At the end of the presentation, when the speaker asked for questions, Professor Sigmar Wittig rose and said flatly, ‘Sir, I have been listening to your talk for the past fifteen minutes, and I don’t believe a word that you have said. In two minutes, using the First Law of Thermodynamics, I can prove that everything you have presented is nonsense.’ The speaker turned pale. But I turned paler, because the next day I was to give my presentation, the first of my career, and Professor Wittig was sure to be in attendance. 1

– Karen Thole

The legend goes that in the 1980s a committee of U.S. scientists was assigned to determine which areas of the country would be finalists for the location of a nuclear waste repository. Most of these places under consideration were rural. After carefully considering the local geography and other criteria, the committee made its selections. Before these selections were to be made public, the Department of Energy requested that these scientists go to the various sites, inform the local residents of the decision for that site, and answer questions that the people had.

At the first location, which was in a western state, the scientists held a meeting in a town hall and adopted the old strategy, Tell them what you’re going to tell them; tell them; tell them what you told them. The strategy failed miserably. As soon as the scientists announced the decision that this site was a finalist for the nuclear waste repository, the crowd of ranchers and farmers unleashed a firestorm of questions: Why were we chosen? What will happen to our livestock? What will happen to our crops? How safe will it be to drink the water? The scientists tried as best they could to reassure the audience that their decision in no way would affect the ranching and farming that went on in the area. In fact, this place was chosen for that very reason: The geography of the area was such that the ranching and farming would be able to continue without effect. However, the attempt to pacify the crowd came too late in the presentation. Everyone in the town hall was speaking at once, and many in the crowd had stopped listening to the scientists. The ruckus continued with many in the crowd leaving in disgust and those who remained holding to their position of “not in my back yard.” When the meeting finally concluded and the scientists walked out to their rental car, they saw that someone had dropped a load of manure on top of it.

Clearly, these scientists had not accounted for the bias of their audience.

Understanding the bias of the audience helps you decide both the strategy and the energy required for a successful argument. For instance, solidifying support with an audience that already leans toward your position or is neutral toward your position is not nearly as challenging as garnering support from an audience that is antagonistic to the position. As discussed in Critical Error 1, engineers at Morton Thiokol were able to persuade their management that the launch of the space shuttle Challenger should be delayed until the temperatures were warmer. However, these same arguments made to NASA later in the day did not succeed. The main reason was that the initial bias of NASA against a delay was much stronger than the initial bias of Morton Thiokol’s managers. 2

Sometimes, the initial bias of an audience is the overriding factor in determining the success of a presentation. Contrast the failed one-on-one presentation of Niels Bohr with Winston Churchill in 1944 with the surprisingly successful one-on-one presentation of Edward Teller with President Reagan in 1982. In Bohr’s meeting with Churchill, his purpose was to have Churchill realize the potential nuclear weapons race that Bohr anticipated would follow the Second World War. However, Churchill, who was already defensive about his decision to relinquish intellectual rights to nuclear weapons, ended the meeting after only 20 minutes and asked Bohr to leave. 3 The purpose of Teller’s meeting with Reagan was to persuade him to change the United States nuclear weapons policy of mutually assured destruction to a policy of a strategic defense initiative. Given the resistance in the military to such a change and doubts by other scientists such as Hans Bethe as to the potential of the initiative, such a goal seemed out of reach. However, the receptiveness of Reagan and some of his advisors to an alternative to mutually assured destruction proved to be an ally for Teller. The result of that meeting and a later meeting between Teller and one of Reagan’s advisors led to the dramatic shift in nuclear weapons policy in March 1983. 4

An audience is more likely to believe your argument if they know and appreciate the assertions

In his widely acclaimed book The Uses of Argument, 5 Stephen Toulmin argues that an audience is much more likely to believe your argument if they know and appreciate your assertions. In a scientific talk, these assertions would be your claims, insights, features, and results. Scientists and engineers would do well to heed this advice. However, when you are putting together a presentation, what exactly does following this advice mean?

