Inside of a Dog_ What Dogs See, Smell, and Know - Alexandra Horowitz [44]
Still, of the sounds dogs make, barks come closest to speech sounds. The dog's bark is, like the phonemes of speech, produced by vibrations in the vocal folds and air flowing along the folds and through the mouth cavity. Perhaps because they are in overlapping frequencies—from 10 hertz to 2 kilohertz—with the sounds of speech, we are inclined to look for speechlike meaning in them. We even name the bark using phonemes from our language: the dog "woofs," "rufs," "arfs," or (although no dog I know says it) "bow-wows." The French hear the dog "ouah-ouah"; Norwegian dogs voff-voff; Italian dogs go bau-bau.
Some ethologists think that barking is not fundamentally communicating anything, though: that it is "ambiguous" and "meaningless." This view is encouraged by the difficulty of deciphering what the meaning of the barks could be, since sometimes dogs bark without an obvious prompt or audience, or continue to bark long after any message therein would have been conveyed. Think of the dog barking continuously, dozens of times in a row, in front of another dog: If there is meaning in that bark, would not one or two repetitions do to convey it?
This strikes at the heart of the trouble in determining the subjective experience of an animal of which you cannot ask questions. Each moment of an animal's behavior is scrutinized for its meaning. Surely few human actions could bear such scrutiny and yield a correct assessment of the human. If you were to videotape me practicing, at home in front of my dog, a speech I am to deliver later in the day, you might well conclude that (a) I believe the dog can understand what I'm saying, or
(b) I am talking to myself. In either case, (c) holds: the noises I am making appear not to be classically communicative—for I do not have an audience who can understand me. Similarly, examples of poor communication by a dog may seem to undermine the notion that dogs communicate at all. But most researchers think that barks do have meaning, albeit one dependent on the context and even on the individual. Barking, especially alarm barking, is one of the clearest distinctions between dogs and other canid species. Wolves bark to convey alarm, but rarely, and they make more of a "woof" sound than anything like the protracted dog barking with which we are familiar. Dogs do not just bark more than wolves; they have developed numerous variations on the theme.
There are a handful of distinguishable barks, used reliably in a handful of distinguishable cases. Dogs bark to get attention, to warn of danger, in fear, as a greeting, in play, or even out of loneliness, anxiety, confusion, distress, or discomfort. The meaning is in the context of their use, but not only in the context: spectrograms of dog barks show that they are mixtures of the tones used in growls, in whimpers, and in yelps. By altering the prevalence of one tone over the others, the bark takes on a different character—a different gist.
Early research into dogs' vocalizations concluded that all dog barking was attention-getting barking. In fact they do attract attention, assuming someone is close enough to hear them. But recent studies have made more subtle discriminations between barks. While in some way all barks come down to some manner of "attention-getting," one might as well say that we speak in order to be heard: true, but incomplete. For instance, when experimenters analyzed the spectrograms of thousands of dog barks during one of three contexts—a stranger ringing the doorbell, being locked outside, or in play—they found three distinct types of barks.
Stranger barks were the lowest in pitch and the harshest: they are nearly spat out. Less variable than the other types, stranger barks are well designed to send a message over a distance, something necessary if caught in a threatening situation alone. They can also be combined into "superbarks," concatenations of barks that together last much longer than the duration of barking in