Sensation and Perception
Lecture 1: Ch1 Foundations, Psychophysics, 13-11-2024
Perception is fundamental to our life → “Man is the measure of all things: of things which
are, that they are, and of things which are not, that they are not.”
In order to survive and reproduce, organisms must respond to physical conditions of their
environment.
Sensation: converting physical features of the environment into electrochemical signals
within specialized nerve cells, and sending those signals to the brain for processing
Perception: the initial sensory signals are used to form a mental representation. It also
includes conscious awareness of the objects and events in a scene.
Some knowledge is innate, complex task require knowledge obtained via multiple senses at
the same time. The starting point for perception is the world itself (distal stimulus), which
gives rise to physical phenomena that can be sensed (proximal stimulus).
- Distal stimulus: something that can be observed (a dog, a text message, etc.)
- Proximal stimulus: how it is observed (light entering the eyes, sound entering the
ears, pressure against the skin)
The specialized neurons that convert proximal stimuli into neural signals are called sensory
receptors. The neural signals are sent to the brain. Often, the speed and accuracy of
perception are enhanced by the perceiver's knowledge about the current scene and by the
expectations about what kind of things are likely to be present or to occur.
- Top-down information: we use our background knowledge and expectations to
interpret what we see
- Bottom-up information: we allow the stimulus itself to shape our perception, without
any preconceived ideas
There are 5 primary senses: vision, audition, touch, smell, and taste. These senses can be
broken down into physical- and perceptual dimensions.
Just like traits, senses have evolved by natural selection as well
Psychophysics investigates the relationship between stimuli and experience in two ways:
1. Investigating the thresholds of perceptual experience: the points at which there are
perceptual transitions
o How intense must a physical stimulus be for the stimulus to be detectable?
o How different must two stimuli be for the difference to be detectable?
2. Investigating the scaling of perceptual experience: how perceptual experience
changes with changes in the physical characteristics of a perceptible stimulus
,Absolute threshold: the minimum intensity of a physical stimulus that can be detected. This
can be tested in 3 ways:
1. Method of adjustment: the observer or the researcher continuously adjusts the
stimulus until they can or cannot perceive it
2. Method of constant stimuli: participant is repeatedly presented with a fixed set of
stimuli in random order, covering a range of intensities, and the participant must
indicate whether or not each stimulus was detected. Stimuli with each intensity are
presented many times, and the frequency of “yes” responses is plotted for each
intensity.
o This results in a psychometric function: As the intensity of the tone increases,
so does the frequency of “yes” responses resulting in a S-shaped curve.
3. Staircase method: participant is presented with a stimulus and indicates whether it
was detected, and based on that response, the next stimulus is either one step up or
one step down in intensity.
Difference threshold (or JND (Just Noticable
Difference): the minimum difference between two
stimuli that allows an observer to perceive that the
two stimuli are different.
Weber’s Law: The size of the JND increases as the
intensity of the standard stimulus (or background)
increases. The perception of change in the intensity
of the stimulus depends on the original strength of
the stimulus. If the original stimulus is of higher
intensity you need a greater additional change of stimulus to perceive the change
Psychophysical Scaling: the process of measuring how changes in stimulus intensity relate to
changes in the perceived intensity. 2 approaches to psychophysical scaling:
1. Fechner’s Law (incorporates Weber’s Law): perceived intensity of a stimulus changes
as its physical intensity changes (S = k ln I/I0), where S is the perceived intensity, k is
the Weber Fraction and ln I/I0 is the natural logarithm of the ratio of the stimulus
intensity, I, to the intensity, I0, of the same stimulus at the absolute threshold.
o Fechner’s law is only correct for some dimentions, usually very high or very
low
2. Steven’s Power Law (discards Weber’s Law): S = k * I^n where S is the perceived
intensity of the stimulus, I is its physical
intensity, and the exponent n is different
for each perceptual dimension (see
table 1.3), and k is a constant that
depends on which units are being used
for S and I.
,Neurons have a cell membrane, nucleus, and a variety of other structures. The cell body
(soma) contains the nucleus. Two prominent types of projections emanate from the cell
body:
1. Dendrites: receive signals from other neurons
2. Axons: conducts signals to the axon terminals, signals are transmitted to other
neurons. A bundle of axons that travel together from one location in the nervous
system to another is called a nerve (or tract).
