Chapter 3: Perception Flashcards
What is a stimulus
- anything that interact with our sensory system/ receptors
- light on retina, sound vibrations In ear drum, molecules that bind to nose/ tongue , touch/ pressure on the skin
- What spectrum of light can humans detect?
- what spectrum of sound can humans detect
- how many basic senses can we detect
- how many smells
- light within 400-700 nm
- south within 20-20 000 hertz
- 5 basic tastes
- hundreds of smells
What is transduction?
Give example
- physical information is converted into neural signals
- ex. light hits retina and activates rods or cones which triggers neural impulses which go to the brain
Why aren’t neural impulses turned back into images/sounds
- because there is no homunculus (little person in our head that controls everything )
- there is no need to because neural impulses are enough
What is perception and what is it based on?
- experience resulting from a stimulation of the senses
- understanding and processing
- perception is not based on direct contact with a stimulus but on neural representation of the stimulus
How does the brain know what kind of sensations are coming in?
- Neural Representation
- specialized cells
- the brain knows specialized cells that respond to each feature of a stimulus, all are individuals integrated to for a big picture
- horizontal, vertical
What is sensation
- receiving information through sense organs
- to perceive is to know / understand the sensation
What is Visual Agnosia
- the inability to recognize objects
- they are able to see the object but cannot recognize it
- they can describe it
Are there pain receptors in the brain
no
when do we perceive things?
- Do you need to be able to perceive information to be able to create output?
- always
- you need information input to be able to think about it
- you need to be able to perceive information to be able to create output
What are the perceptual abilities of humans
(Things that machines find hard to do)
5
- the ability to perceive degraded information (ex blurry images)
- ability to perceive partial objects as complete
- ability to perceive an object from different viewpoints as the same (viewpoint invariance )
- ability to perceive scenes accurately
- the ability to ignore irrelevant / superficial details
(machines cannot use old knowledge to perceive new stimuli)
Why is human perception different than self driving cars
- top-down processing and bottom up
- gestalt principles
- environmental regularities
Why are human perception abilities special?
- top down processes and bottom-up processes
- gastalt principles
- environmental regularities (physical, semantic)
What is Bottom-up processing
- bottom-up information from the environment to the brain
(sensation)
outside- inside
What is Top-Down processing
- Top-down information from higher cortical regions
- reasoning, expectation, prediction, knowledge and experience
- ex. recognizing a scene (air show vs air port) , hearing words in sentence, learning from experience
What is an example of top-down processing
- Hearing words in a sentence
- listening to people speak in an unfamiliar language (cannot tell when one word ends and the next starts)
- continues speech is sent from ear to brain (bottom -up) brain breaks the speech into individual words (top-down)
- learn from the experience hidden figure in picture, once you see it you will always notice it
What are Gestalts 5 principles of perceptual organization?
- built-in/ hard-wired principles (see part of an object and we can figure out what the object is without seeing the whole thing )
- infants are surprised if covered object is exposed to show an incomplete object - Good Continuation
- stimuli that appear to be continuous are perceived as belonging together (people tend to mentally form a physical line
- simplicity is preferred over complexity
- objects that are covered continue out of view - Good figure/ simplicity
- the simplest form is perceived
- related to principle of continuity (circles overlapping are perceived as complete - Similarity
- objects are grouped based on similarity - Proximity
- things that are near each other appear to be grouped together
Why are Gestalts principles useful?
- assumptions we make all the time (broken segments of legs from fence are perceived as the same persons leg)
- automatic processes (someone hiding behind something)
- hard to program this into self driving cars
What are the 2 kinds of Environmental Regularities
physical regularities and semantic regularities
What are physical regularities
physical regularities: certain characteristics occur in the environment frequently (green landscapes or nice weather)
- we incorporate this information in perceptual processing
- we perceive horizontal and verticals more easily than other orientations
- light from above assumption: we assume sun and most artificial light comes from above
- indentations turn into rounded mounds (ex. sand)
What are semantic regularities
- scene schemas (knowledge about what happens in a scene)
- Schemas affect perception
- we recognize objects related to the scene more accurately than unrelated
- meaning of a scene
Perception results from the interaction of?
- bottom-up processes (inputs from sensory systems)
- Top down processes (knowledge and experience )
- Gestalt principles (regularities in the environment )
Where are there more neurons that respond to horizontal and vertical orientations
- there are more neurons in the visual system which respond to vertical and horizontal lines than other orientations
What is Experience- Dependent plasticity
- neural responses are shaped by experiences
- FFA preferentially responds for faces
- can also activate in response to experience and training
how does movement facilitate perception
- we are able to see what we wouldn’t have otherwise
- ex. people of the same size in an optical illusion room, if you stand still you can see illusion, if you move you cant
What is an Ames room
- the left corner is twice as far as the right corner
- window sizes are changed to add to effect
- a person who can move about is not affected by the illusion
- movement facilitates perception
What are the two streams of visual processing
- the ventral (what) pathway for object recognition (primary visual cortex/ striate cortex/V1 to temporal lobe) -Dorsal (where) pathway locating and acting on objects
What are the two types of perception discrimination
- which lesions produce them
- object discrimination: lesion to temporal lobe makes picking shapes difficult
- landmark discrimination: lesioning parietal lobe
