Textbook Notes (381,289)
CA (168,463)
UTSC (19,325)
Psychology (10,054)
PSYA01H3 (1,329)
Steve Joordens (1,150)
Chapter 5

Chapter 5 - Sensation

6 Pages
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Department
Psychology
Course Code
PSYA01H3
Professor
Steve Joordens

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Chapter 5 Sensation
Sensory Processing
- Sensation: The detection of simple properties of stimuli (i.e. brightness, colour, warmth,
sweetness) while perception: Detection of objects, their location, movements and
backgrounds (i.e. red is SENSATION, seeing a red apple is PERCEPTION)
- Transduction "leading across": The conversion of physical stimuli into changes in
activity of receptor cells of sensory organs - transduction is DIVERSE, in most sense senses,
specialized neurons called RECEPTOR CELLS release chemicals that stimulate neurons
which is sent to axon
- Sensory Coding: Coding system of symbols/signals representing information
- Anatomical Coding: Way by which nervous system represents information; different
features are coded by the activity of different neurons
- Since early 1800s, Johannes Muller formulated doctrine of specific nerve energies 
learning in whats happening through the activity of specific area of the brain
- Temporal Coding: Way by which nervous system represents information; different
features are coded by PATTERN of activity of neurons simplest form is RATE
- Psychophysics ("physics of the mind"): Study of measuring quantitative relation
between physical stimuli and perceptual experience
- Principle of Just-Noticeable Difference: Ernst Weber (1795-1878): Anatomist and
physiologist investigated human's ability to discriminate between various stimuli (just
noticeable-difference - smallest change in magnitude of stimulus someone can detect) 
ratio of brightness of light is 1:40 (WEBER FRACTIONS)
- Gustav Fechner (1801-1887): Used Weber's idea to measure people's sensations (jnd was
the unit of sensory experience)
- Signal Detection Theory: Mathematical theory for detecting stimuli - discriminating
signal from noise which takes into account participants' willingness to report signal
detection - EVERY STIMULUS EVENT REQUIRES DISCRIMINATION BETWEEN
SIGNAL AND NOISE
- Methods rely on a THRESHOLD (Point where the stimulus or the change in the stimulus
is DETECTED), difference threshold= Just-noticeable difference (jnd))
- Absolute Threshold: Minimum value of stimulus that can be detected
www.notesolution.com
- Receiver Operating Characteristic Curve (ROV curve): Graph of hits and false
alarms of participants under different motivational conditions; indicates people's ability to
detect the stimulus
Vision
- Light: Consists of radiant energy, the WAVELENGTH (distance between waves of
radiant energy) of visible light is 380-760 nm in the light spectrum
- The Eye and its functions:
1) Cornea: Transparent tissue covering front of eye
2) Aqueous Humour: Space behind the cornea that is "watery fluid"
3) Sclera: Tough outer layer of eye the "white" part
4) Iris: Pigment muscle of eye that controls size of pupil
5) Lens: Transparent organ situated behind the iris of eye; helps focus image on retina
leading to accomodation : Change thickness of lens that focus images (some people need
glasses to focus)
6) Retina: Tissue at the back that contains photoreceptors (receptive cell for vision in
retina [ROD OR CONE], >130 million) and associated neurons
7) Optic Disc: Circular structure located at the exit of retina that forms optic nerve
8) Bipolar Cell: Neuron in retina that receives information from photoreceptors and
passes it on the ganglion cells, from which axons proceed through the optic nerves to the
brain
- Transduction of Light by Photoreceptors:
1) Light strikes the back of the eye stimulating photoreceptor to be either rods (not
responsive to colour but to dim light) or cones (sensitive to colour to provide detailed
image), transduction is done through a bleaching process where photopigments (complex
molecule in photoreceptors when struck by light, it splits and stimulates the membrane of
the photoreceptor in which it reside are split to cause action potentials, rods have 1 type
(sensitive to brightness i.e. shades of grey) while cones come in 3 varieties (only sensitive
to RED, GREEN and BLUE)
2) Signal from photoreceptor is passed to bipolar cells which reprocess signal so it
emphasizes edges and contours, when photoreceptors associated with spatially close parts
of retina are sending different signals, the bipolar cells accentuate these spots to perceive
edges
www.notesolution.com

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Description
Chapter 5 Sensation Sensory Processing - Sensation: The detection of simple properties of stimuli (i.e. brightness, colour, warmth, sweetness) while perception: Detection of objects, their location, movements and backgrounds (i.e. red is SENSATION, seeing a red apple is PERCEPTION) - Transduction leading across: The conversion of physical stimuli into changes in activity of receptor cells of sensory organs - transduction is DIVERSE, in most sense senses, specialized neurons called RECEPTOR CELLS release chemicals that stimulate neurons which is sent to axon - Sensory Coding: Coding system of symbolssignals representing information - Anatomical Coding: Way by which nervous system represents information; different features are coded by the activity of different neurons - Since early 1800s, Johannes Muller formulated doctrine of specific nerve energies learning in whats happening through the activity of specific area of the brain - Temporal Coding: Way by which nervous system represents information; different features are coded by PATTERN of activity of neurons simplest form is RATE - Psychophysics (physics of the mind): Study of measuring quantitative relation between physical stimuli and perceptual experience - Principle of Just-Noticeable Difference: Ernst Weber (1795-1878): Anatomist and physiologist investigated humans ability to discriminate between various stimuli (just noticeable-difference - smallest change in magnitude of stimulus someone can detect) ratio of brightness of light is 1:40 (WEBER FRACTIONS) - Gustav Fechner (1801-1887): Used Webers idea to measure peoples sensations (jnd was the unit of sensory experience) - Signal Detection Theory: Mathematical theory for detecting stimuli - discriminating signal from noise which takes into account participants willingness to report signal detection - EVERY STIMULUS EVENT REQUIRES DISCRIMINATION BETWEEN SIGNAL AND NOISE - Methods rely on a THRESHOLD (Point where the stimulus or the change in the stimulus is DETECTED), difference threshold= Just-noticeable difference (jnd)) - Absolute Threshold: Minimum value of stimulus that can be detected www.notesolution.com
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