Chapter 5 Flashcards
sensation
- stimulus-detection process
- translate stimuli into nerve impulses
perception
organizing and giving meaning to input
sensation vs perception
- sensation is our ability to detect senses like touch, pain, vision, or the movement and positioning of our body
- perception is the way in which the brain processes and communicates these senses to the rest of the body
pathway of stimulus to perception
1.) stimulus - light, sound, smell
2.) sensory receptors - eyes, ears, nose
3.) transduction of neural Impulses
4.) perception: visual, auditory, olfactory areas
what is psychophysics
- studies relations between physical characteristics of stimuli and sensory capabilities
- concerned with two types of sensitivity: absolute and difference threshold
absolute threshold
- asks about the absolute limits of sensitivity
- the lowest intensity at which a stimulus can be detected correctly 50% of the time
- the lower the absolute threshold, the greater the sensitivity
difference threshold
- asks about the difference between stimuli
- the smallest difference between two stimuli that can be detected 50% of the time (just a noticeable difference)
what is Weber’s law?
just noticeable difference (or JND) between two stimuli is a constant proportion of the intensity of the original stimulus
sensory adaptation
diminishing sensitivity to unchanging stimulus
what is the value of sensory adaptation?
frees senses from the unchanging to be more sensitive to changes in the environment
two types of processing
→ turns sensory information into perceptual information
1.) bottom up
2.) top down
bottom up processing
- taking in sensory information and allow the stimulus itself to shape our perception, without any preconceived ideas.
- “What am I seeing?”
top down processing
- using background knowledge, models, ideas, and expectations to interpret sensory information
- “Is that something I’ve seen before?”
perceptual set
when we see what we expect to see (top down influences)
what 2 processes does attention involve?
- focusing on certain stimuli
- filtering out other information
divided attention
multitasking, or paying attention to more than one stimulus or task at a time
selective attention
involves focusing on one stimulus or task while ignoring other stimuli
inattentional blindness
when the effects of attention are so strong that we fail to see stimuli that are directly in front of our eyes
what are Gestalt’s principles of perceptual organization?
1.) proximity: elements that are close together belong together
2.) similarities: similar items belong together
3.) continuity: elements linked to form a continuous line
4.) closure: close open edges to perceive boundaries
what did Gestalt say about perceptual organization?
- suggested perception was governed by laws that
determined how things were grouped together, - figure ground principle!
what is the figure ground principle?
- the most fundamental Gestalt principle
- simplest form of organization = we pick out objects and figures standing against a background
perceptual constancies
refers to our ability to see objects as appearing a constant colour, size, and shape, despite continual changes in our perspective (top down process)
colour constancy
We see a consistent colour in changing illumination conditions
brightness constancy
we see a consistent brightness in changing shadow conditions
shape constancy
we see a constant shape in an object despite receiving different sensory images of the shape
size contancy
we see objects as having a constant size, despite changes to the sensory input with variations in distance
monocular cues
depth can be percieved with one eye
binocular depth cues
- depth perceived with two eyes
monocular depth cue: accommodation
processes by which the lens changes shape in order to bring an object from a distance into focus
monocular depth cue: relative motion
when we are moving, we can tell which objects are farther away because it takes them long to pass by
monocular depth cue: interposition
when one object appears to block the view of another, we assume the blocked object is farther
monocular depth cue: relative size
we interpret similar objects as farther away when they appear similar
monocular depth cue: linear perspective
- we see parallel lines as converging in the distance
- the Ponzo Illusion = our perception of distance affects our perception of length
monocular depth cue: light and shadow
shadows can give clues to the location and sizes of objects
binocular depth cue: retinal disparity
two eyes receive different visual images and then feature detectors analyze differences
binocular depth cue: convergence
when looking at a close-up object, your eyes angle inwards towards each other (you become slightly cross-eyed)
chemical sense
- senses receptive to chemical stimulation and rely on chemical molecules
taste
→ chemical receptors are taste buds, each with several receptors cells
→ 9000 taste buds in different regions, each located on the edges/back of the tongue.
→ responds to 4 basic qualities: sweet, sour, salty, bitterq
olfaction
→ receptors line the upper nasal cavity (about 40 million receptors) and odor molecules “lock” onto certain sites
→ receptors send message to olfactory area in brain
pheromones
chemical signals found in the natural body scents
what stimuli do visual system process?
light, or waves of electromagnetic radiation
how do eyes respond to wavelengths of light?
