Secular Americans’ worst fears have come true: there is now scientific evidence that evangelical churches brainwash believers. They don’t merely teach that Adam and Eve actually existed and that gay marriage is an abomination. They change the way their members’ brains work. But T. M. Luhrmann, a psychological anthropologist at Stanford, argues that this is not as insidious as it sounds. On the contrary, mental conditioning has a noble lineage in the history of religion, and even (or especially) in this modern age, it can help humans flourish. “When God Talks Back” explains how rational people living in the 21st century can believe that God speaks to them — and why the rest of us should take them ­seriously.

Luhrmann did extensive fieldwork in Chicago and Northern California at Vineyard Christian Fellowship, a young “charismatic” denomination that offers a tame, middle-class version of Pentecostal practices that once scandalized most Christians. Members speak in tongues, pray for healing and seek “concrete experiences of God’s realness.” They want “the hot presence of the Holy Spirit to brush their cheeks and knock them sideways.” Some evangelicals frown on the Vineyard’s exuberance, but the denomination has gained outsize influence in evangelical culture, particularly by producing popular worship music. The Vineyard showcases, in amplified form, a style of prayer that has become widespread over the past four dec­ades.

After more than four years of observing and interviewing Vineyard members, and participating in prayer groups, Bible study and weekly worship, Luhrmann arrived at a simple but arresting hypothesis: Evangelicals believe in an intimate God who talks to them personally because their churches coach them in a new theory of mind. In these communities, religious belief is “more like learning to do something than to think something. . . . People train the mind in such a way that they experience part of their mind as the presence of God.” Luhrmann is hardly the first to interpret religious feeling through the lens of psychology. This line of analysis goes back to William James and the German theologian Friedrich Schleiermacher, and today the scientific study of prayer is a growing field. Yet “When God Talks Back” is remarkable for combining creative psychological analysis with a commitment to understanding evangelicals not merely as a scholar’s specimens, but on their own terms. The result is the most insightful study of evangelical religion in many years.

The religious movement that became the Vineyard was born in the 1960s, an era Luhrmann identifies as another “great awakening” when evangelicals’ “interest in the direct personal experience of God exploded.” Her subjects’ spirituality is not as novel as she implies: in the broadest terms, the Vineyard’s emphasis on speaking directly to God and hearing his voice in one’s private thoughts came to America with the Puritans, whose diaries were crammed with pages of self-­interrogation and supplication. Still, her basic point stands: the Vineyard’s conception of God — a confidant who calls on believers to involve him in every aspect of their lives — is a crucial element in an evangelical spirituality that has taken on new power as it has blended with charismatic worship and modern therapeutic culture.