Action potential: ectrochemical signal that begins in the dendrites of a neuron and travels
down the axon to the axon terminals. The membrane potential is a difference in electrical
potentials across the cell membrane, due to a difference in the concentrations of positive
and negative ions inside and outside the cell. The resting potential is the membrane
potential when a neuron is at rest (about -70mV). The membrane potential can be measured
using single-cell recording.
Ik skip dit deel over neurotransmitters enzo, want is allemaal basis bio kennis
The human brain:
- Cerebral hemispheres: Left and right. Separated by the longitudinal fissure. There are
some important functional differences between them, even though they look the
same (structure is the same).
- Corpus callosum: Major connection between the hemispheres, large bundle of axons.
- Gyrus (gyri): Elongated bump on the surface of the cerebral hemispheres.
- Sulcus (sulci): Indentation between two gyri on the surface of the cerebral
hemispheres.
- Cerebral cortex: Outermost layer of cerebral hemispheres.
- Gray matter: Cell bodies of neurons. Making up the cerebral cortex.
- White matter: Interior parts of the cerebral hemispheres. Myelin-covered axons.
The left and right cerebral cortex are each divided into four lobes: Frontal lobe, Temporal
lobe, Parietal lobe, Occipital lobe.
- Lateral sulcus: separates the temporal lobe from the frontal and parietal lobe
- Central sulcus: separates the frontal and parietal lobe
- Parieto-occipital sulcus: separates parietal and occipital lobe
Thalamus: most important brain area involved in perception. Most neural signals originating
in the sensory organs pass through the thalamus on their way to the cortex
Cognitive psychology: investigates perceptual and cognitive deficits in individuals with brain
damage in order to discover how perception and cognition are carried out in the normal,
undamaged brain.
Modularity: the idea that the human mind and brain consist of a set of distinct modules,
each of which carries out one or more specific functions
Functional neuroimaging sla ik ook over
, Signal Detection Theory: relates to the idea that the intensity of the stimuli and the
psychological and physical state of the person contribute to whether or not the person is
able to detect the stimuli. A participant’s response in each trial of a signal detection
experiment () can be classified as belonging to one of four categories:
1. Hits: you say there is a signal, and there is a signal in reality
2. Correct rejection (CR):you say there is no signal, and in reality also no signal.
3. Miss: you say there is no signal, but in reality there is a signal.
4. False alarm (FA): you say there is a signal, but in reality there is no signal.
Lecture 2: Ch2 Light and the Eyes, 15-11-2024
Nog een keer doornemen, want snap er geen hol van
Light: visible illumination, a type of electromagnetic radiation, corresponding to a small slice
of wavelengths in the middle of the electromagnetic spectrum.
Electromagnetic spectrum: the entire range of wavelengths of electromagnetic radiation.
The wavelengths of light vary from 370-730 nm. Within the range, people with normal vision
perceive differences in wavelength as differences in color. The particles of electromagnetic
radiation are called photons → single particles of light; a photon is the smallest possible
quantity of electromagnetic radiation.
Intensity (or luminance): the amount of light (i.e., the number of photons) reflected from a
surface or emitted by a light source.
Brightness: The perceived intensity of the light reflected by a surface or emitted by a light
source.
Optic array: The spatial pattern of light rays, varying in brightness and color, entering your
eyes from different locations in a scene.
Field of view: the portion of the surrounding space you can see when your eyes are in a
given position in their sockets.
Acuity: a measure of how clearly fine detail is seen. The acuity is greatest near where your
eyes are pointed.
Extraocular muscles: three pairs of muscles around each eye that enable us to move our
eyes very rapidly and accurately and keep the eyes always pointed in the same direction.
The human eye is roughly spherical, with a diameter of about 24 mm. The spherical shape
makes it easy to rotate and move. The optic axis: an imaginary diameter line from the front
to the back of the eye, passing through the center of the lens.
The eye has three membranes:
- Sclera: the outer membrane of the eye; a tough protective covering whose visible
portion is the white of the eye.
