Forming Perception

Kafka’s idea

the whole is greater than some of its parts

• Original meaning was supposed to indicate that the whole has an independent representation in the perceptual system, thus cannot be reduced

Gestalt Principles

laws that describe how we organize visual input

• Believe that they are innate, or that we acquired them very rapidly after birth

Figure ground segregation

the ability to distinguish an object from its background in a visual scene

Proximity

helps with grouping, the tendency to group elements that are close together in space

Closure

the tendency to fill in gaps in a contour to perceive a whole object

Similarity

tendency to group together elements that are physically similar

Continuity

the ability to perceive a simple, continuous form rather than a combination of awkward forms

Common Fate

the tendency to group together elements that change in the same way

Bottom up processing

object recognition is guided by the features that are present in the stimulus

Top down processing

object recognition is guided by your own beliefs or expectations

• we re influenced by context

Priming

the processing of a word is more efficient if the participant is primed beforehand to expect a certain category

• a participant can read aloud a word that is flashed on the screen

• If you tell the participant the next word, is a type of animal and thus establish an expectation, you'll often find a priming effect in that subsequently presented words like dog or duck will be recognised and read much faster than non animal words

Bidirectional observation

processing occurs in both directions at once 

• Features of the object in combination with our expectations guide object recognition

Beaderman Theory

suggests that we have 36 different geons or simple geometrical forms stored in our memory (ex. Cones, spheres, etc.)

• Using just these 36 genomes it is possible to recognize over 150 million different objects 

• Ex. an ice cream cone is just a combination of two geons, a cone and a sphere

Negative of the Beaderman Theory

for more complex items like faces or crumpled paper, the are not apart of the 36 geons but we can still recognize them 

• The same goes for brain injury, with this knowledge, if the brain is damaged a person would not be able to identity any items, but that isn't the case

Templates

suggests that we store many different templates in memory, and when we come across an object, we compare that object to all the templates in memory

• If a match is found, then it is a familiar object and the person could name it by activating connections to other language areas across the brain 

• If no match is found than its a familiar object, and a new template is stored in memory

Examplar Theory

allows for a little bit of leeway and an exact match isn't required for categorization

Prototype Theory

we store the most typical or ideal examples of an object 

• You don't need an exact match between the observed object and what is stored in memory 

• Explains how we can easily recognise common objects that we've never seen before (ex. Strangers dog, novel coffee mug, etc)

Perceptual constancy

our ability to perceive an object as unchanging even through the visual image produced by the object is constantly changing

Shape constancy

an object is perceived to have a constant shape despite the shape of its retinal image changing with shifts in point of view or change in object position

Locational constancy

an object is perceived to be stationary despite changing location on our retina due to body movements

Size constancy

an object is perceived to be the same size despite the size of its retinal image varying with distance

Brightness constancy

an object is perceived to be the same brightness despite reflecting more or less light onto our retina

Colour constancy

an object is perceived to have a constant colour despite different illumination conditions

Depth cues

to determine the distance and shape of a stimuli

Muller Lyer Illusion

an example of misapplying size constancy and inaccurately interpreting depth

Ganglion Cells

from the retina, the axons of these cells exit via the optic nerve, travel to the lateral geniculate nucleus and end up in the primary visual cortex in the occipital lobe

Feature detectors

used to examine how individual neurons respond to specific stimuli

Simple cell

respond maximally to a bar of certain orientation in a particular region of the retina 

• The receptive field is organized in an opponent fashion making it sensitive to the location of the bar within the receptive field

• A bar of light in the preferred location only passes through the on region leading to a strong, excitatory response 

• A bar that is not in the preferred location or orientation will pass through the off regions of the receptive field leading to a strong inhibitory response

Complex cell

responds maximally to a bar of certain orientation regardless of location

• Some respond maximally to a specific direction of movement

• Does not care where the receptive field is located and will even continue to fire when the bar is moving within the receptive field

• Some cells do care about the direction of this movement 

  • Ex. the cell in this figure that fires most when it is oriented at a certain angle and moving in a particular direction

Hypercomplex cell

respond maximally to a bar of a particular orientation and direction of movement, ending at specific points within the receptive field

• Ex. in this figure, the cell fires most to a horizontal bar of light, moving upwards that appears anywhere in the on region of the receptive field but gives only a weak response if the bar touches the off region 

  • They have an inhibitory region at the end of the receptive field making them sensitive to the length of the bar

Feature detectors

detect all the components in your view that combine these parts together

Visual scene

preserved in the visual cortex

• Neighbouring objects in your visual fields are processed by neighbouring areas of your brain 

• Mapping to the brain is not exact as the largest amount of cortex is devoted to processing information from the central part of the visual field which projects onto the fovea

Benefit of 3 cell types

allows the brain to optimally balance the function of each while consuming the least possible amount of energy

Extrastriate cortex (visual association cortex)

surrounds the primary visual cortex, has multiple subregions, which each receive a different type of information from the primary visual cortex about the visual scene 

• Information begins to be segregated into two streams according to the information that is processed

Dorsal Stream

processes where objects are located in the visual scene and how they are moving within the visual scene 

• Takes information from the primary visual cortex to the parietal cortex which processes spatial information

Ventral Stream

processes information about what the object is including form and colour

• Takes information from the primary visual cortex and sends it to the temporal cortex where all the bits of feature information come together 

Temporal Cortex

arranged in vertical columns that are oriented perpendicularly to the surface of the cortex

• Neurons in the temporal cortex respond to specific stimuli that are more complex than the stimuli to which neurons in the primary visual cortex responds to

Object

represented by the unique activity patterns across many cells in several brain areas

Poor visual acuity

infants tend to focus on limited segments of an object

Interest based on Complexity and Perception - Newborn

prefer to look at a larger checkerboard pattern, since they have poor visual acuity, and will perceive it one grey square instead of tiny different coloured squares

Interest based on Complexity and Perception - 2 Month Old

prefer to look at a more complex checkerboard patter since they have improved visual acuity

Overlapping objects

must be able to understand cues and patterns in order to distinguish what parts of the object belong together and what parts are separate

Perceptual constancy

recognizing that form is being the same under different viewing conditions 

• Infants start to get a handle on brightness, colour and shape constancy by as young as four months of age

Babies getting their cataracts removed

infants show an increase in visual impairment the later they had their cataracts removed  

• When normal visual input in disrupted by the presence of cataract early development, the impact may not be immediately obvious but visual deficits will be encountered later in life 

Sleeper effect

deficits that are not often revealed or they sleep until the individual is further developed

• We go through a critical period in development where they need a certain amount and type of visual input for visual development to proceed normally

Object agnosia

the inability to perceive objects

• Unable to identify objects by sight even though they can see the objects perfectly, have normal visual acuity and are able to recognize and name the objects by touch

Prosopagnosia

the inability to recognize faces 

• Pattern disorder which may result from damage to the right fusiform gyrus and is not related to memory dysfunction, memory loss or impaired vision