Embed Size (px)
Citation preview
Sensation and Perception
• “Everything you see or hear or experience in any way at all is specific to you. You create a universe by perceiving it, so everything in the universe you perceive is specific to you.” – Douglas Adams
Sensation
•The process of taking in information from the environment
Transduction
• The process of changing raw sensory data into an electrochemical message that will be sent to the brain for interpretation.
Perception
•How we recognize, interpret, and organize our sensations
• Input comes primarily from these five external senses:–Visual (Eyes)–Audio (Ears)–Cutaneous/Tactile (Touch)–Olfaction (Smell) (Nose)–Gustation (Taste) (Tongue)
Kinesthetic Sense• The kinesthetic sense
monitors the position and movements of muscles, bones, and joints. Receptors in the joints and tendons send the brain information about the angle of your limbs.
Vestibular Sense• The system for
balance.• Fluid in the
semicircle canals of the inner-ear maintain the body’s sense of balance.
Detection Threshold or Absolute Threshold
•The minimum intensity of energy required to produce sensation in a receptor cell at least 50% of the time
Difference Threshold or Just Noticeable Difference
•The smallest change in stimulation that you can detect
Weber’s Law • The greater the magnitude of the
stimulus, the larger the difference must be in order to be noticed–IE. If you are carrying 20 lbs. and add 5
lbs., it’s noticeable. If you are carrying 100 pounds and add 5 pounds, it may not be noticeable. You may need to add 20 lbs. to 100 pounds to make it noticeable.
Sensory Adaptation
• Diminished sensitivity as a result of constant and unchanging stimulation.• You jump into a swimming pool of cold
water, but eventually you “get used to it”. Or, you wear your glasses so often that you sometimes forget that they are on.
Subliminal Perception
• Thresholds imply that there must be stimulus below and beyond our current levels of detection. Can human behavior be influenced by stimulus that is below or beyond our level of awareness?
Subliminal Perception
Extrasensory Perception
• Some people claim to have extra powers of perception, or the ability to respond to an unknown event that is not presented to any of the known senses. • Parapsychology
Examples of Extrasensory Perception
• Telepathy: Transfer of information on thoughts or feelings between individuals by means other than the five classical senses
• Precognition: Perception of information about future places or events before they occur.
• Clairvoyance: Obtaining information about places or events at remote locations, by means unknown to current science.
• Does ESP Exist?• Remote Viewing?• Telepathy?
Paranormal Activity
• A&E Series Paranormal State• A&E Series Psychic Kids
Visual Sensation
• How Do We See?• Visual Sensation and Perception• Vision And Behavior
Human Eyeball
Cornea
• transparent protective coating over the front part of the eye
Iris • the colored part of the eye – this muscle
dilates or contracts the pupil to allow more or less light to enter
Pupil
• the small, adjustable center of the iris that allows light to enter the eye
Lens
• flexible enough to focus on objects near or far (accommodation) – if an object is very close is gets smaller and rounder; if an object is further away, it get larger and wider
Retina
• The inner lining of the back of the eyeball. The lens focuses an image from the outside world on the retina, and the retina in turn transduces the image.
Fovea
• On the retina, directly behind the lens. The area of sharpest picture.
• Acuity – the sharpness of vision• Nearsightedness – the misshapen eyeball
focuses light rays in front of the retina – you will see near objects well, but not far away objects
• Farsightedness – the light rays from nearby objects reach the retina before they have been focused – you will see far objects better than near objects
Rods and Cones
• In the retina. Rods determine shades of light and dark and detect motion. Cones determine color.
Optic Nerve
• Carries the transduced visual information from the eye and sends it to the brain for processing.
Blind Spot
• The area closest to the optic nerve, that has no receptor cells. Also known as the optic disc.
Optic Chiasm
• The point in the brain at which messages from the visual fields are split to the appropriate areas of the brain–Prosopagonosia - stroke victim
disorder in which victims cannot recognize faces, but can still see well and recognize emotions on faces
Stereopsis (Contralateral Shift)
Color Vision
• There are two theories of color vision:–Trichromatic Theory–Opponent-Process Theory
Young-Helmholtz TheoryTrichromatic Theory
• Rods and cones are pre-set to be sensitive to RED, GREEN, and BLUE. All of the colors that we see are combinations of those three colors.
