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