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Unformatted text preview: November 17, 2009 IB35ac Class 24: The study of head shape & intelligence, Part 1 We'll move into the science of racial variation before 1900 in Europe, and particularly France. Paul Broca was one of the more influential scientists associating brain size and shape with intelligence. We'll focus on him today and take a critical look at his science. IB35 Human Biological Variation Class #24 Phrenology Austrian Franz-Joseph Gall (1758-1828) phrenos = greek for mind Roots of craniometry and anthropometry Popular throughout the 19th century in the US Topic for today:
The study of head shape & intelligence ->Hypothesis stating that the personality traits of a person can be derived from the shape of the skull ->Now considered a pseudoscience Terms Quantitative data Qualitative data Data measured or identified on a numerical scale ->Described items in terms of some quality or categorization that may be 'informal' ->Uses categories that are based on subjective or intangible ideas ->May give rise to quantitative data if they are summarised by means of counts Stephen J. Gould The Mismeasure of Man (1981) Key Terms/Issues
Skull terminology Frankfurt Horizontal Biased orientation of skulls Monogeny, polygeny, evolutionary theory Ernst Haeckel (1834-1919) Cesare Lombroso Atavism and criminality steatopygia Forced sterilization laws in America Buck vs. Bell, Oliver Wendell Holmes "Hottentot Venus", Saarti Baartman ->History and critique of the methods and motivations underlying biological determinism : the belief that "the social and economic differences between human groups--primarily races, classes, and sexes--arise from inherited, inborn distinctions and that society, in this sense, is an accurate reflection of biology 1 The Scientific Study of Race <1900 Monogenism Origin from a single source Upheld the spiritual unity of all peoples in Eden's perfection Races have declined to various degrees Cli t as a cause f racial di ti ti Climate for i l distinction People to Remember Samuel G. Morton (died in 1851) The empiricist of polygeny Crania Americana 1839 Polygenism Held that races were separate biological species Descendants of different "Adams" Implications for "equality of man" Degenerationism Probably the most popular argument b/c scripture wasn't to be discarded lightly ->Certain groups of people were degenerating, going backwards in terms of evolution so each generation became weaker and weaker ->Cesare Lombroso: Degeneration and criminality Summary of Morton's Data
Internal Capacity (in3) Race
Caucasian Mongolian American Ethiopian Critical Mistakes Morton Made Problem with calculated averages Inconsistent in how he applied caution Did not account for body size variation Did not account for sex composition of the samples Brain size is not so tightly correlated with intelligence N
52 10 144 29 Mean
83 Largest Smallest
109 93 100 94 75 69 60 65 87 X 84.45 X 82 83.79 78 From: Gould SJ. 1981. Mismeasure of Man, page 54 After 1859... Evolutionary theory could satisfy both the monogenists and the polygenists Allure of numbers Francis Galton (1822-1911) (1822 1911) Craniometry and anthropometry Remember problems raised with Morton's work Paul Broca (1824-1880) First to apply statistical methods to the study of human differences and inheritance of intelligence, and introduced the use of questionnaires and surveys for collecting data on human communities 2 Region of the brain with functions linked to speech production Broca's Area & Broca's aphasia The motor homunculus ->Damage to Broca's Area ->Impairment of any language modality ->Difficulty in producing or comprehending spoken or written language ->Physical representation of the primary motor cortex ->Portion of the human brain directly responsible for the movement and exchange of sense and motor information (namely touch: sensitivity, cold, heat, pain etc.) of the rest of the body Paul Broca's Other Research Cranial index Women's brains Broca's work Cranial capacity Lead shot (following Morton) Weighed autopsied brains G l "t determine the relative position of Goal: "to d t i th l ti iti f races in the human series" (1878) Assumption that variation is linear and hierarchical Anthropometry became a search for characters that display the correct ranking Search for meaningful traits Ratio of radius to humerus Higher ratio = longer forearm (i.e., ape-like) Blacks = 0.794 Whites = 0 739 0.739 Eskimo = 0.703 (oops) Hottentot Venus = 0.703 (oops!) Cranial Index
maximal breadth of the skull divided by its length Originally proposed change over time by some German
Ratio < 0.75 Ratio > 0.8 Dolicocephalic Brachycephalic How would you interpret these data if you were Broca? ->Broca proposed Africans who possessed Brachycephalic traits were experiencing growth in the back of the head, i.e. primitive senses ->French who demonstrated Brachycephalic traits were Dolicocephalic but experienced growth both in the front and back eventually leading to the former 3 Brain size: men vs. women Broca claimed that men had larger brains than women and that this difference had increased through time. Recorded height & age as well as brain size Modern statistical re-analysis, removing the effects of height &age Factors that influence brain size Body size Cause of death Degenerative disease results in decrease in brain size The women in his sample were considerably older than the men (on average) The men were approximately 6 inches taller than the women Most of the women samples were from those who died from disease leading to smaller brain sizes Franz Boas (1899) CI varies widely within a population CI varies through ontogeny Th There are significant i ifi t differences in CI between immigrant parents and their American-born children (the role of environment) Other Issues to keep in mind: Cesare Lombroso and criminality (atavism) Intelligence testing Wh were key players in testing IQ in Who k l i t ti i America? How did all of this relate to US immigration policy in the 1900s? ->No hierarchy of cultures 4 ...
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This note was uploaded on 01/19/2011 for the course IB 35AC taught by Professor Hlusko during the Spring '08 term at University of California, Berkeley.
- Spring '08