The GSS survey includes two additional true-or-false science questions that are not included in the index calculation because Americans’ responses appear to reflect factors beyond unfamiliarity with basic elements of science. One of these questions addresses evolution, and the other addresses the origins of the universe. To better understand Americans’ responses, the 2012 GSS replicated an experiment first conducted in 2004 (NSB 2006). Half of the survey respondents were randomly assigned to receive questions focused on information about the natural world (“human beings, as we know them today, developed from earlier species of animals” and “the universe began with a big explosion”). The other half were asked the questions with a preface that focused on conclusions that the scientific community has drawn about the natural world (“according to the theory of evolution, human beings, as we know them today, developed from earlier species of animals” and “according to astronomers, the universe began with a big explosion”).
In 2012, respondents were much more likely to answer both questions correctly if the questions were framed as being about scientific theories or ideas rather than about natural world facts. For evolution, 48% of Americans answered “true” when presented with the statement that human beings evolved from earlier species with no preface, whereas 72% of those who received the preface said “true,” a 24 percentage point difference.14 These results replicate the pattern from 2004, when the percentage answering “true” went from 42% to 74%, a 32 percentage point difference (NSB 2008). For the big bang question, the pattern was very similar: in 2012, 39% of Americans answered “true” when presented with the statement about the origin of the universe without the preface, whereas 60% of those who heard the statement with the preface answered “true.” This represents a 21 percentage point difference. The 2004 experiment found that including the preface increased the percentage who answered correctly from 33% to 62%, a 29 percentage point difference (NSB 2008). Residents of other countries have been more likely than Americans to answer “true” to the evolution question.15
14. Survey items that test factual knowledge sometimes use easily comprehensible language at the cost of scientific precision. This may prompt some highly knowledgeable respondents to believe that the items blur or neglect important distinctions, and in a few cases may lead respondents to answer questions incorrectly. In addition, the items do not reflect the ways that established scientific knowledge evolves as scientists accumulate new evidence. Although the text of the factual knowledge questions may suggest a fixed body of knowledge, it is more accurate to see scientists as making continual, often subtle modifications in how they understand existing data in light of new evidence. When the answer to a factual knowledge question is categorized as “correct,” it means that the answer accords with the current consensusamong knowledgeable scientists and that the weight of scientific evidence clearly supports the answer.15. Although the data clearly show a difference in how respondents answer to different question types, these data do not provide guidance as to what caused the difference. A range of explanations are possible.