What is color?
What is color?• Color is the psychological attribute given to our response to
different wavelengths of visual light• It is psychological because it is perceived • Humans can only perceive colors on the visual spectrum.
Perception has to do with light getting reflected off an object and onto the different types of cones in the eye
Electromagnetic Energy Spectrum
Electromagnetic Energy Spectrum
The Stimulus Input: Light EnergyTransduction conversion of one form of energy to anotherIn sensation, transforming of stimulus energies into neural impulses
Wavelength the distance from the peak of one wave to the peak of the next
Hue (color)
Dimension of color determined by wavelength of light
IntensityAmount of energy in a wave determined by amplitude
The Physical Property of Waves
The Physical Property of Waves
Retina’s Reaction to Light- Receptors
Rodsperipheral retina detect black, white and gray twilight or low light
Conesnear center of retina fine detail and color visiondaylight or well-lit conditions
Rods and Cones
Rods are sensitive only to black and white and are sensitive to light and dark.
Cones come in three types, each sensitive to a different color: red, green, and blue. Cones are concentrated in the center of the retina, while rods form the periphery of the retina.
The EyeThe Retina
•Rods and Cones
RodsCones
Rods versus Cones
How Cones Perceive colors
Different “colors” of light stimulate the different cone cells in different combinations, thus accounting for the different colors we see.
There are 3 different types of cones that respond to different types of wavelengths.
•Short-wavelength cone receptors β•Middle-wavelength cone receptors γ•Long-wavelength cone receptors. ρ
This is called the Trichromatic Theory of Color Vision
The Retina’s Reaction to Light
Color Vision
•Young-Helmholtz trichromatic (three color) theory• Red – Green - Blue• Monochromatic vision • (only can perceive 1 of 3)
vision• Dichromatic vision (2 of 3)• People who can’t read the
number in the box couldbe color blind
Color Vision
•Opponent-process theory• Three sets of colors
• Red-green• Blue-yellow• Black-white
• Afterimage
Color Blindness• The inability to differentiate certain colors• More common in men because on x chromosome (women need 2
genes to inherit but men only have 1 x chromosome)• There are three types:
• Red/ green (95%)• Blue/ yellow• All colors
Color Blindness Simulator
WARM UP:
1.On worksheet fill in definition and one example.
2.How does the eye work like a camera?
Visual Information Processing• There are 4 different “cues” to perception.
They are:- Shape Constancy- Size Constancy- Color Constancy- Monocular and Binocular Depth Cues
How do they work???
Vision
Accommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retina
Acuity- the sharpness of vision
Nearsightedness- condition in which nearby objects are seen more clearly than distant objects because distant objects in front of retina
Farsightedness- condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind retina
Vision
Normal Nearsighted Farsighted Vision (myopic) Vision (hyperopic)
ILLUSIONS
What is an illusion?
What is an illusion?• Also known as Visual Illusions• involves visual deception.• When looking at an illusion our visual system
can perceive misleading visual effects • There is no one good reason• Because Perceptual Constancies (size, shape,
color, etc.) are just merely cues we can misinterpret what we look at
• Also our visual system groups items (gestalts) and this can cause misperception
DEMOS….
• Spinning wheel illusion (after image)
• Magic coins illusion (after image)
• Wundt-Jastrow illusion (effect of context/contrast on perception)
Ponzo Illusion
Ambiguous Figures• In some illusions there is not enough information in the image
to make a decision as to the “best” interpretation• Shows us the importance of “interpretation”• How we see it depends on how we perceptually organize.• Also depends on the context in which we just saw it and
individual bias, etc.
Vase or Face?
“Yes or No” Sculpture by Markus Raetez
Reversible figures
• Follow the same principle
Is the dark side in the front or the back?
How the Brain Perceives
Impossible Figures
• Follow the same principle of not enough information so we interpret it
• Usually a 2-D figure which interpreted by the visual system as representing a projection of a three-dimensional object that is not geometrically possible
Devil’s Tuning Fork
M.C. Escher
“Relativity”
How many legs does this elephant have?
Penrose Triangle (Ernst, 1987)
Hermann Grid Illusion Hermann (1870)
Explanation
Researchers have traditionally used what is known as lateral inhibition to explain why people see these gray areas. This phenomena demonstrates a very important principle of perception: we don't always see what's really there. Our perceptions depend upon how our visual system responds to environmental stimuli and how our brain then interprets this information. New theories suggest there might be a better explanation.
Muller-Lyer Illusion
Zollner Illusion
Illusory Contours
Ponzo Illusion
Ames Room
How it actually looks
• The Ames room forms an identical image of a normal cubic room on your retina even though it is not cubic.
How does it work?
STROOP EFFECT