Family matters: How growing up together molds us

When psychologist Darby Saxbe began studying how parenthood shapes the brain, she made a seismic discovery that upended a long-held assumption: that only mothers undergo major biological shifts after a child's birth. Her pioneering research on what's now called "dad brain"—the subject of her forthcoming book, "Dad Brain: The New Science of Fatherhood and How It Shapes Men's Lives"—revealed that fatherhood changes men's brains, too.