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Chapter 5

Chapter 5 - Sensation, Perception, Attention

18 Pages
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Department
Psychology
Course Code
PSY100H1
Professor
Michael Inzlicht

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Chapter 5 Sensation, Perception, and Attention
How Do We Sense Our Worlds?
Sensor y organs convert forms of physical energy into signals that the brain can
understand
Adaptive, provides information on threats and food varies between animals
depending on their adaptive challenges
Stimuli Must Be Coded to Be Understood by the Brain
Sensory coding the way our sensory organs translate a stimulus’ physical
properties into neural impulses
E.g. a green stoplight will be coded by a particular pattern of neural responses in the
retina, etc.
Transduction receptors, specialized neurons in the sense organs, pass impulses to
connecting neurons when they receive some kind of physical or chemical stimulation
from the environment
Connecting neurons transmit the information to the brain as neural impulses
Most of this sensory information first goes to the thalamus, then to the cortex, where
it is interpreted as sight, smell, sound, touch, or taste
Two categories of sensory coding quantitative and qualitative
Quantitative intensity, brightness, and loudness is often indexed by the neural
firing frequency. Higher frequency means brighter or louder
Qualitative colour, taste, smell different sensory receptors respond to different
qualities of a stimulus. Simplest form would be to have a receptor type for every
possible stimulus.
Coarse coding in most sensory systems, sensory qualities are coded by only a few
receptors, each of which responds to a broad range of stimuli, which are integrated
to compute the final percept
Psychophysics Relates Stimulus to Response
Trying to understand the relationship between physical properties of the world and
how we sense or perceive them
www.notesolution.com
Examines psychological experiences of physical stimuli
How much physical energy is required for our sense organs to detect that energy, and
how much change is required before we notice the change?
Test limits of human sensory systems through careful study
Sensory Thresholds
oAbsolute threshold the minimum intensity of stimulation that must occur
before we can experience a sensation e.g. the faintest sound you can hear
(defined as the stimulus intensity that is detected above chance”)
oDifference threshold the just noticeable difference between two stimuli; the
minimum amount of change required for us to detect a difference.
oWebers law The difference required increases as the stimulus becomes
more intense. The size of a just noticeable difference is based on a relative
proportion of difference rather than a fixed amount of difference.
Signal-Detection Theory
oVariable of human judgement means that the concept of an absolute
threshold is flawed
oSignal-detection theory detecting a stimulus requires making a judgement
about its presence or absence, based on a subjective interpretation of
ambiguous information.
oFour outcomes of a test hit, miss, false alarm, correct rejection
oResponse bias participants tendency to report detecting the stimulus on
ambiguous trials
oCircumstances, beliefs and expectancies can also influence this soldier will
err on the side of caution, so will doctor higher level processes influence
how sensations are perceived.
Sensory Adaptation
oSensory adaptation response to a stimulus changes over time.
oSensitivity to stimuli decreases. If a stimulus is presented continuously, the
responses of the sensory systems that detect it tend to diminish over time.
www.notesolution.com
oSensory systems are tuned to detect change, less critical to keep responding
to unchanging stimuli.
oIf a continuous stimuli stops, there is a large response again.
What Are the Basic Sensory Processes?
Only the sensory neurons respond to anything from the outside world.
How stimuli are detected and sent to the brain for the five senses.
In Gustation, Taste Buds Are Chemical Detectors
Gustation sense of taste
To keep poisons out of our digestive system while allowing good food in
Stimuli chemical substances from food that dissolve in saliva
Taste receptors are part of taste buds of the tongue and mouth
Microvilli, short hair-like structures at the tip of each taste bud, come into direct
contact with saliva. When stimulated, they send electrical signals to the brainstem
region called the medulla, and from there to the thalamus and cortex, where the
sense of taste is produced
Different taste receptors respond most strongly to one of four primary taste
sensations sweet, sour ,salty, and bitter
Every taste is composed of some combination of these coarse coding
Taste relies on sense of smell and texture as well all of these experiences occur in
the brain, not the mouth
Supertasters have six times as many taste buds, very picky eaters
In Smell, the Nasal Cavity Gathers Particles of Odour
Olfaction sense of smell
Most direct route to brain, bypasses hypothalamus
Odorous particles come into contact with olfactory epithelium, a thin layer of tissue
with olfactory receptors
Particles dissolve in a solution and cause a reaction that triggers chemical receptors
www.notesolution.com

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Description
Chapter 5 Sensation, Perception, and Attention How Do We Sense Our Worlds? Sensor y organs convert forms of physical energy into signals that the brain can understand Adaptive, provides information on threats and food varies between animals depending on their adaptive challenges Stimuli Must Be Coded to Be Understood by the Brain Sensory coding the way our sensory organs translate a stimulus physical properties into neural impulses E.g. a green stoplight will be coded by a particular pattern of neural responses in the retina, etc. Transduction receptors, specialized neurons in the sense organs, pass impulses to connecting neurons when they receive some kind of physical or chemical stimulation from the environment Connecting neurons transmit the information to the brain as neural impulses Most of this sensory information first goes to the thalamus, then to the cortex, where it is interpreted as sight, smell, sound, touch, or taste Two categories of sensory coding quantitative and qualitative Quantitative intensity, brightness, and loudness is often indexed by the neural firing frequency. Higher frequency means brighter or louder Qualitative colour, taste, smell different sensory receptors respond to different qualities of a stimulus. Simplest form would be to have a receptor type for every possible stimulus. Coarse coding in most sensory systems, sensory qualities are coded by only a few receptors, each of which responds to a broad range of stimuli, which are integrated to compute the final percept Psychophysics Relates Stimulus to Response Trying to understand the relationship between physical properties of the world and how we sense or perceive them www.notesolution.com Examines psychological experiences of physical stimuli How much physical energy is required for our sense organs to detect that energy, and how much change is required before we notice the change? Test limits of human sensory systems through careful study Sensory Thresholds o Absolute threshold the minimum intensity of stimulation that must occur before we can experience a sensation e.g. the faintest sound you can hear (defined as the stimulus intensity that is detected above chance) o Difference threshold the just noticeable difference between two stimuli; the minimum amount of change required for us to detect a difference. o Webers law The difference required increases as the stimulus becomes more intense. The size of a just noticeable difference is based on a relative proportion of difference rather than a fixed amount of difference. Signal-Detection Theory o Variable of human judgement means that the concept of an absolute threshold is flawed o Signal-detection theory detecting a stimulus requires making a judgement about its presence or absence, based on a subjective interpretation of ambiguous information. o Four outcomes of a test hit, miss, false alarm, correct rejection o Response bias participants tendency to report detecting the stimulus on ambiguous trials o Circumstances, beliefs and expectancies can also influence this soldier will err on the side of caution, so will doctor higher level processes influence how sensations are perceived. Sensory Adaptation o Sensory adaptation response to a stimulus changes over time. o Sensitivity to stimuli decreases. If a stimulus is presented continuously, the responses of the sensory systems that detect it tend to diminish over time. www.notesolution.com
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