Study/lecture notes for first-year psychology on sensation and Perception
*Please note that the information in the document is not my own knowledge, it belongs to the Unversity of the Witwatersrand and is comprised of notes from lectures and textbooks.
Contents
Sensation and perception .................................................................................................................................................... 4
Introduction ..................................................................................................................................................................... 5
Sensation and absolute thresholds .................................................................................................................................. 5
Psychophysics .................................................................................................................................................................. 8
Signal detection theory ................................................................................................................................................ 9
the difference threshold ............................................................................................................................................ 10
Basic concepts and issues .......................................................................................................................................... 10
adaption to stimuli ..................................................................................................................................................... 11
the sensory systems .......................................................................................................................................................... 12
vision.............................................................................................................................................................................. 12
light ............................................................................................................................................................................ 12
Visual Acuity .............................................................................................................................................................. 13
the structure of the eye ............................................................................................................................................. 14
the retina ................................................................................................................................................................... 15
Lateral inhibition/antagonism.................................................................................................................................... 16
Adapting to light and dark ......................................................................................................................................... 17
Colour Vision.................................................................................................................................................................. 18
Trichromatic theory of colour perception: ................................................................................................................. 19
Opponent processing ................................................................................................................................................. 19
theories of colour vision ............................................................................................................................................ 20
Colour blindness - colour weakness ........................................................................................................................... 21
Visual Pathways ............................................................................................................................................................. 22
The bottom-up process of vision ............................................................................................................................... 22
The visual systems ......................................................................................................................................................... 23
The primary visual areas ............................................................................................................................................ 24
Secondary areas ......................................................................................................................................................... 24
tertiary visual areas ................................................................................................................................................... 24
top-down and bottom up processing ........................................................................................................................ 25
modularity ................................................................................................................................................................. 26
A little experiment:What is a feature? ....................................................................................................................... 26
Organising incoming features ........................................................................................................................................ 28
Perceptual expectancy ............................................................................................................................................... 29
Distinguishing between foreground and background ................................................................................................ 29
Perceiving forms, patterns, and objects .................................................................................................................... 29
Perceptual constancy ..................................................................................................................................................... 30
colour constancy ........................................................................................................................................................ 30
Size constancy ............................................................................................................................................................ 30
Shape constancy. ....................................................................................................................................................... 30
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, depth perception ........................................................................................................................................................... 31
Perceiving Depth or Distance ......................................................................................................................................... 33
the top-down monocular processes. ........................................................................................................................ 33
Interposition .............................................................................................................................................................. 35
Texture gradient ........................................................................................................................................................ 35
Ariel perspective – clarity .......................................................................................................................................... 35
moon illusion ............................................................................................................................................................. 35
Monocular movement parallax:................................................................................................................................. 35
Top-down vs bottom-up Routes to perception. ............................................................................................................ 35
Gestalt Principles ....................................................................................................................................................... 36
Gestalt Principles of Visual Perception ...................................................................................................................... 37
TOP-DOWN PROCESSING SENSATION MAY NOT EQUAL PERCEPTION ...................................................................... 37
Visual Illusions ........................................................................................................................................................... 38
Perceptual deficits ..................................................................................................................................................... 40
Apperceptive Agnosia ................................................................................................................................................ 41
associative Agnosia .................................................................................................................................................... 42
The sensory systems: Hearing........................................................................................................................................ 43
The structure of the ear ............................................................................................................................................. 43
The pathway to the brain........................................................................................................................................... 44
The theory explaining how we hear loudness............................................................................................................ 44
Theories explaining how we hear pitch ..................................................................................................................... 44
summary .................................................................................................................................................................... 45
Balance and the vestibular system ............................................................................................................................ 46
Tactile sensation ........................................................................................................................................................ 46
Pain ............................................................................................................................................................................ 46
Phantom limbs ........................................................................................................................................................... 46
Putting it all Together: Multimodal Perception ......................................................................................................... 47
Hearing : the stimulus .................................................................................................................................................... 48
The structure of the ear ............................................................................................................................................. 48
hearing ....................................................................................................................................................................... 49
Theories of Hearing - pitch......................................................................................................................................... 49
Hearing continued ..................................................................................................................................................... 49
The Chemical Senses ...................................................................................................................................................... 50
Chemical Senses - Taste. ............................................................................................................................................ 50
Chemical Senses - Smell ............................................................................................................................................. 51
Touch. ........................................................................................................................................................................ 52
The kinaesthetic sense ............................................................................................................................................... 53
The vestibular sense .................................................................................................................................................. 53
Smell and Taste: The Chemical Senses ....................................................................................................................... 53
, SENSATION AND PERCEPTION
Sensation is a passive process during which the sensory receptors
and the brain receive information from the environment.
You don’t open your eyes and decide to see – it will just happen
Perception is a process that entails actively choosing information
from sensation, organising it and interpreting it to make meaning of
the world. It is always subjective.
Although we may receive light via the eye and sound via the ear, the signal is transduced (sensory
coding) and we see and hear with the brain (sensory location)
*we see with our brains not our eyes
- we pick up on a sensory receptor signal and send it to the brain without using the eyes
- the eyes are merely a tool to pick up on these sensations
Before discussing each of our extraordinary senses individually, it is necessary to cover some basic
concepts that apply to all of them.
It is probably best to start with one very important distinction that can often be confusing:
the difference between sensation and perception.
▪ The physical process during which our sensory organs—those involved with hearing and
taste, for example—respond to external stimuli is called sensation.
During sensation, our sense organs are engaging in transduction, the conversion of one
form of energy into another.
▪ Physical energy such as light or a sound wave is converted into a form of energy the brain
can understand; electrical stimulation.
After our brain receives the electrical signals, we make sense of all this stimulation and begin
to appreciate the complex world around us.
This psychological process—making sense of the stimuli—is called perception. It is during
this process that you are able to identify a song that reminds you of a specific afternoon
spent with friends.
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