Lecture 4: Sensing and Perceiving Flashcards
What is transduction?
1) Outside world sends us signals
2) Sensory transducers (eyes, ears, nose, tongue, skin) encode and convert into bodily sensations (proximal stimuli).
3) Process may take place over vast distances (far senses).
4) Process may take place at the point of contact (near senses).
What is symbolism?
1) Transduction recodes outside world into sensation.
2) We recode environment.
3) In case of human perception, we assume specific brain states give rise to specific perceptual experiences.
What is organisation?
1) Neurones at each stage of processing arranged in highly organised way according to nature of sense.
What is selectivity?
1) Both at sensory and neural level.
2) Sensory: in terms of transduction.
3) Neural: where individual cells prefer certain types of stimulation above others.
What are hierarchies?
1) Perceptual processing involves series of stages.
2) One representation is transformed into another.
3) Each sense contains multiple, hierarchically organised processing stages/
4) basic - medial - complex.
What is tailoring?
1) Our sensory transducers are specifically tailored for its environment and for carrying out survival behaviour.
2) Allow us to view the world in a different way.
3) We have two eyes, nose near mouth, etc.
What is an absolute threshold?
minimum amount of stimulation required to evoke perceptual sensation.
What is a ‘just noticeable difference’ (JND)?
minimum amount of differential stimulation required to note change between sensations.
What is sensory adaptation?
same level of intensity does not generate the same continuous level of response.
-constraint of perception.
What are decision rules?
1) frequently perceptual information is incomplete or ambiguous.
2) therefore, stimulus processing from the bottom-up cannot account fully for perception.
3) top-down decisions also need to be made.
4) receiving information from environment requires decision making.
How much of the electromagnetic spectrum can we experience?
- We are only privy to an incredibly small portion.
- Despite limited access, we are able to perceive in environments which differ 100 million times in terms of light availability.
Can we see radio waves or x-rays?
No, but they are all present as light visible to humans.
What is wavelength?
Distance travelled after one complete oscillation of a certain wave.
How do we ‘see’?
1) Light reflected from objects travelling in straight line ast 30,000 km per second.
2) enter through the pupil.
3) bend via lens.
4) reaches convergence on retina.
What is the sclera?
- tough white bit
- protection
What is the cornea?
- transparent area
- allows light in
What is the iris?
- controls pupil size
- gives eye colour
What is the pupil?
-opening at centre of iris.
What is the lens?
- transparent structure
- focuses light
What is the retina?
- light sensitive cells
- back of the eye
What are the properties of the centre of the eye?
Photoreceptor: Mainly cones Receptive field size: Small Resolution: Good Sensitivity: Poor Optimal condition: Photopic (light).
What are the properties of the periphery of the eye?
Photoreceptor: Mainly rods Receptive field size: Large Resolution: Poor Sensitivity: Good Optimal condition: Scotopic (dim).
How many cones per eye?
6 million.
How many rods per eye?
120 million.
What are most people in terms of viewing colour?
Trichromatic: red, green and blue.
-relative activity of three pigments explain secondary colours.
What are dichromates?
Only have two of three cones (G vs R).
Do we have the same amount of all the colour cones?
- We have fewer B cones than G or R cones.
- Cone pigments become less the further we move from the fovea.
What are tetrachromatics?
- some species have four cone pigments.
e. g. sensitive to UV light