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. 1

Psychics If prediction is right, you believe they are truly psychic If prediction is wrong, shrug it off thinking they can’t be right all the time There’s no way to show that its false to believe in this person’s psychic ability Note: most psychics make such vague predictions that they are always right, their predictions can explain anything 2

The Girl with X-ray Eyes 3 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

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 4

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 5

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. 6

Karl Popper 7 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”

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 8

Freud & Falsifiability 9 Psychodynamic theory failed the falsifiability criterion It explains things after the fact, but does not predict behavior (Tourette’s)

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 10

Confirmation of a Theory 11 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

Its OK to be Wrong! 12 Observation TheoryPredictionTestModify Risky & specific

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 13