Upload
cynthia-ryan
View
249
Download
0
Tags:
Embed Size (px)
Citation preview
Come to your senses!?!
Chapter 4
Sensation and Perception: The Basics
Life is but an illusion.
Section 1: Basics
On the Threshold of Discovery Earliest psychologists were fascinated by
this relationship between the physical and the mental.
In fact, psychophysics, the study of psychological reactions to physical stimuli, is the oldest field of psychology.
Creepyboyfriend??
Defining Sensation and Perception
Sensation The detection of physical energy emitted or
reflected by physical objects. It occurs when energy in the external
environment or the body stimulates receptors in the sense organs.
Perception The process by which the brain organizes and
interprets sensory information.
Colored surface can be either the outside front surface or the inside back surface Cannot
simultaneously be both
Brain can interpret the ambiguous cues two different ways
Ambiguous Figure
The Riddle of Separate Sensations Sense receptors
Specialized cells that convert physical energy in the environment or the body to electrical energy that can be transmitted as nerve impulses to the brain.
Sensation & Perception Processes
Measuring Senses Absolute threshold Difference threshold Signal-detection theory
Absolute Threshold The smallest quantity of physical energy that can
be reliably detected by an observer.
Absolute Sensory Thresholds Vision:
A single candle flame from 30 miles on a dark, clear night
Hearing: The tick of a watch from 20 feet in total quiet
Smell: 1 drop of perfume in a 6-room apartment
Touch: The wing of a bee on your cheek, dropped from 1 cm
Taste: 1 tsp. Sugar in 2 gal. water
Difference Threshold …the minimum amount of difference that
can be detected between two stimuli. …people’s individual difference thresholds
vary slightly.
Absolute and difference thresholds are constantly in use to guide safety regulations.
For example, when warning lights are built into cars, safety engineers must make sure that they’re bright enough to take your attention away from other dashboard lights. Without psychology, there’d be a lot more car accidents!
Signal-Detection Theory …method of distinguishing sensory stimuli that takes
into account not only their strengths but also such elements as the setting, your physical state, your mood, and your attitudes.
…also considers psychological factors such as motivations, expectations, and learning.
We focus on whatever we consider important.
Sensory Adaptation and Deprivation Adaptation
The reduction or disappearance of sensory responsiveness when stimulation is unchanging or repetitious.
Prevents us from having to continuously respond to unimportant information.
Deprivation The absence of normal levels of sensory
stimulation.
Sensory Overload Overstimulation of the senses. Can use selective attention to reduce
sensory overload. Selective attention
The focusing of attention on selected aspects of the environment and the blocking out of others.
Section 2: Vision
Vision What we see An eye on the world Why the visual system is not a camera How we see colors Constructing the visual world
What We See Hue
Visual experience specified by color names and related to the wavelength of light.
Brightness Lightness and luminance; the visual experience
related to the amount of light emitted from or reflected by an object.
Saturation Vividness or purity of color; the visual
experience related to the complexity of light waves.
What We See
Hue Brightness Saturation
An Eye on the World Cornea
Protects eye and bends light toward lens.
Lens Focuses on objects by
changing shape. Iris
Controls amount of light that gets into eye.
Pupil Widens or dilates to let
in more light.
An Eye on the World Retina
Neural tissue lining the back of the eyeball’s interior, which contains the receptors for vision.
Rods Visual receptors that respond to dim light.
Cones Visual receptors involved in color vision. Most
humans have 3 types of cones.
The Structures of the Retina
Why the Visual System is not a Camera
Much visual processing is done in the brain. Some cortical cells respond to lines in
specific orientations (e.g. horizontal). Other cells in the cortex respond to other
shapes (e.g., bulls-eyes, spirals, faces). Feature-detectors
Cells in the visual cortex that are sensitive to specific features of the environment.
Hubel & Wiesel’s Experiment
How We See Colors Trichromatic theory Opponent process theory
Trichromatic Theory Young (1802) & von
Helmholtz (1852) both proposed that the eye detects 3 primary colors: red, blue, & green
All other colors can be derived by combining these three.
Opponent-Process Theory
A competing theory of color vision, which assumes that the visual system treats pairs of colors as opposing or antagonistic.
Opponent-Process cells are inhibited by a color, and have a burst of activity when it is removed.
Afterimages
Test of Color Deficiency
Constructing the Visual World Form perception Depth and distance perception Visual constancies: When seeing is
believing Visual illusions: When seeing is misleading
Form Perception
Gestalt principles describe the brain’s organization of sensory building blocks into meaningful units and patterns.
Figure and Ground Proximity
Seeing 3 pair of lines in A.
Similarity Seeing columns of
orange and red dots in B.
Continuity Seeing lines that connect
1 to 2 and 3 to 4 in C. Closure
Seeing a horse in D.
Depth and Distance Perception Binocular Cues:
Visual cues to depth or distance that require the use of both eyes.
Convergence: Turning inward of the eyes, which occurs when they focus on a nearby object.
Retinal Disparity: The slight difference in lateral separation between two objects as seen by the left eye and the right eye.
Depth and Distance Perception
Monocular Cues: Visual cues to depth or distance that can be
used by one eye alone.
