History of Psychology
Modern History
History of Psychology
“Psychology has a long past, but only a short history”
- Hermann Ebbinghaus (1908)
History
• We will discuss the history of Psychology
–
–
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
Cognitive Psychology
Neuroscience
• Then cover key points in the history of psychology
History
• We will discuss the history of Psychology
–
–
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
Cognitive Psychology
Neuroscience
• Then cover key points in the history of psychology
Voluntarism
• Founder: Wilhelm Wundt
• Goals:
– To understand how
Voluntary Action is formed
– To discover the basic
elements of thought
– To discover how the laws
that operate on elements
of thought combine to form
more complex mental
processes
Voluntarism
• Founder: Wilhelm Wundt
• Goals:
– To understand how
Voluntary Action is formed
– To discover the basic
elements of thought
– To discover how the laws
that operate on elements
of thought combine to form
more complex mental
processes
The Thought Meter
• A pendulum (B) was
arranged along a
calibrated scale (M),
and set to ding at points
(d) and (b).
• Wundt would get people
to watch the scale and
note the position of the
pendulum whenever
they heard a ding.
The Thought Meter
• Wundt noted that
people were
consistently 1/10th of a
second off when noting
the position of the
pendulum at the sound
of the ding.
The Thought Meter
• From his experiments, Wundt concluded that
one could either attend to the position of the
pendulum, or to the position of the bell, but
not both at the same time.
• Furthermore, it took approximately 1/10th of a
second to voluntarily change our attentional
focus from one thing to another.
• Much of Wundt’s research focused on
voluntary decisions, hence his paradigm is
called Voluntarism.
Voluntary Action
• Wundt believed that voluntary action (what
we might call choice) was what defined
Psychology as a topic of study.
• Our behaviors are sometimes chosen, not
merely reflexive.
Causation
• Wundt held a unique
perspective.
• He accepted that
causation existed, and the
physical world was lawful.
– e.g., If I line up a row of
dominoes and tip the first,
they will all fall down, fully
obeying the laws of physics.
Causation
• Despite accepting Causality, he argued that mental
events could not be described in terms of causation.
• Why?
– To establish causality, we must be able to:
• 1) Observe an event (cause)
• 2) Observe a second event (effect) that immediately follows
• 3) Rule out all extraneous reasons for the second event occuring
(e.g., a gust a of wind blew the second domino over!)
– However the effects of psychological causes are delayed
(remember the thought meter?).
– This means a mental event never immediately follows its
cause, so we can never be 100% certain which of the previous
possibly infinite mental events was the real cause.
Causation
• The effects of psychological events can be
observed (i.e., we can observe someone
making a choice).
• However, due to the delay between
psychological cause and effect, we cannot
study psychology in terms of causation.
• Despite this, psychological causes can be
introduced and effects can be observed.
Voluntarism
• Founder: Wilhelm Wundt
• Goals:
– To understand how
Voluntary Action is formed
– To discover the basic
elements of thought
– To discover how the laws
that operate on elements
of thought combine to form
more complex mental
processes
Sensations and Feelings
• According to Wundt, sensations and feelings
are the two basic types of mental experiences
• Sensations:
– Can be described in terms of modality (visual,
auditory, tactile, etc)
– And intensity (how bright, how loud, how sharp)
• Feelings:
– Accompany sensations, and describe how
pleasant/unpleasant, excitable/calming,
strained/relaxed the sensation is.
Sensations and Feelings
• Sensations begin psychological events.
• Example from the Thought Meter:
–
–
–
–
–
–
–
A bell vibrates, which causes
The sense of a ding, which causes
Some unknown mental event, which causes
Some unknown mental event, which causes
…
Some unknown mental event, which causes
The choice of the participant to shift attention to
the position of the pendulum.
Introspection
• Wundt utilized experimental introspection to
discover elements of thought.
• Wundt is often misattributed as using pure
introspection in his research. This is wrong!
Pure Introspection
• Pure Introspection
– Relatively unstructured, freeform self-observation
– e.g., “hmm, my stomach is growling. I notice I feel
unhappy. When I think back to other times my
stomach has been growling, I have been unhappy
then too! I wonder if these things are related?”
