CHapter 4: Sensation & Perception Flashcards
What is the stimulation/absorption of energy of sense organs known as?
Sensation
What is the selection, organization and interpretation of sensory input into something meaningful?
Perception
What is the study of how physical stimuli are translated into psychological experience?
Psychophysics
Who determined that a threshold is required to know what stimuli are requires to cause a sensation?
Gustav Fechner
What is the dividing point between energy levels that do and do not have a detectable effect?
The threshold
What is known as the minimum amount of stimulation that an organism can detect for a specific type of sensory input?
The Absolute threshold
What is the real absolute threshold?
When the stimulus is detected 50% of the time
What is the smallest difference in the amount of stimulation that a specific sense can detect known as?
Just noticeable difference (JND)
As stimuli increase in magnitude, what happens to the JND?
The JND becomes larger
What is the law that the size of a JND is a constant proportion of the size of the initial stimulus?
Weber’s Law
> meaning that as stimuli increase in magnitude, the JND becomes larger
What is the law that says that the magnitude of a sensory experience is proportional to the number of JNDs that the stimulus causing the experience is above the absolute threshold?
Fechner’s law
> meaning that constant increments in stimulus intensity produce smaller and smaller increases in the perceived magnitude of sensation.
What is the theory that detection of stimuli involves decision processes as well as sensory processes, which are both then affected by other factors than stimulus intensity?
Signal -detection theory
What does signal-detection theory replace?
IT replaces Fechner’s sharp threshold with the concept of detectability
What is measured in terms of probability and depends on decision-making processes + sensory processes?
Detectability
What is the registration of sensory input without conscious awareness?
Subliminal perception
What is the gradual decline in sensitivity due to prolonged stimulation?
Sensory adaptation
What does sensory adaption allow people to do?
Focus on changes and not constants
Is there a one-to-one correspondence between sensory input and sensory experience?
No, people’s experience depends on physical stimuli and processing of stimulus inputs
What is the most important requirement for sight?
Light
What is the form of electromagnetic radiation that travels as a wave moving at the seed of light?
Light
What are the four possible outcomes of signal-detection theory?
- Hits (signal there> see signal)
- Misses (signal there> miss signal)
- False alarms (no signal> see signal)
- correct rejections (no signal> no see signal)
What does signal-detection theory depend on in terms of human requirements?
> The criterion set for how sure one must feel before reacting
Level of noise from all the irrelevant stimuli and neural activity they elicit
What are the three measures of light?
- Amplitude > brightness
- Wavelength > colour
- Purity > saturation
What colours are associated with what lengths of waves?
- Shorter = violet > blue
- medium = green > yellow
- Long = orange > red
What colours are associated with what lengths of waves?
- Shorter = violet > blue
- medium = green > yellow
- Long = orange > red
Do people see all light?
No, only a small portion of light wavelengths as the eye is a filter
What are the main components of the eye?
- Cornea (window)
- Lens (focuses light rays> accommodation)
- Pupil (opening that regulates amount of light with the iris)
- Retina (neural tissue lining the back surface of the eye)
- Cones + rods (visual receptors)
- Optic disk (hole where nerve fibres exit eye)
What are the main components of the eye?
- Cornea (window)
- Lens (focuses light rays> accommodation)
- Pupil (opening that regulates amount of light with the iris)
- Retina (neural tissue lining the back surface of the eye)
- Cones + rods
- Optic disk
What is accommodation of the lens and how does it relate to distance?
When the curvature of the lens adjusts to alter visual focus
> lens curves for close-up
> lens flattens for far
What happens in a nearsighted eye?
Focus of light falls short of the retina
> the eyeball is too long
What happens in the farsighted eye?
Focus of light falls beyond the retina
> the eyeball is too short
What happens to the pupil in dim and bright light?
Dim > dilates to allow more light in (less sharp)
Bright > constricts to allow less light in ( more sharp)
What are the constant eye movements called where the eye is scanning the environment and making brief fixations at various parts of stimuli?
Saccades
What is the piece of the central nervous system that is located in the eye?
Retina
What is the blind spot of the eye?
The optic disk
What are the two types of receptors and what are their specialties?
Cones: > daylight and colour vision
> better acuity
> concentrated in centre of retina
Rods: > night and peripheral vision
> more sensitive to dim light
> density greatest just outside of fovea and decrease toward periphery
> far outnumber cones
What is the tiny spot in the centre of the retina that contains only cones and has the greatest visual acuity?
