PS262 - Introduction to Perception Lecture Notes on
Perception and Sensory Processes 2026|2027 update
Wilfrid Laurier University
PS262
Chapter 1
Introduction: studying perception
- The study of perception is the study of the organs and process that connect us with the
outside world
- The five senses: seeing, hearing, touch taste and smell connect us to our world
- They are the basis of everything we experience
- Senses are out only connection with the environment, our only way to find out what
around us
- The “brain in a vat” idea illustrates the volume and complexity of sensory information we
process
Studying perception is useful
- Sensory interfaces connect us to an expanding world of technology and communications
- Understanding human perception is a key success factor
- The more you know about human perception, the more you can help shape your
communications in ways that are both appealing and useful
Medicine
- If we understand perception, we can design devices to help blind and deaf people
- These medical breakthroughs help us all, since we all may experience injury and the
loss of sensory abilities with age
Technology
- Studying the senses can help us build technology better
- Can make technology more usable to we understand how people will interact with it
using their senses
Civil engineering
- We must also think about the demands on our senses when we design roads and
highways
- Understanding the senses cna help in the design of homes, work spaces and public
environments
,Perception is complicated
- Even the most powerful supercomputers in the world cannot do visual object recognition
as well as human beings
- Our visual object recognition abilities are very advances, we can recognise objects from
different views, in different lighting conditions, and when our view of them are partially
blocked
- Perception is also difficult to study because a variety of cues, not just one help out
system figure things out
- Our sensory systems are good at integrating information to make inferences, to solve
problems
Perception spans several sciences
, - The most difficult aspect of studying perception for beginners is that the field requires
knowledge of several branches of science
What is perception
Do we perceive “the world”?
- This is the big picture
- The word perceive is derives from Per - “thoroughly” and capere - “to seize, to take”
- So to perceive means “to seize what is in front of us”
- We do not actually “seize” what’s in font of us
- We extract useful information from the patterns of environmental energy or samples of
matter that our senses are attuned to
- Perception constructs the world we experience
- Perception organizes sensory data and derives structure from the complex patterns
of energy impinging on our sensory receptors - it deters signals using the sense organs
and infers patterns that are relevant for our survival and reproduction
- Well adapted perceptual systems help us ignore irrelevant input, as well as helping up
perceive useful input
- Perceptual world usefully excludes information that is irrelevant to human survival and
reproduction
Is perception direct?
- Our perceptions are representation of information in “the outside world” based on
signals detected by our sense organs and processed by our brain
- There have to be systematic relations between these representations and the objects
and events in the world around us
How
- The perceptual processing areas of our brain rely on electrochemical signals from
sensory organs
- Our sense organs respond to matter and energy in the environment. But they do not
send environmental matter and energy directly into our brain. They transduce it
Transduction
Is the transformation of one form of energy to another. It combines the idea of
conducting energy with the idea of transforming energy
Sensory transduction
Is how the nervous system converts patterns of physical energy into neural events
Light energy
Falling on the retina is transformed into electrical signals in the visual receptors
- These ideas that we do not perceive the world directly took a long time for people to
realize and accept.
- Was debated in western philosophy until the publication of The Critique of Pure Reason
by Immanuel Kant
, - Kant argues that we never perceive “things in themselves” but on;y things as they
appear to us (phenomena), shaped by our faculties of sensation and understanding
- He argues that did not mean that phenomena are all that exists - things in themselves
must exists because we keep learning things about the world that we didn't know before
- Kant's insight has been called a “COpernican Revolution” in the study of human
subjectivity
- It recentered out understanding of how we perceive the world
Is perception veridical?