Perhaps the most important step in following this advice is for you to recognize exactly what it is that you are asserting. In one of his much publicized talks, 6 Hans Rosling shows a graph of life expectancy of people in different countries versus fertility rates of women in those countries. Here, fertility rate was defined as how many children the women typically bear. Figure 3-11 shows the graph for 1962, which was the first year. In the talk, Rosling showed how this graph changes from 1962 until the present. In other words, Rosling had the data for 1962 be replaced by the data for 1963, which was replaced by the date for 1964, and so forth. In the talk, these updates occurred at a quick pace—about 1 year a second. In addition, during these updates, Rosling excitedly called out detail after detail on what was occurring in different countries: for instance, how China moved, how India moved, and so forth.

What unified all these details and what inevitably made this presentation so powerful was that every detail supported Rosling’s main assertion: Since 1960, most under-developed countries have gone from large families and relatively short lives to small families and relatively long lives. For Rosling, the assertion or what he calls the “punch line,” was where the preparation for the presentation began. 7 In other words, before putting together the presentation, Rosling identified the main assertion or result of the data. Then, once he knew what the main assertion was, he was in a position to decide on the best way to graph the data and present the graph to the audience. In his talk, every detail spoken and shown led the audience to understand the main assertion.

A second important step in having the audience understand and appreciate your assertions is making sure that the audience is in a position to accept the assertion. Put another way, some assertions are so high up the mountain that you cannot with a single graph or set of data expect the audience to reach that point of acceptance. What you have to do instead is create a chain of sub-assertions that allow the audience to move high enough up the mountain that they can accept your main assertion.

For instance, suppose that it is the early 1990s and you are making a proposal presentation to the U.S. Department of Transportation for funds to assess new methods to detect ­plastic explosives in airline luggage. A key section of your proposal will be to persuade the audience of the following assertion: New methods are needed to detect plastic explosives in airline luggage. In the proposal presentation, you have to emphasize this assertion. However, the audience is not yet prepared to accept this assertion. Before the audience will accept this assertion, the audience will have to accept two supporting sub-assertions.

  1. (1)

    Plastic explosives placed in baggage pose a threat to airline safety.

  2. (2)

    Current methods for detecting plastic explosives in baggage are ineffective.

If you can persuade the audience of these two sub-assertions, you can bring the audience high enough up the mountain to accept the main assertion. The ascension up this particular mountain is represented in Figure 3-12.

Now to have the audience accept the sub-assertions, you will need evidence. For instance, to have the audience accept the first sub-assertion, you might discuss the tragic example of Pan Am Flight 103 and then present statistics on the number of other aircraft downed in the previous decade by plastic explosives placed in cargo baggage. To have the audience accept the second sub-assertion, you could provide theory showing that a conventional x-ray machine cannot distinguish plastic explosives.

A third step in having your audience understand and appreciate your assertions is to give the audience key pieces of background (what lawyers call warrants). For example, suppose that you wanted the audience to accept the following assertion: An important goal to improve jet engines is to reduce the leading edge vortices on the engine’s turbine blades.

For a general audience to appreciate that assertion, the audience would have to know certain pieces of background information. First, combustion gases that flow over turbine blades are at a temperature significantly higher than the melting temperature of the blades. A second piece of information would be that to prevent the blades from melting, air from the outside is channeled in through holes on the blades to create a protection film from the hot gases. Yet a third piece of background information is that at the leading edge of the blades, vortices from the combustion gases pull away that protective film, exposing the metal to the hot gases. Knowing those three pieces of background information, the audience can appreciate the assertion. The challenge for scientists and engineers is to step away from their work and to look at the assertions as the audience will look at those assertions. Put another way, scientists and engineers have to overcome what the Chip Heath and Dan Heath, in their book Made to Stick, call the Curse of Knowledge—that is, when experts “forget what it is like not to know what [they] know.” 8

Figure 3-11.
figure 00091

Hans Rosling presenting at TED. 9 In the graph, the y-axis is life expectancy, and the x-axis is fertility rate. Each bubble represents a country, with the size of the bubble reflecting the country’s population. Each color represents a different continent. This graph shows the data for 1962.

