that communication has occurred because the female has changed her
motor behavior in response to the male’s call by approaching the source of
the call (phonotaxis). These and similar examples (see Boughman and
Moss, Chapter 4) presuppose that the signal produces an observable or
measurable response in the receiver. Long-term, subtle effects of a signal
on a receiver’s behavior or physiology are equally important but more difficult to unravel. A classic example of how communication signals produce
more subtle changes in the receiver is the pioneering work of Lehrman
(1964) on the reproductive behavior of ring doves (Streptopelia risoria).
During pair-bond formation, both acoustic and visual signals emitted by one
member of the pair effect subsequent hormonal changes in the other. The
behavior of the receiver thus has an important impact on the physiology
of the sender as well as on its behavior. This interplay between the male
and the female emphasizes the interactive and bidirectional nature of
communication. Yamaguchi and Kelley (Chapter 6) provide further examples of these interactive effects in the context of hormonal mediation
of communication.
2.1. Deciphering the Message
Deciphering the messages conveyed by communication sounds can be a difficult task both for the receiver of the signals and for the experimenter. Part
of this difficulty arises from the process of propagation of the sound through
the environment. Both in air (Ryan and Kime, Chapter 5) and underwater
(Bass and Clark, Chapter 2), the process of propagation alters both the
spectral and the temporal characteristics of the signal. The environment can
introduce distortion or noise (either biotic or abiotic) or it can selectively
attenuate or accentuate certain sound frequencies in relation to others. In
either case, the result would be confusion of the message and interference
with the transmission of information. Because of these factors, the structure
of a signal at its source (the sender) is not necessarily identical to its structure at the receiver, so the receiver’s job in deciphering the signal is made
more difficult unless propagation is taken into account during reception.
Subtle variations in signal meaning may be missed by the receiver because
of interference by the environment. Some behavioral and neural strategies
available to the receiver to circumvent these obstacles are discussed by
Ryan and Kime (Chapter 5) and by Gentner and Margoliash (Chapter 7).
Examination of the physical acoustics of transmission has led to two fundamental insights into the function of acoustic communication systems. As
pointed out in a classic and highly influential paper by Marler (1955), the
structural features of acoustic signals, reflecting the physics of sound transmission, can provide many clues about their functions. For example, mating
or advertisement calls usually contain frequencies that can be localized
easily, whereas certain kinds of alarm calls contain frequencies that can be
localized only with great difficulty. Signals used for species recognition are
6
A.M. Simmons
motor behavior in response to the male’s call by approaching the source of
the call (phonotaxis). These and similar examples (see Boughman and
Moss, Chapter 4) presuppose that the signal produces an observable or
measurable response in the receiver. Long-term, subtle effects of a signal
on a receiver’s behavior or physiology are equally important but more difficult to unravel. A classic example of how communication signals produce
more subtle changes in the receiver is the pioneering work of Lehrman
(1964) on the reproductive behavior of ring doves (Streptopelia risoria).
During pair-bond formation, both acoustic and visual signals emitted by one
member of the pair effect subsequent hormonal changes in the other. The
behavior of the receiver thus has an important impact on the physiology
of the sender as well as on its behavior. This interplay between the male
and the female emphasizes the interactive and bidirectional nature of
communication. Yamaguchi and Kelley (Chapter 6) provide further examples of these interactive effects in the context of hormonal mediation
of communication.
2.1. Deciphering the Message
Deciphering the messages conveyed by communication sounds can be a difficult task both for the receiver of the signals and for the experimenter. Part
of this difficulty arises from the process of propagation of the sound through
the environment. Both in air (Ryan and Kime, Chapter 5) and underwater
(Bass and Clark, Chapter 2), the process of propagation alters both the
spectral and the temporal characteristics of the signal. The environment can
introduce distortion or noise (either biotic or abiotic) or it can selectively
attenuate or accentuate certain sound frequencies in relation to others. In
either case, the result would be confusion of the message and interference
with the transmission of information. Because of these factors, the structure
of a signal at its source (the sender) is not necessarily identical to its structure at the receiver, so the receiver’s job in deciphering the signal is made
more difficult unless propagation is taken into account during reception.
Subtle variations in signal meaning may be missed by the receiver because
of interference by the environment. Some behavioral and neural strategies
available to the receiver to circumvent these obstacles are discussed by
Ryan and Kime (Chapter 5) and by Gentner and Margoliash (Chapter 7).
Examination of the physical acoustics of transmission has led to two fundamental insights into the function of acoustic communication systems. As
pointed out in a classic and highly influential paper by Marler (1955), the
structural features of acoustic signals, reflecting the physics of sound transmission, can provide many clues about their functions. For example, mating
or advertisement calls usually contain frequencies that can be localized
easily, whereas certain kinds of alarm calls contain frequencies that can be
localized only with great difficulty. Signals used for species recognition are
6
A.M. Simmons