SENSATION

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SENSATION PERCEPTION

• CHAPTERS 4 5
• AP PSYCHOLOGY

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PERCEPTION
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Three Approaches to Perception

• Computational tries to determine the
  computations that a machine would have to solve
  perceptual problems
• Constructivist reality is constructed from
  fragments of sensory information
• Ecological environment contains most of the
  information needed to form perceptions

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Psychophysics

• Describes the relationship between the physical
  energy in the environment and the psychological
  experience of that energy
• Absolute Threshold the minimum detectable
  amount of environmental energy a sensory system
  can detect

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Absolute Thresholds Table 5.1
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Signal-Detection Theory

• Sensitivity a persons ability to pick out a
  particular stimulus or signal
• Response Criterion a persons willingness or
  reluctance to say that a stimulus is present
• Signal-Detection Theory model of our personal
  sensitivity and response criterion combined to
  determine whether or not a near-threshold
  stimulus has occurred

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Figure 5.4 Signal Detection
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Judging Differences Between Stimuli

• Difference Threshold or Just-Noticeable
  Difference (JND)
• JND determined by two factors
• How much of a stimulus was there to begin with?
• Which sense is being stimulated?

Click the link below to see how JND impacts the
consumer world http//www.psfk.com/2009/03/media-
arts-mondays-just-noticeable-difference.html
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Webers Law

• Webers Constant
• Law States That JND KI
• K is the Webers constant for a particular sense.
• I is the amount, or intensity, of the stimulus.
• The smaller K is, the more sensitive a sense is
  to stimulus differences

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Magnitude Estimation

• Magnitude estimation is how our perception of
  stimulus intensity is related to actual stimuli
  strength
• Fechners Law
• Constant increases in physical energy will
  produce smaller increases in perceived magnitude
• Stevens Power Law
• Describes a wider range of sensations

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Perceptual Illusions

• Illusion incorrect perception of a stimulus
• Delusion a false belief
• Hallucination a perception in the absence of a
  stimulus

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Figure 5.5 Length Illusions
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Figure 5.6 Organize This!
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Perceptual Illusions
Ames room
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Perceptual Illusions
Ames room
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Basic Processes in Perceptual Organization

• Figure-Ground Organization
• Perceptual apparatus picks out some objects to be
  figures, while others are less relevant in the
  background
• Grouping
• Inherent properties of the stimulus environment
  lead people to group them together
• Grouping Principles
• Proximity--group nearby figures together
• Similarity--group figures that are similar
• Continuity--perceive continuous patterns
• Closure--fill in gaps
• Common fate objects moving in the same
  direction at the same speed are perceived as
  together
• Synchrony occur at the same time
• Common region located within some boundary
• Connectedness--spots, lines, and areas are seen
  as unit when connected

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Figure 5.7 Reversible Images
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Figure-Ground
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Figure 5.8 Gestalt Principles of Perceptual
Grouping
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More Grouping Principles
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Perceptual Organization

• Likelihood Principle
• We perceive objects in the way that experience
  tells us is the most likely physical arrangement
  (consistent with Constructivism)
• Simplicity Principle
• We organize stimulus elements in a way that gives
  us the simplest possible perception

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Figure 5.9 Impossible Objects
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Perception of Location and Distance

• Two-Dimensional Location uses an equation that
  takes information about where an image strikes
  the retina and adjusts it based on information
  about movement of your eyes and head
• Visual dominance bias toward using visual
  information when it conflicts with information
  from other senses

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Depth Perception

• Our ability to perceive distance, allowing people
  to experience the world in three-dimensions
• Interposition closer objects block the view of
  things further away
• Relative Size the object producing a larger
  image on the retina is perceived as closer
• Height in the Visual Field more distant objects
  are higher in the visual field
• Texture Gradient graduated change in texture
  less detailed as distance increases
• Linear Perspective the closer together 2
  converging lines are, the greater the perceived
  distance
• Clarity, Color, Shadow distant objects appear
  hazier
• Motion Parallax objects closer appear to move
  rapidly, while those distant appear motionless

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Figure 5.10 Stimulus Cues for Depth Perception
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Cues Based on Physiology

• Accommodation muscles surrounding the lens
  either tighten (to focus on close objects) or
  relax (to focus on distant objects)
• Convergence each eye rotates inward to see
  closer objects
• Binocular Disparity the difference between the
  two retinal images of an object provides distance
  cues

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Perceptual Organization Depth Perception
Visual Cliff
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Perceptual Organization Depth Perception
Relative Size
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Perceptual Organization Depth Perception
Interposition
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Perceptual Organization Depth Perception
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Perception of Motion

• Looming a rapid expansion in the size of an
  image so that it fills the retina and is
  perceived as an approaching object
• Stroboscopic Motion our tendency to perceive
  motion through a series of flashing rapid light

