Week 5 - Sensation And Perception Flashcards
What is sensation?
The process by which the sense organs (eg. Eyes, ears, skin etc) gather information about the environment
No 1:1 correspondence between physical and physiological reality
What is perception?
The process by which sensory information is selected, organised and interpreted.
But there isn’t a 1:1 correspondence between physical and psychological reality (sensation and perception).
Describe transduction
(Environmental) energy -> neural impulses
Coded in terms of
- intensity
- quality
Sense receptors “transduce” stimuli into signals
Sensory adaptation
Define psychophysics
Study of how we perceive sensory stimuli based on their physical characteristics
Absolute threshold in psychophysics
Is the lowest level of a stimulus (on its own) that we can detect 50% of the time
- a candle 30km away
- 50 odorant molecules
Fechner’s model demonstrates the absolute threshold
Just noticeable difference in psychophysics
Just noticeable difference is the:
-smallest change in intensity of a stimulus that we can detect
Depends on:
- level of intensity of new stimulus
- level of stimulation already present
Eg. Distinguish a quiet and a loud voice
What is attention?
Mental phenomenon of concentration and it’s shifts in focus
- influences by external and internal events
- limited capacity
What is selective attention?
Allows us to select some inputs for further processing and ignore others.
- reticular activating systems (RAS) and basal forebrain activate regions of cortex (eg frontal cortex).
Bottleneck theory of attention in selective attention
Broadbent (1958) - bottleneck theory of attention
- early filtering mechanism (early selection model)
- limited capacity channel
What does the cocktail party phenomenon suggest about selective attention?
Suggests some information gets through the filter.
Even when we selectively attend to a conversation we are subconsciously monitoring other conversations around us.
(Slightly refutes the bottleneck???)
What’re some errors of attention?
Inattentional blindness: a failure to see something in plain sight
Change blindness: the inability to detect changes in scenes when looking directly at them
What is divided attention?
Attention has a limited capacity.
Divided attention: performing multiple tasks simultaneously.
We really shift attentional resources between tasks. The faster and more efficiently we can make these shifts the better we can “multi-task”.
What is considered one wavelength and wave amplitude?
Wave between two peaks. Amplitude height and it determines intensity.
We can only see a very small part of the light spectrum.
Parts of the eye. (Basic)
Sclera (white part)
Pupil (light comes in)
Iris
What’re the two processes of the eye inside ?
- Focussing light on retina
2. Transfixing the image into nerve signals
Features of photoreceptors
Photoreceptors (Rods and cones) turns light energy into electrical signals
Electrochemical process mediated by photo pigments
- rods use rhodopsin
- light bleaches rhodopsin causing fatigue (leads to “after” images like after you turn away from an illusion you feel like you can still see it)
Describe the photo receptors (rods and cones)
Rods:
- low light
- monochromatic
- peripheral vision
Cones:
- bright light
- colour vision
- central vision (fine detail)
Photoreceptors to ganglion cells
Convergence to rods and cones
Light comes in ->Retinal ganglion cell -> amacrine cells -> bipolar cells ->horizontal cells -> cone receptors -> Rod receptors/ back of the eyeball
Low convergence in come fed circuits
1 Retinal ganglion cell -> 1 bipolar cell ->1 cone
High convergence in Rod fed circuits
Multiple Retinal ganglion call -> multiple bipolar call -> multiple Rod
GET COMFORTABLE WITH THE PRIMARY PROJECTION PATHWAYS OF THE VISUAL SYSTEM
Yay
Describe parts of the visual cortex
Different cortical cells respond best to different stimuli.
Simple cells: light if specific orientation at a particular location
Complex cells: specific orientation but less dependant on location
Feature detectors: lines and edges (simple/complex cells), length of lines, shapes, movement, colour etc.
Diagrammed parts of the occipital lobe.
Separated info colours
V1/Primary part of the visual cortex
V4 for colour
What is colour vision?
Different theories explain different aspects of colour vision: opponent and trichromatic theory.
The two theories have BOTH been shown to be correct.
What is one theory of colour vision?
Trichromatic theory: colour vision is based on our sensitivity to three primary colours
- explains colour blindness
- consistent with three types of cones in eyes
What is the opponent process theory of colour vision?
Colour vision as a function of complementary, opposing colours
- red vs. green
- blue vs. yellow
- black vs. white??
Activated vs. inhibited.