Fovea
Why do people look slightly above or below an object in dim light?
To move it to the rod-dominated area which don’t need as much light to create a clear image
What is the process in which the eyes becomes more sensitive to light in low illumination?
Dark adaptation
What is the process in which the eyes becomes less sensitive to light in high illumination?
Light adaptation
Once an images reaches the cones what is the order of signals to the brain?
Cones/rods> bipolar cells > ganglia > optic nerve
- complex info processing
What is the retinal area that affects the firing of that cell when stimulated?
The receptive field
> rod and cone receptors funnel signals to a particular visual cell
What is the shape of the receptive field?
centre-surround, where light falling in the centre (increase in firing) has the opposite effect (decrease of firing) of light falling in the surrounding area
What happens when receptive fields are stimulated?
The retinal cells send signals to both the brain and laterally toward neighbouring visual cells
> interactive effects on each other
What is the effect called when neural activity in a cell opposes activity in surrounding cells?
Lateral antagonism > opposing effects of the inner vs outer centre-surround receptive field
What does lateral antagonism enable the visual system to do?
Compute the relative amount of light at a point instead of reacting to absolute light levels
> discerning of contrast
Where in the eye are receptive fields smaller?
Fovea
What is the point called at which the optic nerves from the inside half of each eye cross over and then project to the opposite side of the brain?
Optic chiasm
> ensures signals from both eyes go to both hemispheres of the brain
Which side of the brain do axons from the left half of each retina go?
To the left side
> vice versa for the right
After the nerves cross at the optic chiasm, where do they go?
2 pathways:
1st (main) - optic chiasm > thalamus > synapse in the lateral geniculate nucleus > occipital lobe (primary visual cortex)
2nd- optic chiasm> superior colliculus (midbrain) > thalamus > occipital lobe
(coordination of visual with other sensory input)
How is the main visual pathway organized?
Into 2 specialized pathways:
- Magnocellular channel > brightness
- Parvocellular channel > colour
What is parallel processing?
The simultaneous extraction of different information from the same input
What are individual visual cells most responsive to?
More complicated stimuli such as lines and edges
Who identified that simple and complex cells in the visual cortex respond to different stimuli?
Hubel and Wiesel
What do simple and complex visual cells respond to best respectively?
Simple cells- angled line in particular spot of the receptive field
Complex cells- angled line in any position in receptive field or movement
What is the key takeaway of Hubel and Wiesel’s work?
That cells in the visual cortex are highly specialized > feature detectors
What are the neurons that respond to very specific features of more complex visual stimuli?
Feature detectors
After processing in the primary visual cortex, where does visual input go?
To other cortical areas via 2 streams: dorsal and ventral
What do the dorsal and ventral streams process respectively?
Dorsal: where objects are + ACTION
Ventral: what objects are + PERCEPTION
What happens to neurons as they travel through visual system?
They get fussier and more specialized > faces
What is the inability to recognize objects?
Visual agnosia
What is the inability to recognize familiar faces?
Prosopagnosia
What are the typical methods applied to vision research?
- fMRI
- ESB
- observation of brain damaged patients
What happens to neurons as they travel through visual system?
They get fussier and more specialized > faces
What demonstrates how people see colour (hue, brightness & saturation)?
Colour solid
What is the inability to recognize familiar faces?
Prosopagnosia
What are the theories of colour vision?
- Trichromatic theory by Young and Helmholtz
- Opponent process theory by Hering
What is colour?
A psychological interpretation of the mixture of wavelengths (light)
What are the two types of colour mixingand which parallels how humans see colour?
- Subtractive colour mixing: removal of light leaving less light than was originally there (paint, cellophane)
- Additive colour mixing: putting more light in the mixture than exists in any one light itself
> additive colour mixing closest to human perception
What is the theory that the human eye has 3 types of receptors with differing sensitivities of different light wavelengths and what evidence supports this?
Tichromatic theory
> light of any colour can be matched with additive mixing of three primary colours
explains the three deficiencies among dichromats
What is the theory that colour perception depends on receptors that make antagonistic responses to 3 pairs of colours and what is the evidence to support this?
Opponent process theory
> explains complimentary afterimages
resolves the need for four names to describe colours
explains grapheme-colour synesthesia (coloured letters)
What is colour blindness and what are dichromats?
- variety of deficiencies in the ability to distinguish among colours
- most colour blind people are dichromats who have only two colour channels and are insensitive to either red, green or blue
What are the three pairs of colours in the opponent process theory of colour?
