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CONFIRMATION BIAS. Confirmation Bias: A Ubiquitous Phenomenon in Many Guises Raymond Nicholson, TUFTS Review of General Psychology 50+ pages non-technical 7 full pages of references Francis Bacon (1620) “…great and pernicious predetermination…” Poyla (1954)

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  • Confirmation Bias: A Ubiquitous Phenomenon in Many Guises

    • Raymond Nicholson, TUFTS

    • Review of General Psychology

    • 50+ pages

    • non-technical

    • 7 full pages of references

  • Francis Bacon (1620)

    • “…great and pernicious predetermination…”

  • Poyla (1954)

    • “…scientific thought as distinguished from everyday thought.”


BIAS

Building a Case

**no expectation of impartiality

Treatment and

Evaluation of Evidence

Motivated Bias

Philosophy

Logic

Statistics

Psychology

Impartial Evaluation

Unmotivated Bias

Hempel (1945)

Observed: A white shoe

Concluded: All ravens are black.

Logic: All observed non-black things are non-ravens (the Contrapositive)

Silly? All these insurgents are Muslim…


Incarnations of confirmation bias
Incarnations of Confirmation Bias

  • Evidence interpretation

  • Evidence censoring

  • Restriction of alternative hypotheses

  • Seeking confirmatory evidence

  • Reification – over-estimating the salience of a taxonomy

  • Illusory Correlation

  • Primacy – becoming biased by the beginning of a stream of evidence, early hypothesis building


Wasson 1966
Wasson(1966)

  • Four cards presented. Cards have a number on one side and a letter on the other.

  • Confirm or deny: All vowels have even numbers on the other side.

A

B

4

7

  • Most subjects (~90%) flip “A” and/or “4”

  • People seek to confirm the hypothesis, they do not seek countervailing evidence.


Taylor and smyth 1860 s
Taylor and Smyth (1860’s)

  • Egyptologists and Numerologists, they discover “too strange” relationships in Pyramid dimensions.

    • (2 x base)/height = p

    • base/casing stone = 365

    • height * 109 = distance from earth to sun

    • density of the earth

    • period of the procession of the earth’s axis

    • mean temp of the earth’s surface

  • Conclusion: Space aliens directed the construction of the Pyramids


Einstein and the expanding universe
Einstein and the Expanding Universe

  • Universe assumed static until mid-50’s

  • Expanding universe model could have been discovered by any post-Newton astronomer (S. Hawking, 1988)

  • Einstein actually had evidence of expansion as a by-product of General Relativity, but covered it with his now-infamous Cosmological Constant.

  • Called this the biggest mistake of his career.


Type 1 error
Type 1 Error

  • recall P[type 1] = P[reject Ho|Ho] = a

  • Typical 1-tailed test runs on a = 0.025

  • In 40 independent tests, you EXPECT one false rejection

  • Sequential testing is a great temptation in simulation analysis

  • Ability to make STDERR arbitrarily small means that meaningful indifference zone needs to be determined a priori.


Confirmation bias1
Confirmation Bias

  • Our leaders and customers have it

  • Our families and neighbors have it

  • We have it, but we can protect ourselves


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