| Home
| People
| Research
| Links | Contact | Publications
|
Presentations |
 |  |
Poster presented at the 4th International Conference on the Evolution of Language. Cambridge, MA.
Evidence for Semantic Complexity in Large-Brained Mammals
Christopher M. Conway
Abstract
Many theories of language evolution implicitly hold that an increase in
semantic complexity must have been a key driving force in the emergence
of syntax. After all, you don't need complex syntactic machinery if you
only have a few concepts to express. In other words, complex syntax
would seem to presuppose a high degree of semantic or conceptual
complexity. Semantic complexity (SC) may result from high levels of
cortical specialization in the brain (Schoenemann, 1999). Because
cortical specialization is a natural by-product of increased brain size,
a reasonable assumption is that increases in brain size led to
increasing SC in the hominid lineage. One natural implication of this
line of thinking is that non-human animals with large brains ought to
display a high degree of SC. To explore this hypothesis, this paper
investigates recent studies of large-brained mammals (dolphins,
elephants, and whales) and finds that certain observable behaviors
(e.g., social and communicative interactions) are consistent with the
notion that advanced conceptual systems are present. For example,
dolphins display impressive comprehension of human-taught, artificial
languages (Herman, et al., 1984; Herman, et al., 1993), arguably
superior to that of language-trained apes. Additionally, dolphins can
understand referential gestures (i.e., pointing; Herman, et al., 1999),
display conceptual knowledge of their own body parts (Herman et al.,
2001), and in the wild, appear to use "signature whistles" to address
one another (Janik, 2000). Elephants and whales also reveal behaviors
that could be evidence of SC. Both have complex societies characterized
by social facilitation (Christal & Whitehead, 2001; Schulte, 2000);
elephants have sophisticated means of multi-modal communication
(Langbauer, Jr., 2000; McComb, et al., 2000); and whale song, which has
recently been suggested to display complex hierarchical structure
(Suzuki, Buck, & Tyak, 1999), can change via a form of "cultural
transmission" in a manner that is unprecedented in the animal world
(Noad et al., 2000).
The evidence reviewed here, although not unambiguous, indirectly
supports the notion that large brained animals have an increased
conceptual representation of the world. The paper will conclude by
addressing possible objections to this proposal. For instance, why
don't animals with brains larger than humans have a correspondingly more
advanced semantic repertoire? I will argue that language, once
developed, further acts to increase SC. Thus, a kind of feedback loop
exists, in which a sufficient amount of SC enables syntax and language
to emerge, which in turn, injects additional conceptual richness into an
organism's mental life. Another objection is that if these animals have
a sufficient level of SC, why do they not display advanced language? I
will suggest that SC alone does not guarantee language. Language
presumably requires certain selection pressures beyond increasing brain
size, such as the means and motivation to convey complex concepts to
conspecifics. For instance, for language to emerge, organisms must not
only have SC, but must be able to encode and process complex sequential
information (Conway & Christiansen, in press); additionally, pressures
for communicative interactions, perhaps motivated by threat of
predators, may also be necessary.
