Exam #2 Flashcards
Sensation
The reception of stimulation from the environment
Stimulus
Any form of energy that activates a sense receptor (light waves, chemicals, sounds)
Perception
- physiological process whereby meaning is given to the sensation
- involves memories of past sensory experiences
- the interpretation of a physical sensation
Absolute threshold
the smallest intensity of a stimulus that can be detected
- we have different thresholds of sounds, same person varies in sensitivity over time
- more sound to detect in noisy environment
- magnitude at which person can detect stimulus 50% of the time
Signal Detection Theory
present stimulus on only some trials, some they aren’t, 4 categories
Signal present, response yes
Hit
Signal absent, response yes
Miss
Signal present, response no
False alarm
Signal absent, response no
Correct rejection
D’
- ratio of hits to false alarms
- higher ratio, more sensitive –> relative sensitivity
Conservative response bias
detected stimulus only when you are certain that you have (more rejecting and more misses)
Liberal response bias
you detected stimulus even when you are unsure (more hits and false alarms)
Expectations and motivations
if you expect and are motivated, you tend to have a more liberal bias
Difference threshold
- the smaller amount of change in stimulus intensity that can be detected (aka noticeable difference)
- different senses have different noticeable differences
Weber’s Law
- noticeable difference depends on intensity of the original stimulus
- greater magnitude of original stimulus, greater amount of change needed to be detected (delta I/I = k) where the weight ration is 1/30
Sensory adaptation
- stimulus is continually presented in an unchanging intensity or a very rapid repetition at a constant intensity
- sensation is reduced until you no longer notice the sensation
Why is sensation reduced until you no longer notice the sensation?
Sensory receptors get fatigued, sense receptors are designed to notice changes in environment
Subliminal Perception
when a stimulus is presented too fast to be consciously perceived, yet it might be registered below our awareness (could affect our behavior)
Semantic priming (research done by Marcel)
you can identify a word more quickly than if it had been preceded by another word
Behavior by Barch et al.
- presented negative stereotypes about old peeps or neutral words
- people present with stereotypes found to walk quicker to elevator
- no direct impact in advertising
Why is there a difference between lab and real world due to semantic priming?
- conditions must be just so (no distractions or competing stimuli)
- measurement of effect must be very sensitive
- for these effects to occur, first and second words must be close in time and space
Vision stimulus
Activates eye, electromagnetic radiation/light (not all is visible)
Amplitude of Vision
- height
- determines brightness of visual sensation
- low amplitude of dim, higher is brighter
Frequency of Vision
- wavelength, amount of time between crests of waves
- determines color, different wavelengths = different colors
Retina
actual receptor site, translates into neural impulse
Rods
- more responsable for vision in darkness
- responsible for peripheral vision and sides of retina
Cones
- fewer cones than rods
- concentrated in fovea (central spot in retina)
- responsible for color and visual acuity in bright light
- less responsive to light and dark, lots of light must hit them before they fire (best in bright light)
Brightness
- # of both rods and cones, more rods and cones the brighter light is
- both rods and cones respond to light and dark
Night vision
- color is only indistinct forms of black and gray
- activity: focus image away from fovea
- responses to visual stimuli slow down (rods less directly connected to optic nerve)
- –>axons of nerve connect to optic nerve, neural impulses of rods take longer to get to brain, slows down reaction time
Blind spot
- we tend to know what should be there
- no receptors (rods or cones)
- entry of optic nerve to retina where light is insensitive
Micro-saccades
Tini jumps in eye, in between jumps drifts occur
Physiological nystagmus
Tini constant tremor, constant looking at one thing will lead to fading of image
Dark adaptation
- rods and cones firing frequently they get tired and lose sensitivity
1) when you go into darkness rods aren’t sensitive enough to be in darkness so they stop firing
2) while receptors rest they regain sensitivity by making fresh supply of chemicals (depleted by intense light)
3) improvement in vision is fairly rapid
4) cones become as sensitive as it gets in 5 min
5) rate of improvement continues at a slower pace until rods reach max sensitivity in 30 min (not very noticeable)
Light adaptation
1) when exposed to intense light after darkness rods and cones go crazy
2) a lot of them are firing simultaneously
3) when some chemicals are used up sensitive to light is reduced
4) takes only about a min
Optic Chiasm
where half of neurons from each eye cross over to opposite hemisphere of brain, from there visual info is in 2 pathways
Main pathway for visual pathway
processing color, form, contrast, and motion
-thalamus first then occipital lobe
2nd pathway for visual pathway
perception of motion and coordinating visual input with other sensory info
