Ch 6 Flashcards
Sensation
The processes of sensory responding and
of the sensory receiving areas of the
brain.
Perception
The process by which the brain organizes
and interprets sensory information.
Our Sensational Senses
Most students learn there are five senses, corresponding to five sense organs: Vision → eyes Hearing → ears Taste → tongue Touch →skin Smell → nose
The Riddle of Separate Senses
Doctrine of Specific Nerve Energies
The principle that different sensory modalities exist because signals received
by the sense organs stimulate different nerve pathways leading to different
areas of the brain.
Examples
Signals from the eye → travel along the optic nerve to the visual cortex.
Signals from the ear → travel along the auditory nerve to the auditory
cortex.
Synesthesia
A condition in which stimulation of one sense also evokes another. Examples Colour purple smells like a rose. Aroma of cinnamon feels like velvet.
Three Limitations of the Doctrine of Specific Nerve Energies
- Difficult to link the different senses to distinct nerve pathways.
- Can not explain variations within a particular sense.
Sight of pink versus red
Sound of a piccolo versus the sound of a tuba
Feel of a pinprick versus the feel of a kiss - Explains the experience of different kinds of sense sensations using only
anatomical codes.
Anatomical codes → Specific neural circuits signify particular sensory
experiences.
Functional codes→ Information about which cells are firing, how many
cells are firing, the rate at which cells are firing, and the patterning of
each cell’s firing signify particular sensory experiences.
Measuring our Senses
- Absolute Threshold
The smallest quantity of physical energy that can
be reliably detected by an observer.
Measuring our Senses: Absolute Sensory Thresholds
Vision
Candle flame on a clear, dark night from almost 50 km away.
Hearing
Tick of a watch in a perfectly quiet room from over 7 m away
Smell
1 drop of perfume diffused through a 3-room apartment.
Touch
Wing of a bee on your cheek, dropped from a height of 1 cm.
Taste
1 teaspoon of sugar in 2 gallons of water.
- Difference Threshold
The smallest difference in stimulation that can be reliably detected by an
observer when two stimuli are compared.
3.The Signal-detection theory
A psychophysical theory that divides the detection of a
sensory signal into a sensory process and a decision
process.
Sensory process is depends on the intensity of the
stimulus.
Decision process is influenced by the observer’s
response bias.
Sensory Adaptation
The reduction or disappearance of sensory
responsiveness when stimulation is unchanging or
repetitious.
Example
Sense of a watch on your wrist.
Sensory Deprivation
The absence of normal levels of sensory stimulation. Often occurs through prolonged isolation. The effects of sensory deprivation Hallucinations Disorientation Depression Irritability Restlessness
Two Types of Isolation
Involuntary Isolation Locked in a room for an indefinite period of time. Voluntary Isolation Choosing to take a little time-out. Visit to a luxury spa or a monastery
Sensing without Perceiving
Sensory overload
Overstimulation of the senses.
Selective attention
The focusing of attention on selected aspects of
the environment and the blocking out of others.
Protects from sensory overload.
Inattentional blindness
Failure to consciously perceive something you are looking at
because you are not attending to it.
Example
Focusing on listening to a voice on your cell.
Fail to see a pedestrian crossing the street in front of you.
Hue, Saturation and
Brightness
Perception of a colour depends on a mix of 3 dimensions. Hue Wavelength of light. Saturation Purity of light. Brightness Intensity of light.
The Visual Pathway
1. The Main Visual Pathway Thalamus: sensory relay. Primary visual cortex. Lateral geniculate nuclei. Secondary visual cortex. Temporal and parietal lobes. 2. The Second Visual Pathway: Coordination of visual input with other sensory input. Superior colliculus (midbrain). Thalamus. Occipital lobe.
The Main Visual Pathway
a. Magnocellular channel “Where pathway”. Perception of motion and depth. b. Parvocellular channel “What pathway”. Perception of colour, form and texture.
Feature Detector Cells
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 different shapes
(e.g., bulls-eyes, spirals, & faces).