- red + green
- blue + yellow
- white + black
What are complimentary colours?
Opposite colours that when additively mixed produce grey
What is theory is correct re colour vision, why and who figured this out?
- Both theories correct
- eye has 3 types of cones that correspond to different wavelengths
- the visual system has cells that respond in opposite ways to red vs green and yellow vs blue
- George Wald, nobel prize
In what order does perception of colour occur?
In stages:
- Stage 1> cones behave as per trichromatic
- Stage processing> cells in retina, LGN and cortex follow opponent process
What are the origins of colour effects on behaviour?
1- learned associations based on colours being paired with certain repeat experiences
2- colours have adaptive significance for survival or reproduction via evolution
What is the significance of the reversible figure?
the same visual input can result in different perceptions
What does perception involve and how can it be manipulated?
Perception involves interpretation which can be manipulated by influencing people’s expectations
What is the effect called where people view black and coloured gratings (alternating bw opposing colour) and then perceive the complimentary colour in the after image?
The McCullough effect
What is the effect called where people view black and coloured gratings and then perceive the complimentary colour in the after image?
The McCullough effect
What is known as the failure to see fully visible objects or events in a visual display?
Inattentional blindness
> particularly when unexpected
What is known as the failure to see fully visible objects or events in a visual display?
Inattentional blindness
What increases inattentional blindness?
When people work on tasks that require a lot of attention or create a heavy perceptual load
What is the process of detecting specific elements in visual input and assembling them into a more complex form and what does it assume?
Feature analysis
> assumes bottom-up approach
What is the final step in both bottom-up and top-down processing?
Recognizing the stimulus
What gave rise to the idea of top-down processing?
That feature analysis could not explain all in form perception
> form processing
> subjective contours: perception of contours when none exist
What is required first in top-down processing?
A perceptual hypothesis about the nature of the stimulus as a whole
What is the illusion of movement created by presenting visual stimuli in rapid succession?
Phi phenomenon
> movies
What is the illusion of movement created by presenting visual stimuli in rapid succession?
Phi phenomenon
What was the purpose of the Gestalt Principles?
To describe how the visual system organizes a scene into discrete forms
What are the 6 Gestalt principles?
> Figure and ground: reversible object and background
Proximity: things close belong together
Closure: people group elements to complete picture
Similarity: grouping of stimuli that are similar
Simplicity: Praganz/’good form’, simplest way and most general principle
Continuity: tendency to follow in whatever direction being led
What is the stimuli that lie in the distance, outside of the body?
Distal stimuli
What are the stimulus energies that impinge directly on sensory receptors (light falling on the retinas) and are distorted 2D versions of the actual?
Proximal stimuli
What is the inference about which distal stimuli could be responsible for the proximal stimuli sensed?
Perceptual hypothesis
> the bridge bw distal and proximal stimuli
> guided by context
What type of perception involves interpretation of visual cues that indicate how near or far away objects are?
Depth perception
What are the two types of cues for judging distance?
Binocular cues and Monocular cues
What is the cue based on the differing views of the two eyes and what are its two sub-cues?
Binocular cues
> retinal disparity: each eye sees slightly diff view
> convergence: objects are closer when one can sense the eyes converging toward each other
What is the cue based on the image in either eye alone and what are its two sub-cues?
Monocular cues
> Motion parallax: closer objects appear to move faster than farther objects when person is moving
> Pictorial depth cue: depth cues that can be given in a flat picture- 6 sub-cues!!!
What is the cue based on the image in either eye alone and what are its two sub-cues?
Monocular cues
> Motion parallax: closer objects appear to move faster than farther objects when person is moving
How does people’s motivation impact depth perception?
Desirable objects appear closer
What is the tendency to experience a stable perception in the face of continually changing sensory input?
Perceptual constancy
What are apparently inexplicable discrepancies between the appearance of a visual stimulus and its physical reality?
Optical illusion
What is the Muller-Lyer illusion and what does it illustrate?
- Two vertical lines with regular and reverse arrows that make the centre lines appear different lengths
- Misperception of depth and the nature of visual representations underlying perception, motor control and planning.
What are the Pnzo illusion and Ames room?
Ponzo: A-frame with two lines in the middle, top looks longer
Ames: room constructed with angles that make a person appear way smaller than other person of same size, depending on placement in the room
What are objects that can be represented in 2D pictures but that cannot exist in 3D space?
Impossible figures
What is the moon illusion?
