study notes on sensation, perception & attention. date not accurate
SENSATION PERCEPTION ATTENTION
SENSATION: how sense organs detect and respond to energy from external stimuli,
as well as how these responses are transmitted to the brain.
PERCEPTION: these signals are further processed. Understanding perception
requires an understanding of sensory processes.
Perceptual Constancy: we know snow is white and a tire is black, even snow at
night and a tire in really bright light (even if they send identical luminance cues) a
door is a rectangle even though we rarely, if ever, see 4 right angles projected onto our
retina. There is size constancy, shape constancy, colour constancy, lightness constancy.
We need to understand the relationship between at least two factors (how far the
object is from us, how much light is reflecting off the surface, etc) in order to
understand what we are seeing.
**THE BRAIN COMPUTES A RATIO BASED ON RELATIVE MAGNITUDE
RATHER THAN ABSOLUTE MAGNITUDE OF EACH SENSATION**
Classic Perceptual Theory:
Perceptual experience& (maybe) innate knowledge info about ratio relationships
that determine CONSTANCIES.
Sensations impulsesbraininterprets according to previous learning/evolution.
“visual perception is ALWAYS based on unconscious inferences”
Stimuli provide information in themselves & we are hardwired to interpret visual
cues in ways that benefit survival.
We don’t need addit.l memories, calculations or inferences to understand sensory
***Helmholtz is right***
ATTENTION: How the brain selects which sensory stimuli to discard, and which to
pass along to higher levels of processing.
Binding: since the brain processes features automatically & separately,
attention helps us to bind features together in order to determine that certain
features belong to a certain object.
Selective Attention: filtering attention pay attention to only 1 thing.
Early Selection: we choose which stimuli we will attend to even before we
process their basic features- allowing us to ignore things without processing
oFilter Theory: we have a limited capacity for sensory info & our brains
only allow the most important info to pass through.
Late Selection: attention stage (whether or not you pay attention to a
stimulus) occurs when a perception enters conscious awareness. Therefore,
even if you are not aware of a stimulus because you didn’t “pay attention,” you
have processed it and may have extracted some meaning from it.
SENSATION PERCEPTION: HIERARCHICAL PROCESSING
•SENSORY DETECTION: sensory receptors make contact with reality
•TRANSDUCTION: physical stimulus’ energy is converted to electrical energy
•THALAMUS: energy thalamus sends info somewhere in cerebral cortex
•PRIMARY PROCESSING: info primary sensory cortex initial “rough
draft” processing of info
•FURTHER PROCESSING: more complex processing in various areas of the
brain linked to cognitive & perceptual tasks (ex: semantics, memory…)
“what” & “where” pathways
- What: info ventral pathway inferior temporal lobes (memory & hearing)
- Where: info dorsal pathway superior t.l. parietal lobes (spatial info)
•DECISION& ACTION: information is transmitted to the motor cortex
***(Real Sexy Transgenders Teach Paul Four Degrading Acts)***
More specifically, the brain first processes on a coarser level (noticing basic features
such as shape), then refines its processing (recognizing 3D space) further and further
(recognizing symbols recognizing faces recognizing facial expressions)
PROBLEMS WITH NEUROLOGICAL PERCEPTION:
- SPLIT BRAIN: SEVERED CORPUS COLLOSUM: 2 hemispheres are not
A “split-brain” patient can have emotional reactions to stimuli without being able to
verbalize what he/she saw.
- BLINDSIGHT: say the left side of the visual cortex is damaged. Though his eyes
function normally, the patient cannot see a dot moving in his “blind spot”.
However, he can often accurately guess the color/movement of the dot!!
Ex 2: 53 year-old man is functionally “blind” but can accurately “guess” f. expression
- OBJECT AGNOSIA: damage to “what” pathway (ventral)
The patient can draw an apple when asked, but can’t identify an apple when shown
- AKINETOPSIA: An inability to perceive motion. (neurons that fire when movement
occurs don’t work correctly)
- CORTICAL SPECIALIZATION: well, Hubel & Wiesel forced this upon cats
They were only allowed to see stripes. Later, they could only IDENTIFY or “SEE”
things which closely resembled the stripes they were raised on
Top-Down Processing: hierarchical recognition from basiccomplex
Bottom-Up Processing: where information at higher, more complex, levels of
processing can influence our more basic/“earlier” levels of perception
for example, context affects perception: what we EXPECT defines (to a certain
level) what we PERCEIVE