Chapter 8

Principles of Communication

1. Animal interactions involving information transfer occur in a variety of contexts. Whether these interactions constitute communication or something else depends on the costs and benefits that senders and receivers incur. Honest signaling occurs when both the sender and the receiver obtain fitness benefits. Deceitful signaling results in costs to the receiver. Eavesdropping results in benefits for the receiver but costs for the sender. Communication includes cases when the sender receives fitness benefits (honest and deceitful signaling).

2. Animal signals are critical to evolved communication systems because they contain information that affects the fitness of senders and receivers. Animal signals evolve via preexisting traits or preexisting biases. Preexisting traits are behavioral, physiological, or morphological characteristics that already provide informative cues to receivers, which can be modified into a signal via a process called ritualization. Preexisting biases are biases in the sensory systems that detect some features of an organism’s world better than others and that can be exploited by sender signals in a process called sensory exploitation.

3. Darwin’s theory of descent with modification tells us that the adaptive traits of an animal living today (including its communication system) are the products of past changes layered on still older changes that occurred during the history of the species.

4. Changes will spread through populations by selection when individuals with the modified signal (or response) gain fitness from their altered behavior. Awareness of this rule helps researchers identify attributes that seem to reduce rather than increase the individual’s fitness, such as a female spotted hyena’s use of a pseudopenis (an enlarged clitoris) in greeting displays with other members of her clan.

5. Honest signals are those that indicate the quality of the sender, facilitate decision making by a receiver, and cannot be easily produced by the sender. Honesty is enforced either because signals are costly to produce or to socially maintain or because of trade-offs between the signal and other communication traits.

6. Deception and eavesdropping reduce the fitness of receivers and senders, respectively. Despite deceptive senders and exploitative eavesdroppers, some evolved communication systems can persist because of the net benefits they provide to legitimate senders and legitimate receivers.