Chapter 3 - Sensation and Perception Flashcards
What was the early philosophy of perception?
Concept of reality depends on what we learn about the world through our senses (eyes, ears, nose, tongue and skin).
Why have senses evolved?
Senses evolved to help increase our chances of survival.
What is sensation?
The ability to detect a stimulus and, perhaps, to turn that detection into a private experience.
What is perception?
The act of giving meaning to a detected sensation.
How does sensation become perception?
Receptor cells detect stimuli, convert into neural impulses and then transmit them to the brain – ‘transduction’. Brain organizes & interprets messages
What is the absolute threshold?
The point sensory info. can/cannot be detected 50% of the time
What is the Just Noticeable Difference?
Slightest + or - in physical stimulus required to produce Just Noticeable Difference (JND)
What is Weber’s law?
Psychological law quantifying the perception of change in a given stimulus. The law states that the change in a stimulus that will be just noticeable is a constant ratio of the original stimulus. Depends on percentage of change!
What is the signal detection theory?
Discriminating a stimulus from background noise & deciding whether the stimulus is actually present
What does signal detection involve?
Physical stimulus, Motivation to detect stimulus, previous experience, expectations, alertness
What is sensory adaptation and give an example?
Becoming accustomed to unchanging, constant stimuli (i.e. Smell of your home); firing rate slows
What is the visible spectrum?
400-700nm (between ultra violet and infared)
What does the cornea do?
Transparent covering that bends light rays into pupils
What is the pupil?
Small opening in center or Iris
What is the iris?
Coloured, circular muscle (reflexive), dilates/contracts to regulate entering light
What is the lense?
Disc that flattens to focus on distance and bulges for close images
What is Presbyopia?
Old eyes
What are the three layers of cells?
The first two send signals to the visual cortex but they do not respond directly to light.
Third layer (at the back of the retina) is where rods and cones are located
What are cones of the retina?
Color, fine-detail, work in bright light, focus on red, green, blue.
What are the rods of the retina?
Focus on black & white, work in dim light, helps adapt to dark places, bright places.
How do rods and cones transduce light?
Via the optic nerve to occipital lobe
Why do we have a blind spot?
No rods or cones in that area
What are the sensory receptors and location for vision?
Rods and cones in the retina
What are the three dimensions of colour that we experience?
Hue; colour
Saturation: purity
Brightness; intensity of the light energy we perceive
What is the trichromatic theory?
3 types of cones that respond best to different colours (blue, green or red).
What is the Opponent-process theory?
Three classes of cells respond by increasing or decreasing their rate of firing when different colours are present.
What is the Opponent-process theory?
Three classes of cells respond by increasing or decreasing their rate of firing when different colours are present. Red/green; yellow/blue; black/white
How are both theories of colour vision correct?
The trichromatic theory is consistent with what happens with the cones
The opponent-process theory is consistent with what happens with the ganglion cells.
If a tree falls in the woods does it make a sound?
No because there is no receptor
What is needed for sound ?
It require a medium - air, water or solid
What are the characteristics of sound?
Frequency, amplitude, timbre
What is the frequency of sound?
determined by the number of cycles completed by a sound wave in one second (Hz)
What is pitch?
how high (more vibrations) or low (fewer vibrations) the sound is - determined by frequency
What is the amplitude of sound?
Loudness (force which air molecules move) - Measured using ‘Bel’ (A.G.Bell) units – or decibels (dB).
What is the timbre?
Distinctness of sound with same pitch/amplitude. Flute almost pure sound; a tuning fork completely pure sound
What consists of the outer ear?
pinna, auditory canal (lined with hair), eardrum (tympanic membrane) - thin and flexible
What does the middle ear consist of?
Ossicles link eardrum to oval window - hammer (malleus), Anvil (Incus), Stirrup (stapes)
What is the smallest bone?
Stirrup (Stapes)
What consists of the inner ear?
cochlea and hair cells
What are the sensory cells of hearing?
Hair cells in the cochlea. Transduce message via auditory nerve
What is the choclea?
Fluid filled, snail shaped,
bony chamber.
Stirrup creates vibrations on oval window, which moves fluid in the cochlea’s in waves.
The waves reach thousands of receptors in Basilar Membrane
What is place theory (Helmholtz)?
Each individual pitch is determined by the particular spot or place along the basilar membrane that vibrates the most.
Doesn’t hold for frequencies below 150Hz
What is the Frequency theory?
The hair cells vibrate the same number of times per second as the sounds that reach them.
Not valid for high frequencies.
What are potential causes of hearing loss and deafness?
Disease, birth defects, aging, injury, excessive noise, wax
What is conduction deafness?
Middle ear deafness- sound waves cannot be
conducted to the cochlea- Hearing aid or surgery.
What is sensorineural hearing loss?
Inner ear or auditory nerve damage. Birth defect,
disease, aging
Almost always irreversible – Now… cochlear implants.
What is the effect of excessive noise?
Tinnitus
Why a sense of smell?
smelling chemicals, survival and evoke memories/emotions (limbic system)
How many different odours can the olfactory system detect?
