Sensation Flashcards
Senses (what is it? how many?)
- how we experience the world
- 5 basic senses, but we have many more (ie. subgroups of somatonsensory)
Importance of audition, vision and smell, and taste and touch
- Audition important for social behaviour
- Vision and smell give us info about distant events
- Taste and touch give us info about immediate, nearby events
sensation
- detecting STIMULI (brightness, colour, warmth)
- Ie. Seeing the colour red
perception
- detecting OBJECTS (apples, chairs, soccer balls)
- Ie. Seeing a red apple
transduction
sense organs converting energy from environmental events into neural activity that the brain can respond to
role of sense organs in transduction
detect stimuli, then transmit it to the brain via neural impulses -> brain analyzes these impulses to reconstruct what has occurred
role of receptor cells in transduction
respond to physical stimuli like light, vibrations, etc.
anatomical coding
- interpreting the LOCATION and TYPE of stimulus (depends on which nerve fibers are active)
- Ie. Rubbing eyes -> stimulate light-sensitive receptors -> brain doesn’t know that those receptors were stimulated by a non-visual stimulus -> we see stars and flashes
temporal coding
- encoding INTENSITY (time/rate)
- The rate at which neurons fire tells us how intense that stimulus is
psychophysics (and what it relies on)
- study of relation between physical characteristics of stimuli and the sensations they produce
- Rely on thresholds (line between perceiving and not perceiving)
difference threshold
minimum detectable DIFFERENCE BETWEEN 2 STIMULI
absolute threshold
minimum VALUE OF A STIMULUS that can be detected
just-noticeable difference (JND)
Weber measured this - smallest change in stimulus that a person can detect (aka: difference threshold)
weber fractions
different ratios of the just-noticeable difference
How did Fechner use the JND system?
to measure people’s sensations - used lights behind frosted glass, brightening one of them until person could tell the difference -> showed how a logarithmic function could be derived from Weber’s principle
signal detection theory
Every stimulus requires discrimination between signal and noise
signal (in signal detection theory)
stimulus
noise (in signal detection theory)
background stimuli and random activity of nervous system
response bias (in signal detection theory)
tendency to say yes or no (ie. When a light flashes and you have to say whether or not it was accompanied by a tone)
hit
saying yes when the stimulus was presented
miss
saying no when the stimulus was presented
correct negatives
saying no when the stimulus was not presented
false alarms
saying yes when the stimulus was not presented
manipulation of response bias
Examples:
- promising the participant a dollar every time they make a hit with no penalty for false alarms -> they would say yes all the time
- giving them a dollar for every hit but fine a dollar for every miss -> will be very conservative with their answers
receiver operating characteristic curve
a graph of hits and false alarms of participants under different motivational conditions; detects a person’s ability to detect a particular stimulus
light
stimuli that consists of radiant energy that has wavelengths between 380 and 760 nm
wavelength
- distance between adjacent waves of radiant energy
- different visible wavelengths have different hues/colours
- we can’t see invisible wavelengths like UV, X, Gamma, etc. but some animals can (ie. bees can see UV, snakes can see infared)
electromagnetic spectrum
entire range of wavelengths
visible spectrum
the wavelengths our eyes can detect and see as light
eye is protected by
- eye-sockets
- eyelid (keeps out dust and dirt)
- eyelashes (keep stuff from falling in eye)
- eyebrows (prevent sweat from dripping into eye)
- reflexes (automatic eyelid closure and withdrawal of head)
cornea
transparent tissue covering front of the eye, admits light
sclera
tough other layer of eye; the “white” of the eye
iris
pigmented muscle of the eye that controls the size of the pupil and thus the amount of light emitted into the eye (brain controls the 2 muscles in the pupil)
aqueous humor
- fluid-filled space behind the cornea; filters fluid from blood to nourish cornea and other parts of eye
- problem with aqueous humour can cause glaucoma
how does the eye view things
upside-down and reversed from left to right, but the brain compensates for this and interprets it appropriately
lens
- transparent organ situated behind iris of eye; helps focus image on the retina
- as people age, it becomes less flexible -> vision become fuzzier and less focused
accomodation
changes in thickness of the lens that focus images of near or distant objects on the retina
nearsightedness
- eyes are too long
- image focused in front of fovea
- require concave lenses
farsightedness
- eyes are too short
- image focused behind fovea
- require convex lenses
retina
- tissue at the back of the eye that contains photoreceptors and associated neurons; performs sensory functions
- no photoreceptors in front of optic disk -> this part of retina is blind
photoreceptors
receptive cell for vision in the retina (either rod or cone) that transduce light into neural activity
optic disc
at back of eye; information from photoreceptors is sent here before going to optic nerve and then to brain
Order in which light passes through retina
- ganglion cell layer
- bipolar cell layer
- photoreceptor layer
Order in which visual information passes to brain
- photoreceptor layer
- bipolar cell layer
- ganglion cell layer
bipolar cell
neuron in the retina that receives information from photoreceptors and passes it on to the ganglion cells, from which axons process from optic nerves to brain
ganglion cell
neuron in retina that receives info from photoreceptors by means of bipolar cells and from which axons proceed through the optic nerves to the brain
rod
photoreceptor that is very sensitive to light but cannot detect changes in hue
cone
photoreceptor that is responsible for acute daytime vision and colour perception