3 - Perception Flashcards
define perception
experiences that result from stimulation of the senses
what are some basic properties of perceptions
- they’re a process - something like reasoning but somewhat automatic
- perception occurs together with action
- perception plays a central role inn cognition in general - essential for creating memories and knnowleedfge, solving problems, communicating, etc.
what is the main issue with computers trying to perceive?
dont have all the knowledge that people do, we have a bunch of data that helps solve this problem
what are the difficulties in designing a perceiving machine? (4)
- stimulus ambiguity
- hidden or blurred objects
- varying view points
- scenes contain higher level information
explain stimulus ambiguity in perception
inverse projection problem - start from the stimulus on the eye and try to figure out what is causing it
- retinal images in this way can be created by more than one object
explain viewpoint invariance
the capacity to recognize an object from any perspective - very hard for computers
what is bottom up processing
the sequence of events that takes information from the eye and transmits it to the brain for processing
what is top down processing
bringing knowledge to bear on deliverances of bottom up processing
explain the ‘multiple personalities of blob’
can place the same blob into several blurred images and it appears to fit with each - ‘perceived as different objects depending on their orientation and the context within which they are seen’
what does the multiple personalities of blob tell us about why humans are superior to computers perceptually
the influence of top down processing on perception is easy for people but requires explicit programming in computers, so its hard to get gong
what are translational probabilities
the likelihood a sound with follow another within a word in a given language - computed implicitly by humans during language learning
what do we call the process of learning speech segmentation through translational probabilities
statistical learning - infants as young as 8 mo are capable of this
explain saffran’s study on stat learning in infants
4 nonsense words, produced in random strings with no break
- TP within words was always 1.0, between was always .33
- tested with three syllable stimuli, some of which were full words (that they’d heard already), others were part words
- kids would listen to part word for longer bc of habituation
- factual
Explain Helmoltz’ theory of unconscious inference
- what ‘principle’ is this based on?
- realized that the image on a retina is ambiguous
- how does the perceptual system decide that the patter was created by one over another possibility?
- likelihood principle - we perceive the object that is most likely to have caused the stimuli
- this is the unconscious inference
- relies one knowledge of the environment
Explain the Gestalt theory of perception and its justifications w reference to Wundt
- reject Wundt’s structuralism
- can’t explain the phenomena of apparent movement; nothing in between the two lights that shows us movement
- the whole is not the sum of its parts; led to the principles of perceptual organization
what are the main principles of perceptual organization?
- Good continuation
- pregnanz
- similarity
what is the principle of good continuation
- points that are best connected by a smooth or straight line are seen as a line, and this line tends to be perceived as following the smoothest path
- objects that are overlapped by other objects are perceived to continue behind the other
what is the law of pragnanz
aka principle of good figure, every stimulus pattern is seen in such a way that the resulting structure is as simple as possible - think the Olympic Rings
what is the law of similarity
similar things appear to be grouped together
where do gestalt laws come from?
- wertheimer - innate laws built into the system
- contra helmhooltz who thought it was all learning
how do modern perceptual psychologists take experience into account in shaping gestalt like laws?
environmental regularities that shape perceptual laws
what are physical regularities in the environment
regularly occurring physical properties, such as the prevalence of horizontal/vertical lines relative to oblique ones - creates the oblique effect (obliques are harder to perceive)
explain the light from above assumption from physical regularities
- we perceive light as shading as though it comes from above, because light does come from above
what are semantic regularities
characteristics associated with the functions carried out in different types of scenes
what is a scene schema
our mental representation of what a given scene would typically contain
explain bayesian inference
- Prior probability - initial belief about the probability of an outcome
- likelihood - extent to which the available evidence is consistent with that outcome
- calculate the two to find the highest probable outcome
map bayesian inference onto the inverse projection problem
- take a rectangular object
- priors; book, paper, iPad, food tray
- likelihood; distance from the object and the angle ur seeing it from, the context (cafeteria, maybe), ect.
