few primate species. This suggests either that the cost of being deceived may
be very low or that perceptual or cognitive constraints may limit the ability
of perceivers to become effective skeptics.
2. Physical and Anatomical Constraints on
Signal Production: The Physics of Honesty
This section is focused on the mechanisms involved in vertebrate vocal production and is divided into three parts. First, we briefly review the basic
acoustics of vocal production, showing how a few easily understood physical principles combined with anatomy and physiology can have profound
consequences on the sounds a particular animal is able to produce. Then,
we examine the morphology of vertebrate sound-production systems in
greater detail, surveying the vast and mostly unexplored diversity of vocal
tract anatomy in terrestrial vertebrates. Finally, we attempt to make some
sense of this diversity, describing how evolutionary constraints can act in
some cases to enforce honest communication in the absence of any specific
selection for honesty. We also describe how novel morphological or physiological mechanisms can allow the evasion of certain anatomical and physiological constraints, suggesting that many morphological oddities are best
understood as constraint-evasion mechanisms. For example, the “key innovation” of the syrinx has opened the door to vocal adaptations in birds that
are inaccessible to other tetrapods due to their reliance on the larynx as a
sound-producing source.
2.1. Vertebrate Vocal Production: Anatomy and Acoustics
Our intent in this section is to survey vocal production in tetrapods. With
9,000 species of birds, 6,000 reptiles, 4,500 amphibians, and 4,000 mammals,
we could not hope to be exhaustive. Due to space limitations and the significant differences between sound production and transmission in air and
water, we will have little to say about fish or cetaceans (see Bass and Clark,
Chapter 2). Furthermore, available research on terrestrial vertebrate vocal
production is unevenly distributed: the best-researched groups are oscine
birds (Nowicki and Marler 1988; Gaunt and Nowicki 1998), anurans (see
Ryan and Kime, Chapter 5; see also Schneider 1988), and, among mammals,
echolocating bats (Suthers and Fattu 1973; Suthers 1988) and humans (Fant
1960; Lieberman and Blumstein 1988;Titze 1994). Much less is known about
reptile vocal production (see Gans and Maderson 1973), and little or
nothing is known about vocal production in most nonpasserine birds and
most mammalian orders. Significant unresolved questions remain about
production in virtually all vertebrate groups other than for humans. Even
in our own species, vocalizations other than speech and singing are little
studied. However, because research in speech science also has provided the
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W.T. Fitch and M.D. Hauser
be very low or that perceptual or cognitive constraints may limit the ability
of perceivers to become effective skeptics.
2. Physical and Anatomical Constraints on
Signal Production: The Physics of Honesty
This section is focused on the mechanisms involved in vertebrate vocal production and is divided into three parts. First, we briefly review the basic
acoustics of vocal production, showing how a few easily understood physical principles combined with anatomy and physiology can have profound
consequences on the sounds a particular animal is able to produce. Then,
we examine the morphology of vertebrate sound-production systems in
greater detail, surveying the vast and mostly unexplored diversity of vocal
tract anatomy in terrestrial vertebrates. Finally, we attempt to make some
sense of this diversity, describing how evolutionary constraints can act in
some cases to enforce honest communication in the absence of any specific
selection for honesty. We also describe how novel morphological or physiological mechanisms can allow the evasion of certain anatomical and physiological constraints, suggesting that many morphological oddities are best
understood as constraint-evasion mechanisms. For example, the “key innovation” of the syrinx has opened the door to vocal adaptations in birds that
are inaccessible to other tetrapods due to their reliance on the larynx as a
sound-producing source.
2.1. Vertebrate Vocal Production: Anatomy and Acoustics
Our intent in this section is to survey vocal production in tetrapods. With
9,000 species of birds, 6,000 reptiles, 4,500 amphibians, and 4,000 mammals,
we could not hope to be exhaustive. Due to space limitations and the significant differences between sound production and transmission in air and
water, we will have little to say about fish or cetaceans (see Bass and Clark,
Chapter 2). Furthermore, available research on terrestrial vertebrate vocal
production is unevenly distributed: the best-researched groups are oscine
birds (Nowicki and Marler 1988; Gaunt and Nowicki 1998), anurans (see
Ryan and Kime, Chapter 5; see also Schneider 1988), and, among mammals,
echolocating bats (Suthers and Fattu 1973; Suthers 1988) and humans (Fant
1960; Lieberman and Blumstein 1988;Titze 1994). Much less is known about
reptile vocal production (see Gans and Maderson 1973), and little or
nothing is known about vocal production in most nonpasserine birds and
most mammalian orders. Significant unresolved questions remain about
production in virtually all vertebrate groups other than for humans. Even
in our own species, vocalizations other than speech and singing are little
studied. However, because research in speech science also has provided the
72
W.T. Fitch and M.D. Hauser