The Science of Persuasion: Aristotle's Pillars to the Left-Ear Whisper

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Persuasion is defined as influencing someone's beliefs, attitudes or behavior without coercion, and its playbook goes back to ancient Athens, where trials were held before large assemblies of citizens and were won or lost on the speaker's words alone. Aristotle argued that truth and justice are naturally superior, so if they lose an argument the speaker is to blame, and he broke persuasion into ethos, logos and pathos. Modern psychology asks how that information is digested. The elaboration likelihood model describes a central route of careful, effortful evaluation and a peripheral route that relies on cues like a speaker's attractiveness or confidence. Immanuel Kant condemned rhetoric that bypasses reason as treating the mind like a machine, while scholars William Keith and Christian O. Lundberg call persuasion the civilized alternative to force.

Robert Cialdini mapped the shortcuts the peripheral route follows, including reciprocity, scarcity, social proof, authority and consistency, each traced to evolutionary survival instincts. Leon Festinger's 1957 theory of cognitive dissonance explains how people rewrite their beliefs to match their actions. Defenses exist, from inoculation theory to the folk knowledge described by the 1994 persuasion knowledge model. The final turn is biological: fMRI studies link agreement with the left prefrontal cortex and defensive repression with the right, and messages delivered only to the left ear, which is processed by the right hemisphere, produced higher levels of persuasion.

• In Festinger's 1959 experiment, subjects turned wooden pegs for an hour and were paid $1 or $20 to tell the next person it was fun.
• The $20 group still admitted the task was boring, while the $1 group convinced themselves it had been enjoyable.
• In the Milgram experiments of the 1960s, many participants went to what they believed were lethal shock levels because a researcher told them to continue.
• Inoculation theory holds that hearing a weak version of an argument builds resistance to the full-strength version later.
• Narrative transportation theory finds that people absorbed in a story shift their real-world attitudes toward the narrative.