- 360 to 750 nm
- we perceive the wavelength/frequency of the light waves as colours
- we perceive the amplitude/height of the light waves as brightness
how does light travels through the eye?
- light travels through the cornea and pupil, and gets focused and inverted by the lens
- the light then lands on the retina where the light waves are transduce into a neural signal
layers of the retina
1.) photoreceptors
2.) bipolar cells
3.) ganglion cells
4.) optic disc
photoreceptors in the retina
- transduce light waves into a neural impulse
- two kinds of photoreceptors: rods and cones
- able to adapt to brightness and darkness
rods
- function best in low illumination
- found mostly in periphery of retina and none in fovea
- take 30 minutes to adapt to low illumination
cones
- for colour and detail
- function best in high illumination
- concentrated in fovea/center of retina
- take 10 minutes to adapt to low illumination
bipolar cells in the retina
- rods and cones have synaptic connection with bipolar cells
→cones have one to one connection
→many rods connect to single bipolar cell
ganglion cells in retina
- bipolar cells synapse with ganglion cells
- axons of ganglion cells form optic nerve
optic disc in retina
an area of the retina that contains no rods or cones, because this is the point where the optic nerve leaves the eye
what is the trichromatic theory (Young-Hemholtz)?
- colour vision
- there are 3 types of colour receptors in the retina
- individual cones most sensitive to blue, green or red wavelengths of light
- visual system combines activity from these cells to allow us to perceive all the colours
problems with the trichromatic theory?
- cannot explain why red-green colour blind individuals can perceive yellow
- cannot explain afterimages
what is the opponent-process theory?
3 cone types, and each responds to two different wavelengths
→Red or green
→Blue or yellow
→Black or white
how does the opponent process theory explain afterimages?
- neural processes become fatigued
- have rebound effect with receptor responding with its opponent, opposite reaction
why are both trichromatic and opponent-process theory correct?
→ 3 types of cones, each maximally sensitive to blue, green or red wavelengths of light = fits with trichromatic theory
→ opponent mechanisms occur further along in the visual system = fits with opponent-process theory
how do visual neural impulses travel in the brain ?
- impulses go from: thalamus to primary visual cortex (occipital lobe)
→specific regions of retina are processed in specific areas of cortex
→fovea has large representation in visual cortex
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feature detectors
- cells in the primary visual cortex that are very particular about what will make them fire
- feature detectors begin the visual process by firing to specific shapes, colours, depths, movements, directions of a stimulus
what are the two pathways from the feature detectors?
1.) The ventral stream
2.) The dorsal stream
how is the stimulus of light turned into the mental act of seeing?
light waves → transduction → neural signal → features → objects
parallel processing
different areas of the brain process different aspects of a stimulus
2 characteristics of soundwaves
- frequency (pitch)
- amplitude (loudness)
how does hearing loss occur?
- conduction hearing loss = when the middle ear isn’t conducting sound well to the cochlea
- sensorineural hearing loss = when the receptor cells aren’t sending messages through the auditory nerves
causes of hearing loss
- exposure to sounds that are too loud can cause damage to the hair cells
- structures in the middle and inner ear can also be damaged by disease
treating hearing loss
- conduction hearing loss helped with hearing aids that amplify the sounds
- sensorineural hearing loss helped with cochlear implant that translates sound waves into signals the brain can process
how does the brain interpret loudness?
- the firing rate of the hair cells = higher amplitude sound waves cause greater release of neurotransmitter, resulting in higher firing rate
- the number of hair cells firing = high amplitude sound waves move more hair cells than softer sounds
- the type of hair cells firing =certain neurons fire only to specific amplitudes
frequency theory
- the frequency of the auditory nerve’s impulses “match” the frequency of a wave, which allows us to detect its pitch
- doesn’t work above 1000 Hz
place theory
- specific frequencies peak at certain places on the cochlea, depending on the pitch
- the brain reads pitch by reading the location where the signals are coming from
binaural hearing
is the ability to hear in two ears
how does binaural hearing help localize sound?
1.) timing of sounds = sounds arrive at the closest ear first
2.) intensity of sounds = sound arriving at closest ear will be more intense
how do hearing neural pathways travel in the brain?
impulses go from:
- thalamus to the primary auditory cortex (temporal lobe) = specific regions of the cochlea are represented in specific areas of the cortex
- from there, signals go to the secondary auditory cortex = interprets complex sound (speech and music)
