chapter 5: perceiving objects and scenes Flashcards
what is the process of object recognition
detecting objects in an image and matching those objects with existing, stored representations of what those objects are
what is the inverse projection problem
task of determining the object responsible for a particular image on the retina
define viewpoint invariance
ability to recognize an object seen from different viewpoints
what are the three problems machines face when perceiving objects
- inverse projection problem (ex. shadow illusion)
- objects can be hidden or blurred
- objects are often viewed from different angles
define perceptual organization
process by which elements in a person’s visual field become perceptually grouped and segregated to create a perception
what are the two components involved in perceptual organization?
- grouping: visual scene are “put together” into coherent units or objects
- segregation: separating one area or object from another
define structuralism
sensations combine to create complex perceptions
what is apparent movement
although movement is perceived, nothing is actually moving
what are the two conclusions drawn from the phenomenon of apparent movement
- apparent movement can’t be explained by sensation alone
- the whole is different than the sum of its parts, because the perceptual system creates the perception of movement where there actually is none
what are illusory contours
illusion that there are physical edges present when there are none
what are gestalt principles of perceptual organization
- principle of good continuation
- principle of good figure
- principle of similarity
- principle of proximity
- principle of common fate
- principle of common region
- principle of uniform connectedness
what is reversible figure-ground
when the front and the background can be alternated
what are some properties of figure and ground
- figure is more “thinglike”
- figure is in front of ground
- ground is seen as unformed material, without a specific shape, and seems to extend behind the figure
- border ownership
name the figural cues that determine figure-ground
- lower areas in viewfield are more likely to be perceived as figure
- convexity
- symmetry
- smaller region
describe the gestalt ideas about the role of meaning and past experience in determining figure-ground segregation
- segregation of figure from the ground
- figure must stand out from the ground before it can be recognized and assigned a meaning
describe gibson and peterson’s experiment that showed that meaning can play a role in figure-ground segregation
- black figure that looked like a standing women on white background
- when figure flipped upside down, Ps were less likely to see that area as being the figure
conclusion: since meaningfulness influences the assignment of an area as figure, process of recognition must be occurring before or at the same time as figure segregation
define the recognition by components theory (RBC)
objects are comprised of individual geometric components called geons, and we recognize objects based on the arrangement of those geons
According to Biederman, what are examples of geons and how many are there
three-dimensional shapes like pyramids, cubes and cylinders
- 36 different geons that can be assembled to form different objects
why does the RBC theory account for viewpoint invariance
because whether you see an object from the side or from the front, it is still comprised of the same geons, so it should still be recognized as the same object
what are 3 aspects that the RBC theory could not explain
- doesn’t account for grouping or organization like the Gestalt principle
- some objects can’t be represented by assemblies of geons (clouds)
- doesn’t allow for distinguishing between objects within a given category
what is the definition of a scene
view of a real-world environment that contains
1. background elements
2. multiple objects that are organized in a meaningful way relative to each other and to the background
define what the gist of a scene is
being able to identify important properties of most scenes after viewing them for only a fraction of a second
what is the phenomenon called persistence of vision
the perception of a visual stimulus continues for about 250 ms after the stimulus is extinguished
how can persistence of vision be eliminated
by presenting a masking stimulus, a random pattern that covers the original stimulus
what enables observers to perceive the gist of a scene. name 5 of them
global image features: information that can be perceived rapidly and is associated with specific types of scenes
- degree of naturalness
- degree of openness
- degree of roughness
- degree of expansion
- color
what are regularities in the environment
characteristics of the environment that are frequent, such as:
- the color blue being associated with an open sky
- landscapes are often green and smooth
etc
what are the two types of regularities and explain them
physical: regularly occurring physical properties of the environment
semantic: characteristics associated with activities that are common in different types of scenes
define scene schema
knowledge of what a given scene typically contains
describe Palmer’s experiment of scene schema
- presents context scene
- presents target objects, one that fits with scene and others that don’t
- asked Ps to identify target objects.
- 80% time can identify object that fits with scene
- 40% time can identify object that doesn’t fit with scene
what is the “multiple personalities of a blob”
a blob can be perceived as different objects depending on its orientation and the context within which it is seen
define retinal ambiguity
particular pattern of stimulation on the retina can be caused by many different possible objects in the environment
what is the likelihood principle
we perceive the object that is most likely to have caused the pattern of stimuli we have received
what is Helmholtz’s theory of unconscious inference
our perceptions are the result of unconscious assumptions, or inferences, that we make about the environment
what is the Bayesian inference and what are the two factors that determine it
our estimate of the probability of an outcome is determined by
1. prior probability
2. likelihood: extend to which the available evidence is consistent with the outcome
define predictive coding
theory that describes how the brain uses our past experiences to predict what we will perceive
according to predictive coding, what happens when new incoming visual input reaches the receptors?
it is sent upward in the visual system, and is compared to the predictions flowing downward from higher levels.
- brain determines whether what we’re seeing matches with what we expect to be seeing
when is the lateral occipital complex (LOC) activated
when looking at objects, regardless of their size, orientation, position or other basic feature
true or false? the LOC can differentiate between types of objects
false
what is the role of the fusiform face area (FFA)
specialized to respond to faces
what is prosopagnosia
inability to recognize faces
when is the extrastriate body area (EBA) activated
activated by pictures of bodies and parts of bodies, but not by faces or other objects
what is the amygdala responsible for
emotional reactions and familiarity
what is the frontal lobe responsible for
evaluation of attractiveness
what is the superior temporal sulcus (STS) responsible for
gaze direction, mouth movements, and general face movements
explain what neural representation is
a representation that goes beyond modules.
combination of modular and distributed representation appears to underlie our perception of objects and faces
what is the function of the parahippocampal place area (PPA)
responds to places, not objects or faces
spatial layouts
what does the spatial layout hypothesis entail about the PPA/PHC
PPA/PHC responds to the surface geometry or geometric layout of a scene
define binocular rivalry
observer perceives either the left-eye image or the right-eye image, but not both at the same time
what is neural mind reading
use of neural response to determine what a person is perceiving or thinking
describe the neural mind-reading procedure
- measure brain’s response to different stimuli to determine relationship between stimulus and voxel pattern
- creates decoder
- decoder is tested by measuring brain activation as a person is looking at different stimuli
what is the expertise hypothesis
idea that our proficiency in perceiving faces, and the large face response in the FFA, can be explained by the fact that we have become “experts” in perceiving faces since we’ve been exposed to them for our entire lives