- outcome - automatic calculation of priors and likelihood
relate bayesian inference to Helmholtz
we perceive what is most likely to have created the stimulation new have received, but reformatted inn terms of probabilities
what do the three considered theories of perception have in common?
importance of top down processing - we use data about our environment gathered through our past experiences
do we have more neurons for horizontals and verticals than obliques?
yes
what explains the finding that we have more neurons for horizontals and verticals than obliques? (2)
- natural selection - we were more likely to survive given better perceptions of these than obliques, so more neurons were selected for this
- experience-dependent plasticity
how did we find experience dependent plasticity in the brain (greebles)
fMRI
- fusiform face area in the temporal lobe - neurons respond to faces
- Gauthier (1999) experience dependent plasticity might play a role in determining neurones responses to faces and objects called greebles
- higher activation to faces than grebes before training
very similar after training (naming greebles w recognition)
- FFA just responds to complex visual stimuli we have expertise with (cars or birds also do the same thinig
how does movement facilitate perception
gets us into different viewing perspectives
what were the 2 methods used to discover the perception and action streams in the brain
- brain ablation
2. neuropsychology
what is another term for brain ablation
lesioning
what is an object discrimination problem
show the participant an object (target), then present it with another object; reqarded for knocking over the target
- used in monkeys
what is a landmark discrimination problem
a landmark is beside one of two containers with food, monkey receives reward if they knock over the containier closest to the landmark
explain Ungerleider and Mishkin’s study on brain ablation in monkeys - what pathway
- removed part of the temporal lobe in monkeys after recording their responses in landmark and object discrimination tasks
- object discrimination became very difficult for them
- neural pathway (calle the WHAT pathway) responsible for object discrimination
what is the ‘what’ pathway (location and function)
location - pathway leading from striate cortex to the temporal lobe function - object recognition
explain Ungerleider and Mishkin’s study on brain ablation in monkeys - where pathway
removed the parietal lobes of some other monkeys in thhe study
- had trouble with the landmark discrimination problem
- responsible for object location - where pathway
what is the scientific name for the what and where pathways
- what = ventral pathway
- lower part of the brain (where the temp lobe is) is the ventral side - where = dorsal pathway
- vice versa for parietal lobe
Explain Milner and Goodale’s findings using the neuropsychological approach on what and where pathways
revealed two brain streams in a 34 year old woman who suffered damage to temp. lobe following CO poisoning
- incapable of rotating a card to match the orientation in a shifting slot
- but could do it if she was asked to ‘mail’ the card through the slot
- once she started moving the card she could rotate it fine, just couldn’t start the rotation
- outcomes:
1. pathway from visual cortex to temporal lobe = perception pathway
2. visual cortex to parietal lobe = action pathway
what do the perception and action pathways correspond to?
perception = what pathway action = where pathway
what are mirror neurons
neurons that respond both to the action and perception of that action
- they respond selectively to the action, not what the action’s object is
are there mirror neurons in people
suggested by research - seen in studies on epilepsy
what is the mirror neuron system
the distributed network of mirror neurons distributed across a humans brain
what is the purpose of mirror neurons?
- determining the goal or intention behind an action, maybe
evidence that mirror neurons are for interpreting intentions?
- Iacoboni et al 2005; measured brain activity while watching short film clips
- each had them pick up a cup in different conditions (x3)
- clip one - table with food, full cup// clip 2 - table with empty messy plates and an empty cup // clip 3 - just the hand and the cup
- the 2 films with intention behind them had greater mirror neuron responses (1, 2 then 3 in order)
how do mirror neurons signal intentions?
response of the neurons may be determined by the sequence of motor activity that would be expected to happen in a given context
- respond to the actual action plus the best guess as to what is coming next
what is the size-weight illusion and what does it tell us about prediction
- people are presented with two objects, same weight but different sizes
- the larger one seems lighter when lifted together
- explanation - we predict larger objects to be heavier so we expect it to be heavier and it feels lighter
