Chapter 4 Study Notes
How Does Stimulation Become Sensation?
Sensation
Process by which stimulation of a sensory receptor produces neural impulses that the brain interprets as a sound, a visual image, an odor, taste, a pain, or other sensory image. Sensation represents the first series of steps in processing incoming information
Perception
A process that makes sensory patterns meaningful. It is perception that makes these words meaningful, rather than just a string of visual patterns. To make this happen, perception draws heavily on memory, motivation, and other psychological processes
Brain itself never recieves stimulation
Stimulation
Neither can brain recieve light from sunset
Relies on second hand information from the sensory system
Transduction
Sensation
Perception
Transduction: Changing Stimulation to Sensation
transduction
Transformation of one form of energy into another-especially the transformation of stimulus information into nerve signals by the sense organs. Without transduction, ripe tomatoes would nto appear red
When appropriate stimulus reaches sense organs, it activates specialized neurons, called receptors
respond by converting their excitation into a nerve signal
similar to bar code
Sensory Adaptation
Loss of responsiveness in receptor cells after stimulation has remained unchanged for a while, as when a swimmer becomes adapted to the temperature of the water
Thresholds
Absolute threshold
Amount of stimulation necessary for a stimulus to be detected.
Difference threshold
The smallest amount by which a stimulus can be changed and the difference be detected half the time
Just Noticeable Difference
Same as difference threshold
Weber's Law
Size of JND is proportional to the intensity of the stimulus; the JND is large when the stimulus intensity is high and small when the stimulus intensity is low.
Fechner's Law
Expresses relationship between actual magnitude and its percieved magnitude
can be estimated by formula S=k log R
S= sensation
R= stimulus
k= a constant that differs for each sensory modality
Steven's Power law
Addresses issues with Fechner's law
A law of magnitude estimation that covers a wider variety of stimuli than Fechner's Law
Represented by formula S=kla
S= sensation
k= a constant
a=power exponent
l=stimulus intensity
Signal Detection Theory
Explains how we detect signals consisting of stimulation affecting our eyes, ears, nose, skin, and other sense organs
Often occurs outside of our conciousness
Takes observer characteristics into account
helps us understand why thresholds are variable
Ignored the effects of the perciever's physical condition, judgements, or biases
How Are The Senses Alike? And How Are They Different?
Each sense organ has a different design
Each sends neural messages to its own specialized region in brain
different sensations occur because different areas of the brain become activated
Vision: How the Nervous System Processes Light
The Anatomy of Visual Sensation
Transduction happens in retina
Retina
The thin, light sensitive later at the back of the eyeball. Contains millions of photoreceptors and other nerve cells
Real Work is performed by photoreceptors
Light sensitive cells in the retina that convert light energy to neural impulses. Photoreceptors are as far as light gets into the visual system
Rods
Photoreceptors in the retina that are especially sensitive to dim light but not to colours. Strange as they seem, they are rod shaped
Cones
Photoreceptors that are especially sensitive to colours but not to dim lights. Cones are cone shaped
Fovea
Tiny area of sharpest vision in the retina
Optic Nerve
The bundle of neuron that carries visual information from the retina to the brain
Processing Visual Sensations in the Brain
Blind Spot
The poin where the optic nerve exits the eye and where there are no photoreceptors. Any stimulus that falls on this area cannot be seen
We look with our eyes but see with our brain
In visual cortex, brain transforms neural impulses into visual sensations of colour, form, boundary, and movement
Visual cortex takes 2d patterns from each eye and then assemble them into 3d world of depth
How the visual system creates brightness
Brightness
A psychological sensation caused by the intensity of light waves
How the Visual System Creates Colour
Colour
Also called hue
Colour is not a property of things in external world
Rather it is a psychological sensation created in the brain from information obtained by the eyes from the wavelengths of visible light
Electromagnetic spectrum
The entire range of electromagnetic energy, including radio waves, X rays, microwaves, and visible light
Visible Spectrum
Tiny part of electromagnetic spectrum to which our eyes are sensitive
Visible spectrum of other creatures may be slightly different from our own
Two Ways of Sensing Colours
trichromatic theory
The idea that colors are sensed by three different types of cones sensitive to light in the red, blue, and green wavelengths.
