Functional hypotheses about animal signalling often refer to mental states of the sender or the receiver. Mental states are functional categorizations of neurophysiological states. Functional questions about animal signals are intertwined with causal questions. This interrelationship is illustrated in regard to avian distraction displays. In purposive signalling, the sender has a goal of influencing the behavior of the receiver. Purposive signalling is innovative if the sender's goal is unrelated to the biological function of the signal. This may be the case (...) in some instances of false alarm calling. Biological functionalism differs from philosophical functionalism in its concept of identity and in the specification of relevant inputs and outputs. (shrink)