I am interested in the evolution of complexity in communication systems and how this complexity can affect social interaction. This work takes two different approaches. On the one hand I investigate environmental constraints that influence the design of vocal communication systems, and on the other I study the underlying cognitive skills required to overcome or circumvent such constraints. Much of this work concentrates on vocal communication in the bottlenose dolphin (Tursiops truncatus). This species combines the ability of vocal learning with complex cognitive skills that exceed those of most other animals. Furthermore, dolphins rely almost exclusively on acoustic communication which avoids the difficulties connected with studying multi-modal communication systems.