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Perceptual Constancy

• The perception of objects as constant in size,
  shape and color
• Size Constancy occurs as objects move closer or
  farther away
• Shape Constancy occurs as an object appears the
  same, even though the shape of its retinal image
  changes
• Brightness Constancy occurs so that no matter
  how the amount of light striking an object
  changes, its perceived brightness remains constant

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Figure 5.12 A Size Illusion
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Perceptual Organization Muller-Lyer Illusion
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Figure 5.13 Brightness Contrast
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Recognizing the Perceptual World

• The brain analyzes the incoming pattern of the
  stimulus and compares that pattern to information
  stored in the memory
• Top-down processing guided by knowledge and
  expectations
• Our experiences create schemas, or mental
  representations of what we know about the world
• Bottom-up processing relies on specific,
  detailed information from sensory receptors that
  are integrated and assembled into a whole

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Parallel Distributed Processing Models (PDP)

• Units in a network operate parallelsimultaneously
  
• Each element is connected to all other
  computational elements
• Recognition occurs as a result of the
  simultaneous operation of connected units

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Attention

• The process of directing and focusing certain
  psychological resources to enhance perception,
  performance, and mental experience

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SENSATION
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How do we take in information?

• A sense is a system that translates information
  from outside the nervous system into neural
  activity.
• Messages from senses are called sensations
• For example, vision is the system through which
  the eyes convert light into neural activity.
  This tells the brain something about the source
  of the light (brightness) or about the objects
  from which the light is reflected (round, red,
  etc).

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Elements of a Sensory System

1. Energy (light, sound waves, etc) contains info
   about the world
2. Accessory Structures (lens, ear, etc) modify
   energy.
3. Transduction- the process of converting incoming
   energy into neural activity through sensory
   receptors
4. Sensory nerves transfer the coded activity to the
   Central Nervous System.
5. Thalamus processes and relays the neural response
   (except in smell).
6. Cortex receives input and produces the sensation
   and perception

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Figure 4.1 Elements of a Sensory System
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How does physical energy get converted into
neural activity?

• CODING - translation of the physical properties
  of a stimulus into a pattern of neural activity
  that specifically identifies those physical
  properties.
• Doctrine of Specific Nerve Energies - stimulation
  of a particular sensory nerve provides codes for
  that one sense, no matter how the stimulation
  takes place
• Temporal Code - involves changes in the timing of
  the neurons firing. Ex A bright light will
  cause some neurons in the visual system to fire
  faster than a dim light.
• Spatial Code - the location of the firing neurons
  provides information about the stimulus (tells us
  where the sensation is coming from).

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Vision

• Light electromagnetic radiation
• Visible light has a wavelength from just under
  400 nanometers to 750 nanometers
• Light intensity
• How much energy the light contains
• Determines the brightness of light
• Light Wavelength
• The difference between peaks in light waves
• Determines what color we see

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Figure 4.7 Spectrum of Electromagnetic Energy
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The spectrum of electromagnetic energy
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Physical Properties of Light Waves
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Accessory Structures of the Eye

• Cornea curved, transparent layer through which
  light rays enter the eye
• Pupil opening in the eye through which light
  passes
• Iris colorful part of the eye which adjusts the
  amount of light entering the eye
• Lens bends rays, focusing them on the retina
• Retina Surfaces at back of the eye onto which
  the lens focuses light rays

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Figure 4.8 Major Structures of the Eye
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Vision

• Accommodation- the process by which the eyes
  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

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Converting Light into Images

• Visual transduction is the conversion of light
  energy into neural activity.
• Conversion done by photoreceptors in the retina.
• Two main types of photoreceptors Rods and cones.

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Rods and Cones

• Rods
• peripheral retina
• detect black, white and gray
• twilight or low light
• Cones
• near center of retina
• fine detail and color vision
• daylight or well-lit conditions

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Interactions in the Retina

• Photoreceptor cells connect to bipolar cells and
  then to ganglion cells
• Axons of the ganglion cells form the optic nerve,
  which extends out of the eye and into the brain
• Each neuron of a sensory system has a receptive
  field part of the retina and the region of the
  environment to which that cell responds

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Figure 4.11 Center-Surround Receptive Fields of
Ganglion Cells
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Figure 4.12 The Hermann Grid
The cell whose receptive field includes the space
at the intersection has more whiteness shining on
its inhibitory surround than the cell whose
receptive field is just to the right of the
intersection. The output of the intersection cell
will be lower than that of the one on the right,
creating the impression of a shadow.
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Visual Pathways