When the full moon appears to be up to 50% smaller overhead than near the horizon
> due to size constancy effects with misperception of distance
What 2 functions does vision serve and what condition revealed them?
1- creates an internal representation or model of the external world > perception (ventral)
2- process control of actions that are directed at perceived objects > action (dorsal)
-agnosia in a brain damaged woman and her ability to draw objects from memory that she could not visually recognize
What are waves that are vibrations of molecules that must travel through some physical medium (air)?
Sound waves
How are sound waves characterized?
- Amplitude > loudness
- Frequency (wavelengths) > pitch
- Purity > timbre
What are waves that are vibrations of molecules that must travel through some physical medium (air)?
Sound waves
What is the human’s range of sound?
What are animal ranges?
20Hz: 20,000Hz
- pigeons < 10Hz
- bats + porpoises < 20,000 Hz
What are the units used to measure frequency?
Hz
OR
cps = cycles per second
What are the units to measure amplitude?
decibels (dB)
What frequency is the human ear most sensitive to?
2,000Hz
Perceived loudness depends on what?
Interaction of amplitude + frequency
How does each section of the ear conduct sound?
- External ear > vibration of air molecules
- Middle ear > vibration of movable bones
- Inner ear > waves in a fluid
What are the components of the external ear?
- Pinna >
- auditory canal >
- eardrum: taught membrane that vibrates in response to sound waves
What are the components of the middle ear and what do they do?
3 ossicles that amplify air pressure: - Hammer - Anvil - Stirrup > convert large movements w little force into smaller movements with greater force
What are the components of the inner ear?
- Oval window: sound entry, vibrated by ossicles
- Cochlea: fluid filled coiled tunnel that contains auditory receptors > neural tissue
How is neural tissue organized in the cochlea?
It sits on the basilar membrane that divides the cochlea into upper and lower chambers
What holds the auditory receptors and runs the length of the spiralled cochlea?
The basilar membrane
How many hair cells (auditory receptors) are in the cochlea?
About 25,000
How are auditory signals sent to the brain?
- Waves of fluid in the inner ear stimulate the hair cells >
- Hair cells convert into neural impulses sent to thalamus >
- Thalamus sends signals to auditory cortex which has specialized cells (similar to feature detectors)
What are the theories of hearing try to explain?
How sounds waves are translated into perception of frequency, pitch and timbre
What are the two theories of pitch perception?
- Place theory: perception corresponds to vibration of different places along basilar membrane (Helmholtz)
- Frequency theory: corresponds to frequency at which the entire basilar membrane vibrates (membrane matches Hz)
Which theory of pitch perception is valid?
Both
- place theory correct but hairs are not independent> they vibrate together as per frequency theory
> wave peaks at a particular place depending on Hz
What is the term for localizing the source of a sound in space and what contributes to it?
- Auditory localization
- The ears being set apart
What are the 2 cues for auditory localization?
- Intensity (loudness) > shadow of head
- Timing of sound arrival to each ear
What is the connection of the brain to music?
- Brains of musicians are identifiable and larger in in motor, auditory and visuospatial areas of cerebellum
- mood modulation
- stimulate brain plasticity
- facilitate sensitivity to emotions via speech parsody
What is the effect when something is so easy that not further manipulation will affect performance?
Ceiling effect
What are the chemical senses?
Gustatory + Olfactory
What are the physical stimuli for the gustatory system?
Chemicals that are soluble
How are the gustatory receptors organized?
In clusters of taste cells found in the taste buds that line the trenches around tiny bumps on the tongue
What is the effect when something is so easy that not further manipulation will affect performance?
Ceiling effect
What are the primary tastes?
- Sweet
- Sour
- Bitter
- Salty
- Umami: savoury taste of glutamate
What are the physical stimuli for the gustatory system?
Chemicals that are soluble
How are the gustatory receptors organized?
In clusters of taste cells found in the taste buds that line the trenches around tiny bumps on the tongue
What is the pathway for gustatory messages to the brain?
Taste cells > thalamus> insular cortex in frontal lobe for initial cortical processing
How long to taste cells live and how do they move around?
- live about 10 days
- they are born at edge of taste bud> migrate in> die at the centre
What are super-tasters?
People who have specialized taste receptors that are not found in non-tasters
> more sensitive to bitter and sweet
> 25% of population
> more women than men
Why might more women being super-tasters be an evolutionary trait?
- women more involved in feeding children
- more sensitive to high-calorific foods
- helps avoid toxic substances
Are taste preference learned or innate?
- Basic preferences are innate for newborns
- most are learned by social processes
What are non-tasters?