Experimental Introspection
• Experimental Introspection
– Directed, binary, and replicable
• Example:
– Researcher: “Have you eaten today?”
– Participant: Yes/No
– Researcher: “Do you feel pain in your stomach?”
– Participant: Yes/No
– Researcher 5 days later: “Have you Eaten Today?”
–…
Wundt’s Approach
• Wundt was interested in taking an
Experimental Approach in understanding
Psychology.
• This requires:
– Objective observation (i.e., measured from a
source outside the system generating the
behavior)
– Observations can be repeated on separate
occasions
• Experimental Introspection provides these
things, whereas Pure Introspection does not
Introspection
• Why does the distinction matter?
– Despite believing cause and effect could not be
applied to Psychology, Wundt still believed that
mental processes were lawful (just really
complicated and likely impossible to measure
directly).
– If we are to understand lawful processes, rigorous,
repeatable methods of observation must be
employed.
– Pure introspection, though informative, is not
rigorous and definitely not repeatable!
Misinterpretations
• Psychology gained immense popularity in America
and England during Wundt’s time
• Many students from these countries would move to
Germany to study with Wundt, and then take
professorships at American universities
• Most of Wundt’s students spoke poor German, which
introduced a communication barrier
• They would then be mostly cut off from European
research after moving to America
• This resulted in large misinterpretations of Wundt’s
work during the following years, particularly with what
he meant by “element of thought” and “introspection”
History
• We will discuss the history of Psychology
–
–
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
Cognitive Psychology
Neuroscience
• Then cover key points in the history of psychology
Structuralism
• Founder: Edward Titchener
• Goals
• Problems
Structuralism
• Founder: Edward Titchener
• Goals
– To expand on Wundt’s work
and catalog the basic mental
elements that account for all
of conscious experience
• Problems
Structuralism
• The goal of structuralism was to create a
psychological equivalent of the periodic table
of elements.
• Structuralism wanted to identify the complete
set of basic elements that compose
conscious experience.
• Structuralism approached this task through
introspection
Introspection
• Unlike Wundt who employed empirical
introspection, structuralists used pure
introspection.
• Method:
– Researchers would relax and think of a simple
object, such as an apple, and then reflect on all of
the basic qualities that consciously could not be
reduced to something simpler.
– For example, a researcher might report the
curvature, and the color, of an apple, but not the
fact that it has a stem, since that can be reduced
to a collection of curves.
Structuralism
• Founder: Edward Titchener
• Goals
• Problems
– Lack of Replicability
– Imageless Thought
Structuralism
• Founder: Edward Titchener
• Goals
• Problems
– Lack of Replicability
– Imageless Thought
Lack of Replicability
• One major problem with structuralism was
that its findings were very hard to replicate.
• If two researchers were to sit down and be
asked separately to list the elements of the
same object, they would come up with
different properties.
• Often, this would result in unresolvable
arguments between researchers about who
was correct (if either one was) rather than
any substantial progress being made.
Structuralism
• Founder: Edward Titchener
• Goals
• Problems
– Lack of Replicability
– Imageless Thought
Imageless Thought
• Some thoughts aren’t accompanied by any
definable mental elements
– e.g., If you ask someone to add 10 and 5, most
will quickly respond 15, but be unable to tell you
how that number came to mind
• This was taken to mean there must be more
to psychological experience than
Structuralism’s basic elements
• Structuralism was ultimately viewed as a
dead end.
