Photo credits

Photographs are historical images from Wikimedia Commons, shown in black and white. Each is used under the license listed.

• 
  Traveling salesman demonstrating a typewriter to a prospect abroad

  National Photo Company Collection, Library of Congress · Public domain · source
• 
  Men at a table negotiating and signing a sales contract for a rotary press, 1958

  Museovirasto (Finnish Heritage Agency) via Finna.fi · CC BY 4.0 · source
• 
  Men at a table negotiating and signing a sales contract for a rotary press, 1958

  Museovirasto (Finnish Heritage Agency) via Finna.fi · CC BY 4.0 · source
• 
  Men in a tense negotiation across a table

  Yrjö Yli-Vakkuri, Museovirasto (Finnish Heritage Agency) via Finna.fi · CC BY 4.0 · source
• 
  Salesperson and customer talking warmly in a clothing shop, 1966

  Kosken Kuvaamo, Lappeenranta museums via Finna.fi · CC BY 4.0 · source
• 
  Interviewer taking notes during a personal interview at a general store, TVA survey

  Lewis Hine, U.S. National Archives and Records Administration · Public domain · source
• 
  Busy telephone switchboard room, operators at work, 1958

  Seattle Municipal Archives · CC BY 2.0 · source
• 
  Crowd listening intently to a speaker

  Sam Hood, State Library of New South Wales · Public domain · source
• 
  Women practicing at rows of typewriters, vocational typing class

  U.S. National Archives and Records Administration · Public domain · source
• 
  Benjamin Franklin, portrait by Joseph-Siffred Duplessis, 1778

  Joseph-Siffred Duplessis, National Portrait Gallery (Smithsonian) · Public domain · source
• 
  Robert Cialdini

  Viktorbuehler · CC BY-SA 3.0 · source
• 
  Daniel Kahneman

  nrkbeta (Flickr) · CC BY-SA 2.0 · source
• 
  Chris Voss, CEO of The Black Swan Group

  80Phoenix · CC BY-SA 3.0 · source
• 
  Richard Thaler

  Chatham House, London · CC BY 2.0 · source
• 
  Carl Rogers, 1947, as president of the American Psychological Association

  American Psychological Association (public submission) · CC0 · source