The Trichromatic Theory
Support for the
Trichromatic Theory
The Trichromatic Theory proposes that the eye contains 3 colour receptors each differently sensitive to the various wavelengths of light. For any colour, the 3 receptors will produce a unique ratio of activity.
Evidence indicates 3 types of cone receptors as proposed by the Trichromatic theory.
Rod Monochromats
Non-functional cones,
poor visual acuity,
shades of grey.
Deuteranopia
Defective medium,
shades of blue and
yellow.
Tritanopia
Defective short, shades
of blue and red.
Phenomena not explained by Trichromatic
theory
- The Number of Primary Colours
Participants in some studies described various
colours using 4 instead of 3 primary colours:
Blue, green, yellow and red. - Complementary colours
Opposite colours mixed in equal proportions
yield neutral grey. - Afterimages
A visual image that persists after a stimulus is removed.
The color of the afterimage will be the complement of the color you
originally stared at.
For example:
Blue and Yellow
Red and Green
Opponent Process Theory
Opponent Process Theory proposes that the eye contains 3 opponent-process receptors: 1. Red and Green 2. Blue and Yellow 3. Black and White
The Theories of Colour Vision
It takes both theories to explain colour vision. Trichromatic Theory The eye has three types of cones. Opponent Process Theory Cells in the retina, the LGN, and the visual cortex respond in opposite ways to red versus green, and blue versus yellow.
The Theories of Colour Vision
Perception of colour involves sequential stages of information processing. First stage of processing → Trichromatic theory. Later stages of processing→ Opponent processing theory
Monocular Cues
Light and Shadow
Give objects the appearance of three
dimensions.
Visual Constancies
Perceptual constancy
Five Visual Constancies
Perceptual constancy The accurate perception of objects as stable or unchanged despite changes in the sensory patterns they produce. Five Visual Constancies 1. Shape constancy 2. Location constancy 3. Size constancy 4. Brightness constancy 5. Colour constancy
erception →Vision →Visual Constancies
Visual Constancies
1.Shape Constancy
Shape of retinal image produced by an
object changes when our point of view
changes.
Still see object as having a constant shape
Visual Constancies
2. Location Constancy
Retinal image moves about as we move our
eyes, head, and body.
Still perceive stationary objects as
remaining in the same place.
Visual Constancies
3. Size Constancy
Retinal image becomes smaller or larger.
Still perceive object as having a constant size
Visual Constancies
4. Brightness Constancy
Amount of light objects reflect changes as the
overall level of illumination changes.
Still see objects as having a relatively constant
brightness.
Visual Constancies
5. Color Constancy
The wavelength of light reaching our eyes
from the object may change as the
illumination changes.
Still perceive object as maintaining its hue
What We Hear
1. Loudness → Amplitude Amplitude The maximum height of a sound wave What We Hear 2. Pitch → frequency (16 Hz- 20,000 Hz) Frequency The number of times per second the sound wave cycles through a peak and a low point. 3. Timbre → complexity Complexity The relative breadth of the range of frequencies that make up the sound wave
Gestalt Psychology & Hearing
1. Figure and Ground
1. Figure and Ground Certain sounds stand out while other sounds fade into the background. Example Figure → Your psychology instructor’s voice. Ground → hum of a passing airplane. → cheers from the athletic field. → voices of other students.
Many other Gestalt principles apply to
hearing:
proximity continuity similarity closure common fate
Auditory Localization
1. Time of Arrival Sounds arrive at the left and right ear at different times. Calculate time difference to locate sound. Most effective for low frequency sound waves
2. Intensity of wave Head casts a sound shadow producing intensity differences between ears. Effective for higher frequencies only. Both cues: Hard to localize sounds coming from directly behind you or directly above your head.
