PSYC1001 Lecture Notes - Lecture 4: Thomas Kuhn, Sigmund Freud, Subliminal Stimuli
19 May 2018
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Modern history and psychophysics (lecture 4)
• Intermezzo
o Psychophysics - Fechner (sensory systems) and Weber
• The central idea: we are a product of evolution in a physical environment so,
why shouldn't our brain, as a product of this process, not obey physical rules?
• Rules are called the Weber Fraction
• Famous concept - just noticeable difference (smallest difference between
stimuli you can perceive)
o Weber's law
• Ernst Weber 1795
• Just noticeable difference concept
• Weber's law: the change in a stimulus that will be just noticeable is a constant
ratio of the original stimulus
• The problem of demarcation - What is science and what is not?
o The scientific method
• Fact - direct observation
• Theory - an idea of how to explain observation
• Hypothesis - prediction
• Test/experiment - testing in a methodological way
• e.g. Clever Hans the horse, removal of trainer and sight to show horse cannot
do maths
o Subliminal perception
• Stimulus is registered and processed without subject's awareness
• e.g. advertising
o Karl Popper
• Logic of scientific discovery
• 1902
• Falsifiability or refractability - hypothesis tested so potentially can be proven
false
• Good scientists defines theory such that it can be tested
• e.g. can't say all swans are black, but can say "not all swans are black" by
finding just one that is not black
o Sigmund Freud
• Pseudoscience
• Denied
o Thomas Kuhn
• Didn't believe that scientific changes/revolutions work like Popper suggested
• Agreed with Max Planck "a new scientific theory does not triumph by
convincing its opponents and making them see the light, but rather because
its opponents eventually die, and a new generation grows up that is familiar
with it"
• No obvious science/non-science demarcation
• Paradigm shifts
• Old theory and new theory idea
• Often key players in psyc don't change
• As new generation appears, slowly old theory is taken over by a new theory
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