History
• We will discuss the history of Psychology
–
–
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
Cognitive Psychology
Neuroscience
• Then cover key points in the history of psychology
Functionalism
• Functionalism was largely a reaction to the
failings of Structuralism
• It had many contributors, and because of this
did not have well-defined goals
• However, common themes ran through the work
of functionalist researchers:
– Primarily:
• An interest in “how” and “why” thought is the way it is, rather
than “what” it is composed of
• Pragmatic goals rather than purely academic goals
• An interest in both mind and behavior, not just mind
William James
• Major Contributions:
– Stream of Consciousness
– Pragmatism
William James
• Major Contributions:
– Stream of Consciousness
– Pragmatism
Stream of Consciousness
• James developed a detailed and influential
theory of consciousness
• It was opposed to the Voluntarism and
Structuralist ideas of static “elements”
Stream of Consciousness
• Key Points:
– Consciousness is constantly changing
– Consciousness is selective
– Consciousness is personal
Stream of Consciousness
• Key Points:
– Consciousness is constantly changing
– Consciousness is selective
– Consciousness is personal
Stream of Consciousness
• When we introspect, it becomes quickly
evident that our thoughts are constantly
changing
• There is a continuous ebb and flow to
consciousness, not a series of static
“elements” like the Structuralists and
Voluntarists believed
• Since consciousness is continuous, it cannot
be divided up for analysis
Does this mean we cannot study consciousness? No! Why?
Stream of Consciousness
• Key Points:
– Consciousness is constantly changing
– Consciousness is selective
– Consciousness is personal
Stream of Consciousness
• We are not conscious of everything we could
be conscious of
• Consciousness requires attention
– e.g., writing this, I am aware of my computer in
front of me and my book to the side. My TV plays
on low volume in the background, which I am only
now aware of as I lift my head from the computer
screen. I could have being attention to this earlier,
but instead I chose to focus on writing my slides.
Stream of Consciousness
• Key Points:
– Consciousness is constantly changing
– Consciousness is selective
– Consciousness is personal
Stream of Consciousness
• Consciousness is continuous, thus every
future thought depends on what came before
• Therefore, to understand an individual’s
conscious life, we must know their own
personal idiosyncratic past history
• As such, it is foolhardy to search for elements
common to all minds, as the structuralists did.
Stream of Consciousness
“Consciousness, then, does not appear to
itself chopped up in bits. Such words as
‘chain’ or ‘train’ do not describe it fitly as it
presents itself in the first instance. It is
nothing jointed; it flows. A ‘river’ or a ‘stream’
are the metaphors by which it is most
naturally described. In talking hereafter, let
us call it the stream of thought, of
consciousness, or of subjective life.”
- William James (1890, Vol. 1, p. 239)
William James
• Major Contributions:
– Stream of Consciousness
– Pragmatism
Pragmatism
• Development of Pragmatism:
–
–
–
–
–
James’ upbringing
James’ belief in Materialism
James’ belief in lack of free will
James’ depression that followed
James’ attempt to deal with this depression
Development of Pragmatism
• Trying to deal with his depression, James
(1920) wrote in his diary:
– “I will assume for the present -- until next year -that [free will] is no illusion. My first act of free will
shall be to believe in free will.… Hitherto, when I
have felt like taking a free initiative, like daring to
act originally, without carefully waiting for
contemplation of the external world to determine
all for me, suicide seemed the most manly form to
put my daring into; now I will go a step further with
my will, not only act with it, but believe as well;
believe in my individual reality and creative
power.”
Pragmatism
• Pragmatism is the belief that if an idea works,
it is valid; ideas should only be judged in
terms of their “cash-value”, or what they gain
you.
James’ Approach
• James used the scientific method and philosophical
inquiry to understand psychology
• He recognized that each of these methods was
limited, but in different ways.
– The scientific method was limited in answering ‘big’
questions like “why do we have emotions?”
– Philosophical inquiry is limited in understanding how basic
processes work, like chemical or biological reactions
• James took a pragmatic approach to Psychology:
each method of understanding has its own value, and
we should use whichever has more value for the
question at hand. Neither is better than the other,
simply different.
James’ Late Work
• James believed in Radical Empiricism:
– All consistently reported aspects of human
experience are worthy of study
• This is opposed to Logical Positivism, which
was a dominant belief at the time:
– If a statement cannot be verified as true or false
with empirical data or analytic process (math), it is
meaningless
• James’ views led him to write on many topics
other scientists would not touch, such as
ethics, religion, faith healing, and the
existence of spirits and ghosts!
James’ Late Work
• Much of James’ late work went nowhere.
• However the more important point is that
James’ beliefs led him to the perspective that:
– “our interests should determine the methods we
use”
• Rather than:
– “our available methods should determine what we
are interested in”
• It is this mentality that lead to the
development of modern scientific methods
and theories in Psychology.
