PSYC-1105EL Chapter Notes - Chapter 4-6: Ear Canal, Visual Perception, Color Vision
12 Jun 2018
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PSYCHOLOGY CHAPTER 4,5,6 NOTES
TEST: NOVEMBER 9TH 2017
CHAPTER 4: SENSATION AND PERCEPTION
Synesthesia: a condition in which perceptual or cognitive activities trigger exceptional
experiences
Sensation: stimulation of sense organs, body’s detection of external or internal stimulation
Perception: selection, organization, and interpretation of sensory organs
Thresholds: Looking for Limits
- Sensation begins with a stimulus
Stimulus: any detectable input from the environment
Threshold: a dividing point between energy levels that do and do not have a detectable effect
Absolute Threshold: for a specific type of sensory input is the minimum amount of stimulation
that an organism can detect (50% of the time)
Just Noticeable Difference (JND): the smallest difference in the amount of stimulation that a
specific sense can detect
Weber’s Law: states that the size of a just noticeable difference is a constant proportion of the
size of the initial stimulus
Signal-Detection Theory
The detection of stimuli involves decision processes as well as sensory processes, which are both
influenced by a variety of factors besides stimulus intensity
Detectability: measured in terms of probability and depends on decision-making & sensory
processes
Difference Threshold: the amount of change in a stimulus required before a person can detect a
shift
Perception without Awareness
Subliminal Perception: the registration of sensory input without conscious awareness
Sensory Adaptation
A gradual decline in sensitivity due to prolonged stimulation
- Pervasive aspect of everyday life
- A automatic, built-in process that keeps people tuned into the changes rather than the
constants in their sensory input
The Visual System
Light: a form of electromagnetic radiation that travels as a wave
Two Purposes of the Eye
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1. Channel light to the neural tissue that receives it (retina)
2. Creates an image of the visual world on the light-sensitive retina lining its inside back
surface
Occipital Lobe: visual processing center of the brain
Structure of the Eye
Cornea: the curved, transparent layer through which light rays enter the eye
*Pupil: an opening in the eye, just behind the cornea, through which light rays enter the eye
*Iris: the coloured part of the eye that adjusts the amount of light that enters by constricting or
dilating the pupil
Lens: a curved structure behind the pupil that bends light rays focusing them on the retina
*Retina: the surface of the back of the eye containing rods and cones
Cones: sensory receptors in the eye that sense colour & detail; 6.5 million in the retina
Rods: sensory receptors for vision found in the eye that help see in darkness; 100 million outside
the fovea
Fovea: the area in the centre of the retina in which cones are highly concentrated
Optic Nerve: a bundle of nerve fibers that exit the back of the eye and carry visual information to
the brain
Blind Spot: the point in the back of the retina through which the optic nerve exits the eye; this
exit point contains no cones or rods and is therefore insensitive to light
Light
- Visible light is only a small portion of the electromagnetic spectrum
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- The wavelength, or distance between successive peaks and valleys of light energy,
determines which colour we experience (400-700 nanometers)
- The intensity of light (amount of energy it carries) is experiences as brightness
- The extent to which light contains only one wavelength or many determines the
saturation of the colour (ie. red vs pink)
Functions of Light
Static Visual Acuity: ability to discriminate different objects when they are stationary
Dynamic Visual Acuity: ability to resolve detail when motion is present
Types of Sight
Nearsightedness: distant objects appear blurry
Farsightedness: close objects appear out of focus
Dark Adaptation: the process by which the visual system increases in sensitivity to light under
low illumination
Saccadic Movements: quick movements of the eye from one point of fixation to another
Visual Pathways to the Brain
Optic Chiasm: the point at which the optic nerves from the inside half of each eye cross over and
then project to the opposite half of the brain
Main Pathway: projects into the thalamus, about 90% of the axons from the retinas synapse in
the LGN
2nd Visual Pathways: branches off to an area in the midbrain called the superior colliculus
before travelling through the thalamus. Function is coordination of visual input with other
sensory input
Information Processing in Visual Cortex
Feature Detectors: neurons that respond selectively to very specific features of more complex
stimuli
Ventral Stream: processes the details of what objects are out there
Dorsal Stream: processes where the objects are
Colour Vision
2 types of colour mixtures
Subtractive Colour Mixing: works by removing some wavelengths of light, leaving less light
than was originally there
Additive Colour Mixing: works by superimposing lights, putting more light in the mixture than
exists in any one light by itself
Trichomatic Theory*
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Document Summary
Synesthesia: a condition in which perceptual or cognitive activities trigger exceptional experiences. Sensation: stimulation of sense organs, body"s detection of external or internal stimulation. Perception: selection, organization, and interpretation of sensory organs. Threshold: a dividing point between energy levels that do and do not have a detectable effect. Absolute threshold: for a specific type of sensory input is the minimum amount of stimulation that an organism can detect (50% of the time) Just noticeable difference (jnd): the smallest difference in the amount of stimulation that a specific sense can detect. Weber"s law: states that the size of a just noticeable difference is a constant proportion of the size of the initial stimulus. The detection of stimuli involves decision processes as well as sensory processes, which are both influenced by a variety of factors besides stimulus intensity. Detectability: measured in terms of probability and depends on decision-making & sensory processes.
