W4 notes Flashcards
sensation
Sensation is the process of detecting environmental stimuli arising from the body
perception
Perception is the process of interpreting sensory info
synesthesia
a condition where the stimulation of one sensory pathway leads to the simultaneous and automatic stimulation of another sensory pathway, the same sensory input can lead to dramatic differences in perception
stimulus
A stimulus is anything that elicits a rxn from our sensory systems
transduction
This process of translation from stimulus to neural signal is known as transduction
sensory adaptation
Sensory adaptation is the tendency to pay less attention to a non changing source of stimulation
bottom-up processing
We refer to the brain’s use of incoming signals to construct perceptions as bottom-up processing
For example, we construct our visual reality from information about light that is sent from the eye to the brain
top-down processing
In top-down processing, we use knowledge gained from prior experience with stimuli to perceive them
For example, a skilled reader has no trouble reading sentences, even the words are jumbled
gustav fechner
Gustav Fechner developed methods, which he called psychophysics, for studying the relationships between stimuli (the physics part) and perception of those stimuli (the psyche or mind part)
absolute threshold
Absolute threshold is the smallest amount of stimulus that can be detected
difference threshold
Difference threshold is the smallest detectable difference between 2 stimuli
weber-fechner law
The amount of difference that can be detected depends on the size of stimuli being compared
As stimuli get larger, differences must also become larger to be detected by an observer, a phenomenon known as Weber-Fechner Law
signal detection
Signal detection is a 2 step process involving the actual intensity of the stimulus, which influences the observer’s belief that the stimulus did occur and; the individual observer’s criteria for deciding whether the stimulus occurred
vision
Vision, the processing of light reflected from objects, is one of the most important sensory systems in humans
visible light
Visible light, or the energy within the electromagnetic spectrum to which our visual systems respond, is a type of radiation emitted by the sun, other stars and artificial sources such as a light bulb
wavelength
Wavelength, or the distance between successive peaks of waves, is decoded by our visual system as colour or shades of grey
height or amplitude
The height or amplitude, of the waves is translated by the visual system into brightness
Large amplitude waves appear bright, and low-amplitude waves appear dim
cornea
Cornea is the clear surface at the front of the eye that begins the process of directing light to the retina
pupil
Travelling light next enters the pupil, which’s actually an opening formed by the muscles of the iris
iris
The iris adjusts the opening of the pupil in response to the amount of light present in the environment and to signals from the autonomic nervous system
lens
Directly behind the pupil and iris is the main optical instrument of the eye, the lens
Muscles attached to the lens can change its shape, allowing us to accommodate, or adjust our focus to see near or distant object
The muscles relax and the lens flattens in order to focus on distant objects, and the muscles contract and the lens becomes more spherical to focus on near objects
retina
Behind the lens is the main chamber of the eye, and located on the rear surface of this chamber is the retina, a thin but complex network of neurons specialized for the processing of light
In the deepest layer of the retina are specialized receptors, the rods and cones, that transduce the light information
why does each eye have a blind spot
The blood vessels serving the eye and the axons that leave the retina to form the optic nerve exit at the optic disk
Because there are no rods and cones in the optic disk, each eye has a blind spot
fovea
Toward the middle of the retina is the fovea, which’s specialized for seeing fine detail
Responsible for central vision
optic nerve
The rods and cones are the only true receptors of the visual system
Axons from the final layer of cells, the ganglion cells, leave the back of the eye to form the optic nerve
The optic nerves cross the midline at the optic chiasm
There, the axons closest to the nose cross over to the other hemisphere, while the axons to the outside proceed to the same hemisphere
This is when if you focus straight ahead, everything to the left of centre in the visual field is processed by the right hemisphere, while everything to the right is processed by left hemisphere
optic tracts
Beyond the optic chiasm, the visual pathways are known as optic tracts
amygdala
The amygdala uses visual information to make quick emotional judgments, especially about potentially harmful stimuli
primary visual cortex
The primary visual cortex begins the processing of visual input
dorsal stream
The dorsal stream extends upward from V1 in the occipital into the parietal lobe
This is the “where” pathway that helps us process movement and localize objects in space
ventral stream
The ventral stream extends downward from V1 in the occipital lobe to the temporal lobe
This is the “what” pathway that responds to shape and colour and contributes to our ability to recognize objects and faces
trichromatic theory
Trichromatic theory is a theory of colour vision based on the existence of different types of cones for the detection of short, medium and long wavelengths
Consistent with the existence of 3 types of cones in the retina that respond best to short (blue), medium (green) or long (red) wavelengths
when does colour blindness occur
Colour blindness occurs when a person has fewer than the typical 3 types of cones
opponent process theory
An opponent process theory is a theory of colour vision that suggests we have a red-green colour channel and a blue-yellow colour channel in which activation of one colour in each pair inhibits the other colour
Which of these two theories of colour vision, trichromatic theory or opponent process theory, is correct?
The trichromatic theory provides a helpful framework for the functioning of the three types of cones in the retina
However, as we move from the retina to higher levels of visual analysis, the opponent process theory seems to fit observed phenomena neatly
Both theories help us understand colour vision but at different levels of the visual system
gratings
The simplest patterns of lines are gratings
Gratings can vary along two dimensions: frequency and contrast.
High-frequency gratings have many bars in a given distance and provide fine detail, while low-frequency gratings have relatively few bars
High-contrast gratings have large differences in intensity between adjacent bars, like black next to white
Low-contrast gratings have subtler differences in intensity between bars, such as dark gray next to black
fusiform face area
The visual processing of faces activates a particular area of the brain known as the fusiform face area (FFA), part of the ventral pathway, located in the inferior temporal cortex
proximity
A second Gestalt principle is proximity
Objects that are close together tend to be grouped together
The dots that make up our Dalmatian are close together, suggesting they belong to the same object
principle of similarity
The principle of similarity states that similar stimuli are grouped together
principle of continuity
The principle of continuity suggests that we assume that points that form smooth lines when connected probably belong together
principle of simplicity
The principle of simplicity, which suggests that we will use the simplest solution to a perceptual problem
depth perception
Depth perception is the ability to use the 2D image projected on the retina to perceive 3D
monocular vs binocular cues
To construct a 3D image, we use both monocular cues (one eye) and binocular cues (two eyes)
occlusion
Among the most powerful monocular depth cues is occlusion, or the blocking of images of distant objects by closer objects
retinal disparity
Retinal disparity is the difference between the images projected onto each eye (requires the use of both eyes → binocular cue)
astigmatism
Astigmatism is when the surface of the cornea is uneven
audition
Audition, our sense of hearing, not only allows us to identify objects in the distance but also plays an important role in our ability to communicate with others through language
pitch
In the case of sound, the height or amplitude of the wave is encoded as loudness or intensity and the frequency of the wave is encoded as pitch
pinna
The outer ear consists of the structures that are visible outside the body
The pinna, the outer visible structure of the ear, collects and focuses sounds, like a funnel
In addition, the pinna helps us localize sounds as being above or below the head
cochlea
The inner ear contains 2 sets of fluid-filled cavities embedded in the bone of the skull
One set is the cochlea which contains specialized receptor cells that respond to vibrations transmitted to the inner ear
May be divided into 3 parallel chambers divided from one another by membranes
basilar membrane
The cochlear duct is separated from the tympanic canal by the basilar membrane
