Introduction to Sensation & Perception
PSY2134 Lecture 1
Dr Lee Ai-Suan
Psψchology@SUNWAY
Please share movies/series that are related to
Sensation and Perception
• https://sunwayeducat
iongroup.padlet.org/ai
suanl1/moviesharing_
aug23
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Coursework run-through
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Coursework
1) Experiment report (GROUP) – 50%
– Data to be collected as a group of 8
– Report to be submitted as a group of 4
– due Week 10, Friday 17th November, 4pm
2) Final exam (open book) – 50%
– Two hours to answer one essay question
– You may bring ONE A4-sized sheet with notes and
relevant journal articles (printed)
– NO textbook and NO electronic devices
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CW 1: Experiment report (GROUP)
Due Week 10, Friday 17th November, 4pm via eLearn
• In groups of 8, choose ONE experiment from the given list.
• Collect data as a GROUP. Each group should appoint one group leader
to combine all group data.
• Collate all GROUP DATA (10 pp’s per member x 8 members = 80
participants)
*********
• Write the report in groups of 4.
• Submit the report as groups of 4.
TL;DR
Collect data in groups of 8.
Write & submit report in groups of 4.
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CW1: *Strongly* recommended timeline
Week
1-2
Find group members (Excel sheet)
Week
3-4
In-class consultation for experiment planning
Week
5-6
Groups to generate experiment link and start data
collection
Week 6
Week
7-8
Week
8-9
Week 10
Data collection cont’d
Data collation, cleaning and analysis (in-class
consultation)
Report write-up
Report submission
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Aims of the module
• Demonstrate basic principles of sensory
mechanisms
• Illustrate perceptual processes
• Show a critical understanding of theories
and research concerned with sensation and
perception
• Apply theoretical concepts to practical
problems
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Haunted house example
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Old abandoned house or haunted house?
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Why Study Perception?
• Understanding how you perceive the world
– Color vision
– Depth perception
– Speech recognition
– Skin sensitivity
– Flavour creation
• Application to real-life problems
– Devices to assist people with vision and hearing impairments;
assistive technology for people with learning disabilities
– Classroom design
– Environmental planning
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Or just to take nice photos!
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Let’s play This or That: S&P edition
This
That
Cats meowing fiercely at 1am
Rooster’s crow at 6am
Looking at ocean waves
Listening to ocean waves
Touching soggy bread
Disposing a dead monitor lizard with a
broom (true story)
Taking photos
Being in photos
Listening to music
Listening to coffee house chatter
Sunlight
Vampire
Coffee
Tea
Spicy food
Squishy food
B.O. on a long flight
Damp socks after getting caught in a
heavy rain
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The perceptual process
• Stimuli
– Environmental stimulus
– Principle of transformation
• Receptor processes/Transduction
• Neural processing
• Behavioural response
– Perception
– Recognition
– Action
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Stimuli (Steps 1 and 2)
• Stimulus
– all objects in the environment
available to us
– we selectively attend to objects
– influence on receptors resulting in
internal representation
• Principle of transformation
– change between the environmental
stimuli and perception;
• light from the picture is reflected
and transformed.
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Receptor Processes /Transduction (Step 3)
• Sensory receptors are cells
specialized to respond to
environmental energy
– Visual pigment is what reacts to
light
• Transduction occurs which
changes environmental energy
to nerve impulses;
– Light to electricity
– Sound waves to electricity
– Temperature to electricity
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Neural Processing (Step 4)
• Changes that occur as signals are transmitted
through the maze of neurons
• Primary receiving areas:
– Occipital lobe
– Temporal lobe
– Parietal lobe
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Behavioral Responses (Step 5-7)
• Perception occurs as a
conscious experience
• Recognition occurs when an
object is placed in a category
giving it meaning
• Action occurs when the
perceiver initiates motor
activity in response to
recognition.
often lead to action, eg. increase vigilance,
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Look at this drawing first, then close your eyes and turn the page, so you
are looking at the same place on the page directly under this one. Then
open and shut your eyes rapidly (Adapted Bugelski & D. Alampay, 1961)
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What do you see?