• Axons from ganglion cells converge as a bundle of
  fibers called the optic nerve and exit the
  eyeball at one spot
• The exit point has no photoreceptors and is
  insensitive to light creating a blind spot
• About ½ the fibers of the optic nerve cross over
  to the opposite side of the brain at the optic
  chiasm (part of the bottom surface of the brain)

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Visual Pathways cont

• Axons from most of ganglion cells in retina form
  synapses in the thalamus, in a specific region
  called the lateral geniculate nucleus (LGN)
• Neurons in the LGN relay the visual input to the
  primary visual cortex, located in the occipital
  lobes in the back of the brain

The pathway of light http//www.youtube.com/watch
?v15P8q35vNHw
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Pathways from the Eyes to the Visual Cortex
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Visual Representations

• Receptive fields of neurons are characterized by
  parallel processing and hierarchical processing
• Parallel Processing of visual properties Brain
  conducts separate kinds of analysis
  simultaneously on the same information.
• The what system
• The where system
• Hierarchical Processing of visual properties
• Individual cells in the visual cortex receive
  input from several LGN neurons.
• Cortical cells respond to specific features of
  objects in the visual field Feature detectors

Light Conversion
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Seeing Color

• Hue color determined by the dominant wavelength
  in the mixture of the light (excludes black,
  white, gray)
• Saturation purity of a color
• Brightness overall intensity of the wavelengths
  that make up light

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Visual Information Processing

• Trichromatic (three color) Theory
• Young and Helmholtz
• three different retinal color receptors

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Trichromatic Theory of Color

• Any color can be produced by mixing pure lights
  of blue, green, and red.
• There are three types of cones, each most
  sensitive to particular wavelengths.
• Ratio of the activities of the three types of
  cones indicates what color is sensed.

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Opponent-Process Theory

• Ewald Hering
• Each of the three color sensitive elements are
  organized as pairs, where each pair member
  opposes, or inhibits, the other
• Red-Green
• Blue-Yellow
• Black-White

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Trichromatic and Opponent-Process Theories
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Opponent-Process Theory
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Figure 4.20 Color Coding and Ganglion Cells
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HEARING

• Sound is a repetitive fluctuation in the pressure
  of a medium, such as air.
• In a place like the moon, which has almost no
  atmospheric medium, sound cannot exist
• When you speak, your vocal cords vibrate,
  producing fluctuations in air pressure that
  spread as waves. A wave is a repetitive
  variation in pressure that spreads out in 3
  dimensions.

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Physical Characteristics of Sound

1. Amplitude- (intensity) difference in air pressure
   from the baseline to the peak of a wave.
2. Wavelength- the distance from one peak wave to
   the next.
3. Frequency- number of complete waves, or cycles,
   that pass by a given point in space every second.
   Described in a unit called hertz, (Hz). 1 cycle
   per second is 1 hertz

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Figure 4.2 Sound Waves and Waveforms
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Psychological Dimensions of SoundWhat do we
actually hear?

• Loudness- determined by amplitude. Greater
  amplitude Louder sounds
• Pitch- how high or low a tone sounds. Determined
  by frequency.
• High frequency High Pitch
• Low Frequency Low Pitch
• Timbre- (pronounced tamber) is the quality of
  the sound

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The Ear

• Auditory accessory structures modify sound waves
  before information affects neural signals
• Pinna crumpled part of ear that funnels sound
  through the ear canal
• Tympanic Membrane eardrum tightly stretched
  membrane in the middle ear where sound waves
  strike
• Vibrations of the tympanic membrane are
  transferred through 3 tiny bones - malleus
  (hammer), incus (anvil), stapes (stirrup)

Sound Waves 1
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Auditory Transduction

• After sound passes through the oval window, it
  enters the inner ear or cochlea - this is where
  transduction occurs
• The basilar membrane forms the floor of this long
  tube
• Sound waves bend hairs of the organ of Corti a
  group of cells which rest on the membrane
• Hair cells connect with fibers from the auditory
  nerve, a bundle of axons that goes into the brain

Figure 4.4 The Cochlea
Sound Waves 2
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Auditory Pathways

• Auditory nerve ? brainstem ? thalamus
• The information coded in the activity of auditory
  nerve fibers is conveyed to the brain and
  processed further
• Information is relayed from the auditory nerve to
  an area of the cerebral cortex called the primary
  auditory cortex
• Various aspects of sound processed in different
  regions of auditory system.
• Certain parts of auditory cortex process certain
  types of sounds.

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Auditory Transduction
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Sensing Pitch

• Different people may experience the same sound
  as different pitches.
• Pitch-recognition abilities influenced by
  genetics.
• Cultural factors are also partly responsible for
  the way in which a pitch is sensed.

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Locating Sounds

• Determined partly by the very slight difference
  in when sound arrives at each ear.
• The brain also uses information about the
  difference in sound intensity at each ear.