Lecture 1: Ch1 Foundations, Psychophysics, 13-11-2024
Perception is fundamental to our life → “Man is the measure of all things: of things which
are, that they are, and of things which are not, that they are not.”
In order to survive and reproduce, organisms must respond to physical conditions of their
environment.
Sensation: converting physical features of the environment into electrochemical signals
within specialized nerve cells, and sending those signals to the brain for processing
Perception: the initial sensory signals are used to form a mental representation. It also
includes conscious awareness of the objects and events in a scene.
Some knowledge is innate, complex task require knowledge obtained via multiple senses at
the same time. The starting point for perception is the world itself (distal stimulus), which
gives rise to physical phenomena that can be sensed (proximal stimulus).
- Distal stimulus: something that can be observed (a dog, a text message, etc.)
- Proximal stimulus: how it is observed (light entering the eyes, sound entering the
ears, pressure against the skin)
The specialized neurons that convert proximal stimuli into neural signals are called sensory
receptors. The neural signals are sent to the brain. Often, the speed and accuracy of
perception are enhanced by the perceiver's knowledge about the current scene and by the
expectations about what kind of things are likely to be present or to occur.
- Top-down information: we use our background knowledge and expectations to
interpret what we see
- Bottom-up information: we allow the stimulus itself to shape our perception, without
any preconceived ideas
There are 5 primary senses: vision, audition, touch, smell, and taste. These senses can be
broken down into physical- and perceptual dimensions.
Just like traits, senses have evolved by natural selection as well
Psychophysics investigates the relationship between stimuli and experience in two ways:
1. Investigating the thresholds of perceptual experience: the points at which there are
perceptual transitions
o How intense must a physical stimulus be for the stimulus to be detectable?
o How different must two stimuli be for the difference to be detectable?
2. Investigating the scaling of perceptual experience: how perceptual experience
changes with changes in the physical characteristics of a perceptible stimulus
,Absolute threshold: the minimum intensity of a physical stimulus that can be detected. This
can be tested in 3 ways:
1. Method of adjustment: the observer or the researcher continuously adjusts the
stimulus until they can or cannot perceive it
2. Method of constant stimuli: participant is repeatedly presented with a fixed set of
stimuli in random order, covering a range of intensities, and the participant must
indicate whether or not each stimulus was detected. Stimuli with each intensity are
presented many times, and the frequency of “yes” responses is plotted for each
intensity.
o This results in a psychometric function: As the intensity of the tone increases,
so does the frequency of “yes” responses resulting in a S-shaped curve.
3. Staircase method: participant is presented with a stimulus and indicates whether it
was detected, and based on that response, the next stimulus is either one step up or
one step down in intensity.
Difference threshold (or JND (Just Noticable
Difference): the minimum difference between two
stimuli that allows an observer to perceive that the
two stimuli are different.
Weber’s Law: The size of the JND increases as the
intensity of the standard stimulus (or background)
increases. The perception of change in the intensity
of the stimulus depends on the original strength of
the stimulus. If the original stimulus is of higher
intensity you need a greater additional change of stimulus to perceive the change
Psychophysical Scaling: the process of measuring how changes in stimulus intensity relate to
changes in the perceived intensity. 2 approaches to psychophysical scaling:
1. Fechner’s Law (incorporates Weber’s Law): perceived intensity of a stimulus changes
as its physical intensity changes (S = k ln I/I0), where S is the perceived intensity, k is
the Weber Fraction and ln I/I0 is the natural logarithm of the ratio of the stimulus
intensity, I, to the intensity, I0, of the same stimulus at the absolute threshold.
o Fechner’s law is only correct for some dimentions, usually very high or very
low
2. Steven’s Power Law (discards Weber’s Law): S = k * I^n where S is the perceived
intensity of the stimulus, I is its physical
intensity, and the exponent n is different
for each perceptual dimension (see
table 1.3), and k is a constant that
depends on which units are being used
for S and I.
,Neurons have a cell membrane, nucleus, and a variety of other structures. The cell body
(soma) contains the nucleus. Two prominent types of projections emanate from the cell
body:
1. Dendrites: receive signals from other neurons
2. Axons: conducts signals to the axon terminals, signals are transmitted to other
neurons. A bundle of axons that travel together from one location in the nervous
system to another is called a nerve (or tract).