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Man version of the rat-man stimulus
(Adapted Bugelski & D. Alampay, 1961)
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Knowledge
• Knowledge is any information the perceiver brings
to a situation;
• Bottom-up processing;
– based on incoming stimuli from the environment;
– Also called data-based processing;
• Top-down processing;
– based on the perceiver’s previous knowledge (cognitive
factors);
– Also called knowledge-based processing.
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How it works
“promo”
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Figure 1-7 p9
Approaches to the Study of Perception
• Observing perceptual processes at different stages in
the system:
➢ Psychophysical approach (Psychophysics) - the
stimulus-perception relationship
➢ Physiological approach - the stimulus-physiology
relationship
➢ Physiological approach - the physiology and
perception relationship
• These stages are interconnected and communicate
with one another
• Cognitive influences on perception
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Figure 1-8 p10
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Figure 1-8 p10
The stimulus - perception (psychophysical)
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Figure 1-9 p10
The stimulus – physiology (brain activity)
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Figure 1-11 p11
The physiology – perception
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Figure 1-12 p11
Measuring Perception: Absolute threshold
• The minimum stimulus intensity that can be
detected
– E.g. intensity of sound that can barely be heard
• Three classical psychophysical methods to
determine absolute threshold:
• Method of limits
• Method of adjustment
• Method of constant stimuli
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Method of limits
• Stimuli of different intensities presented in ascending
and descending order;
• Observer responds to whether she perceived the
stimulus;
• Cross-over point is the threshold.
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Method of adjustment
• Stimulus intensity is adjusted continuously until
observer detects it
• Observer not experimenter adjusting it
– E.g. increase or decrease sound to hear it
• Repeated trials averaged for threshold
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Method of constant stimuli
• Five to nine stimuli of different intensities were
presented in a random order
• Multiple trials were presented
• Threshold is the intensity that results in the
detection of 50% of trials
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How many sugar sachets
do you put in a cup of tea?
How well can you hear
your friends in the Brain
Forest?
From how far away can
you smell the Starbucks in
uni?
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Some Approximate Absolute Thresholds for
Humans
• Vision – candle flame seen at 30
miles ≈ 48.28 km on a clear, dark
night
• Hearing – tick of watch under quiet
conditions at 20 feet ≈ 6 meters
• Taste – 1 tsp of sugar in 2 gallons of
water ≈ 7.57 liters
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Measuring Thresholds: Difference Threshold
• The smallest difference between two
stimuli a person can detect
• Just Noticeable Difference (JND)
• To be detected as different 50% of the
time;
– The same methods can be used as for
absolute threshold;
– As magnitude of stimulus increases, so
does DL;
– Weber’s Law explains this relationship.
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Weber’s Law
• However, the difference is not absolute.
• Imagine holding a 2.5 kg weight and 500 grams
were added. Most of us would notice this
difference.
• But what if we were holding a 20 kg weight?
Would we notice if another 500 grams were
added?
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Weber’s Law
• The reason many of us would not is because the
change required to detect a difference has to
represent a percentage
• In the first scenario, 500 grams would increase the
weight by 20%
• in the second, the same weight would add only an
additional 2%
• This theory named after its original observer, is
referred to as Weber’s Law
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Beyond Thresholds and Magnitudes
• Phenomenological method involves description of what
they are perceiving or to indicate when a perception
occurs;
• Searching for stimuli;
– Visual search - observers
look for one stimulus in
a set of many stimuli;
• Reaction time (RT) - time
from presentation of
stimulus to observer’s
response is measured.
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Subjectivity: How a Person Chooses to Respond
• There are differences in response
criteria among participants:
– Liberal responder: responds yes if
there is the slightest possibility of
experiencing the stimulus
• Response criterion is a persons
individual response bias
• Signal detection theory is used to take
individual’s response criteria into
account.
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Review Questions
• What are the steps in the perceptual
process?
• How do sensors convert environmental
stimuli to nerve signals?
• What are absolute and difference
thresholds? Give one example each.
• How are thresholds measured?
• Name one thing you can sense at this
moment & your perception of it
https://miro.com/app/board/uXjVMm0nnF4=/?sh
are_link_id=988424602715
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Next week: The
beginnings of
perception
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Announcements
• A Google Sheets link to find
group mates is available on the
course overview.
• Enrol as groups of 4 on eLearn
for report submission.
• Please post all assignmentrelated questions on the eLearn
Discussion Forum. Thank you.
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