Figure 3-12.
figure 00092

Mapping of how sub-assertions can help an audience reach a main assertion in a presentation.

An effective argument provides ample evidence for the assertions

To support your assertions, you can incorporate several different types of evidence. According to Aristotle, this evidence falls into three categories: appeals to logic, appeals to the emotion of the audience, and appeals to your own character. If asked which of these categories exerts the greatest influence on them, most engineers and scientists would name appeals to logic. However, the appeals to character and emotion play much more important roles than most scientists and engineers realize. Moreover, many political decisions about science and engineering are not made by engineers and scientists. Rather, politicians make these decisions, and these individuals often are swayed by appeals to character and emotions. For that reason, you should account for the influence of all three appeals.

Appeals to Logic. Logical evidence includes deductive and inductive reasoning, statistics, referenced findings, examples, and analogies. Not all of these have the same level of strength, as suggested by the ranking in Table 3-1. For instance, deductive reasoning and inductive reasoning are the most powerful, while analogies when used to propel arguments usually follow the axiom as being the “weakest form of argument.”

Deductive reasoning often takes the form of a syllogism: Given A and given B, then C follows. A good example of how deductive reasoning influenced a persuasive presentation occurred in the 1980s decision by the United States Congress on where to place a huge particle accelerator, which was named the superconducting supercollider. Because this experiment was to create hundreds of jobs and bring millions of dollars into the local area, more than 43 proposals were submitted for the site. Ellis County, Texas, which won the contract, used deductive reasoning in its arguments. 10 This reasoning followed the premise that the collider site had to meet several criteria, including relatively flat terrain, few freezing days, little seismic activity, and low rainfall. For each of these criteria, some of which are shown in Figure 3-13a, the presenters of the proposal used referenced facts and the opinions of experts to assign a cut-off value. The establishment of these criteria formed the A-portion of the syllogism. Then with a map of the United States, the presenters used overlays as shown in Figure 3-13b to shade those parts of the country that did not meet the stated criteria. This application of the criteria to the map constituted the B-portion of the syllogism. When all the overlays had been placed upon the map, only one small circle in Ellis County, Texas, remained without shading, as shown in Figure 3-13c. That statement became the C-portion of the ­syllogism and the main evidence that contributed to the awarding of the contract.

Table 3-1. Different types of logical evidence in descending order of strength.

Statistics are a form of logical evidence in which the effectiveness varies widely. At the more persuasive end are experimental data that show definite trends. At the weaker end is the comparison of data that are not comparable. For instance, an often quoted statistic concerns the amount of research funding from the National Institutes of Health (NIH) that has gone to fight the AIDS epidemic. In 1998, for example, NIH distributed $2,400 per patient in research funds to fight AIDS, which was the number-17 killer in the country that year, but spent only $108 per patient to fight heart disease, which was by far the number-one killer in the country that year. 15 The statistic suggests that too much money was being spent on fighting AIDS. That assertion might very well be valid, but the statistic does not account for all variables: how recently AIDS was discovered, how quickly the number of deaths from AIDS had risen, the severity of prognosis for AIDS in terms of life expectancy, or how much progress in fighting AIDS those research dollars had produced.

Figure 3-13.
figure 00093

Deductive reasoning used by presenters to show that Ellis County, Texas, was the best site for the superconducting supercollider. 16 The reasoning involved first establishing the site criteria, some of which are listed in (a). Then, as shown in (b), those criteria were applied in overlays to a map of the continental United States. As shown in (c), only one area of the country, Ellis County, satisfied all the criteria.

As with the power of statistics, the power of examples varies dramatically. The power of an example depends upon the assertion that it is to support. For instance, to support the argument that a drug is dangerous, a single example of someone who was harmed by the drug can be powerful. However, to support the argument that a drug is safe, a single example of someone who used the drug with no side effects does not carry much weight.

Although useful for explaining how things work or how large things are, analogies are generally not effective for supporting assertions in an argument. Essentially, analogies show that two dissimilar things, when looked at from one ­perspective, have a common tie. Given this narrow perspective, a skeptical audience can easily point out differences when those things are compared from other perspectives.

