Mary Ainsworth and John Bowlby founded modern attachment theory on studies of children and their caregivers. Children and caregivers remained the primary focus of attachment theory for many years. In the 1980s, Sue Johnson began using attachment theory in adult therapy. Cindy Hazan and Phillip Shaver furthered research in attachment theory on adult relationships. Hazan and Shaver noticed that interactions between adults were similar to interactions between children and caregivers. For example, romantic or platonic partners desire to be close to one another, similar to how children desire to be close to their caregivers. Adults feel comforted when their attachments are present and anxious or lonely when they are absent. Romantic relationships, for example, serve as a secure base that help people face the surprises, opportunities, and challenges life presents. Similarities such as these led Hazan and Shaver to extend attachment theory to adult relationships.