- people who have an insensitivity to PTC or PROP + have 1/4 of the taste buds per cm2 compared to super-tasters
> 25% of population
What are super-tasters?
People who have specialized taste receptors that are not found in non-tasters
> more sensitive to bitter and sweet
> 25% of population
What is flavour a combination of?
Taste + smell + tactile sensation of food
How are olfactory messages sent to the brain?
- Axons synapse w cells in the olfactory bulb > areas in the cortex
- DOES NOT GO THROUGH THALAMUS
What are the olfactory receptor cells?
Olfactory cilia> hairlike structures located in the upper nasal passages
What do specific odours trigger?
Responses in different combinations of receptors
How many types of olfactory receptors are there and how many genes are in the sets that affect their operation?
- 350 types of receptors
- 1,000
> highly specialized receptors
What is the time frame for sensory adaptation to odours?
Fades by less than 1/2 in 4 minutes
How many odours can humans distinguish?
10,000
> women can distinguish better than men
What are the chemical messages that can be sent by one organism and received by another member of the same species?
Pheromones
> species specific
> synching of periods
What are the physical stimuli for touch and what perceptions do they produce?
- mechanical + thermal + chemical energy
- perceptions of tactile stimulation + warmth + cold + pain
How many sensory receptors does skin have?
6 types of receptors that are specialized for different functions
How is the sense of touch set up?
For tactile localization
How are touch cells similar to visual cells?
They are in patches on the skin similar to receptive fields > centre-surround formation
> sensory adaptation
How do touch messages get to the brain?
Touch> sensory receptors> spinal cord> brainstem (cross-over) > thalamus > somatosensory cortex
> some cells in cortex behave like feature detectors
What are pain receptors in the skin?
Free nerve endings in the skin
Pain is transmitted to the brain via which 2 pathways?
1) Fast path- localized pain is registered> ventrobasal nucleus in thalamus> somatosensory cortex
> via myelinated A-delta fibres in fraction of a second
2) Slow path- carries less localized long-lasting/ temperature info > midline nucleus in thalamus> somatosensory cortex
> via unmyelinated C-fibres at a 1-2 second lag
What influences the perception of pain?
- Mood
- expectations
- personality
- higher mental processes
What illustrates well the subjective nature of pain?
The placebo effect
How does culture affect pain perception?
Mainly the willingness to tolerate pain
What theory was used to explain how the CNS blocks peripheral incoming signals due to cognitive and emotional processes?
Gate-control theory
What did the gate-control theory posit?
That a pattern of neural signals from the brain and peripheral receptors known as the ‘gate’ inhibits incoming pain signals
> explains how attention and expectations can shut off pain signals
What did the McGill Pain Questionnaire generate?
The Neuromatrix theory that pain is a multidimensional phenomenon produced by many influences
What is the main mechanism to replace the ‘gate’ theory?
The discovery of a descending neural pathway that suppresses pain
> originates in PAG (periaqueductal gray)
> activated by endorphines and triggers release of seratonin
> synapse in the spinal cord to release more endorphines
> inhibit neurons transmitting pain impulses
What types of glia cells contribute to pain modulation?
- astrocytes
- microglia
> role in amplifying chronic pain
What system monitors positions of various parts of the body?
Kinesthetic system
Where are the receptors for the kinesthetic system and how are messages transmitted to the brain?
- receptors are in joints and muscles
- messages transmitted via the tactile stimulation pathway
What system responds to gravity, balance and keeps awareness of the body’s location in space?
Vestibular system
What is the largest part of the vestibular system?
Semicircular canals in the inner ear> 3 inner tubes joined at the base of the cochlea
>shifts in fluid detected by hair cells with motion of head
What principles are applied in art?
Visual perception principles
What was lacking in art pre-renaissance?
depth cues
What did Picasso apply in his art?
Gestalt principles
What technique did Seurat apply?
Additive colour mixing
What did the surrealists apply in their art?
Unconcious
What was Escher’s goal with his art?
Stimulate thoughts re the nature of reality and visual perception
What is the technique of making a large request that is likely to be turned down as a way to increase the chance of agreement to a smaller request?
Door-in-the-face technique
What are people easily swayed by?
Contract effects
> comparitors: standards used as a baseline for comparison in making judgments> manipulation of judgments
What facilitates critical thinking?
Councious awareness of the way comparitors can influence and distort judgements
How can comparitors be countered?
By considering camparitors that are both worse and better to balance the two extremes
