Phil 3318: Philosophy of Phil 3318: Philosophy of ScienceScience

Observation Case Studies

Places where observation Places where observation bias may creep inbias may creep in

• Artifacts of instruments– Psychological Bias

• Data collection & manipulation– Outright cheating– Confirmation Bias– Categorization of ambiguous

phenomena– Statistical analyses exaggerate

categorization bais

Artifacts of Instruments: Artifacts of Instruments: GalileoGalileo

Theoretical and Psychological Theoretical and Psychological Biases (see what you want to Biases (see what you want to

see)see)

Data Collection and Data Collection and ManipulationManipulation

Outright Cheating:

• Anand and Brobek: What part of the brain controls the desire to eat?– Lesion lateral hypothalamus– Animal stops eating– Conclude: Hunger Center– But, Lesion also severed the Nigro-Striatal

Bundle– Animals also didn’t move.

• Return to this in a few classes

• Strong Claim: Observation Sentences and Observation Terms Cannot Serve as Epistemic Foundations For Theoretical Sentences and Theoretical Terms Because Observations are themselves tinged with Theory

Biases in the Biases in the characterization of characterization of

ambiguous phenomenaambiguous phenomena

American 19American 19thth century century ‘Polygeny’‘Polygeny’

• The hypothesis: the ranking of races according to intelligence can be established objectively by a physical measurement, namely brain size– (for a brilliant discussion, see Stephen

Jay Gould, The Mismeasure of Man).• Samuel George Morton 1830s – 1850s

studied the cranial capacity of a library of skulls categorized by race.

Morton:Morton:

• Obtained a collection of over 600 skulls, mostly of native Americans & published a study Crania Americana in 1839

• Then obtained a collection of mummy skulls from Egypt and published Crania Aegyptiaca in 1844.

• His final work was published in 1849 that compared these data with european skulls.

• Measurement device? – = mustard seed, that is, until it started producing

unfavorable results, then switch to BBs (1/8 inch diameter steel ball).

Egyptians:Egyptians:

Crania AmericaCrania America Categories Categories

• Malay• American• Ethiopian• Caucasian• Mongolian

The DataThe Data

Race N Mean Largest Smallest

Caucasian

52 87 109 75

Mongolian

10 83 93 69

Malay 18 81 89 64

American 144 82 100 60

Ethiopian 29 78 94 65

11stst: Crania America: Crania America

• Morton: mean 82 inches.– Morton divided the ‘American’ skulls into

‘Toltecans’ and ‘Barbarous tribes’. • 82 inches is the average of the ‘Barbarous tribes’.• The real average is 80.2• BUT, Morton’s failed to distinguish other groups =

such as the Incan Peruvians who have an mean of 74.36, BUT make up 25% of the sample.

• Iroquois, on the other hand, contribute only 3 skulls that have a mean near 87.

• Gould corrected the biases and came up with an mean of 83.79

22ndnd: Over-count : Over-count CaucasiansCaucasians

• The 17 ‘Hindu’ skulls, whose mean is 75, were eliminated from the Caucasian sample BUT 3, whose mean was near 87 were admitted. Why?

• Once these are restored, and the samples weighted, the Caucasian mean is 84.45

• (And Eskimos, if pulled out from the ‘Mongol’ group, get a mean of 86.8)

22ndnd: : Crania Aegyptiaca Crania Aegyptiaca CategoriesCategories

• Caucasian– Pelasgic– Semitic– Egyptian

• Negroid• Negro

People Mean Capacity

N

Caucasian

Pelasgic 88 21

Semitic 82 5

Egyptian 80 39

Negroid 79 6

Negro 73 1

Creeping Bais 1: Creeping Bais 1: CategorizationCategorization

• The skulls were from Mummies – so on what grounds is he categorizing & sub-categorizing race?

• “Negroid” is someone he believed was black, but had some ‘caucasian’ blood.

• His subdivision of the Caucasian race is based on, guess what? The bulbous-ness of the forehead. The mean of the entire group is 82.15

Creeping Bias 2: GenderCreeping Bias 2: Gender• Male heads tend to be bigger than female

heads (because male bodies tend to be bigger than female bodies). Since this data is based on mummified remains, we can adjust for gender.

Race Female Male

Caucasian 77.2 (22) 86.5 (24)

Negroid 75.5 (4) 87.5 (2)

Negro 73 (1)

Incidentally…Incidentally…

• There is a great variation in the body size of native Americans. If we rank Morton’s Crania America categories according to typical body size (Seminole largest, Peruvians smallest), we match his cranial capacity ranking exactly.

Creeping Bias 3: Creeping Bias 3: Subconscious mis-Subconscious mis-

measurementmeasurement• Morton published his entire data tables,

including a couple of the tables measured with both seed AND lead shot. The averages were adjusted thus:– 111 Indian skulls: +2.2 inches– 19 Caucasians: +1.8 inches– 18 Africans: +5.4 inches

– The measurement tool most likely to exemplify a priori bias did.

Here are the full Here are the full categories:categories:

• Modern Caucasian Group– Teutonic Family

• Germans• English• Anglo-Americans

– Pelasgic Family– Celtic Family– Indostanic Family– Semitic Family– Nilotic Family

– Malay Group– Malayan Family– Polynesian Family

•Mongolian Group–Chinese Family

•Ancient Caucasian Group–Pelasgic Family–Nilotic Family

•Negro Group–Native African Family–American-born Negros–Hottentot Family–Australians

•American Group–Toltecan Family

•Peruvians•Mexicans

–Barbarous Tribes

And here’s his data:And here’s his data:

• Excel File

Summary: Biases creep:Summary: Biases creep:

1. Shifting categories2. Ambiguous measurements will

reveal prejudices (artifacts of instruments)

3. Failure to consider alternative hypotheses (I.e. body size / gender)

4. Miscalculations (confirmation bais)