Task 5 mechanisms of middle and high level perception Flashcards
Structuralism
o Sensation: elementary processes that occur due to stimulation of the senses (seeing a flash of light)
o Perceptions: more complex conscious experiences such as our awareness of objects (accounts for the vast majority of our sensory experience)
Apparent movement
o 1. One image flashes on and off 2. There is a period of darkness, lasting a fraction of a second 3. The second image flashes on and off
o Physically there are only two pictures but our perceptual system adds something during period of darkness
Gestalt organizing principles
Parts of the gestalt theory, they determine how elements in a scene become grouped together. The starting point are things that naturally occur (more like heuristics than laws)
Good continuation
points that when connected result in straight or smoothly curving lines are seen as belonging together, and the lines tend to be seen in such a way as to follow the smoothest path, Objects that are partially covered by other objects are seen as continuing behind the object
Pragnanz
Every stimulus pattern is seen in such a way that the resulting structure is a simple as possible
Similarity
Similar things appear to belong together, can occur because of similarity of shape, size or orientation
Proximity
Things that are near each other appear to be grouped together
Common fate
things that are moving in the same direction appear to belong together, even if the objects in group are dissimilar
Common region
Elements that are within the same region of space appear to belong together
Uniform connectedness
a connected region of the same visual properties, such as lightness, colour, texture, or motion is perceived as a single unit
Closed contour
closed contours are more preferred than open ones
Structural encoding
is based on the relationship between voxel activation and structural characteristics of a scene, such as lines, contrast, shapes. First it was calibrated by observing activity when certain stimulus was presented and then it has been reversed to make predictions other way around
Sematic encoding
is based on the relationship between voxel activity and the meaning or category of a scene. Voxel activation is measured with number of stimuli that origin from one category. After the calibration the data was used to predict the other way around
Subtraction
One measurement with stimulus and one with out to find activation in the brain caused by the stimulus
Bayesian approach
Estimate of probability of an outcome determined by 2 factors
Prior probability – initial estimate of the probability of an outcome
Likelihood of the outcome –the extent to which the available evidence is consistent with the outcome
Binocular rivalry
When both eyes see a totally different scene the brain perceives only one scene
Recognition by components Model
The geons are based on the gestalt laws
Structural description theory
objects are specified in terms of its parts and the relationship between the parts
E.g. A = three lines – two flanking lines meet and a third spans the angle created by those two lines
Geons
geometric icons as a collection of non-accidental features
Viewpoint invariant – visual system should be able to recognise them equally accurately & quickly no matter what the orientation (as long as it’s not an accidental view)
Minor shape variations won’t alter structural descriptions
Combining geons can create a wide variety of object representations
How do children learn to read and write?
- Have to unlearn invariant viewpoint to learn reading to distinguish between p and Q
- Literate people have a better pathway between visual and language areas
What happens in the brain once we learn how to read?
- Letters are perceived by the visual word form area
- Visual wordform area: is massively affected
- Lateral occipital areas: increased their activation not just to words but also to all kinds of stimuli (faces, houses, checkerboards), learning to read has refined the capacity to recognize any picture
- V1: gets enhanced
Inverse projection problem
The task of determining the object responsible for a particular image on the retina
Because it starts with the retinal image and extending rays out from the eye
View point invariance
The ability to recognize an object seen from different viewpoints
Perceptual organization
the process by which elements in the environment become perceptually grouped to create our perception of objects
o Grouping: the process by which objects visual events are put together into units or objects
o Segregation: the process of separating one area or object from another (borders)
Neuronal recycling hypothesis
o We are able to learn and read because of our preexisting circuits, there is one that links the left ventral visual pathway to the left-hemispheric language areas. This area is already capable of recognizing many letter-like shapes
Naïve Template Theory
Recognise object by matching every pixel/low-level feature of input to a representation in memory
Array of spot detectors serves as a template
Problem: too many templates required to not run out of brain as every “A” looks different
Differentiates between objects with the same geon (improvement to Biederman)
