Grappling with different definitions of emotional infidelity can be a challenge for couples, and a mismatch in expectations could threaten a relationship. But it hasn’t always been this way. The concept of emotional fidelity is relatively new – the product of social changes that have shaped what people expect from relationships, beyond basic needs. Today, people generally expect partnership to mean a shared emotional intimacy exclusive to the relationship. And as the digital age creates more ways for us to communicate, understanding which interactions outside the relationship cross the line into dangerous territory has become more difficult than ever.