PSYO 1021 Lecture 4: Lecture 4 unit 2
27 Jun 2018
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lecture 4
Chapter 4 – sensing an perceiving our world
Outline – sensation and perception
Sensation
Response of sense organs to stimulation
Eyes sense light waves, ears sound, skin touch and pressure, tongue taste, nose odors
Perception
Psychological process of organizing and interpreting sensory experience
Receive the sensory input and translates it form what we already know, remember (makes sense
out of it)
How our psychological world represents our physical world
Explain why the same stimuli can be different from one person to the other
Human most of the perception from what we see
Dogs most of the perception from what they smell
Psychophysics
Study of how people psychologically perceive physical stimuli like light, odor, sound waves,
touch. Over a century of research (back in chapter 1)
Transduction
Conversion of physical stimuli to a neuronal stimulus that the brain can process
Photons that turn into neurons
Process: occurs at sensory receptors (different for different sense organs)
Receptor potentials make the change (action potentials for receptor organs)
Ex: Cells in the retina change light waves into neural energy
Sensory adaptation
If we would always process every sense in our surrounding the brain would overload
We only pay attention to some stimuli = sensory adaptation
Your senses decrease in sensitivity to certain stimuli – the ones that are constantly stimulated
Process ensures that your brain pays attention to relevant stimuli – usually the ones that change
We pay more attention to change in stimuli than stimuli itself
Example: moving your watch to the opposite arm, felt it at the start (change), end of the lecture
you don’t feel it anymore (constant stimuli)
Perceptual processing
Perception happens in the brain, after transduction
Our experience of seeing, hearing, tasting is a result of processing of information stimuli by the
brain
You can process the information in 2 different ways: bottom up processing/top-down processing
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lecture 4
Bottom-up processing
Building a perceptual experience from the smaller (basic) elements into a general experience
Ex: walking up into a room perceive the smell, the visual details and assemble that into one
experience of the room
Mostly used for new experiences
Top-down processing – most common
Opposite of the other
Perception of the hole guides perception of the smaller elements
Ex: walk in to the room and you have an overall experience and from that overall experience you
look at the individual that make the experience
Mostly used for familiar situations
Perceptual set
The effect of the frame mind/state of mind on perception
Ex: perceptual set is different the first day than now
First day: state of mind all was new = used bottom-upprocessing
Now: habit of being in the room= top-down processing
Example of manipulating a perceptual set
Group 1: sees letters before= sees the last one as a B
Group 2: sees numbers before = sees the last one as a 13
Both group saw the same stimulus, likely used the same bottom-up processing processes to
assemble the elements, but used a different top-down to interpret the image
** often use both
TED TALK – watch over and makes notes
Basic sensory processes
Absolute threshold
Measurement of the lowest intensity of a stimulus that a person can detect half of the time
Way to assess: present a stimulus of different intensities to participants, the one that they can
hear 50 percent of the time is their absolute threshold
For sound, amount of dB that the person confirmed hearing at 50%
Threshold of perception measured by the time a person can spot seeing something in the distance
Taste = the quantity of salt tasted in water
Changes from person to person, from species to species
Dogs threshold is much lower than ours
Difference threshold
Minimum amount of change between 2 stimuli that can be noticed half of the time
“just noticeable differences” (JND)
Ex: noticing that 103g brick is heavier than a 100g brick
- Webber’s law
The difference threshold is a constant fraction/ratio of the intensity of the stimuli
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lecture 4
Ex: 100 g and 103 g – that’s your difference threshold
This means that a 3% weight difference is the threshold, the one that’s always noticed
If its 1g can detect the difference with 0.3g…
Signal detection theory
Problem with measuring absolute thresholds: few variables that influence a person’s threshold..
Signal detection theory includes:
- Intensity of the stimulus
- Decision making process of the perceiver
- Situation (can have an influence)
Intensity of stimulus
The more intense is the stimulus, the more likely a person is going to perceive it
Decision making process
Near absolute threshold:
Some people are more likely to say they perceive it even if they don’t
Some people are more likely to say they don’t even if they do
= decision making of the person comes into play
Situation
Situation can influence a person to say yes or no
If there is a consequence if you don’t perceive it, more likely to perceive it
Ex: nurse in emergency patient – will perceive the vital sign changes
Situations like these make people more sensitive to sensory input
So much that some people might say they heard something that wasn’t there
Signal detection research
Present the participants sometimes with the stimulus and sometimes with no stimulus
2 options of answers, 4 possibilities of result:
-Hit
The stimulus is detected while its present
-Miss
Failing to detect a present stimulus
-False alarm
Detecting an absent stimulus
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Chapter 4 sensing an perceiving our world. Eyes sense light waves, ears sound, skin touch and pressure, tongue taste, nose odors. Psychological process of organizing and interpreting sensory experience. Receive the sensory input and translates it form what we already know, remember (makes sense out of it) How our psychological world represents our physical world. Explain why the same stimuli can be different from one person to the other. Human most of the perception from what we see. Dogs most of the perception from what they smell. Study of how people psychologically perceive physical stimuli like light, odor, sound waves, touch. Over a century of research (back in chapter 1) Conversion of physical stimuli to a neuronal stimulus that the brain can process. Process: occurs at sensory receptors (different for different sense organs) Receptor potentials make the change (action potentials for receptor organs) Ex: cells in the retina change light waves into neural energy.