Action potential: ectrochemical signal that begins in the dendrites of a neuron and travels
down the axon to the axon terminals. The membrane potential is a difference in electrical
potentials across the cell membrane, due to a difference in the concentrations of positive
and negative ions inside and outside the cell. The resting potential is the membrane
potential when a neuron is at rest (about -70mV). The membrane potential can be measured
using single-cell recording.
Ik skip dit deel over neurotransmitters enzo, want is allemaal basis bio kennis
The human brain:
- Cerebral hemispheres: Left and right. Separated by the longitudinal fissure. There are
some important functional differences between them, even though they look the
same (structure is the same).
- Corpus callosum: Major connection between the hemispheres, large bundle of axons.
- Gyrus (gyri): Elongated bump on the surface of the cerebral hemispheres.
- Sulcus (sulci): Indentation between two gyri on the surface of the cerebral
hemispheres.
- Cerebral cortex: Outermost layer of cerebral hemispheres.
- Gray matter: Cell bodies of neurons. Making up the cerebral cortex.
- White matter: Interior parts of the cerebral hemispheres. Myelin-covered axons.
The left and right cerebral cortex are each divided into four lobes: Frontal lobe, Temporal
lobe, Parietal lobe, Occipital lobe.
- Lateral sulcus: separates the temporal lobe from the frontal and parietal lobe
- Central sulcus: separates the frontal and parietal lobe
- Parieto-occipital sulcus: separates parietal and occipital lobe
Thalamus: most important brain area involved in perception. Most neural signals originating
in the sensory organs pass through the thalamus on their way to the cortex
Cognitive psychology: investigates perceptual and cognitive deficits in individuals with brain
damage in order to discover how perception and cognition are carried out in the normal,
undamaged brain.
Modularity: the idea that the human mind and brain consist of a set of distinct modules,
each of which carries out one or more specific functions
Functional neuroimaging sla ik ook over
, Signal Detection Theory: relates to the idea that the intensity of the stimuli and the
psychological and physical state of the person contribute to whether or not the person is
able to detect the stimuli. A participant’s response in each trial of a signal detection
experiment () can be classified as belonging to one of four categories:
1. Hits: you say there is a signal, and there is a signal in reality
2. Correct rejection (CR):you say there is no signal, and in reality also no signal.
3. Miss: you say there is no signal, but in reality there is a signal.
4. False alarm (FA): you say there is a signal, but in reality there is no signal.
Lecture 2: Ch2 Light and the Eyes, 15-11-2024
Nog een keer doornemen, want snap er geen hol van
Light: visible illumination, a type of electromagnetic radiation, corresponding to a small slice
of wavelengths in the middle of the electromagnetic spectrum.
Electromagnetic spectrum: the entire range of wavelengths of electromagnetic radiation.
The wavelengths of light vary from 370-730 nm. Within the range, people with normal vision
perceive differences in wavelength as differences in color. The particles of electromagnetic
radiation are called photons → single particles of light; a photon is the smallest possible
quantity of electromagnetic radiation.
Intensity (or luminance): the amount of light (i.e., the number of photons) reflected from a
surface or emitted by a light source.
Brightness: The perceived intensity of the light reflected by a surface or emitted by a light
source.
Optic array: The spatial pattern of light rays, varying in brightness and color, entering your
eyes from different locations in a scene.
Field of view: the portion of the surrounding space you can see when your eyes are in a
given position in their sockets.
Acuity: a measure of how clearly fine detail is seen. The acuity is greatest near where your
eyes are pointed.
Extraocular muscles: three pairs of muscles around each eye that enable us to move our
eyes very rapidly and accurately and keep the eyes always pointed in the same direction.
The human eye is roughly spherical, with a diameter of about 24 mm. The spherical shape
makes it easy to rotate and move. The optic axis: an imaginary diameter line from the front
to the back of the eye, passing through the center of the lens.
The eye has three membranes:
- Sclera: the outer membrane of the eye; a tough protective covering whose visible
portion is the white of the eye.
