2 Introduction
Communication is defined as optimising the effect of a message on a receiver sent over a channel by a sender at a particular time [3, 4, 6]. This optimisation of altering the receiver’s opinions, beliefs, or actions is also referred to as persuasion. The study of communication or persuasion as a universal human practice is among the most ancient of human concerns. Persuasion has been looked at as the art and science of how we get anything done. Once, it helped our ancestors to plan and execute hunting expeditions, and today, it helps us plan massive projects like the Large Hadron Collider and even inter-planetary expeditions like Europa Clipper.
Persuasion enables making ourselves understood sufficiently well so that we can coordinate our actions. The ability to persuade is not unique to our species. Persuasion is observed in both conspecific [1] and interspecific [2] scenarios. For example, both monkeys and apes yielded episodes indicating they were able to judge very finely how to obtain or hide desirable objects deceptively from the gaze of others [1]. We humans are exceptional in our capacity to cooperate with strangers. Language allowed our ancestors to cooperate, and helped to resolve conflicts by exchanging information, though this includes invented fictions, social constructions, and other imagined realities.
For example, on encountering the explorer James Cook, two Fuegian islanders stepped forward to display and then throw aside large sticks, gestures that Cook interpreted as indicating peaceful intentions. Indeed, the Fuegians and Cook were soon exchanging gifts and eating together on board ship.
4 years were children very competent in recognizing that others’ mental representations of the world could be very different to their own and need to be computed to predict their future actions accurately, as seen most revealingly in the context of deception and false beliefs (Wimmer & Perner 1983).
A second, and no less important, reason involves influencing other Homo sapiens (Mercier & Sperber, 2011). Sloman and Fernbach (2017) assure us of the very real limits of our individual knowledge and its inadequacy for accomplishing many, perhaps most, of the tasks that we face daily.
One of the oldest books on persuasion, called Precepts, written by Ptah-Hotep for the Pharaoh, is 4,500 years old (2375 BCE). Rhetoric — the use of symbols to persuade other humans — began in ancient Greece and its Mediterranean colonies in the fifth century BCE when there were situations of collective decision making that inspired some practitioners to ask how persuading others was best accomplished.
The study of persuasion as a discipline is in its third millennium. It was Plato’s student, Aristotle, who provided the first comprehensive theory of rhetorical discourse. He defined rhetoric in terms of “observing in a given case the available means of Persuasion,” instructing that the “available means” encompassed a range of appeals, some grounded in logic (logos), others in emotion (pathos), and still others in the communicator (ethos). Aristotle urged communicators to base judgments about the most appropriate means of Persuasion on the nature of the audience. His views had long-lasting impact: “Aristotle’s theory of rhetorical discourse has withstood the test of time, furnishing axioms that guide today’s practitioners of Persuasion and campaigns.”
In the West, the tumultuous emergence of democracy in fourth-century BCE Athens gave rise to a class of civic intellectuals teaching persuasive speaking — known as Sophists — to the establishment of rhetoric as a field of study, and to clashes with another new field, philosophy, over explanations of the linguistic features running through belief, knowledge, argumentation, and human conduct. The early modern period was another epoch of intensified interest, with the rise of print, the Reformation, technoscience, and the colonial pursuits of Europe. The middle of the twentieth century was still another, when propaganda studies, argumentation studies, and the New Rhetoric all arose from the trauma of the Second World War.
We are in another such period now. Large Language Models have opened a new chapter in the history of persuasion — one in which the sender of a message may be a machine, the message may be tailored to a single individual at a cost approaching zero, and the channel may be every screen simultaneously. This review documents what we know, what we do not, and what the field must now answer.
“Persuasion is ubiquitous in the political process; it is also the central aim of political interaction. It is literally the stuff of politics.”
— Mutz, Sniderman & Brody, 1996
When people think of persuasion they often think of debates over controversial topics, where distinct individuals and groups invested in different viewpoints confront one another. In these situations, successful persuasion amounts to convincing people to cross over from one side to the other. However, most fully formed persuasive discourse is not aimed at people who disagree anyway; in fact it is usually aimed at people who already agree, but whose agreement can be lessened or intensified.
Persuasion is also aimed at forming beliefs in the first place in people who have no stance on an issue at all. Response shaping is roughly the acquisition of an attitude, whereas response reinforcement can be equated with strengthening a preexisting attitude. By contrast, response changing references movement across the midpoint of an attitude scale.
At both a more subtle and a more powerful level, it has been argued that the Persuasion profession “serves not so much to advertise products as to promote consumption as a way of life” (Lasch, 1978, p. 72). But many of these same marketing techniques are also used to help solve pressing social problems such as improvement of the nation’s health.
In 1985, “Don’t Mess With Texas” bumper stickers began appearing on cars in Texas, beginning the launch of what turned out to be the most successful anti-littering campaign ever conducted in the United States. The campaign, commissioned by the Texas Department of Transportation, targeted young male truck drivers. The advertising team recruited well-known masculine icons — members of the Dallas Cowboys, Willie Nelson, Matthew McConaughey — who looked sternly into the camera as they crushed beer cans and proclaimed the slogan.
The campaign capitalised on Texan pride, reduced litter by 72% in six years, and is now a textbook example of message–audience fit in persuasion.
Charismatic leaders such as Nelson Mandela, Martin Luther King Jr., and Mahatma Gandhi have stirred the masses and brought about radical social change, even when lacking significant institutional power or money. And in 2014, the “Ice Bucket Challenge” persuaded people to donate, ultimately taking in over $115 million, funding groundbreaking ALS research.
People, however, can be remarkably resistant to persuasion. Many well-designed, well-funded efforts to encourage people to practice safe sex, stop using drugs, or improve their diet have failed [5]. People can be stubbornly resistant to changing their minds, even when their health or economic well-being is affected.
2.1 Why This Survey?
The basic difference between the sciences that study persuasion can be characterised as: the how of persuasion vs the what of persuasion. Right now, machine learning is not given a seat at the table where rhetoric and persuasion are discussed. Top academic programmes in rhetoric do not discuss the advances that computers have enabled.
Similarly, in the machine learning field, there has been comparatively little research on persuasion. Further, whatever research there has been has been in the context of optimising content for persuasion. On the other hand, persuasion should be seen as optimising across the source, channel, time, message, and even the audience — the full SCEMA framework.
What makes the study of persuasion interesting and difficult at the same time is that every field has tried to answer the same fundamental question from a different vantage point, accumulating incompatible vocabularies, incommensurable measures, and siloed literatures. This review attempts a unification.
2.2 Early Beginnings
- Language itself is believed to have developed largely because of the need for cooperation — therefore, persuasion is coextensive with sociality.
- Aristotle’s Rhetoric (4th c. BCE) remains the founding document of the field.
- Mythology is an artefact of persuasion: narratives that mobilise groups around shared values.
- Linguistic devices — tropes, metaphors, humour — are the micro-mechanisms through which persuasion operates.
2.3 Common Misconceptions and Ethical Challenges
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