10 000
Young people are more sensitive
What are the receptor cells for smell and where are they located?
Olfactory neurons, 10 millions make up two patches located on the olfactory epithelium. They have a lifespan of 30-300 days.
Where do olfactory neuron axons relay the message to?
Olfactory bulb
What are pheromones used for in animals?
Emit and respond to the same species, mark territory, sexual receptivity and sense predators
What are pheromones used for in humans?
Androsterone causes changes in mood &
heart rate
Menstrual synchrony
Men can recognize fertility
What are the tastes sensations?
Sweet, sour, salty, bitter and unami (glutamate in meat cheese, MSG)
What are the receptors for taste and where are they located?
Paillae located on the tongue, palate, cheeks, lips, throat and tonsils
What is flavour?
Combined sensory experience-
taste, smell & touch
How many types of papillae do we have?
4, three contain taste buds with 60-100 receptor cell. non tasters - 96 while supertasters have 425
What is the lifespan of a taste bud?
10 days
What is the largest organ in the body?
Skin
What are the receptors of touch?
Nerve endings on the skin - relays messages to somatosensory cortex (parietal lobe)
Explain two-point threshold
there must be a threshold distance, above which subjects can differentiate between two different sensations. … The subject responded that they felt sensation only at a single point
What is the use of pain?
To tell us to remove ourselves form it, Chronic pain persists long after it serves any function.
What is the Gate control theory?
pain signals can be transmitted or inhibited by spinal cord. We feel pain when the slow-conducting nerve fibers reach the spinal cord
What does the gate control theory also explain?
This theory also explains how cognitive and emotional factors can numb or enhance pain
What are endorphins?
block pain and produce feelings of well- being…naturally!
What does acupuncture do?
stimulates the release of endorphins
How can we control pain?
distraction, counter-irritation,
relaxation, positive thoughts.
* attention and sympathy make pain worse!
What are the spatial orientation senses?
Kinesthetic sense and Vestibular sense
What is the kinesthetic sense about?
Position of body parts (posture/orientation). Movement of the entire body
Where are the receptors for our kinesthetic sense?
Receptors in muscles, joints, tendons
What is the vestibular sense about?
Movement & orientation and balance: Up, down,
speed
What are the receptors of the vestibular sense?
Semicircular canals & vestibular sacs in the ear. Filled with fluids that move hair cells (receptors) that detect ‘changes’ (take off and landing… not in between)
What is synesthesia?
The mixing of the senses
What is synesthesia?
The mixing of the senses like hearing colours, seeing music and tasting shapes
What is perception?
sensory information interpreted by the brain - like we sense sounds but perceive melodies
What was Gestalt’s theory>
an organized whole that is perceived as more than the sum of its parts - our brain organizes our sensory experience
How do we group things that we perceive?
Similarity, proximity, continuity, closure
What the perceptual constancies?
Size, shape, brightness, and colour
Examples of our brains making too much sense out of things we perceive
Cylinder illusion, dress colour
What is convergence in relation to depth cues?
eyes turn inward as they focus on nearby objects (cue for distance)
What is binocular disparity in relation to depth cues?
resulting from differences between the two retinal images cast by objects
The farther away the objects are the less the binocular disparity.
Interposition
When one object partially blocks your view of another, you perceive the partially blocked object as being father away.
Linear Perspective
Parallel lines are the same distance apart but appear to grow closer together, or converge, as they recede into the distance.
Relative size
Larger objects are perceived as being closer to the viewer, and smaller objects as being farther away.
Texture Gradient
Objects close to you appear to have sharply defined features, and similar objects farther away appear progressively less well defined, or fuzzier in texture.
Atmospheric perspective
Objects in the distance have a bluish tint and appear more blurred than do objects close at hand (sometimes called aerial perspective)
Shadow or shading
When light falls on objects, they cast shadows, which add to the perception of depth.
Motion parallax
When you ride in a moving train and look out the window the objects you see outside appear to be moving in the opposite direction and at different speeds; those closest to you appear to be moving faster than those in the distance.
Methods of depth perception
Interposition, Linear Perspective, Relative size, Texture Gradient, Atmospheric perspective, shadow or shading and motion parallax
What is real motion?
perception of moving when something else moves
What is apparent motion?
Illusion - phi phenomenon, sequence of lights moving, autokinetic illusion
What is the delboeuf illusion
perceived difference in the size of two identical circles when one of the circles was surrounded by a much larger circle and the other one was surrounded by only a slightly larger circle.
What are the two information processing techniques?
Bottom-up processing (unfamiliar)
Top-down processing (familiar)
What is the bottom-up processing?
Individual bits processed to make a whole. The ideal approach.
What is the top-down processing?
Experience, knowledge & context influence perception
Our ‘perceptual set’: what you expect to perceive determines what you actually see, hear, feel, taste, and smell (green ice cream?)
What influences perception?
Paying attention and inattentional blindness (attention carries perceptual costs to other things)
