Terms Commonly Used in Communication

The technical terms used when discussing the ecology of communication often originated in different subject areas, such as physics and applied mathematics, and the original meaning of some terms has altered. The meanings of terms listed below reflect their current use.

Transmission Medium

The transmission medium conveys the signal from the signaler to the receiver and, depending on the specific signal, can be air, water, or solid objects. For example, the transmission medium for frog calls and firefly flashes is air, whereas for whale song it is water.

Signal Modality

The signal modality (or channel) refers to the sense used to detect the signal. We are most familiar with senses of hearing, vision, and smell/taste. Three less common modalities use the vibration detection sense, the sense of touch, and the electrical sense. Some signals are referred

Figure 1 A schematic representation of some possible patterns of signaling and receiving in a communication network. In the center of the figure, two males (distinguished from females by crest and longer tails) are involved in a signaling interaction (paired arrowed lines), that is, have signaling and receiving roles (S/R). The male on the right is also signaling to a female receiver (R, toward bottom left of figure) and another female (center bottom) is intercepting (dotted line) this signal (interceptive eavesdropping, E|). A third female (toward bottom right) is social eavesdropping (ES) on the interaction between the central males (dot and dash line), as is a male (toward top left). The central male on the left is also signaling to a male receiver (toward top right) and a predatory species (top left) is intercepting the signal.

Figure 1 A schematic representation of some possible patterns of signaling and receiving in a communication network. In the center of the figure, two males (distinguished from females by crest and longer tails) are involved in a signaling interaction (paired arrowed lines), that is, have signaling and receiving roles (S/R). The male on the right is also signaling to a female receiver (R, toward bottom left of figure) and another female (center bottom) is intercepting (dotted line) this signal (interceptive eavesdropping, E|). A third female (toward bottom right) is social eavesdropping (ES) on the interaction between the central males (dot and dash line), as is a male (toward top left). The central male on the left is also signaling to a male receiver (toward top right) and a predatory species (top left) is intercepting the signal.

to as multimodal because more than one sense is required to receive them.

Visual signals most commonly utilize reflected light, as few species are capable of generating light for signaling. Movement is often a feature of visual signals, for example, the claw waving display of fiddler crabs. Acoustic signals encode information in pressure differences of the transmission medium (i.e., air or water) and at extremely close range by displacement of the medium itself. Chemical signals use the sense of smell/taste and differ from other modalities in that they can persist in the absence of the signaler (e.g., scent-marked vegetation).

Seismic (vibration) signals transmit information through the substrate; an example is the foot-stamping signal used by rabbits. Tactile (touch) signals require the signaler and receiver to be in physical contact. Electrical signals are used by two taxonomic groups of freshwater fishes with a well-developed ability to detect electric fields and also organs specialized to generate electricity.

Each of these six modalities differs in transmission speed, persistence, inherent directionality, and the effect obstacles have on them. These differences strongly influence the form of signals used in different contexts and also how the environment affects signals during transmission.

We tend to consider humans good receivers of visual and acoustic signals; however, some animal signals in these modalities are outside of our perceptual range. Acoustic examples include the infrasonic rumbles of elephants and ultrasonic calls of bats; visual examples include the ultraviolet coloration of butterflies and the flashes of infrared light produced by some deep-sea fish.

Information

Information is a fundamental concept to communication because all communication involves information (however, not everything involving information is communication). Confusingly, information is used in two senses in the communication literature. In the everyday sense it means knowledge, but in a technical sense (derived from information theory) it means the reduction in a receiver's uncertainty following reception of a signal. (Uncertainty, H, is calculated by the Shannon-Weaver (or Shannon-Weiner) function: H =—^p; log2p; where i is the number of possible behavior patterns and pi is the probability that the ith will occur.) Often authors fail to mention which of the two meanings of information they are using. Where they do, information in the everyday sense is sometimes referred to as semantic information and information meaning reduction in uncertainty is referred to as statistical information. Information will be used in the everyday sense in this article.

Semiotics

Semiotics is the study of signs and symbols, with communication often considered under the heading of biosemiotics; it is dealt with elsewhere in this encyclopedia (see Abiotic and Biotic Diversity in the Biosphere).

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