Edward Thorndike
• Major Contributions:
– The Law of Effect
The Law of Effect
• Behavior changes because of its
consequences
– A behavior that leads to a satisfying state of affairs
will be more likely to occur again
– A behavior that leads to a dissatisfying state of
affairs will be less likely to occur again
The Law of Effect
• Thorndike demonstrated the Law of Effect in
his research on Cats
– http://www.youtube.com/watch?v=BDujDOLre-8
• This suggested that animals, not just humans,
engaged in complex psychological processes
such as learning and, more importantly, these
processes could be studied empirically.
History
• We will discuss the history of Psychology
–
–
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
Cognitive Psychology
Neuroscience
• Then cover key points in the history of psychology
Behaviorism
• A few events influenced behaviorism’s
emergence:
– Psychologists were frustrated by the lack of
progress on understanding the mind
– Interesting advancements were being made in
animal physiology
– Animals could be taught complex behaviors
without even referring to their ‘minds’
• Behaviorists focused on how the environment
shapes our behavior, and ignored mental
processes
Pre-Behaviorism
• Ivan Pavlov was a
physiologist studying how
the digestive tract worked
• However, his dogs began
producing some
interesting behavior!
Pavlov’s Dog
• Demonstrations:
– http://vimeo.com/5371237
– http://www.youtube.com/watch?v=CpoLxEN54ho
• Key Terms:
– Stimulus: Sensory input from the Environment
– Response: A reflexive action or physiological
change elicited by a stimulus
How are these terms similar to Wundt’s “sensations” and
“voluntary action”? How are they different?
Behaviorism
• John Watson
• Believed behavior was
heavily influenced by
the environment
• Major Contributions:
– Baby Albert
Little Albert
• http://www.youtube.com/watch?v=0FKZAYt77
ZM&feature=related
• Main points:
– Behavior is heavily influenced by the environment
– Learned behavior generalizes to similar
circumstances
Behaviorism
• Burrhus Skinner
• Major Contribution:
– Reinforcement
Reinforcement
• The concept of reinforcement states:
– The consequences of a behavior determine
whether it will be more or less likely to occur again
• Remember Thorndike’s law of Effect?
– A behavior that leads to a satisfying state of affairs
will be more likely to occur again
– A behavior that leads to a dissatisfying state of
affairs will be less likely to occur again
How are these concepts similar? How are they different?
Conditioning
• Humans and other animals can be
conditioned to perform an action more often
by reinforcing it when it occurs
• Pigeons can be taught to turn in a circle:
– http://www.youtube.com/watch?v=TtfQlkGwE2U&f
eature=related
• And even play ping-pong!
– http://www.youtube.com/watch?v=vGazyH6fQQ4
Conditioning Complex
Behavior
• We can’t tell pigeons “go play ping-pong and
I’ll give you a snack!”
– (well we can, but they wouldn’t understand)
• To condition complex behavior:
– First break the behavior into simple steps
• Peck at a ball
• Peck a ball toward another bird
• Peck a ball off a table where another bird is
– Use reinforcement on each step until it has been
fully conditioned, then move to the next step
History
• We will discuss the history of Psychology
–
–
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
Cognitive Psychology
Neuroscience
• Then cover key points in the history of psychology
History
• We will discuss the history of Psychology
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
• We will talk about Gestalt Psychology later
– Psychoanalysis
– Cognitive Psychology
– Neuroscience
• Then cover key points in the history of psychology
History
• We will discuss the history of Psychology
–
–
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
Cognitive Psychology
Neuroscience
• Then cover key points in the history of psychology
History
• We will discuss the history of Psychology
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
• Same with Psycholanalysis
– Cognitive Psychology
– Neuroscience
• Then cover key points in the history of psychology
History
• We will discuss the history of Psychology
–
–
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
Cognitive Psychology
Neuroscience
• Then cover key points in the history of psychology
Read This
• http://penta.ufrgs.br/edu/telelab/2/war-of-t.htm
Cognitive Psychology
• Behaviorism dominated Psychology from
around 1920 - 1950
• However it seemed incapable of a few things:
– It could not explain why some things can be
associated easier than others (e.g., nausea with
food vs. nausea with a light)
– It could not explain processes that commonly
generated unique, unreinforced behaviors such as
never-before-said sentences in language
– It told us nothing about the mind, which many
Psychologists were still deeply interested in
Cognitive Psychology
• Then came a very important invention…
Cognitive Psychology
• Computers could:
– Store information
– Make decisions based on this information
– Distinguish between different shapes and colors
• They seemed like rudimentary minds!
