Teenagers who send and receive six to eight thousand texts a month and spend hours a day on Facebook. Mourners who send text messages during a memorial service because they can’t go an hour without using their BlackBerries. Children who see an authentic Galapagos tortoise at the American Museum of Natural History and can’t understand why the museum didn’t use a robot tortoise instead. High school students who wonder how much they should tilt their Facebook profiles toward what their friends will think is cool, or what college admissions boards might prize.

As Sherry Turkle notes in her perceptive new book, “Alone Together,” these are examples of the ways technology is changing how people relate to one another and construct their own inner lives. She is concerned here not with the political uses of the Internet  as manifested in the current democratic uprisings in Egypt and other countries in the Middle East  but with its psychological side effects.

In two earlier books, Ms. Turkle  a professor of the social studies of science and technology at the Massachusetts Institute of Technology and a clinical psychologist  put considerable emphasis on the plethora of opportunities for exploring identity that computers and networking offer people. In these pages, she takes a considerably darker view, arguing that our new technologies  including e-mail messages, Facebook postings, Skype exchanges, role-playing games, Internet bulletin boards and robots  have made convenience and control a priority while diminishing the expectations we have of other human beings.

Image Sherry Turkle Credit... Erik Jacobs for The New York Times

Ms. Turkle’s thesis here  some of which will sound overly familiar, but some of which turns out to be savvy and insightful  is that even as more and more people are projecting human qualities onto robots (i.e., digital toys like the Furby and computerized companions like the Paro, designed to provide entertainment and comfort to the elderly), we have come to expect less and less from human encounters as mediated by the Net.