This post is coauthored by Josh Levy, the Manuscript Division’s historian of science and technology, and Jackie Katz, 2022 Albert Einstein Distinguished Educator Fellow. It is one in a series on teaching scientific literacy using primary sources related to pseudoscience.
What’s the difference between science and pseudoscience? The designation of a discipline as a science indicates that it involves the study of observable, natural phenomena that can be better understood through tests that produce consistent and predictable results. The findings of these tests must always be considered tentative. If any of the above tenets are absent, the research is pseudoscientific.
In 1724, Benjamin Franklin was a teenager in London, working at a print shop that made a practice of drying out cases of wet lead type in front of a fire. When it was cold, Franklin started heating up the type that was already dry and using it to warm himself. “But an old Workman observing it,” he later wrote, “advis’d me not to do so, telling me I might lose the Use of my Hands by it.” When Franklin noticed “a kind of obscure pain” growing in the bones of his hand, questioning his coworkers left him unsure whether their central nervous systems were failing because they’d inhaled lead fumes, or eaten their lunches with lead-covered hands. But he knew that lead scared him.
Point your students to the final line in Franklin’s 1786 letter describing his youthful encounters with lead: “You will see by it, that the Opinion of this mischievous Effect from Lead, is at least about Sixty years old; and you will observe with Concern how long a useful Truth may be known, and exist, before it is generally receiv’d and practis’d on.” Ask your students for other examples of “useful truths” that have gone ignored and list them on the board. Then ask the class to consider reasons that useful scientific findings have sometimes failed to change policy or community behavior.
More than a century later, the “mischievous Effect from Lead” was investigated again. In 1923, General Motors and Standard Oil formed the Ethyl Corporation to produce lead fuel additives. By 1924, several industrial poisonings had already caught the attention of the media.
The Ethyl Corporation responded to the controversy, in part, by hiring a promising young physiologist named Robert Kehoe as its medical director.
Kehoe conducted numerous experiments to help industry develop workplace safety procedures, and to create lead exposure guidelines for the general population. Decades later, scientists began to question some of the assumptions behind those experiments.
Ask students to read two short pieces that describe some of Kehoe’s experiments, written 47 years apart. In a newspaper article dated April 1, 1931, students can read about an experiment meant to test the amount of lead in the diet of a typical undergraduate. Ask what assumptions seem to underlie the design of this experiment, and how Kehoe might have designed it differently to produce a different result.
A 1978 issue of the Federal Register detailing new Occupational Health and Safety Administration lead exposure rules critiques another of Kehoe’s experiments, one where subjects were placed inside an experimental chamber with a propane burner to measure their exposure to airborne lead particulates. [See pages 54406-7] Students should again look for assumptions underlying Kehoe’s experimental design. Ask, for instance, how Kehoe might have determined when a subject’s blood lead had reached a dangerous level. Note that Kehoe’s threshold for a safe lead exposure was based on visible signs of poisoning among adult lead workers, and that by the 1960s scientists believed children could be seriously harmed by much lower levels of lead exposure.
Students may have determined that Kehoe’s experiments were poorly designed, that his research was unduly influenced by his relationship with industry, or that he demanded too great a burden of proof for limiting public exposure to lead. Connect to the present day by directing students to locate information about current levels of lead exposure.
Finally, ask students to discuss whether Kehoe’s work was pseudoscience, legitimate science done poorly, or something else. Were Kehoe’s hypotheses testable, or did the design of some experiments prevent him from testing anything of value? Were his conclusions tentative, or did his unwillingness to change his mind in the face of conflicting evidence suggest that his work was becoming pseudoscientific?
Finally, return to Benjamin Franklin’s observation: How can scientists work to produce “useful truths” today, and how can non-scientists help bring them into public dialogue?
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