"The smallest indivisible human unit is two people, not one," wrote Pulitzer Prize-winner Tony Kushner, and Professor Eshkol Rafaeli and his team at the Affect and Relationships Lab at Bar-Ilan University have taken that to heart. Funded by the Hope Optimism initiative, they have been investigating how hope functions in a couple—or a 'dyad', the most romantic term of all—especially as a dyad becomes a triad. Their research focuses on the emotional and mental health of couples having their first child, as it's a major life transition. So does hope fluctuate? Is it contagious? Must both be hopeful, or is one optimist enough to carry everyone through? Here, Rafaeli discusses his team's findings, and future work. This video was filmed as part of the Los Angeles Hope Festival, a collaboration between Big Think and Hope Optimism.