Chapter 3 perception distinction between sensation

Chapter 3: Perception

Distinction between sensation (stimulus detection) and perception (the
interpretation of sensory information)

Other important concepts: subliminal perception (perceiving a stimulus
without awareness), change blindness (failure to consciously detect a
change in a scene), blindsight (patients with brain damage cannot
consciously experience objects in their blind area but can still make
judgments about them), backwards masking (second stimulus masks the
first, if presented fast enough)

According to Gibson, perception is intricately tied to our environment:
Ecological Optics
o
Ambient optical array contains all visual information from any
vantage; this info can change as we move around
o
We use gradient of texture density, topological breakage , and
scatter reflection as clues to our visual surroundings
o
As the observer moves, the entire AOA undergoes
changes/transformations

optic flow field (parallax)

Patten & Object recognition (ability to recognize an event is an instance of
a category of event); many theories of how we do this:

1. Template Matching/Prototype Theory
2. Feature Detection ( Selfridge’s Pandemonium Model )
3. Recognition by Components ( Biederman’s geons )

Context can also influence our perception (Ex. Moon illusion )- we use
contextual cues from the environment to determine size of objects
o
Letters in context (word superiority & jumbled word effects)
o
Colours in context (“What colour is that dress?”
o
Cross-modal context (McGurk Effect, out vision & hearing do not
agree, we try to accommodate all incoming info)

Feature Integration Theory (FIT) proposes that we recognize things by first
extracting features pre-attentively

The Gestalt Approach to perception: proposes that an examination of small
components of a perceptual image does not add up to the whole
o
Similar elements that are close to each other tend to be grouped
o
The visual system tends to provide closure to figures that are almost
enclosed
o
We’re biased to perceive good continuation in figures
o
Tendency toward visual organization applies also to movement- items
that move together in a similar way tend to be grouped together

Top down vs. bottom-up processing (also encountered during guest
lecture):
o
Reading: good ex. of use of context in (top-down) processing

When reading a paragraph, you are not paying much attention to individual
marks that make up each of the letters (barely even perceive these details)

Words are so familiar that we recognize them by their overall shapes instead
of having to read individual letters

Eye movements skip over short, familiar words
