“Once a niche profession more commonly associated with chairs,” product design “is now talked of as a solution to the world’s ills,” Cliff Kuang and Robert Fabricant declare in “User Friendly,” their new book on what’s known as user-experience design. To advocates, it’s a transformative paradigm for everything from bus scheduling to city management. To naysayers, it’s a “boondoggle” (The Chronicle of Higher Education), “b.s.” (Fast Company), or, worse, “fundamentally conservative” (Harvard Business Review).Lay people can now reach their own conclusions more easily. Few previous books have surveyed the history of user-centered design from the origins of American product design as a profession in the 1920s to the latest wearables and beyond. Some applications of design thinking are literally matters of life or death. The many admirers of Donald Norman’s general-interest design books, including his 1988 best seller, recently reissued as “The Design of Everyday Things,” may not realize that he became an activist for usability only after he helped write a report on the 1979 Three Mile Island nuclear accident. As Kuang, a journalist and designer, and Fabricant, a former vice president of creative at the legendary firm Frog Design, explain, that near tragedy resulted not from faulty reactor design or from failures of the plant’s managers, but from the arrangement of the facility’s host of dials and lights, which bore little obvious relationship to the sequence of reactors and boilers they monitored and controlled.Already in World War II, the mathematicians Norbert Wiener and Julian Bigelow understood the importance of feedback: the ability of devices to deliver intelligible information to users. In this case, the men devised an algorithm that converted radar signals about the movement of German bombers into data that would automatically guide antiaircraft guns to the best positions for a likely hit. The psychologist Alphonse Chapanis discovered that the confusing similarity of adjacent controls for wing flaps and landing gear had misled highly competent pilots into crashes. Such controls had to provide easily distinguishable tactile feedback when there was no time to look at the instrument panel. Chapanis’s work resulted in principles still in use: knobs clearly differentiated by function, and controls that responded to users’ intuitions of up and down, right and left. Yet postwar design initially overlooked such lessons in the interest of marketing gimmicks like the 1958 Ford Edsel’s push-button automatic gearshift, perilously situated at the conventional location of the horn in the center of the steering wheel.Not that all wartime insights were lost. Another of the authors’ protagonists, the designer Henry Dreyfuss, reinvented himself and transformed the profession by looking beyond the marketing-driven streamlining of the 1930s — in which he had excelled — to scientific studies of the human body, inspired by his efforts to improve tank seating. Leaving the drawing board, he took the controls of a tank to understand soldiers’ needs. (Empathy, the authors observe, has since been essential to user-experience design.) Dreyfuss soon surpassed the older generation of industrial designers by painstakingly fitting technology to the systematic measurements of real people. His masterpiece was probably the Bell System’s Model 500 telephone. Every detail was optimized based on studies of real fingers, heads and shoulders, and of telephone habits, such as cradling the handset between head and shoulder. Dreyfuss’s specifications worked so naturally that few people thought of the phone as a designed instrument. In fact, the shape of that handset is still the basis of the telephone icon on today’s smartphones.The dawn of personal computing in the 1980s presented a new set of design challenges. Computers introduced metaphor into design as early as 1968, when the computer scientist Douglas Engelbart, of the Stanford Research Institute, unveiled a radical system for organizing electronic work: a user interface combining text and graphics that could be navigated with a pointer controlled by what was later called the mouse, and which could be used to click on links to other pages. This story has been told many times, but the authors put it in a new context as a novel master metaphor: the computer no longer an electronic beast demanding human care and feeding as in the punch-card era but a compact and conscientious personal assistant.The digital era evolved another set of metaphors: “navigation,” from sailing, and “browsing,” from library reading, and introduced the once ubiquitous phrase “information superhighway.” Today we are more likely to think of information as a rapidly flowing river, hence “streaming.” The Amazon Kindle, true to the book metaphor, allows “pages” to be “turned” virtually.For user-centered design, metaphors are not enough. Successful products often give people what they’ve wanted all along without realizing it, rather than what they say they want. The authors invoke the phrase “industrialized empathy” to describe the patient fieldwork required to understand how people use objects and software, and the rounds of prototype testing frequently needed for successful product development. Such industrialized empathy led to the discovery that DVR viewers often wanted dialogue clarified and thus the two-second rewind was born.Empathy creates social dividends. Subway station elevators and cuts in sidewalk curbs benefit not only people with special needs but almost everybody — examples of what’s called “universal design.” Kuang and Fabricant cite the thick-handled OXO peeler, designed to ease the pain of arthritis, which became a best seller among unaffected people. They also observe a Microsoft researcher as he discusses the limitations of the company’s Xbox console with a deaf gamer and concludes that the design could be tweaked in a way that would benefit hearing players as well.User-experience designers have explored other social dimensions of technology: how electronic assistants should interact with owners, for instance, and how hybrid and electric automobiles can encourage energy-efficient driving through gentle feedback. A display in the Ford Fusion depicted multiplying leaves on a vine when drivers optimized behavior, turning energy conservation into a game of greening the dashboard.Kuang and Fabricant also consider design in the context of the now-familiar debates over screen addiction and social media’s effect on politics, but another topic they address may be even more important. The better technology is at automating tasks and anticipating our behavior, they argue, the greater the threat to our own skills, and to the serendipity that can result from delay and deliberation. One of their most intriguing observations involves the contrast they draw from an argument between Douglas Engelbart and Marvin Minsky, a pioneer in artificial intelligence. The former regarded information technology as a tool for extending and augmenting our intelligence, the latter as a system for replacing and improving on human beings. The authors favor Engelbart, but the Minskians, they point out, are still with us, in the form of self-driving car manufacturers, for example, who have recently begun lobbying for the abolition of steering wheels and pedals.On balance, “User Friendly” is a tour de force, an engrossing fusion of scholarly research, professional experience and revelations from intrepid firsthand reporting.The book’s single weakness may be that it shortchanges the history of user-friendly design in this country. Already in the late 18th century, members of the Shaker religious sect used special vises to craft the forerunners of our current flat straight-edged brooms — in the interest of godly cleanliness. Shakers also helped spread another early American folk favorite, the rocking chair, a masterpiece of empathetic design. The superbly balanced American felling ax, celebrated in Walt Whitman’s immortal “Song of the Broad-Axe,” was a favorite of the British prime minister and gentleman woodcutter William Ewart Gladstone. User friendliness is as American as five-minute microwaved apple pie.The greatest challenge for designers may be the unintended consequences of promising ideas. The founders of the e-cigarette company JUUL — graduates of Stanford’s celebrated graduate program in product design — originally aimed to make a safer nicotine alternative for adult smokers. Now they’re confronting a firestorm over the health risks of their product. JUUL’s ease of use, proclaimed in a winning entry to an international design award, paradoxically has become part of the case against it.Finally, new research suggests that user-friendly design can sometimes be too convenient. Harder-to-read fonts promote better learning, according to psychologists who call this paradox “disfluency.” Other studies have shown that the difficult work of taking lecture notes in longhand instead of with laptops forces paraphrase, leading to deeper understanding. Will user tough love become the new user friendliness?