Explains the earliest stage of colour sensation
Opponent process theory
Cells in visual system process colours in complementary pairs
The opponent process theory explains colour sensation from the bipolar cells onward in the visual system
Afterimages
Sensation that linger after the stimulus is removed
Color Blindness
Typically a genetic disorder
prevents individual from differentiating between colours
most common form is red-green colour blindness
Hearing
The Physics of Sound: How Sound Waves Are Produced
Frequency
The number of cycles completed by a wave in a given amount of time, usually a second
Amplitude
The physical strength of a wave. This is usually measured from peak to valley on a graph of the wave
Sensing Sounds: How We Hear Sound Waves
tympanic membrane
cochlea
basilar membrane
thin strip of tissue sensitive to vibrations in the cochlea
contains hair cells connected to neurons
Primary organ of hearing
Coiled tube in the inner ear
eardrum
Psychological Qualities of Sound
pitch
A sensory characteristic of sound produced by the frequency of the sound wave
Sensations of Loudness
loudness
A sensory characteristic of sound produced by the amplitude of the sound wave
Sensations of Timbre
Timbre
The quality of a sound wave that derives from the wave's complexity.
Comes from the Greek Word for Drum
Deafness
Conduction Deafness
Nerve Deafness
An inability to hear resulting from damages to structures of the middle or inner ear
An inability to hear linked to a deficit in the body's ability to transmit impulses from the cochlea to the brain
How the Other Senses Are Like Vision And Hearing
Position and Movement
Smell
Taste
Based on chemistry
has cooperative working relationship with smell
gustation
The sense of taste
Vestibular Sense
The sense of body orientation with respect to gravity
Closely associated with the inner ear
Carried to the ear by a branch of the auditory nerve
Kinesthetic Sense
The sense of position and movement of body parts relative to each other
olfaction
the sense of smell
Phenomes
Chemical signals released by organisms to communicate with other members of their species
Often used by animals as sexual attractants
unclear whether or not humans employ phenomes
The Skin Senses
sensory systems for processing touch, warmth, cold, texture, and pain
The Gate Control Theory
An explanation for pain control that proposes we have a neutral gate that can, under some circumstances, block incoming pain signals
Dealing with Pain
Placebo Effect
A response to a placebo caused by subjects' belief that the drug is real
pain serves as essential defense signal
helps us survive hostile environment
get treatment for sickness and injury
because placebo effect is so common, any drug must prove itself stronger than a placebo
Pain tolerance
varies enourmously from person to person
Relationship Between Sensation and Perception
Percept
The meaningful product of perception-often an image that has been associated with concepts, memories of events, emotions, and motives
not just sensation but associated meaning as well
Perceptual Processing: Finding Meaning In Sensation
Feature detectors
Cells in the cortex that specialize in extracting certain features of a stimulus
Binding Problem
Refers to thr process used by brain to combine the results of many sensory operations into a single percept
Occurs when sensastion of colour, shape, boundary, and texture are combined to produce the percept of a person's face
No one knows how the brain does this
Major Unsolved Mystery
Bottom-Up Processing
Perceptual analysis that emphasizes characteristics of the stimulus, rather than our concepts and expectations.
Bottom refers to stimulus
Which occurs at step one of perceptual processing
Perceptual Constanies
The ability to recognize the same object as remaining constant under different conditions, such as changes in illumination, distance, or location
Illusions
demonstrably incorrect perception of a stimulus pattern
Especially one that also fools others who are observing the same stimulus
Ambigous Figures
Images are capable of more than one interpretation
Theoretical Explanations for Perception
Perceptual Organization: The Gestalt Theory
argues that brain is wired to not only percieve not just stimuli by patterns in stimuli
Called such a pattern a gestalt
Gestalt Psychology
From a Geman word that means "whole" or "form" or "configuration"
Believed tht much of perception is shaped by innate factors built into brain
Figure and Ground
Figure
The part of a pattern that commands attention
figure stands out against the ground
Ground
The part of a pattern that does not command attention
the background
Closure
The Gestalt principle that identifies the tendency to fill in gaps in figures
see incomplete figures as complete
Laws of perpetual grouping
Gestalt principles of similarities
These laws suggest how our brains prefer to group stimulus elements together to form a percept
Binocular cues
law of similarity
tend to group similar objects together in our perceptions
law of continuity
tend to group objects together when they are near us
Law of common fate
tend to group objects together that share a common motion or destination
Law of Pragnatz
most general Gestalt principle
our perceptual system sees a fully develop gestalt
Information taken in by both eyes that aids in depth perception, including binocular convergence and retinal disparity
Monocular Cues
Information about depth that relies on the input of just one eye
relative size
light
shadow
interposition
relative motion
atmospheric perception
Learning based inference
perception is formed by learning instead of innate factors
for example
babies learn to expect faces to have certain features in certain arrangements
Perceptual set
Readiness to detect a particular stimulus in a given context- as wgen a person who is afraid interprets sound in middle of night as thret
Cultural influence on perception
Transduction
Transformation of one form of energy into another
Top-Down Processing
emphazises expectations, concept memories and other cognitive factors rather than being driven by the stimulus
"Top" refers to mental set in brain
which is at the "top" of the perceptual processing system