The laughter of tiny babies is endearing, entrancing, and infectious. Powerful enough to reinvigorate even the most weary parent, it is also a fascinating window into what they are learning. Long before they can talk, babies communicate their experience of the world through laughter and tears. Until now, however, psychologists and parenting experts have largely focused on moments of stress and confusion. Dr Caspar Addyman is a developmental psychologist who decided to change that. For six years Caspar has run the Baby Laughter project, collecting data, videos, and stories from parents all over the world. He learned that laughter and smiles are of central importance at the start of life, defining our cognitive and emotional development. Squeals of joy accompany all of a baby's little breakthroughs, connecting them to their nearest and dearest. The Laughing Baby is the culmination of Caspar's research. Moving chronologically through the first two years of infancy, it shows how babies provide the origin story for our incredible abilities, and how understanding them is key to understanding ourselves.