Chapter 4 - Sensation & Perception Flashcards
Sensation
the sense organs’ detection of external stimuli, their responses to the stimuli, and the transmission of these responses to the brain
Perception
the processing, organization, and interpretation of sensory signals; it results in an internal representation of the stimulus
Psychologists divide the world into two distinct phases, what are they?
Sensation and Perception
Sensory Coding
Process of our sensory organs translate the physical properties of stimuli into patterns of neural impulses
Transduction
a process by which sensory receptors produce neural impulses when they receive physical or chemical stimulation
Sensory Receptors
specialized cells in the sense organs, that receive physical or stimulation and pass the resulting impulses to connection neurons (most of this goes through the thalamus)
Steps of Sensation to Perception
1) Stimulus 2) Sensation (sensory receptors DETECT a stimulus) 3) Sensory Coding (stimulus TRANSDUCED - translated into chem/elec signals transmitted to the brain) 4) Perception (neural sigs processed and representation made in brain)
What types of information about a stimulus does the brain need to function effectively?
Qualitative (most basic qualities - ex: horn honk) and Quantitative (degree or magnitude of those qualities - loudness of honk)
What do sensory receptors do in terms of telling the brain about information?
They do coarse coding, called this because sensory qualities are only by a few different receptors - combined responses from different receptors allow us to differentiate between stimuli
Taste (Stimuli, Receptors, Pathways to the Brain)
Molecules dissolved in fluid on the tongue; cells in taste buds on the tongue; portions of facial, glossopharyngeal, and vagus nerves
Smell (Stimuli, Receptors, Pathways to the Brain)
Molecules dissolved in fluid on mucous membranes in the nose; sensitive ends of olf neurons in mucous memb; olfactory nerve
Touch (Stimuli, Receptors, Pathways to the Brain)
Pressure on skin; sensitive ends of touch neurons in skin; Cranial nerves for touch abv the neck spinal nerves for touch elsewhere
Hearing (Stimuli, Receptors, Pathways to the Brain)
Sound waves; pressure-sensitive hair cells in cochlea of inner ear; auditory nerve
Vision (Stimuli, Receptors, Pathways to the Brain)
Light waves; light-sensitive rods and cones in retina of eye; optic nerve
Psychophysics
a subfield developed in 1800’s (Weber & Fechner), examines our psychological experiences of physical stimuli
Absolute Threshold
minimum intensity of stimulation that must occur before you experience a sensation (level of intensity at which participants correctly detect a stimulus on 50% of the trials in which it is presented)
Difference Threshold
the just noticeable difference two stimuli (ex: minimum change in volume for you to notice difference between TV show and commercials)
Weber’s Law
the just noticeable difference between 2 stimuli is based on the proportion of the original stimulus rather than the fixed amount of difference (the more intense the stimulus, the bigger the change needed for you to notice)
What was the problem with classical psychophysics that had to be corrected?
it’s based on the idea of a sensory threshold, so you either notice or don’t notice something (above or below a sensory threshold), but human judgement is what they forgot that comes into play - if you’re doing research on someone, then someone will make the judgement something is happening they wouldn’t normally notice
SDT
(Signal Detection Theory) a theory of perception based on the idea that the detection of a faint stimulus requires a judgement- it is not an all-or-nothing process (classical psychophysics thought of sensory judgements as a yes/no deal)
What are the different outcomes for a signal detection study?
participant tries to figure out if they sensed a stimulus - 4 outcomes - hit (detect real signal), miss (don’t detect signal), false alarm (detect signal not presented), correct rejection
How do you determine a participant’s sensitivity in a signal detection study?
compare hit rate with the false alarm rate - helps correct for biases participant might bring in
Response bias
participant’s tendency to report detecting the signal in an ambiguous trial - some participants take a lot of evidence, others don’t to respond
Sensory adaptation
a decrease in sensitivity to a constant level of stimulation (ex: you don’t notice sound of constant construction or trains going by after a while) - you’ll notice a change either way though - an increase or stopping the cts stimulation
Haptic Sense
the sense of touch (conveys sensations of temperature, pressure, and pain, along with where our limbs are in space)
Tacile stimulation
anything that makes contact with our skin provides this and gives us the experience of touch (skin is largest organ for sensory reception)
How is temperature information sent to the brain?
