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Chapter 5

Psychology 1000 Chapter Notes - Chapter 5: Semicircular Canals, Statistical Hypothesis Testing, Soltyrei

Course Code
PSYCH 1000

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Psychology 1
Chapter 5: Sensation and Perception
Synesthesia—“mixing of the senses”. Experience sounds as colours or tastes as touch
sensations that have different shapes, women are more likely, it is suggested we’re all born
with it
Binding problemhow do we bind all our perceptions into one complete whole while keeping
its sensory elements separate?
Sensationthe stimulus-detection process by which our sense organs respond to and translate
environmental stimuli into nerve impulses that are sent to the brain
Perceptionmaking sense of what out senses tell usis the active process of organizing this
stimulus input and giving it meaning
Nerve impulses is the only language the nervous system understands
Transductionthe process whereby the characteristics of a stimulus are converted into nerve
Human sensory systems are designed to extract from the environment the information
that we need to function and survive
Psychophysicsstudies relations between the physical characteristics of stimuli and sensory
Studies 2 kinds of sensitivity
1. Absolute limits of sensitivity
2. Differences between stimuli
Absolute Thresholdthe lowest intensity at which a stimulus can be detected correctly 50% of
the time; the lower the absolute threshold the great the sensitivity
Decision criterionin signal detection theory, the potentially changing standard of how certain
a person must be that a stimulus is present in order to report its presence. Depends on fatigue,
expectation, and the potential significance of the stimulus
Signal detection theorya theory that assumes that stimulus detection is not based on a fixed
absolute threshold but rather is affected by rewards, punishments, expectations, and
motivational factors

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Psychology 2
Difference thresholdthe smallest difference between two stimuli that people can
perceive 50% of the time. Sometimes called the just noticeable difference
Weber’s lawstates that the difference threshold, or jnd, is directly proportional to the
magnitude of the stimulus with which the comparison is being made, and can be expressed
as a Weber fraction. The smaller the fraction the greater the sensitivity to differences
Sensory adaptationsensory neurons are engineered to respond to a constant stimulus by
decreasing their activity, and the diminishing sensitivity to an unchanging stimulus is
called sensory adaptation
Adaptation, also called habituation, reduced our sensitivity to certain things that become
monotonous (wrist watch)
The normal stimulus for vision is electromagnectic energy
Light-- ROY G BIV
Light waves enter the eye through the corneaa transparent protective structure at
the front of the eye
Behind the cornea is the pupilan adjustable opening that can dilate or constrict to
control the amount of light that enters the eye
The pupil’s size is controlled by muscle in the coloured iris that surrounds the pupil
Behind the pupil is the lens, an elastic structure that becomes thinner to focus on
distant objects and thicker to focus on nearby objects
Retinaa multilayered tissue at the rear of the fluid-filled eyeball and is actually an
extension of the brain. Has 2 types of light-sensitive receptor cells: the rods and
The lens reverses the image from right to left and top to bottom when it is projected
on the retina
Myopia (nearsightedness)the lens focuses the visual image in front of the retina resulting
in blurred image for far away objects. The eyeball is usually longer, front to back
Hyperopia (farsightedness)occurs when the lens does not thicken enough and the image
is therefore focused on a point behind the retina

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Psychology 3
Rodsfunction best in dim light, are primarily black and white brightness receptors.
They are 500x more sensitive to light than the cones but do not give colour sensations
Conescolour receptors; function best in bright illumination
Humans have a mixture of rods in cones since they see in the night and day
Rods are found throughout the retina except in the fovea
Foveaa small area in the centre of the retina that contains only cones
Cones decrease in concentration as you move away from the centre of the retina
Periphery of the retina contains mainly rods
Rods and cones send their messages to the brain via 2 additional layers of cells:
bipolar cells and ganglion cells
Bipolar cellshave synaptic connections with the rods and cones and in turn, synapse
with a layer of about 1 million ganglion cells
Ganglion cellswhose axons are collected into a bundle to form the optic nerve
Rods and cones not only form the rear layer of the retina, but their light-sensitive
ends actually point away from the direction of the entering light so that they
receive only a fraction of the light energy that enters the eye
Rods and cones are connected to the bipolar and ganglion cells
We can more easily detect a faint stimulus if we look slightly to one side so that
its image falls not on the fovea but on the peripheral portion of the retina, where
rods are packed more densely
In the fovea the densely packed cones each have their own “private line” to a
single bipolar cell. As a result our visual acuity, or ability to see fine detail, is
greatest when the visual image projects directly onto the fovea
The optic nerve formed by the axons of the ganglion cells exits through the back
of the eye not far from the fovea, producing a blind spot, where there are no
Rods and cones translate light waves into nerve impulses through the action of
protein molecules called photopigments. The absorption of light by these
molecules produces a chemical reaction that changes the rate of
neurotransmitter release at the receptor’s synapse with the bipolar cells
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