Define and describe perceptual organization and the existing theories on it

Perceptual organization: The process by which elements in the environment become grouped to create perception of objects

Theories of perceptual organization structuralism and gestalt grouping

Structuralism: perception is created by combining many tiny sensations, proposed by Wilhelm Wundt

Any sensation could be explained by the elementary sensations it’s based on

Illusory contours cannot be explained by elementary sensation

Gestalt psychology: the whole is greater than the sum of its parts, founded by Wertheimer, Koffka and Kohler

motivated by Wertheimer’s observations on apparent movement

If you flashed on object in one position, followed by darkness and then flashed in a different position this would be perceived as a movement despite the two images being separate

Drew two conclusions:

apparent movement Cannot be explained by elementary sensation as there was nothing in the dark space between the two images

The whole is different than the sum of the elementary parts.

Pragnaz is what? What perceptual organization theory is it an example of? What are the other components of the theory?

Pragnanz or the law of simplicity

Every pattern is seen in such a way that the resulting structure is as simple as possible

Gestalt principal of organizations consists of: the law of simplicity, similarity, good continuation, continuity and common fate

Similarity                                                     

similar things appear to be grouped together

Good continuation

Points are seen to be connected, even when covered or boundaries blurred. one whole object

Proximity

Appearance of organization due to proximity (clustered)

Common Fate

Objects seem to be “moving” in one common direction

More recent additions include

Grouping by common region (enclosed area)

Uniform connectedness (grouping by connectedness)

Appearance of grouping due to a physical connection

Grouping by action

Actions or occurrences that are synchronous across objects (i.e the flashing of lights) are seen as a group

Perceptual segregation is also known as what? What are its properties?

a.k.a figure-ground segregation Objects seen as figures against a background

Properties of figure-ground

The figure is more memorable

The figure is seen in front of the ground

Factors that influence figure-ground

Location

Convexity

Relative Size

Meaning of region

What type of source did Potter perform an experiment on  to show that people can gather information it rapidly? What follow up experiments was done and by who?

A scene

A scene is a real world environment that contains background elements and objects organized in meaningful ways with each other and the background

A scene is acted within

An object is acted upon

Potter showed that people can do this when a picture is only presented for ¼ of a second

Fei-Fei used masking to show that the overall gist is perceived first followed by the details

Olive & Torralba argued we use global features  (regularities) get the gist of a

What are regularities and what assuption is based on their usage?

Regularities are common associations that occur between details and types of environments

Based on assumption the visual system evolved to take advantage of properties of environment

 Some global features are:

Degree of naturalness (to environment)

Degree of openness

Degree of roughness

Degree of expansion (distance)

Color (based on environment i.e beach)

Palmer’s study was to show the effects of what?

Semantic regularities

Semantic regularities are characteristics associated with the functions of scenes,

Palmer would flash a context and a target image briefly

When the target fit the context the observers were correct 80% of the time and only 40% when there was no fit

perceptions are the result of unconscious assumptions about the environment is the main assumption of what theory?

Theory of unconscious inference

states we infer what we’re seeing based on the regularities we’ve experienced with the environment

Proposed by Helmholtz

What area of the brain responds to Gestalt grouping and perceptual (figure-ground) segregation?

Neurons in the visual cortex respond to Gestalt grouping principals

Neurons that respond to figure-ground are in area V1 &2

Why are Faces are given special status as stimuli?

They provide critical information such as

Identity

Mood

Intentions

Attraction

What Brain areas and neurons are specialized for fast processing?

Fusiform face area (FFA)

Amygdala (AG) is activated by emotion aspects of faces

Superior temporal sulcus (STS) responds to where the person is looking and to mouth movements

Frontal Cortex( FC) activated when evaluating facial attractiveness

The face elicits the fastest eye movements

Inverted faces are difficult to process

Faces are processed holistically

What is viewpoint invariance?

Viewpoint invariance: the ability to recognize an object in spite of change in viewpoint

What is and when does contexual modulation occur?

Contextual modulation: stimuli outside of a neuron’s receptive field can affect neural firing

Occurs when stimuli follow good continuation and perceived as part of a figure