There are sensory receptors that reach to the skin (long axons go from skin to CNS through spinal cord/cranial nerves), temp receptors have separate cold/hot receptors (intense stimuli can trigger both and make you feel wet)
How is pressure information sent to the brain?
There are sensory receptors that reach to the skin (long axons go from skin to CNS through spinal cord/cranial nerves), pressure works on skin hair movement, also pressure receptor capsules in skin (respond to cts vibration, light fast pressure, light slow pressure, stretching&steady pressure)
How is pain info sent to the brain?
receptors found throughout body, not just in skin send signals through nervous sys
How are pain signals different from temp and pressure?
Nerve fibers that convey pain are thinner and found in all body tissues that sense pain (not so for temp/pressure), also, actual experience of pain is totally created in the brain, and is why phantom limb syndrome patients can feel pain in a missing limb - brain misinterprets it
What the types of nerve fibers for pain? What makes them different?
Fast fibers (sharp, immediate pain), slow fibers (chronic, dull, steady pain), different because fast are myelinated and slow aren’t, so signal that travels from receptors to spinal cord go faster
How do we react and benefit from fast fibers, and how is it activated?
react by recoiling, so it benefits us by protecting us, activated by strong physical pressure/temp extremes
How do we react and benefit from slow fibers, and how are they activated?
react by not using the affected body plans and helps with recuperation, and activated by chemical changes in tissue when skin is damaged
How does sensation occur and where does this info go?
Sensory receptors transduce stimuli into electrical impulses, and nerves then transmit those impulses to the brain, all info except olfaction goes through thalamus
Where does all touch information go?
goes to thalamus, then projected to the primary somatosensory cortex, in parietal lobe
Gate Control Theory
to experience pain, pain receptors must be activated and neural “gate” in the spinal cord must allow the signals through to the brain (revolutionary bc characterized pain as a perceptual experience w/in brain rather than just response to nerve stimulation) - pain can be reduced/prevented through firing of larger sensory nerves (pain is small diameter nerve fibers) - rubbing skin reduces needle sting
What three factors does pain depend on?
biological, physiological, cultural
How can pain be lessened or increased
Distractions, music, focus, and interpreting it positively all help; focusing on it, worry, depression, and poor rest make it worse
Audition
hearing, second to vision as a source of information about the world - the sense of sound perception
Sound wave
a pattern of changes in air pressure during a period of time - it produces the percept of sound
eardrum
a thin membrane that marks the beginning of the middle ear - sound waves cause it to vibrate
A sound wave’s amplitude determines?
Loudness
A sound wave’s frequency determines?
Pitch
Cochlear implant
First ever neural implant, connected to the auditory nerve but disables the natural sys - used for those with loss of hair cells in the inner ear
Cornea
the clear outer covering of the eye
retina
the thin inner surface of the back of the eyeball, it contains the photoreceptors that transduce light into neural signs
pupil
the small opening in the eye - it lets in light waves
iris
the colored muscle on the surface of the eye, it changed shape to let in more or less light
rods
retinal cells that respond to low levels of illumination and result in b B&W perception
cones
retinal cells that respond to higher levels of illumination and result in color perception (there are three types in humans - S, M, L)
fovea
the center of the retina, where cones are densely packed
How do we perceive color in the brain?
our perception of different colors is determined by the ratio of activity among the three types of cone receptors
What are the three different types of cones?
S - short, blue to violet, M - yellow to green, L - long, red to orange
Why are some colors opposites?
Opposite colors activate opposite wavelength ganglion cells (SML)
How do we categorize color?
three dimensions - hue (distinctive char - dominant wavelength), saturation (colors’ purity - vividness of hue), and brightness (color’s perceived intensity, or luminance)
Lightness
lightness of a visual stimulus is determined by the brightness of the stimulus relative to its surroundings
subtractive color mixing
a process of color mixing that occurs within the stimulus itself - a physical, not psychological process
How do we perceive pigment color?