Appeals to emotion. While scientists and engineers agree that appeals to logic are important in an argument, scientists and engineers often underestimate the importance of appeals to emotion, especially when the audience making the decision is nontechnical. For instance, greatly influencing the political decision to stop building nuclear power plants in the 1980s was the appeal to the emotion of fear made by antinuclear groups. Although the nuclear power industry countered with logical evidence such as the statistic that coal plants emit far more radiation than the typical nuclear power plant, the appeal to fear by the antinuclear groups had the larger influence.

Numerous examples exist in which appeals to emotion significantly influenced decisions: protecting the habitat of endangered wildlife, protecting wetlands and coasts from oil spills, and increasing the research funds to fight a disease. As mentioned, an interesting case has been the amount of research funding from the National Institutes of Health (NIH) that has gone to fight the AIDS epidemic. Certainly, the relatively recent discovery of AIDS and its rapid increase in cases account for much of this funding, but also contributing have been the emotional and widely publicized appeals for research funding from AIDS activists.

Appeals to character. An appeal to the character of the speaker can have a deep influence in a persuasive presentation. If a relatively unknown scientist suggests that Vitamin C is the most important vitamin for a long and healthy life, that suggestion does not receive nearly as much attention as when Linus Pauling, a Nobel Prize winner, makes the same suggestion. Likewise, when some relatively unknown engineer expresses concern that the size of a neutron bomb could be reduced to the dimensions of a soccer ball (thus making it an extremely dangerous weapon for terrorists), that statement does not carry nearly as much weight as when it is made by Sam Cohen, the inventor of the neutron bomb. 17

Even those of us without such credentials can use this type of appeal effectively, such as when we adopt a position that is counter to our background or history. For instance, Walter Mossberg’s argument a few years ago against a proposed ­operating system for Apple’s Macintosh computer began with the point that he did not relish taking that position. After all, over the years, he had been a staunch Macintosh supporter and was quoted widely in many of Apple’s advertisements. However, he felt that the released operating system demanded too much faith on the part of Macintosh’s users. 18

Character includes your reputation with audiences. Chien-Shiung Wu, the physicist who performed the first experiment showing that nuclear particles violate the law of parity, earned a reputation as a physicist whose work was to be trusted. 19 Such reputations come only after hard work and many tests. When Wu found a result that did not agree with the results of someone else, she did not end her argument by simply showing that her results were correct. She also worked to show why the other results were incorrect.

Character also includes your connection to the audience. As mentioned, Michael Faraday and Ludwig Boltzmann in their talks made personal connections to their audiences. These personal connections were appeals to character that were designed to earn respect. Faraday believed that for a speaker to be effective, the audience must like and trust the speaker. 20 To achieve that respect, Faraday believed that the speaker should first respect the audience. Boltzmann held that same respect for his audience. According to Fritz Hasenöhrl, who was a student of Boltzmann, “[Boltzmann] never exhibited his superiority. Anybody was free to put questions to him and even to criticize him. The conversation took place quietly and the student was treated as a peer. Only later one realized how much he had learned from him.” 21

With an antagonistic audience, building credibility is crucial

In cases in which you desire to win over an audience antagonistic to your position, do not set your expectations too high. As the physicist Max Planck asserted, “An important scientific innovation rarely makes its way by winning over and converting its opponents—it rarely happens that Saul becomes Paul.” 22 Although you might have little success winning over your opponents, using one of the following strategies given in this subsection can help you reduce the opposition to your position and perhaps win over those who are neutral on the subject.

One strategy is to define the question up front, but not to give away your results. If those in the audience who are opposed to your results do not know your position, they are much more likely to listen to your arguments. In essence, if your position is unknown to an audience antagonistic to the results, you have much more credibility than if your position is known. Granted, if the initial bias of the audience is strong, you probably will not change their minds by the presentation’s end, but you are in a much better position to reduce their vehemence against your position. The reason is that they are much more likely to listen to your arguments.

