Perceiving Objects and Scenes

structuralism

perception is equal to the individual sensory inputs; the experience is nothing more than the individual parts

Gestalt Approach

the whole (perception) is more then the sum of parts; Wertheimer invented

apparent movement

we perceive movement even though there is no movement, its just a static image moving around

Gibson experiment

modern research found that meaning and past experiences can affect the separation process

gist processing

ow long it takes to understand the meaning of a scene

persistence of vision

visual stimuli are still available to the sensory system immediately after an image disappears; why gist processing is hard to test

Fei-Fei et al in gist processing

if you put a visual mask over a picture, people could get the gist in 1/10 of a ms and then details after 500 ms

why is object perception difficult?

the stimulus on the receptors is ambiguous (2D image)

inverse projection problem

we must project the image on the retina back out into the environment; we see many things that look similar

viewpoint invarience

recognizing objects from numerous different perspectives

perceptual grouping

process in which elements of an object or scene are bound, linked, or connected to one another

perceptual segregation

process of separating elements of an object or scene

illusory contours

perceiving edges or lines even though they don’t physically exist

5 Gestalt principles of organization

1. 1. Prognanz (good figure/simplicity): put things together using simplest strategy possible

2. 2. similarity: group similar objects, colors, and shapes together

3. 3. good continuation: connect lines so they follow smoothest path possible

4. 4. proximity (nearness): objects near each other are grouped together

5. 5. common fate: objects moving in same direction are grouped together

reversible figure ground

what we perceive as the object/figure and the background in an image can be switched

qualities of a figure

-looks like an object
-figure appears to be on top of the background
-figure seems to own the border but the border can switch

qualities of ground

does not appear to have shape

What did Vecera and colleagues find out about figure ground?

most of what we say are figures, the figures are said to be on the bottom most of the time but what if there is a left and right side?

heuristic processing

general rules or guideline that guide a process; emphasis on speed
EX: tell me the number of people in this stadium right now

algorithmic processing

rigid rules or steps that much be specifically executed in a process; emphasis on accuracy
EX: you get an A in the class if you can tell me the exact number of people in this stadium right now

global image features

aspects in scenes that help us quickly identify what we are looking at

4 global image features

1. 1. degree of openness: is it opening or closing in

2. 2. degree of expansion

3. 3. degree of naturalness: natural scenes have oblique lines compared to human made scenes

4. 4. degree of roughness: how many small elements are present

2 principles guiding perception

physical regularities: physical properties in the environment

• -oblique effect: human made scenes heavily emphasize horizontal and vertical lines (oblique lines=nature)

• -light from above: we are accustomed to the fact that light often comes from above, causing unconsiousness interpretation of shadows

semantic regularities: properties in the environment that we have learned are associated

• -scene schema: meaning of a scene

What did Olivia and Toralba discover in "multiple personalities of a blob"?

people perceive blobs as different things