Figure 1
Left: schematic of a specific communication network among 4 zebra finches. In this example, the communication links within two male–female couples are symmetric, but only male A can hear the other couple. In other words, there are links from birds C and D to bird A but there is no link in the reverse direction. Right: this network can be represented as a binary 4-by-4 connection matrix in which the diagonal elements are zero and six off-diagonal elements are one.