A second strategy, named the Rogerian strategy for the psychologist Carl Rogers, 23 is to show that you truly understand the opposition’s main arguments. In other words, you extend an olive branch to the opposite side by recognizing the strengths of their argument before you begin with a defense of your own. What this olive branch does is to reduce the initial antagonism that the audience has to you and makes them more inclined to listen to your arguments. In essence, this strategy builds your credibility with the audience. Such a strategy works well when the goal is not to win the other side over, but to reach a compromise with the other side.

Notes

1 K.A. Thole, Professor and Department Head, Mechanical and Nuclear Engineering, Pennsylvania State University, private communication to the author (31 July 1991)

2 Report of the Presidential Commission on the Space Shuttle Challenger Accident, vol. 1 (United States Government Printing Office, Washington, D.C., 1996), chap. V

3 R.V. Jones, Bohr and politics, in Niels Bohr: A Centenary Volume, ed. by A.P. French, P.J. Kennedy (Harvard University Press, Cambridge, 1985), p. 285

4 S.A. Blumberg, L.G. Panos, Edward Teller: Giant of the Golden Age of Physics (Charles Scribner’s Sons, New York, 1990), pp. 7–9

5 S.E. Toulmin, The Uses of Argument (Cambridge University Press, New York, 2003)

6 H. Rosling, Debunking Third World Myths with the Best Stats You’ve Ever Seen, www.ted.com/ (ED.com, Monterey, Feb 2006)

7 H. Rosling, Professor of Global Health, Karolinska Institute, Stockholm, phone interview with author (3 Mar 2009)

8 C. Heath, D. Heath, Made to Stick: Why Some Ideas Survive and Others Die (Random House, New York, 2007), p. 46

9 H. Rosling, Debunking Third World Myths with the Best Stats You’ve Ever Seen, www.ted.com/ (TED.com, Monterey, Feb 2006)

10 State of Texas, A Proposed Site for the Superconducting Supercollider (Texas State Railroad Commission, Amarillo, 1985)

11 K.A. Thole, Professor and Department Head, Mechanical and Nuclear Engineering, Pennsylvania State University, private communication to the author (Nov 2001)

12 H. Cohen, F.G. Rogers, H.I. Saravanamuttoo, Gas Turbine Theory, 3rd edn. (Longman Scientific and Technical, New York, 1987), p. 275

13 Space.com, Earthquake Casualties Doubled in 1999 (2000), http://explorezone.com/archives/00_01/31_1999_earthquake.htm, Accessed 31 Jan 2000.

14 Sam Cohen, inventor of the neutron bomb, http://tribune-review.com/ruddy/061597.html, interview with Christopher Ruddy (Pittsburgh Tribune-Review, Los Angeles, 15 July 1997)

15 J. Stossel, Lobbying for our lives, ABC News 20/20 (1999), http://abcnews.go.com/onair/2020/transcripts/. Accessed 11 Oct 1999.

16 State of Texas, A Proposed Site for the Superconducting Supercollider (Texas State Railroad Commission, Amarillo, 1985)

17 S. Cohen, inventor of the neutron bomb, http://tribune-review.com/ruddy/061597.html, interview with Christopher Ruddy (Pittsburgh Tribune-Review, Los Angeles, 15 July 1997)

18 W.S. Mossberg, Sticking with the Mac will require patience and big leap of faith, Wall Street Journal (3 Oct 1998), p. B1

19 S.B. McGrayne, Nobel Prize Women in Science (Citadel Press Book, Secaucus, 1998), p. 269

20 G. Cantor, Michael Faraday: Sandemanian and Scientist (St. Martin’s Press, New York, 1991), pp. 151–152

21 C. Cercignani, Ludwig Boltzmann: The Man Who Trusted Atoms (Oxford University Press, Oxford, 1998), pp. 37–38

22 M.K.E. Planck, Scientific Autobiography and Other Papers (Philosophical Library, New York, 1949)

23 C. Rogers, On Becoming a Person (Houghton, Boston, 1961)