New problems for defining animal communication in informational terms

Exactly what makes an interaction between two organisms a case of communication is contentious. Historically, debate has taken place between definitions of communication invoking information transmission vs definitions invoking causal influence. More recently, there has been some convergence on a hybrid definition: invoking (co-adapted) causal influence mediated via the transmission of information. After proposing an understanding of what it means to say that a receiver is causally influenced by the transmission of information, I argue that an information-mediated influence definition overextends to include most, indeed maybe all, co-adapted interactions. This is because the transmission of correlational information is actually a feature of most, if not all, co-adapted interactions. I end by considering whether adding an arbitrariness criterion to an information-mediated influence definition helps. After giving an account of what arbitrariness amounts to, I argue that it swings things too far in the opposite direction: we go from a definition of communication that is too liberal to one that is too restrictive. This is because many signal kinds are not arbitrary. It turns out to be extremely difficult to capture what makes communication unique.