PSYC101 Lecture Notes - Lecture 4: Binocular Disparity, Parallax, Simple Features
PSYC101
Introduction to behavioural sciences
Wk 4 Lecture:
Sensation and Perception
Sensation vs perception
Senses: feelings from stimuli/physical properties ?
- senses take physical properties of the world and convert them into a psychological phenomena -
psychological phenomena = perception
-5 senses
•Vision, hearing, taste, touch, smell
-Proprioception/ Kinesthesia
•Sense of the position/location of parts of the body
-Vestibular senses
•Detect gravity, linear acceleration, rotary acceleration, and overall provide balance
-Sensory receptors
•Cells specialised for converting physical energy into neural impulses (transduction)
-Rods + cones in retina
-Cilla in ear
-Pressure, vibration, heat + pain receptors in skin
-Chemical receptors in nasal cavities and mouth
Vision
-Stimulus = light (em radiation)
•Amplitude: perception of brightness
•Wavelength: perception of colour
•Purity: perception of saturation
-The eye: Transduction
•Light reflects off objects into our eyes, light stimulates rod + cone recpetors on our retinas
(convert light into electrical energy)
-Retina
•Network of neutrons covering the back of the eye
-A Neuron
•Ganglion cells in the eye + cortical cells have same general structure
•Eye does preliminary processing of visual input
-Senses = stimulation of our sense organs
-Perception = “selection, organisation and interpretation of sensory input” (mostly by brain)
-Visual agnosia (disorder in the parietal lobes causing a condition where a person can see but is
unable to recognise or interpret visual information) , prosopagnosia (face blindness)
•Evidence that sensation is separate from perception
•https://www.youtube.com/watch?v=k5bvnXYIQG8
-Perception: not always correct
•Works well, not perfect
•Visual system can & does get it wrong
•Illustrations
-Show that we don’t know exactly where things are in the word around us
-Helps us understand how vision works
-Make pretty good guesses tho
•We use information that is available on our retina array
•E.g. Depth perception: don’t have a direct measure of X,Y,Z coordinated
-What information is available in the environment?
-What mechanisms does the brain have for exploiting this information?
-Colour perception
•Light reflects off objects into our eyes
•Lights travels in waves and different coloured lights have different wavelengths
-Short wavelength light (400-500nm) appears Violet\blue
-Medium wavelength light (500-590nm) appears Green\Yellow
-Long wavelength light (590-700nm) appears Orange\Red
•We are rarely exposed to single wavelengths
•Additive colour mixing
-Involves multiple sources of light w/ different colours in each source
-E.g. lights
•Subtractive colour mixing
-Involves single source of light w/ different colours absorbing various wavelengths of the
colour spectrum
-E.g. paints
•Absorption and reflections
-Properties of the objects surface determine the wavelengths of light reaching our eye
-They determine which wavelengths are absorbed and which are reflected
•Trichromatic theory
-Proposed there are 3 different receptor types, each respond to diff. Wavelengths of light
•Red - long wavelength
•Green - medium
•Blue - short wavelength
-The colour seen is determined by relative levels of activity in the 3 receptors
-Evidence
•Colour mixing experiments: observers can match any colour by varying the proportions of
red, green, blue light
•Eye has 3 types of cone: each sensitive to a different range of wavelengths
•Colour blindness : colour vision deficiency
-Dichromats - insensitive to red, green, or blue
-Trouble w/ trichromatic theory
•Has trouble accounting for some types of colour blindness, colour afterimages
-Colour blindness
•Red-green blind ppl can see white + yellow
-Opponent Process Theory
•Coloured afterimages suggests that certain colours are coded as opposites of each other
•Hering (1878) proposed there are cells that are
-Excited by green, inhibited by red
-“ blue, “ yellow
-“ Black, “ white
•Evidence:
Document Summary
Senses take physical properties of the world and convert them into a psychological phenomena - psychological phenomena = perception. 5 senses: vision, hearing, taste, touch, smell. Proprioception/ kinesthesia: sense of the position/location of parts of the body. Vestibular senses: detect gravity, linear acceleration, rotary acceleration, and overall provide balance. Sensory receptors: cells specialised for converting physical energy into neural impulses (transduction) Pressure, vibration, heat + pain receptors in skin. Chemical receptors in nasal cavities and mouth. Stimulus = light (em radiation: amplitude: perception of brightness, wavelength: perception of colour, purity: perception of saturation. The eye: transduction: light re ects off objects into our eyes, light stimulates rod + cone recpetors on our retinas (convert light into electrical energy) Retina: network of neutrons covering the back of the eye. A neuron: ganglion cells in the eye + cortical cells have same general structure, eye does preliminary processing of visual input. Senses = stimulation of our sense organs.