The Sense of Taste
Papillae Knoblike elevations on the tongue, containing the taste buds. 1. Fungiform papillae 2. Circumvallate papillae 3. Foliate papillae
The Sense of Taste
The Five basic tastes:
Salty→ table salt Sour → lemon Bitter → coffee Sweet → piece of cake Umami → aged cheeses
The Sense of Taste
Different people h
tastes based on: Genetics Culture Learning Food attractiveness
The Sense of Smell
Humans can detect approximately 10, 000
different odours.
None of which are considered more “basic” than
the others.
Humans have as many as 1000 different smell
receptors.
Distinct odours activate unique combinations of
receptor types
The Importance of Smell
Smell is vital for human survival. Smelling smoke Food spoilage Gas leaks Odours have psychological effects on human beings. Smell of perfumes Sniff of flowers Smell of freshly baked cookies
Senses of the Skin
There are four basic skin senses: 1. Touch (or pressure) 2. Warmth 3. Cold 4. Pain Certain spots on the skin are especially sensitive to these four basic senses. Scientists have had difficulty finding distinct receptors for these sensations
The Mystery of Pain
Acute pain
Short-term pain.
Often fast, sharp and centralized in one area.
Body’s warning of current damage to tissue or disease.
Chronic pain
Long-term, continuous pain.
Physical injury, arthritic damage to joints, and degeneration of bones
The Mystery of Pain
The Gate-Control Theory
Experience of pain depends on whether pain
impulses get past a neurological “gate” in the spinal
cord and thus reach the brain.
Thoughts and feelings influence our reactions to pain. Dwelling on pain →Intensifies the pain. Distracted from pain →Decreases the experience of pain.
Neuromatrix Theory of Pain
Matrix of neurons in the brain
is capable of generating pain
in the absence of signals from
sensory nerves.
The Mysteries of Pain
1. Pain comes in many varieties
Pin prick Bruise Stomach ulcer 2. Pain’s psychological effects vary with time. Moment-to-moment unpleasantness. Worry about the long-term implications. 3. The experience of pain varies among individuals. Genetic differences. Different expectations
The Environment Within
Kinesthetic System
The sense of body position and movement of
body parts.
Mechanics
Information provided by pain and pressure
receptors located in the muscles, joints and
tendons.
The Environment Within: Vestibular System
Sense of balance or equilibrium.
Specifies the position of the head in space
The Environment Within: Semicircular canals
3 sense organs (tubes) in the inner ear.
Movement of the head leads to unique combinations of fluid
flow in canals.
Fluid flow stimulates hair cells in the canals.
Nerve connections feed information to the brain
Inborn Abilities
Most basic sensory abilities and perceptual skills are inborn or develop early. Distinguishing tastes. Discriminating among odours. Recognizing voices. Discriminating sizes and colours.
Critical Periods
Period of time during development in which the brain is optimally capable of acquiring a specific ability. Appropriate environmental stimuli must be present. Cells in the nervous system respond to stimuli and form or strengthen appropriate neural pathways.
Critical periods of sensory develop exist in
human beings.
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.
Blakemore & Cooper (1970)
Kittens were exposed to either vertical or horizontal lines: 1. Exposure to horizontal lines Bumped into vertical lines Ran to horizontal lines 2. Exposure to vertical lines Bumped into horizontal bars Ran to vertical lines
Psychological and Cultural Influences
Psychological factors influence what we perceive and how we perceive it:
1. Needs
More likely to perceive something we need
2. Beliefs
Affect our interpretation of ambiguous sensory signals
3. Emotions
Influence our interpretation of sensory information
Negative emotions prolong and intensify pain
4. Expectations
Affect how we perceive the world
Perceptual set- Habitual way of perceiving, based on expectations
Subliminal Perception
Perceiving without awareness. Visual stimuli can affect your behaviour even
when you are unaware that you saw it.
Nonconscious processing also occurs in memory, thinking, and decision
making.
These effects work best with simple stimuli.
Subliminal Perception vs. Persuasion
Empirical research does not support “Subliminal
Persuasion”.
Examples:
Subliminal slogans in magazine advertisements.
Subliminal images in television advertisements.
Subliminal messages in rock songs.
