Quiet: The Power of Introverts in a World That Can't Stop Talking

Cain argues that Western institutions, particularly American schools and workplaces, are designed around what she calls the extrovert ideal, and that this wastes the contributions of the roughly one third to one half of people who are introverted. She traces the cultural shift historically, arguing that a nineteenth-century culture of character valuing inner virtue gave way in the early twentieth century to a culture of personality valuing charisma and self-presentation, driven by urbanisation, the rise of large corporations and the sales profession.

The research she draws on includes Jerome Kagan's longitudinal work on high-reactive infants, which found that temperament measured in infancy predicts adult introversion; Elaine Aron on sensory processing sensitivity; and Anders Ericsson's finding that deliberate practice is best done alone, which she uses against open offices and group work.

Her strongest practical arguments concern group work. She reviews the evidence that brainstorming in groups produces fewer and worse ideas than the same people working separately, that open-plan offices reduce productivity and increase stress, and that groups converge on the views of whoever speaks most rather than of whoever knows most. She also covers free trait theory, the argument that people can act out of character in service of goals they care about, and the cost of doing so continuously.

The personality science is contested, since introversion and extroversion are a continuum rather than types and the trait is only one of five in the standard model. Cain selects supportive research and the cultural history is broad. The material on group decision-making and on brainstorming is well supported and directly applicable.