Form Perception 1 and 2

Gestalt Philosophy

The whole is other than the sum of its parts and has an independent representation

Gestalt Principles

Laws that describe how we organize visual input and include:

Figure ground

Proximity

Closure

Similarity

Continuity

Common Fate

Figure-ground

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

Proximity

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

The 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 guided by features present in the stimulus

Top-Down Processing

Object recognition guided by beliefs, expectations, and prior knowledge

Bidirectional Processing

Interaction of bottom-up and top-down processing where top-down processing cannot work alone because you need input from the stimulus itself before your expectations about that stimulus can influence your recognition of it

Geon Theory

Objects are recognized using basic geometric shapes called geons and we have 36 different “geons”

Geon Theory Limitation

Cannot fully explain recognition of complex objects or brain injury effects where damage to specific areas can affect recognition for different classes of objects

Template Theory

Objects are recognized by matching them to stored templates in memory

Template Theory Limitation

Requires exact matches and large storage capacity

Prototype Theory

Objects are recognized by comparing them to an ideal or average representation

What does prototype theory not explain?

how we can categorize unique specific objects

Perceptual Constancy

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

Shape Constancy

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

Location 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

Muller-Lyer Illusion

Lines appear different lengths due to arrow-like ends, cultures and environments without right angles (round huts) are less susceptible

Ames Room

Trapezoidal room where the person that is closer appears to be much larger than the person that is further

Manipulates distance to trick size constancy

Ponzo Illusion

Depth cues make identical lines appear different in size

Hodgkin and Huxley discovery

discovered neurons in the optic nerve of a frog respond only to movign black dots “bug detectors”

hubel and weisley discovery

• Accidentally discovered feature detector cells where they used cats and showed them a light moving and expanding at various different points

• As a result, the cell would fire more frequently when the light was in the preferred position

Feature Detector Cells

Neurons in the visual cortex that respond to specific visual features

Simple Cell Maximal Response

• Preferred orientation and location in the receptive field

• Strong excitatory response

Simple Cell Below Baseline Response

• When stimulus is not in preferred orientation or outside of the “ON” region of the receptive field

Complex Cell Maximal Response

Responds maximally to a certain orientation and direction of movement regardless of location

Complex Cell Below Baseline Response

a bar of light that is not preferred orientation or direction of movement

Hypercomplex Cell Maximal Response

Respond maximally to a bar of a particular orientation and direction of movement ending at specific points within the receptive field(lengths)

Hypercomplex Cell Basline Response

No stimulus

Hypercomplex Cell Below Baseline Response

when the stimulus is not in the preferred orientation or direction of movemen

Topographic Organization Function

Spatial arrangement that allows parallel processing for faster perception

Extrastriate cortex

region which has multiple subregions that each receive a different type of information from the primary visual cortex (colour, movement, orientation, etc.)

Dorsal Stream

• “Where” stream

• Location and movement

• Sends the information to the parietal cortex which processes spatial information

Ventral Stream

• “What” stream

• Form and colour

• Sends information to the temporal cortex

Temporal Cortex

• Respond to more complex stimuli than what primary visual cortex responds to

• Can include hands, faces, apples, chairs

Temporal Cortex Arrangement

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

• Respond to different complex stimuli

Temporal cortex columns

• in each column there are six layers of neurons with each layer responding to complex stimuli that came from the same category (red apples vs green apples)

Infant Recognition

• Infants have the machinery to perceive patterns and objects but they cannot necessarily recognize

• Infants prefer more complex patterns (than simple patterns) that they can perceive (could be due to visual acuity, bigger vs smaller checkers)

Whole Form Perception

• Infants only begin focusing on whole objects after 2 months of age

• Whole form perception is an emerging process over the first two months of life

Partial Form Perception

• Infant can perceive partial forms as whole forms by 3 months of age

• Suggests that they are guided by the Gestalt principle of closure

Partial Form Perception Test

Tested through habituation of a whole square vs four circle square vs four circle circle

Perception of Overlapping Objects at 3 months

can identify separate objects if objects move independently of one another

Perception of Overlapping Objects at 5 months

Begin to use cues like colour or texture to distinguish objects to distinguish between overlapping objects

Form Recognition at 4 months

Recognition of brightness, colour, and shape constancy begins

Size Constancy (Infants)

Begins developing around 4–5 months, infants have some sense of size constancy and understand that an object that is farther away should produce a smaller retinal image

Face Recognition 2 months

• Infants at 2 months old like looking at attractive faces over unattractive faces and look at their mother over stranger

• Focus their gaze on the outer contours of the face until 2 months old

Face Recognition 5 months

Infants at 5 months can detect different emotional expressions

Cataract Effect on visual development in infants

• if they have it removed and replaced with artifical lens, not many visual impairments

• if they have it removed later, there is an increase in visual impairment which may not be immediately obvious but visual deficits will be encountered later in life

Sleeper Effect

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

Visual Agnosia

Damage to the extrastriate cortex disrupts object recognition

Object Agnosia

Inability to perceive and recognize objects

Prosopagnosia

Inability to recognize faces

Pareidolia

Interpreting vague stimuli as something familiar

configural face processing

emphasis on face as a whoel

featural face processing

emphasis on features individually

composite face effect

perceptual phenomenon where aligning the top half of one face with the bottom half of another makes it difficult to identify the individual halves, as they are automatically blended into a new, single "whole" face

Thatcher Illusion

Where distorted facial features (upside down eyes and mouth) are difficult to detect when the face is upside down) but upright, it looks grotesque

Flashed Face Distortion Effect

Visual illusion where rapidly alternating, normal faces viewed in the periphery appear grotesque, distorted, or cartoonish.

Hollow Face Illusion

Hollow face which is actually concave appears to be convex due to top down processing