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Coding Intensity and Frequency

• The more intense the sound, the more rapid the
  firing of a given neuron.
• Frequency appears to be coded in two ways place
  theory and frequency-matching theory

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Coding Frequency Place Theory

• Sounds produce waves that move down the basilar
  membrane.
• Where the wave peaks depends on the frequency of
  the sound.
• Hair cells at a particular place on the membrane
  respond most to a particular frequency.

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Coding Frequency Frequency Matching Theory

• Firing rate of an auditory nerve matches a sound
  waves frequency.
• Sometimes called the volley theory of
  frequency coding.

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Smell, Taste, and Flavor

• Smell and taste act together to form system known
  as flavor.
• Tastes and odors can prompt strong emotional
  responses.
• Nutritional state can affect taste and flavor of
  food and motivation to eat particular foods.
• Flavor includes other characteristics of food.

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Somatic Senses and the Vestibular System

• Somatosensory systems are spread throughout the
  body
• Somatic senses include
• Skin senses of touch, temperature, and pain
• Kinesthesia
• Vestibular system tells the brain about the
  position and movement of the head

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Touch

• Energy detected is physical pressure on tissue.
• Many nerve endings in the skin act as touch
  receptors.
• Touch is both an active and passive sense.
• Changes in touch provide most important sensory
  information.

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Coding of Touch Information

• Intensity of the stimulus is coded by
• Firing rate of individual neurons and
• The number of neurons stimulated.
• Location is coded by the location of the neurons
  responding to the touch.

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Temperature

• Some of the skins sensory neurons respond to a
  change in temperature.
• Warm and cold fibers
• Sensations of touch and temperature sometimes
  interact.
• Stimulation of the touch sense can have
  psychological and physiological effects.

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Pain

• Pain provides information about impact of world
  on body.
• Information-carrying aspect of pain very similar
  to that of touch and temperature.
• Two types of nerve fibers carry pain signals from
  skin to the spinal chord.
• Cerebral cortex plays role in the experience of
  pain.

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Figure 4.25 Pain Pathways
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Modulating Pain

• Gate Control Theory
• theory that the spinal cord contains a
  neurological gate that blocks pain signals or
  allows them to pass on to the brain
• gate opened by the activity of pain signals
  traveling up small nerve fibers
• gate closed by activity in larger fibers or by
  information coming from the brain
• Natural Analgesics
• Serotonin
• Endorphins

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Proprioceptive Senses

• Sensory systems that provide information to the
  brain about
• The position of the body.
• What each of part of the body is doing.
• Vestibular sense indicates the position of the
  head in space and its general movements.
• Sense of balance.

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Vestibular Sense

• Organs
• Vestibular sacs
• Otoliths
• Semicircular canals
• Neural connections to
• The cerebellum
• The autonomic nervous system
• The eye muscles

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Kinesthesia

• Sense that indicates where the parts of the body
  are with respect to one another.
• Necessary guide for movement.
• Kinesthetic information comes primarily from the
  joints as well as muscles.

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The Chemical Senses

• Olfaction detects airborne chemicals
• Our sense of smell
• Gustation detects chemicals in solution that come
  into contact with receptors inside the mouth
• Our sense of taste

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Figure 4.23 The Olfactory System
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Olfactory System

• Employs about 1,000 different types of receptors.
• Only sense that does not send its messages
  through the thalamus.
• Processing in several brain regions including
  frontal lobe and amygdala
• Strong relationship between olfaction and
  emotional memory

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Olfactory System (contd.)

• Only sense that does not send its messages
  through the thalamus.
• Pathways from olfactory bulb sends information on
  for further processing in several brain regions.
• Including frontal lobe and amygdala.
• Strong relationship between olfaction and
  emotional memory.

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Pheromones

• Chemicals released by one animal, and when
  detected by another, can shape the second
  animals behavior or physiology.
• Role of pheromones in humans not clear

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Age, Sex and Sense of Smell
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Articles

• http//www.hhmi.org/senses/

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Illusions

• http//psylux.psych.tu-dresden.de/i1/kaw/diverses
  20Material/www.illusionworks.com/index.html

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Blind Spot Demonstration

• http//serendip.brynmawr.edu/bb/blindspot1.html

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Jeopardy

• http//www.uni.edu/walsh/jeopardy.html

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More Information on Sensation and Perception

• http//www.muhlenberg.edu/depts/psychology/lsnodgr
  ass/sp/dem_links.html

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References

• http//college.cengage.com/psychology/bernstein/ps
  ychology/7e/instructors/index.html
• http//www.lbusd.k12.ca.us/millikan/Teacher_folder
  /HawkinsS/AdPlPsychology2.htm