L1 theories of perception Flashcards
gestalt
The whole is more than a sum of its parts
9 principles:
–pragnanz –continuation –similarity –proximity –common fate –connectedness –closure –invariance
Gibson
Ecological theory of perception:
observed the world on train rides and and noticed optic flow.
Biological innate ability to perceive. (bottom up,, not based much on the previous experience of the perceiver).
The information we receive fro the world is suffciently detailed to make interpretations fro, we don’t need top down processing.
Invariants, affordances, motion
Invariants
aspects of the environment that don’t change with observer movement.
Part of gibsons theory. 1. Horizon ratio (proportion of the figure above the horizon remains constant as distance changes, but not as size changes).
2. Texture - changes in texture tell su about distance, curvature and orientation of the object.
horizon ratio relation
The ratio above and below the horizon is constant for objects of the same size standing on the same ground. (gibson)
gestalt type of model
bu and td
gibson model type
bu
constructivist model type
td
marrs model type
bu and computational
marrs stages
- greyscale 2.primal sketch 3. 2 1/2 D 4. 3D
greyscale stage
photoreceptor activation monitored at each point on the retina to determine light intensity
primal sketch: raw
to identify object edges - gausian blurring - then intensity differecnes at level 2 used to form primitives (bars/edge segments/blobs/termination)
full primal sketch
to determine object outline - primitives organised into place tokens and then higher order place tokens using clustering an linear aggregation (continuity)
2.5 D sketch
primitives are vectors - identifies the depth and form of objet and how all the surfaces relate to one another
3D sketch
Allows object to be recognised from all angles - find the central axis and forma . general hierarchy (arms hands fingers)
marrs criticism
retinal image isn’t always enough