The Ames Room A specially-built room
that makes people seem to change size as they move around in it
The room is not a rectangle, as viewers assume it is
A single peephole prevents using binocular depth cues
Visual Constancies The accurate perception of objects as stable
or unchanged despite changes in the sensory patterns they produce. Shape constancy Location constancy Size constancy Brightness constancy Color constancy
Shape Constancy Even though these images cast shadows of
different shapes, we still see the quarter as round
Visual Illusions
Illusions are valuable in understanding perception because they are systematic errors. Illusions provide hints about perceptual strategies.
In the Muller-Lyer illusion (above) we tend to perceive the line on the right as slightly longer than the one on the left.
The Ponzo Illusion Linear perspective
provides context Side lines seem to
converge Top line seems
farther away But the retinal
images of the red lines are equal!
Fooling the Eye
The cats in (a) are the same size The diagonal lines in (b) are parallel You can create a “floating fingertip frankfurter” by
holding hands as shown, 5-10” in front of face.
Section 3: Hearing
Hearing What we hear An ear on the world Constructing the auditory world
What We Hear Loudness
The dimension of auditory experience related to the intensity of a pressure wave.
Pitch The dimension of auditory experience related to
the frequency of a pressure wave. Timbre (pronounced “TAM-bur”)
The distinguishing quality of sound; the dimension of auditory experience related to the complexity of the pressure wave.
An Ear on the World
Auditory Localization Sounds from different
directions are not identical as they arrive at left and right ears Loudness Timing Phase
The brain calculates a sound’s location by using these differences.
Other Senses Taste: savory sensations Smell: The sense of scents Senses of the skin The mystery of pain The environment within
Taste: Savory Sensations Papillae
Knoblike elevations on the tongue, containing the taste buds (Singular: papilla).
Taste buds Nests of taste-receptor cells.
Taste Buds Photograph of tongue
surface (top), magnified 75 times.
10,000 taste buds line the tongue and mouth. Taste receptors are
down inside the “bud”
Children have more taste buds than adults.
Four Tastes Four basic tastes
Salty, sour, bitter and sweet.
Different people have different tastes based on: Genetics Culture Learning Food attractiveness
Smell: The Sense of Scents
Airborne chemical molecules enter the nose and circulate through the nasal cavity. Vapors can also enter through the mouth and pass into nasal cavity.
Receptors on the roof of the nasal cavity detect these molecules.
Olfactory System
Sensitivity to Touch
Gate-Control Theory of Pain Experience of pain
depends (in part) on whether the pain impulse gets past neurological “gate” in the spinal cord and thus reaches the brain.
Neuromatrix Theory of Pain Theory that the
matrix of neurons in the brain is capable of generating pain (and other sensations) in the absence of signals from sensory nerves.
The Environment Within Kinesthesis
The sense of body position and movement of body parts; also called kinesthesia.
Equilibrium The sense of balance.
Semicircular Canals Sense organs in the inner ear, which
contribute to equilibrium by responding to rotation of the head.
Perceptual Powers: Origins and Influences
Inborn abilities Critical periods Psychological and cultural Influences on
perception
The Visual Cliff
Glass surface, with checkerboard underneath at different heights Visual illusion of a cliff Baby can’t fall
Mom stands across the gap Babies show increased
attention over deep side at age 2 months, but aren’t afraid until about the age they can crawl (Gibson & Walk, 1960)
The Visual Cliff
Critical Periods If infants miss out on
experiences during a crucial period of time, perception will be impaired.
When adults who have been blind since birth have vision restored, they may not see well
Other senses such has hearing may be influenced similarly.
Psychological and Cultural Influences on Perception
We are more likely to perceive something when we need it.
What we believe can affect what we perceive. Emotions, such as fear, can influence perceptions
of sensory information. Expectations based on our previous experiences
influence how we perceive the world. Perceptual Set
A habitual way of perceiving, based on expectations.
All are influenced by our culture.
Perceptual Set
What you see in the centre figures depends on the order in which you look at the figures: If you scan from the left, see an old woman If you scan from the right, see a woman’s figure
Context Effects The same physical
stimulus can be interpreted differently
We use other cues in the situation to resolve ambiguities
Is this the letter B or the number 13?
Puzzles of Perception Subliminal Perception Extrasensory Perception: Reality or
Illusion?
Subliminal Perception Perceiving without awareness
visual stimuli can affect your behavior even when you are unaware that you saw it
nonconscious processing also occurs in memory, thinking, and decision making
these effects are often small, however, and difficult to demonstrate and work best with simple stimuli
Subliminal Perception Perception versus Persuasion
there is no empirical research to support popular notions that subliminal persuasion has any effect on a person’s behavior
persuasion works best when messages, in the form of advertising or self-help tapes, are presented above-threshold, or at a supraliminal level
Extrasensory Perception Extrasensory Perception (ESP):
The ability to perceive something without ordinary sensory information
This has not been scientifically demonstrated
Three types of ESP: Telepathy – Mind-to-mind communication Clairvoyance – Perception of remote events Precognition – Ability to see future events
Parapsychology The study of purported psychic phenomena
such as ESP and mental telepathy. Persinger suggests that psychic phenomena
are related to signs of temporal lobe epilepsy in otherwise neurologically normal individuals.
Most ESP studies produce negative findings and are not easily replicated.
Parapsychology
J. B. Rhine conducted many experiments on ESP using stimuli such as these.
Rhine believed that his evidence supported the existence of ESP, but his findings were flawed.