Identical twins often speak and gesture in unison because they share all their genes, which shape how the brain processes speech and behaviour in similar ways. Growing up together adds to this: close twins mimic each other the way most people unconsciously mirror those close to them. Some identical twins also develop private speech, sometimes called cryptophasia, a set of sounds and gestures outsiders cannot understand. Research estimates about 40% of twins show it, though estimates range from 2% to 47% depending on how it is measured. It usually fades by around age three.

In 1909 D. W. Griffith made a 14-minute film about a speculator who corners the wheat market and doubles the price of bread. A farmer sows his field while a 'Wheat King' gambles in the Chicago wheat pit; bakers raise the loaf from five cents to ten and the poor line up for bread. Griffith cut back and forth between the farm, the feast and the breadline, a technique called parallel editing, so audiences saw both ends of the economy at once. The film drew on Frank Norris's stories and on a real scheme: months earlier Chicago financier James Patten had cornered wheat, sent bread prices up and made about $5 million, roughly $185 million today.