Topic 3 - Perception Flashcards
There are a myriad of problems associated with perception, mainly due to the
sensations that we receive being incomplete or ambiguous.
Is perception active or passive?
Active
What are the 2 problems with perception?
1- inverse projection problem
2- size
inverse projection problem identifies that for any
2D retinal image there are a potentially infinite number of 3D shapes that could have produced that activity
Starting point for visual perception is the
registry for sensory info at the back of the retina.
Visual perception is the interpretation of
retinal info
Size effecting perception
2 hypothesis
1) tiny object in hand
2) object is far from distant
Example of size being an issue for perception?
Moon illusion
Moon illusion
Moon looks larger when there is no horizonal objects. When horizon is clear moon looks a lot larger.
Transitional probabilities
We have learnt that certain pairs of sound are more likely to belong to the same word (par-ty) while others more likely belong to different words (ty-go).
Which sounds predict others sounds? And what are there probabilities?
Bi —-> Da —-> Ku = 1.0
Pa —-> Do —-> Ti = 1.0
Go —-> La —-> Bu = 1.0
Ku —> Pa, Go, Bi = 0.33
8 month old infant are more interested in
Parts of words rather then whole words. More interested in the starts and ends of words.
Perception is entirely
Continuous
The more predictable the words are, then infants are more
Interested in them
What are the general principles that apply to all sensory systems?
1) transduction
2) organization
3) symbolism
4) selectivity
5) hierarchies
6) tailoring
7) thresholds
8) decision rules
Sensation is what
Perception is what
- Sensation is bottom-up processing
- Perception is top-down processing
Sensation is relieved from the outside world via… hows it processed?
Sensory systems and process through bottom-up processing
What is perception and what does it require?
It’s the best prediction of what’s happening.
It requires previous information and experience for top-down processing.
What does decision rules emphasize
The difference between sensation and perception
Transduction
The outside world (distal stimuli) sends us signals which our sensory transducers (eyes, ear, nose, tongue, skin) encode and covert into bodily sensations (proximal stimuli).
The process of transduction may take place over
vast distances (far senses) or has to take place at the point of contact (near senses).
Symbolism
Characteristics of the object or sensation are recoded neurally and are represented symbolically. Characteristic like smell or colors.
For symbolism, certain brain states give rise to
Specific perceptual experiences
Organization
Neurons at each stage of processing are arranged in a highly organised way, according to the nature of the sense.
- auditory organization
- visual organization
Auditory organization
Frequency selective in the basilar membrane
- low frequencies at apex (20Hz)
- high frequencies at the base (20KHz)
Visual organization
Spatial location selectivity in the striate cortex
- fine grained analysis at focal point,
- cruder analysis around periphery
Selectivity
There is selectivity both at a sensory level in terms of transduction specialisation, and also at a neural level where individual cells prefer certain types of stimulation above others.
TOUCH -
AUDITION -
VISION -
TOUCH - Pacinian corpuscle (squashing sensation)
AUDITION - Inner hair cell
VISION - Orientation selectivity
Which eye parts are involved in selectivity and what do they each do?
- Sclera = tough white bit for protection
- Cornea = transparent area that allows light in
- Iris = controls size of pupil and gives eye colour
- Pupil = Opening at the centre of the iris
- Lens = Transparent structure that bends to focus light
- Retina = Light-sensitive cells at the back of the eye
Selectivity in colour perception
- 3 kinds of cones, B, G, R.
- mixing these cones give different colours like purple or orange.
- fewer B cones then R and .