Falsifiability

1
Falsifiability

• One requirement for a valid scientific theory is
  that it satisfies the Falsifiability criterion
• Predictions derived from it could potentially be
  shown to be false.

2
Psychics

• If prediction is right, you believe they are
  truly psychic
• If prediction is wrong, shrug it off thinking
  they cant be right all the time
• Theres no way to show that its false to believe
  in this persons psychic ability
• Note most psychics make such vague predictions
  that they are always right, their predictions can
  explain anything

3
The Girl with X-ray Eyes

• Natasha Demkina
• 17 y/o girl from Russia
• claims to be able to see
• medical illnesses that
• doctors miss
• Mother claims she is 100 accurate
• Makes a pretty good living!
• Tested by Committee for the Scientific
• Investigation of Claims of the Paranormal
• (CSICOP) for a Discovery Channel
• Documentary

4
Testing the Girl with X-ray Eyes

• 7 volunteers, 6 with known medical conditions and
  1 in perfect health
• Given list of ailments, just had to match them to
  the correct person
• Refused use of fabric screen
• Everyone agreed to the criteria Correctly ID 5
  of 7

5
The Girl with Normal Eyes

• She only got 4 right
• Missed the man with the
• metal plate in his skull- thought he
• was the one missing his appendix
• Took 4 hours to complete the test
• Reading on journalist many vague/misread
  symptoms, missed true ailments

6
Martians in your head

• Someone in this class told me that Martians live
  in his head.
• If you X-ray his head and show no Martians, he
  says they're invisible to X-rays.  If you open
  his head up surgically and see no Martians, he
  says they disappear when exposed to oxygen. 
• No matter what test you come up with, you never
  show any evidence of the Martians in his head,
  but that makes no difference.  He always has an
  explanation. 
• His idea about the Martians cannot be falsified
  and therefore is not scientific.

7
Karl Popper

• Developed the idea of
• falsifiability as a criterion
• for scientific research
• the criterion of the
• scientific status of a theory
• is its falsifiability, or
• refutability, or testability

1902 - 1994
8
Violating Falsifiability

• Theories that are so vague they can explain
  anything (ex. Psychic readings P.T. Barnum
  Effect)
• The more specific a theory it is, the more likely
  it is falsifiable (Knocking Rhythms)
• Theories that multiple outs
• Ex. Martians in my head disappear when exposed to
  oxygen

9
Freud Falsifiability

• Psychodynamic theory failed the falsifiability
  criterion
• It explains things after the fact, but does not
  predict behavior (Tourettes)

10
Freud Falsifiability

• Psychoanalytic theorizing of this kind in effect
  leaves no base untouched. Tics are a conversion
  symptom but not hysterical, anal but also erotic,
  volitional but also compulsive, organic but also
  dynamic in origin These papers, because of their
  subsequent widespread influence, had a calamitous
  effect on the understanding and treatment of this
  syndrome
• Psychodynamic theories can explain everything and
  are therefore scientifically useless

11
Confirmation of a Theory

• Not all confirmations are created equal
• More impressive when the confirmation is of a
  risky prediction (30 y/o female vs under 100)
• While replication is important, quality of the
  replication must be considered

12
Its OK to be Wrong!
Risky specific
13
Uncertainty

• Psychological scientists are at the front line of
  uncertainty
• Pro this is where the interesting questions are
• Con makes us look uncertain to the public