All other colors can be derived by combining these three.
Opponent-Process Theory
• Sensory receptors in the retina come in pairs:–Red/Green–Yellow/Blue–Black/White
Opponent-Process Theory• If one sensor is stimulated, the other is
inhibited• If one sensor is over-stimulated, and fatigues,
the paired sensor will be activated, causing an afterimage
• If a person is missing a particular pair of sensors, they will be colorblind to those hues– Dichromatic Color Blindness have difficulty seeing
shades of red and green, or yellow and blue
• Hue – the color that we see is determined by the wavelength (the distance from one wave peak to the next) of the light wave that the eye is receiving
• Brightness is influenced by the height of the waves (amplitude) of light that are received by the eye
• The shorter the wavelength, more bluish colors• The longer the wavelength, more
reddish colors• The higher the wave, more yellowish• The lower the wave, more greenish
Color Range
The Visual Cliff
Figure/Ground Dynamic
• The ability to distinguish different objects from one another• Analyzing separate information
allows us to re-act to each individual object accordingly–Camouflage – when figures blend into
the background
Figure-Ground Dynamic
Camouflage
© E.R. Degginger/Anils Animals
Gestalt Rules–Gestalt Psychologists focused on how
we normally perceive images as groups, not isolated elements–Several factors influence how we will
group objects:• Proximity• Similarity• Continuity• Closure
Proximity
•When objects are close together we tend to perceive them as together rather than separate
Proximity
Similarity
•Objects that are similar in appearance are more likely to be perceived as belonging in the same group
Similarity
Closure
• The tendency to overlook incompleteness, and tocomplete objects so that they fit into our mental preconceptions of what objects are supposed to look like
Closure
Continuity
• To perceive lines and motion in fluid forms rather than jagged motions
Continuation
Constancy• Despite changes in distance or
lighting, objects still maintain their original properties–Size Constancy–Shape Constancy–Brightness Constancy
Size Constancy
• Objects closer to us will produce bigger images on our retinas, and as they move away they project a smaller image. The actual size of the object does not change.– IE. When a man is right in front of us, he is 6
ft. tall. As he walk further and further away, his image gets smaller. He hasn’t shrunk; he is still 6 ft. tall.
Size Constancy
Shape Constancy
• Objects viewed from different angles will produce different shapes on our retina. Though we may change our position, the shape doesn’t change. – IE. Looking at the top of a glass one way
makes it look round; from another angle it looks elliptical. The actual shape hasn’t changed…it is still round.
Brightness Constancy
• We perceive objects as having a constant color, despite lighting, shading, etc.–A brick wall is still red, whether bright
sunlight is on it, or darkness has made it look gray.
Depth Cues
• Depth Cues allow us to perceive the world in three dimensions.–Monocular Cues are depth cues that do not
depend on having two eyes working in conjunction together–Binocular Cues are depth cues that depend
on having two eyes working in conjunction with each other
Monocular Cues
• Linear Perspective• Relative Size• Interposition• Texture Gradient• Shadowing• Motion Parallax
Linear Perspective
• Parallel lines seem to converge the further they get from us. The gradual reduction of image size as distance from the object increases
• Vanishing Point – where two parallel lines connect in the distance
Relative Size
• Objects that project a smaller image on the retina are perceived as further away; larger images are closer
Elevation
• Objects on top of our horizon are smaller and further away, objects below are closer and larger
Interposition
•Near objects partially obscure objects further away
Texture Gradient
• Patterns of distribution tend to grow more dense with distance – things further away seem more smooth, up close more detailed
Shadowing
•Lighted objects seem closer, darker further away
Motion Parallax
• As images move across the retina, the perception of movement is created. Objects further away move slower across the retina, closer objects move faster.
Binocular Cues
•Binocular Disparity/Retinal Disparity•Convergence
Binocular Disparity
• Each of our eyes sees an object from a slightly different angle and projects that image onto the retina. The closer an object is, the further apart the two retinal images are. Further, closer images.
Convergence
• As objects get closer and further from us, our eyes move towards each other or away. The closer they are, the closer the object.
