PSYC 212 Lecture Notes - Lecture 2: Immortal Souls, Pineapple, Psychophysics
6 Nov 2018
School
Department
Course
Professor
Psychophysics
Historical introduction
Epistemology - how can we know the world
Plato (428-348 B.C.)
○
Rationalism: we can't trust our senses at all, what matters is the
realm of "ideal forms" that we can only know using our reason
○
Navitism/innatism: we are born already knowing the world
○
Anamnesis (Plato):
Our immortal souls are made of left-overs of a greater
"cosmos-soul" that had universal knowledge
1.
We lost is knowledge when our souls were incarnated in
our imperfect bodies
2.
We must recover this knowledge by trying to "remember"
what we "forgot"
3.
○
Hobbes (1588 -1679)
○
Locke (1632 - 1704)
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Empiricism: knowledge is obtained by means of perceptual
experiences
○
Simple ideas:
Cannot be reduced to, or defined by, anything else (e.g. the
"blueness" of the colour blue)
§
Have to get into the mind by experience (e.g. impossible to
know what a pineapple tastes like if you have never tasted
one)
§
○
Complex ideas: are made from simpler ideas (e.g. "a horse is an
animal that has four legs, it is taller than a man", etc…)
○
Berkeley (1588 - 1679)
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Hume (1632 -1704)
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Idealism: human knowledge is a construction of the mind and
does not necessarily correspond to the external reality
E.g. we perceive the world in 3D but our retina is flat
§
We think that we "observe" causation, but in reality all we
"see" is co-occurrence
§
○
Realism: human knowledge tries to reveal the properties of the
outside world; the truth of knowledge is determined by the
correspondence of the knowledge with the outside world
But we have no "proof" of the external reality
§
Still, we wouldn't advise jumping out of a window to check
whether or not it will kill you
§
○
Immanuel Kant (1724 -1804)
○
Critique of pure reason: attempt to reconcile idealism with
realism
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We may never really know the thing-in-itself (Nomenon)
○
All we can know is the impression that the nomenon exerts on
our senses (Phenomenon)
○
Our minds have to contribute innate knowledge in order to make
sense of our sensations (space, time, cause, and effect)
○
Perception is extremely rich and reliable and allows us to interact
optimally with out environment
○
Such perception could not have arisen in an environment
completely at odds with our sensations (i.e. there has to be an
external reality with objects located in space and time and
interacting with each other in a cause-and-effects manner)
○
•
Thresholds and the dawn of psychophysics
Principia Mathematica (1687): Newton formulates the first laws
of physics
Explains all movements of the universe with three laws and
the postulate of gravitational force
§
1st law (of inertia): an object at rest will remain at rest
unless acted on by an unbalanced force. An object in
motion continues in motion with the same speed and in the
same direction unless acted upon by an unbalanced force
§
2nd law: acceleration is produced when a force acts upon a
mass. The greater the mass (of the object being
accelerated) the greater the amount of force needed (to
accelerate the object)
FORCE = MASS x ACCELERATION
§
3rd law: for every action there is an equal and opposite
reaction
§
○
Can psychology be a science?
Introspection is the main method of investigation
Psychology can be a historical doctrine of nature:
introspection allow us to collect a certain number of
empirical facts about the mind
□
But science requires rational analysis, axioms and
demonstrations
□
A proper science requires the axioms and
demonstrations to be written as a mathematical laws
□
Chemistry isn't a proper science□
§
○
Ernst Heinrich Weber (1795 - 1878)
Just noticeable difference: what is the smallest weight
difference that someone can perceive
§
Weber fractions: the JND between the standard and
comparison weights is always close to 1/40 (or 0.025) of
the standard weight
For other types of stimuli, the fraction is different, but
there is always a fraction
□
Touch 0.04
Taste 0.2
Smell 0.07
Loudness 0.3
Pitch 0.003
Brightness 0.08
Length of lines 0.001
□
§
○
Gustav Theodor Fechner (1801 -1887)
Background in medicine and physics and mathematics
§
Suffered severe eye damage from gazing too much at the
sun while performing his experiments, he then fell into a
deep depression
§
Then Fechner experiences what he believed to be a miracle
when his vision began to recover
§
He became a very spiritual man and was obsessed with the
relationship between mind and matter
§
What is the role of the k variable?
K is related to Weber's fraction. It allows to account
for different slopes of logarithmic functions for
different senses
□
Discriminability: how easy it is to discriminate two
different intensities
□
§
○
Difference threshold: smallest difference you can perceive
○
Absolute threshold: smallest physical intensity you can perceive
The limit at which a stimulus is "detected" vs "not detected"
is not sharp
§
The function has a logistic "S" shape
§
The threshold is defined as the sensory intensity at which a
stimulus is detected 50% of the time
§
○
Why isn't the threshold sharper?
Signal and noise: because what we subjectively perceive
isn't 100% determined by the "signal" present in the
environment, there is also "noise" in the signal
Attention fluctuates□
Criterion for saying "yes" may also fluctuate□
Spontaneous activity in the nervous system□
etc□
§
○
•
Lecture 2
Tuesday, January 9, 2018
1:15 PM
Document Summary
Epistemology - how can we know the world. Rationalism: we can"t trust our senses at all, what matters is the realm of "ideal forms" that we can only know using our reason. Navitism/innatism: we are born already knowing the world. Our immortal souls are made of left-overs of a greater. We lost is knowledge when our souls were incarnated in our imperfect bodies. We must recover this knowledge by trying to "remember" what we "forgot" Empiricism: knowledge is obtained by means of perceptual experiences. Cannot be reduced to, or defined by, anything else (e. g. the. Have to get into the mind by experience (e. g. impossible to know what a pineapple tastes like if you have never tasted one) Complex ideas: are made from simpler ideas (e. g. "a horse is an animal that has four legs, it is taller than a man", etc )