- Veridicality means “true-ness”, or accuracy
- No
Reasons
1. Our interpretation of stimuli can vary
- The same image can look different to different people
- Different representation emerge even though the same image is being perceives
- Necker cube is an ambiguous image - demonstrates things about how out perceptual
systems resolve ambiguities and construct representation of objects on sparse data
2. Our brains can create perception that aren’t present physically
- Seen in Hermann Grid - grey dots appear
- The dots are not there but our brain perceives them to be
3. Our perception can be different from the physical stimulus
* VIsion is as accurate as it needs to be
The 7 basic stages of visual processing
- Information from sensory organs is transduced into nervous signals, and the perceptual
areas of our brain construct perceptions using those signals as well as our memories
Step 1
- Light emitted by a source is reflected and refracted form objects
- These interactions modify the direction and frequencies of the light
- Modifications are regular and systematic, following the laws of optics
- Sensation and perception can only operate if environmental energy of some kind
interacts with external objects, and is changed by that interaction
- In the case of vision, light energy carries the information
Step 2
- Light bouncing off objects enters through the pupil of the eye, and is focused by the
lens into optical images on the retina
- We can interact with the light energy in other ways (ie. sun warming up our face)
Step 3
- Light in the retinal image is absorbed by photoreceptor cells, stimulating nerves to
produce signals (transduction”
- These receptor cells contain pigments
Perception and Sensory Processes 2026|2027 update
Wilfrid Laurier University
PS262
Chapter 1
Introduction: studying perception
- The study of perception is the study of the organs and process that connect us with the
outside world
- The five senses: seeing, hearing, touch taste and smell connect us to our world
- They are the basis of everything we experience
- Senses are out only connection with the environment, our only way to find out what
around us
- The “brain in a vat” idea illustrates the volume and complexity of sensory information we
process
Studying perception is useful
- Sensory interfaces connect us to an expanding world of technology and communications
- Understanding human perception is a key success factor
- The more you know about human perception, the more you can help shape your
communications in ways that are both appealing and useful
Medicine
- If we understand perception, we can design devices to help blind and deaf people
- These medical breakthroughs help us all, since we all may experience injury and the
loss of sensory abilities with age
Technology
- Studying the senses can help us build technology better
- Can make technology more usable to we understand how people will interact with it
using their senses
Civil engineering
- We must also think about the demands on our senses when we design roads and
highways
- Understanding the senses cna help in the design of homes, work spaces and public
environments
,Perception is complicated
- Even the most powerful supercomputers in the world cannot do visual object recognition
as well as human beings
- Our visual object recognition abilities are very advances, we can recognise objects from
different views, in different lighting conditions, and when our view of them are partially
blocked
- Perception is also difficult to study because a variety of cues, not just one help out
system figure things out
- Our sensory systems are good at integrating information to make inferences, to solve
problems
Perception spans several sciences
, - The most difficult aspect of studying perception for beginners is that the field requires
knowledge of several branches of science
What is perception
Do we perceive “the world”?
- This is the big picture
- The word perceive is derives from Per - “thoroughly” and capere - “to seize, to take”
- So to perceive means “to seize what is in front of us”
- We do not actually “seize” what’s in font of us
- We extract useful information from the patterns of environmental energy or samples of
matter that our senses are attuned to
- Perception constructs the world we experience
- Perception organizes sensory data and derives structure from the complex patterns
of energy impinging on our sensory receptors - it deters signals using the sense organs
and infers patterns that are relevant for our survival and reproduction
- Well adapted perceptual systems help us ignore irrelevant input, as well as helping up
perceive useful input
- Perceptual world usefully excludes information that is irrelevant to human survival and
reproduction
Is perception direct?
- Our perceptions are representation of information in “the outside world” based on
signals detected by our sense organs and processed by our brain
- There have to be systematic relations between these representations and the objects
and events in the world around us
How
- The perceptual processing areas of our brain rely on electrochemical signals from
sensory organs
- Our sense organs respond to matter and energy in the environment. But they do not
send environmental matter and energy directly into our brain. They transduce it
Transduction
Is the transformation of one form of energy to another. It combines the idea of
conducting energy with the idea of transforming energy
Sensory transduction
Is how the nervous system converts patterns of physical energy into neural events
Light energy
Falling on the retina is transformed into electrical signals in the visual receptors
- These ideas that we do not perceive the world directly took a long time for people to
realize and accept.
- Was debated in western philosophy until the publication of The Critique of Pure Reason
by Immanuel Kant
, - Kant argues that we never perceive “things in themselves” but on;y things as they
appear to us (phenomena), shaped by our faculties of sensation and understanding
- He argues that did not mean that phenomena are all that exists - things in themselves
must exists because we keep learning things about the world that we didn't know before
- Kant's insight has been called a “COpernican Revolution” in the study of human
subjectivity
- It recentered out understanding of how we perceive the world
Is perception veridical?
- Veridicality means “true-ness”, or accuracy
- No
Reasons
1. Our interpretation of stimuli can vary
- The same image can look different to different people
- Different representation emerge even though the same image is being perceives
- Necker cube is an ambiguous image - demonstrates things about how out perceptual
systems resolve ambiguities and construct representation of objects on sparse data
2. Our brains can create perception that aren’t present physically
- Seen in Hermann Grid - grey dots appear
- The dots are not there but our brain perceives them to be
3. Our perception can be different from the physical stimulus
* VIsion is as accurate as it needs to be
The 7 basic stages of visual processing
- Information from sensory organs is transduced into nervous signals, and the perceptual
areas of our brain construct perceptions using those signals as well as our memories
Step 1
- Light emitted by a source is reflected and refracted form objects
- These interactions modify the direction and frequencies of the light
- Modifications are regular and systematic, following the laws of optics
- Sensation and perception can only operate if environmental energy of some kind
interacts with external objects, and is changed by that interaction
- In the case of vision, light energy carries the information
Step 2
- Light bouncing off objects enters through the pupil of the eye, and is focused by the
lens into optical images on the retina
- We can interact with the light energy in other ways (ie. sun warming up our face)
Step 3
- Light in the retinal image is absorbed by photoreceptor cells, stimulating nerves to
produce signals (transduction”
- These receptor cells contain pigments