• Best of all, we had easy access to their wiring
and could understand how they produce
mind-like behavior
• Cognitive Psychology was born with the
computer, and focused on treating the mind
as if it were an elaborate computer
Cognitive Psychology
• Early Cognitive Psychologists would:
– Write computer programs
– Observe them producing “thoughtful” behavior
– Describe the rules that the programs followed to
produce the behavior
• They would also:
– Find humans
– Observe them producing “thoughtful” behavior
– Describe possible rules that could be used to
produce this behavior
Cognitive Psychology
• The mind is a series of “rules” that are
followed to produce behavior. The goal of
Cognitive Psychology is to uncover these
rules
Pattern Matching
• Computers can be programmed to perceive
and think about their world. Cognitive
Psychology argues that how they do this may
give insights into how animals do it too:
– http://www.youtube.com/watch?v=bNAnUygqOYc&feature=r
elated
Robots
• It has been observed that placing simple
agents in rich environments can lead to
complex and “intelligent” behavior:
– http://www.youtube.com/watch?v=pPTQ4DcdAeE
&feature=related
– http://www.youtube.com/watch?v=y3W8dm5JxFc
• We sometimes also sympathize with their
“dumb” behavior when it appears lifelike:
– http://www.youtube.com/watch?v=c3s0BjHvRfc&fe
ature=related
Chatterbots
• Chatterbots were an early demonstration of
how detailed conversations could be
constructed from simple syntactic rules.
• Examples:
– http://www.manifestation.com/neurotoys/eliza.php3
– http://www.jabberwacky.com/
– http://www.stanford.edu/group/SHR/4-2/text/dialogues.html
Artificial Intelligence
• As computers are used to do more
complicated things, they make weirder and
weirder errors:
– http://www.youtube.com/watch?v=Y2wQQ-xSE4s
Memory Test
• Try to recall the story you read earlier. Don’t
peek! After you are done, compare and look
for your errors:
• http://penta.ufrgs.br/edu/telelab/2/war-of-t.htm
Memory
• Computers store information, and so do
humans
• How they store and later access this
information is different though
• While it may be useful to try and uncover the
rules that describe how our minds work,
these rules will likely be very different from
the types computers follow to do the same
thing
Human vs. Computer
• It has been observed that the more
“intelligent” we try to make computers, the
less “lifelike” they become
• This may suggest the mental rules we follow
are actually quite simple
Cognitive Psychology
• Cognitive Psychology is an approach that is
still very popular today.
• Most psychologists do not literally think the
mind is like a desktop computer
• However, they do believe the mind can be
described in terms of rules, and we should try
to figure out what these rules are
History
• We will discuss the history of Psychology
–
–
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
Cognitive Psychology
Neuroscience
• Then cover key points in the history of psychology
History
• We will discuss the history of Psychology
–
–
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
Cognitive Psychology
Neuroscience
• Already falling behind! Cutting this section.
• Then cover key points in the history of psychology
History
• We will discuss the history of Psychology
–
–
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
Cognitive Psychology
Neuroscience
• Then cover key points in the history of psychology
History
• We will discuss the history of Psychology
–
–
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
Cognitive Psychology
Neuroscience
• Then cover key points in the history of psychology
– Ancient Greece
– Post-Renaissance
History
• We will discuss the history of Psychology
–
–
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
Cognitive Psychology
Neuroscience
• Then cover key points in the history of psychology
– Ancient Greece
– Post-Renaissance
Plato
• 424-347 B.C.
• Contributions:
– Theory of Forms
Plato
• 424-347 B.C.