-midbrain first then thalamus then occipital lobe
Ventral stream
further processing info about form and color (what the object is)
Dorsal stream
processes motion and depth perception (where the object is)
Color perception, Youg-Helmholtz Trichromatic theory
3 kinds of cones where each cone is responsive to only one range of lightwaves (one for red, green, blue wavelengths)
- color perception depends on relative activation of these three cones
- other colors are combos of these cones (variation of cone activation gives variation in colors)
- does not explain after images
Color perception, Opponent Process theory
3 opponent systems in visual systems (pairs of color receptors)
- red-green, yellow-blue, black-white
- within each pair some neurons are excited by wavelengths that reduce one color, those same ones are inhibited by the wavelengths that produce the other color
- some are excited by red but inhibited by green and vice versa
- if you stare at red you exhaust the neurons that are excited by red
Color blindness
total blindness is rare, partial is more common
- 5-8% men, 0.3-0.7% women
- in some cases person is missing one of three pigments (dichromats)
Opponent Process theory and Youg-Helmholtz Trichromatic theory Validity
- both are true at different levels of processing system
- cone-level: trichromatic theory is accurate
- beyond cones: opponent theory is accurate
Basic tenant of Gestalt principles of organization
- “the whole is greater than the sum of its parts”
- structuralism: understand basic bits, add them up to create overall sensation but Gesalt disagrees
- perception has meaning only looking at an object as a whole
Figure-Ground differentiation rule, Gesalt
-center of attention is figure, the rest is indistinct background
Proximity rule, Gesalt
things that are proximal (close together) belong to each other
Closure rule, Gesalt
we favor perception of a more enclosed or complete figure (we fill in spaces)
Continuity rule, Gesalt
Elements that appear to flow in same direction are perceived as forming a group
Similarity rule, Gesalt
We tend to group elements together that are similar to one another
How do we classify sets of stimuli into meaningful object categories?
- Also noticing what features are not there
- Not many features are set in concrete (object will be missing feature, feature is not necessary to classify object)
- Can take on a range of values (big leaves vs. needle leaves)
Bottom-up theories
-Perception begins with basic stimulation of sense receptors
-Then it moves up to the cortex where abstract categories are found
-Near bottom of visual processing system: cells called feature detectors
-Specialized cortical cells that are sensitive to a narrow range of stimuli
-After leaving receptors, depends on feature detectors, allows us to begin to recognize shape of object
-When in cortex we can bring more info stored to process object
-When we make errors we typically make errors within a group of objects that share common features
E vs F instead of A vs C
Top-down theories
- pattern recognition begins at cortical level and works it way down stimulus
- Pattern recognition involves active recognition of stimulus
- Eyes actively move around picture
- Incorporate the fact that previous experience and info influences our perception
Top-down theories basic idea
- If hypothesis is confirmed, pattern recognized
- Not confirmed, devise a hypothesis again and retest it
- Allows us to speed up processing
Perceptual Set
- See something in a certain way, makes certain expectations that guide our perceptions
- Derive from: experience/knowledge, what people tell us to expect, and context
Why is Context important in perceiving speech
- Speech is never clear enough to fully understand
- Helps explain why we have difficulty with a new language
- Also ambiguous figures and subject contours
- In reality, we have to use integrative theories
- Context will help what feature detectors are activated, cortical will activate top down processes
Binocular cue, Convergence
- Infer how close something is
- From other info coming from eye
Binocular cue, Binocular disparity - stereopsis
- Visual field of one eye is slightly different than other eye
- Difference between images is binocular disparity
- 2 images are blended, difference contributes to depth
Elevation, Monocular cue
Objects that appear higher in visual field are perceived as farther away
Relative size, Monocular cue
- 2 similar objects of different sizes: the larger one appears closer to you
- Helps us with judging unfamiliar things
Linear perspective, Monocular cue
- Systematically decreasing size of further objects and decreasing the space between them
- Point where lines converge: vanishing point
- To see more depth, look through toilet paper tube
Texture gradient, monocular cue
When you are looking at a textured objects, elements become more textured the closer they are
Interposition, Monocular cue
- Two objects, one object is partially covered by the other, the fully exposed object is perceived as nearer
- Increases familiarity of object
Aerial perspective (haze), monocular cue
An object for which there is a sharp distinct retinal image appears closer than objects that are more blurry and indistinct
Closer an object, clearer it appears to be