It’s whatever wavelengths it doesn’t absorb, so it reflects them to the eye
Subtractive primary colors
red, yellow, blue, because together they make black since they absorb basically all of the spectrum
Additive color mixing
a process of color mixing that occurs when different wavelengths of light interact within the eye’s receptors - a psychological process
Additive primary colors
red, green, blue - because add them together and you get white light since different wavelengths of light refract at diff angles
kinesthetic sense
perception of the positions in space and movements of our bodies and limbs
vestibular sense
perception of balance
primary auditory cortex (location, connection, what it does)
located in the temporal lobe, auditory neurons in the thalamus extend their axons into here - neurons code the freq (pitch) of auditory stimuli; front neurons respond to high freq, back respond to lower
primary visual cortex (location, function)
occipital lobe, processes visual information from the retinas, but many other areas process visual information
What other areas process visual info besides the primary visual cortex?
two parallel processing streams, or pathways - the ventral stream (lower, specialized for precept/recog of objs), dorsal stream (upper, specialized for spatial perception - where obj is/relation to other things), the “what” and “where” streams
object agnosia
inability to recognize objects - loss of “what” stream but “where” stream intact - DF case
blindsight
condition in which people who are blind have some spared visual capacities in the absence of any visual awareness (only subconsciously able to process things in blindspot)
Gestalt Principles of Perceptual Organization - what is the overall message?
Gestalt psychologists theorized that perception is more than the result of accumulating sensory data - made series of laws that explain how out brains group the perceived features of a scene into an organized whole (obj is unit, not collection of features)
Figure and ground - how does the brain perceive this?
our brains define the figure, and the rest is considered background - basis of many optical illusions that you can’t only see one way at a time
Proximity (principle of what?)
Gestalt - princip of proximity (the closer 2 figs are to each other, more likely to be grouped/seen as part of same obj) - allows us to cluster
Similarity (principle of what?)
Gestalt - princip of similarity (tend to group figs according to how closely they resemble each other) - allows us to cluster
Good continuation (principle of what?) - cases of when this comes into play
Gestalt - tendency to interpret intersecting lines as continuous rather than changing directions radically - we think objects behind an occluder (view blocker) are continuous, create closure on objects with gaps, and illusionary contours are when we perceive contours as cues to depth
bottom-up processing
a hierarchical model of pattern recognition in which data are relayed from one level of mental processing to the next, always moving to a higher level of processing (what we perceive)
top-down processing
a hierarchical model of pattern recognition in which information at higher level of mental processing can also influence lower, “earlier” levels in the processing hierarchy (what we expect to see)
fusiform gyrus
in the right hemisphere, may be specialized for perceiving faces
binocular depth cues
cues of depth perception that arise from the fact that people have two eyes
monocular depth cues
cues of depth that are available to each eye alone (aka pictorial depth cues - often used in paintings)
binocular dispartiy
a depth cue - because of the distance between a person’s eyes, each eye receives a slightly different retinal image
convergence
a cue of binocular depth perception - when a person views a nearby object, the muscles turn the eyes inward
stereoscopic vision
the ability to determine an object’s depth based on that object’s projections to each eye
What are some pictorial depth cues (monocular) that are often used in paintings?
occlusion, relative size, familiar size, linear perspective, texture gradient, position relative to horizon
Motion parallax
relative movements of objects that are at various distances from the observer - closer things seem to move faster, further things seem to move slower
How does the visual system perceive motion?
Motion aftereffects (when you look at a moving image then look at something stationary), compensation for head and eye motion, and stroboscopic motion perception (brain being unable to process images that move by quickly as separate - like movie reels)
perceptual constancy
correctly perceiving objs as constant in their shape, size, color, and lightness, despite raw sensory data that could mislead perception (if you don’t, you’re falling victim to an illusion)
What allows us to perceive size constancy?
need to know how far away the object is from us
What allows us to perceive shape constancy?
need to know from what angle we are seeing the object
What allows us to perceive color constancy?
need to compare the wavelengths of light reflected from the object with those reflected from its background
What allows us to perceive lightness constancy?
we need to know how much light is being reflected from the object and from its background - brain makes ratio