• Contributions:
– Theory of Forms
Plato’s Theory of Forms
• There are two worlds:
– The empirical
– The abstract
• The abstract is the set of “pure” ideas
• The empirical is the physical world, and is a
rough approximation of the abstract
• Intellectual pursuits should focus on
understanding the abstract world
Plato’s Theory of Forms
• There are two worlds:
– The empirical
– The abstract
• The abstract is the set of “pure” ideas
• The empirical is the physical world, and is a
rough approximation of the abstract
• Intellectual pursuits should focus on
understanding the abstract world
Empirical vs. Abstract
• The abstract is
defined in terms of
laws that hold
absolutely
• The empirical world
reflects the abstract,
but is not a “pure”
copy
Plato’s Theory of Forms
• There are two worlds:
– The empirical
– The abstract
• The abstract is the set of “pure” ideas
• The empirical is the physical world, and is a
rough approximation of the abstract
• Intellectual pursuits should focus on
understanding the abstract world
Understanding The World
• We should understand the world through
mathematics and reason
• We should ignore the physical world, because
it is impure and misleading
• Objective observation is less valuable than
thought
• How does this relate to:
– Structuralism
– Cognitive Psychology
Aristotle
• 384 - 322 B.C.
• Student of Plato with
very different beliefs!
• Contributions:
– Aristotle’s four causes
Aristotle
• 384 - 322 B.C.
• Student of Plato with
very different beliefs!
• Contributions:
– Aristotle’s four causes
Understanding the World
• Aristotle believes:
– There is only the physical world, and no “abstract”
– The physical world is composed of matter and
motion
– Are senses are trustworthy
– Objective observation is more valuable than
subjective observation
Aristotle
• 384 - 322 B.C.
• Student of Plato with
very different beliefs!
• Contributions:
– Aristotle’s four causes
The Four Causes
• Aristotle says to truly understand something,
we must know its four causes:
–
–
–
–
Material: What is it made of?
Formal: What is its shape?
Efficient: What energy made it take its form?
Final Cause: For what purpose does it exist?
The Four Causes
• What would
Aristotle’s causes for
this statue be?
The Four Causes
• How about for this
tree?
The Four Causes
• What about for this guy?
The Four Causes
• Most Sub-Disciplines in Psychology can be
seen as trying to understand one or two of
Aristotle’s four causes
– Cognitive Psychology
– Functionalism
– Behaviorism
History
• We will discuss the history of Psychology
–
–
–
–
–
–
–
–
Voluntarism
Structuralism
Functionalism
Behaviorism
Gestalt Psychology
Psychoanalysis
Cognitive Psychology
Neuroscience
• Then cover key points in the history of psychology
– Ancient Greece
– Post-Renaissance
The Individual Difference
• 1795, Maskelyne & Assistant Kinnebrook
trying to set a ship’s clock according to when
a particular star crosses a hairline in a
telescope
• Maskelyne notices that Kinnebrook’s
observations are appx. 1/2 sec slower than
his own
• Kinnebrook is warned…
The Individual Difference
• …Kinnebrook tries to correct the issue
• But his errors just become compounded, now
he is 8/10 sec off!
• Kinnebrook relieved of duty because of
“incompetence”
The Individual Difference
• 1815, Friedrich Bessel hears of the
astronomer incident
• Suggests discrepancy is not incompetence
but “individual difference”
• Goes on to demonstrate individuals vary on a
range of basic tasks
The Individual Difference
• Bessel argues that subjective experience is
different from objective reality
• The study of how external stimulation is
converted to mental experience suddenly
becomes very important!
Psychophysics
• Ernst Weber
• Although subjective
experience and objective
reality are different, they
are lawfully related
• Contribution:
– Just Noticeable Difference
Just Noticeable Difference
• With a partner:
– Tell your partner to close their eyes
– Poke each other with 1 vs 2 pencils
– When using 2, vary the spacing between the
pencils
– See how well your partner can distinguish
between being poked with 1 vs 2 pencils
– Be gentle!
– Try on back of hand, palm of hand, finger tips,
forehead (if you trust each other!)
Just Noticeable Difference
• Different body parts have different sensitivity
to pressure