Phil 3318: Philosophy of Science Observation Case Studies

Places where observation bias 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: Galileo

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

Data Collection and Manipulation

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 characterization of ambiguous phenomena

American 19 th century ‘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: 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 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:

Crania America Categories Malay American Ethiopian Caucasian Mongolian

The Data RaceNMeanLargestSmallest Caucasian Mongolian Malay American Ethiopian

1 st : 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

2 nd : Over-count Caucasians 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 (And Eskimos, if pulled out from the ‘Mongol’ group, get a mean of 86.8)

2 nd : Crania Aegyptiaca Categories Caucasian –Pelasgic –Semitic –Egyptian Negroid Negro

PeopleMean CapacityN Caucasian Pelasgic8821 Semitic825 Egyptian8039 Negroid796 Negro731

Creeping Bais 1: Categorization 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: 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. RaceFemaleMale Caucasian77.2 (22)86.5 (24) Negroid75.5 (4)87.5 (2) Negro73 (1)

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: Subconscious mis- measurement 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 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: Excel File

Summary: Biases creep: 1.Shifting categories 2.Ambiguous measurements will reveal prejudices (artifacts of instruments) 3.Failure to consider alternative hypotheses (I.e. body size / gender) 4.Miscalculations (confirmation bais)