In section 2, we noted that Brian Skyrms’ work on signalling systems has made this framework a very natural fit for a quite large range of biological phenomena. As we remarked above, it is very intuitive to see hormones such as insulin, testosterone, and growth hormone as signals, as they are produced in one part of the body, and travel to other parts where they interact with “receptors” in a way that modifies the activities of various other structures. It is routine to describe hormones as “chemical messages”. The Skyrms framework fits these designed cause and response systems within biological agents for three reasons. First, as noted, this framework shows that signalling does not require intelligence or an intelligent grasp of signal meaning.