Week 9 Flashcards
steps in sensing
- accessory structures
2. transduction
specific energy doctrine
discovery that stimulation of a particular sensory nerve provides codes for that sense, no matter how the stimulation takes place
temporal code
reflects changes in the timing pattern of nerve firing
spatial code
reflects the location of neurons that are firing and those that are not
psychophysics
Psychophysics: an area of research focusing on the relationship between the phsyical characteristics of environmental stimuli and the psychological experiences those stimuli produce
absolute threshold
the smallest amount of light, sound, pressure or other physical energy we can detect
subliminal stimulation
stimulation that is too weak or brief to be perceived
supraliminal stimulation
stimulation that is strong enough to be consistently perceived
signal detection theory
a mathematical model of what determines a person’s report of a near-threshold stimulus
sensitivity
ability to detect a particular stimulus from a background of competing stimuli
Influenced by internal noise, the intensity of the stimulus, and the capacity of your sensory systems
just noticeable difference JND
smallest detectable difference in stimulus energy
Weber’s law
a law stating that the smallest detectable difference in stimulus energy is a constant fraction of the intensity of the stimulus
Weber’s law says that JND=KI
K= Weber’s constant for a particular sense; I= amount, or intensity, of the stimulus
Weber’s constant
K; different for each of the senses
Smaller k is, the more sensitive a sense is to stimulus differences
Fechner
used Weber’s law to study the relationship between the physical magnitude of a stimulus and its perceived magnitude
If just-noticeable differences get progressively larger as stimulus magnitude increases, then the amount of change int he stimulus required to double or triple its perceived intensity must get larger too
Fechner’s law
Constant increases in physical energy will produce progressively smaller increases in perceived magnitude
Steven’s power law
formula for magnitude estimation that works for a wider array of stimuli
loudness
determined by the amplitude of sound wave
Decibels; dB
0dB= minimum detectable sound for normal hearing
pitch
how high or low a tone sounds
Humans hear from 20 to 20,000 Hz
Relative pitch
almost everyone; tell whether one note is higher than or lower than or equal to another note
Absolute pitch
ability to identify the musical notes associated with specific sound frequencies
timbre
the mixture of frequencies and amplitudes that make up the quality of sound
Determined by complex wave patterns that are added onto the lower, or fundamental, frequency of a sound
pinna
crumpled part of the outer ear; funnels down through ear canal
tympanic membrane
a membrane in the middle ear that generates vibrations that match the sound waves striking it
cochlea
auditory transduction occurs
basilar membrane
floor of the fluid-filled duct that runs through the cochlea
acoustic nerve
bundle of axons that carries stimuli from the hair cells of the cochlea to the brain
Tells the brain about amplitude and frequency of the incoming sound waves
conduction deafness
problems with bones of middle ear
Over time fuse together, preventing accurate conduction of vibrations from one bone to the next
Surgery or hearing aids
nerve deafness
acoustic nerve or hair cells damaged
Gradually with age
Happens more quickly with extended exposure to loud noises
place theory
von Bekesy; a theory that hair cells at a particular place on the basilar membrane respond most to a particular frequency of sound (characteristic frequency)
Frequency matching theory
for lower frequencies than place theory
Certain neurones in the acoustic nerve fire each time a sound wave passes
So a sound wave whose frequency is 25 cycles per second would cause those neutrons to fire 25 times per second
volley theory
the view that some sounds are coded by matching the frequency of neural firing
cornea
curved, transparent, protective layer through which light rays enter the eye
pupil
an opening in the eye, just behind the cornea, through which light passes
iris
the colourful part of the eye, which constricts or relaxes to adjust the amount of light entering the eye
lens
the part of the eye behind the pupil that bends light rays, focusing them on the retina
retina
surface at the back of the eye onto which the lens focuses light rays
Light rays from the top of an object are focused on the bottom of the image on the retinal surface
Light rays from the right side of the objects end up on the left side of the retinal image
ocular accomodation
ability of the lens to change its shape and bend light rays so that objects are in focus
photoreceptors
specialised cells in the retina that code light energy into nerve cell activity
photopigments
chemicals in photoreceptors that respond to light and assist in converting light into nerve cell activity
Light strikes a photopigment, photopigment breaks apart, changing the membrane potential of the photoreceptor cell; generates a signal that can be transferred to the brain
New photopigment molecules are created
rods
highly light-sensitive but colour insensitive photoreceptors in the retina that allow vision even in dim light
rhodopsin
cones
photoreceptors that help us distinguish colours
have one of three kinds of iodopsin
fovea
region in the centre of the retina where cones are highly concentrated
visual acuity
visual clarity, which is greatest in the fovea because of its large concentration of cones
optic nerve
bundle of fibres composed of axons of ganglion cells that carries visual information to the brain
feature detectors
cells in the cortex that respond to a specific feature of an object
hue
essential colour determined by the dominant wavelength of light
colour saturation
purity of a colour
Colour is more saturated if just one wavelength is relatively more intense than others
If many wavlelengths added to a pure hue, desaturated
brightness
overall intensity of all the wavelengths that make up light
additive colour mixing
If lights of two different wavelengths but of equal intensity are mixed, the colour you sense is at the midpoint of a line drawn between the two original colours on the colour circle
This process is called additive colour mixing as the effects of the wavelengths from each light are added together
subtractive colour mixing
Subtractive colour mixing: when paints are combined
Lights reflected from paints or other coloured object is seldom a pure wavelength, so predicting the colour resulting from mixing paints is not as easy as combining pure wavelengths of light
trichromatic theory of colour vision
Young-Helmholtz theory
A theory of colour vision identifying three types of visual elements (cones), each of which is most sensitive to different wavelengths of light
Short wavelength: most sensitive to light in the blue range
Medium wavelength: green range
Long wavelength: reddish-yellow range
It is the ratio of responses by the three types of cones that determine the colour you see
Opponent process theory of colour vision
Trichromatic theory cannot explain afterimages
Opponent-process theory: colour-sensitive visual elements are grouped into red-green, blue-yellow and black-white elements
Hering
Members of each pair oppose, or inhibit each other
When one member of an opponent pair is no longer stimulated, the other is activated
colour blindness
condition where the lack of certain photopigments leaves a person unable to sense certain colours; born with cones containing only two of the three possible colour-sensitive pigments
synaethesia
a blending of sensory experience that causes some people to see sounds or taste colours etc.
subliminal advertising
minimal effect on peoples’ thinking
functions of attention
altering function
selective attention
divided attention
vigilance or sustained attention
sclera
white part of the eye which maintains, protects and supports the shape of the eye and includes the cornea
chloroid
provides oxygen and nourishment to the eye and includes the pupil, iris and lens
size constancy
tendency to perceive an object as being the same size regardless of whether it is close or far away
colour constancy
tendency to perceive colour of objects as remaining stable despite constant variation in illuminating conditions
Wundt
structuralism; we build perception by creating and combining much smaller things or elements which he called sensations
Structuralism doesn’t explain why bottom up processing needs to be complemented by top down processing
Also cannot explain the illusory contour illusion; perceiving lines filling in gaps
Gestalt approach
provides rules and regulations for top down processing and this influenced the bottom up ideas of structuralism
The whole is greater than the sum of its parts
Came up with many principles of perceptual organisation
sensory adaptation
process through which responsiveness to an unchanging stimulus decreases over time
