BRAIN EVOLUTION AND NEUROLINGUISTIC PRECONDITIONS
Wilkins, W.K. & Wakefield, J. (1995).
ww> Second, we take very seriously the distinction between language (as
ww> a formal grammatical system), on the one hand, andcommunicative
ww> abilities and devices, on the other. It is important
ww> to our argument that the ability to communicate be treated
ww> separately from the possession of a
ww> language faculty and,further, that linguistic ability be
ww> distinguished from any other(modular) cognitive capacity. We do not
ww> argue that the ability to communicate arose with Homo habilis,
ww> but rather that the basic neurolinguistic capacity for language
ww> acquisition did.Additionally, we
ww> clearly distinguish linguistic competence from speech. [...] It
ww> might seem obvious, when we think of modern humans, thatlanguage is
ww> an adaptive trait, one
ww> that makes us more able tosurvive in our environment. It would then
ww> seem equally obviousthat,
ww> ceteris paribus, survival would be enhanced by linguisticcapacity
ww> (see especially Pinker and Bloom, 1990). But direct selection for
ww> an adaptive capacity is not the only evolutionary process
ww> conducive to the emergence of structural or behavioral innovation;
ww> a structure may arise through adaptively selective mechanisms and,
ww> by its conformation alone, be neutrally preadaptive (Darwin, 1871)
ww> or exploitable for some function independent of the original
ww> function. It may, in fact, produce a new capacity not already in
ww> the repertoire of the organism.
ww> This manner of exploitation converts the raw material provided by
ww> adaptation (or by the laws of
ww> growth and form) to a function which may itself prove beneficial to
ww> the organism or taxon.Darwin's term for this is preadaptation.
ww> Because this term has developed an unintended,
ww> premeditative connotation, we wish to avoid it and instead will
ww> refer to this phenomenon as evolutionary reappropriation. By the
ww> term "reappropriation", we mean specifically to highlight
ww> the means by which a structure or function in the repertoire of a
ww> species reaches an evolutionary
ww> state that is compatible with, and facilitates, a new function.This
ww> new function may or may not
ww> be behaviorally related to the original. [...] The neuroanatomical
ww> structures that underlie linguistic ability, we will argue, arose
ww> in human
ww> taxa as a direct result of evolutionary reappropriation (also see
ww> Calvin, 1992). They evolved to
ww> the state at which they were available for incipient linguistic
ww> capacity to emerge by gradual, adaptive changes in brain
ww> organization that were the result, in the hominid line, of natural
ww> selection for other behaviors that require specific,highly
ww> sophisticated neural processing mechanisms. These neuroanatomical
ww> structures were not, however, adaptations originally serving
ww> communicative functions. Our investigation of the origins of
ww> language concerns itself
ww> specifically with there appropriative basis of these structures
ww> rather than subsequent adaptive mechanisms that may have shaped
ww> language as a communicative device.[L]anguage is unlikely
ww> to have evolved directly from communication-based precursors, nor
ww> is it likely to have been based on those structures that subserve
ww> communication.A communication-based account can
ww> parsimoniously motivate neither the precise neural character nor
ww> the apparent localization of human language cortex. Rather, as we
ww> will show in detail,language came to utilize the processing
ww> strategies available from newly evolving premotor cortex paired
ww> with those aspects of
ww> neural organization that allow for amodal concept formation and
ww> yield structured abstract representations.
Comment: I find it most interesting that they divorce language from
communicational functions. This constitues, in my opinion, one of the
novelties of this theory. In earlier hypotheses (bow- vow theory,
social origin of language, language as a tool for working in community
etc.) the need to communicate was the drive for language development.
By separating communication from language, the authors do away with the
telicity in previous theories, which is a welcome result in an
evolutionary perspective (see for example the 'Evolutionary
Perspectives' chapter in the Cognitive Neuroscience textbook, edited by
Gazzaniga). This way, they can also free themselves from the heatly
debated and very uncomfortable question of whether (the sophisticated
structures of) syntax appeared all of a sudden, as if my chance or
miracle or under selectional pressure. Their answer is neither, since
language was a reappropriation.
ww> Incipient linguistic capacity
ww> With respect to the evolutionary emergence of cytoarchitectonic
ww> regions compatible with linguistically formatted cognition, we
ww> suggest the following scenario. During the neocortical expansion
ww> associated with selection for the hand and manipulatory capacities,
ww> frontal and parietal corticesevolved in a manner consistent with
ww> the principles outlined in the preceding subsection. At some point
ww> between the time of the australopithecines and H. habilis, the frontal
ww> motor association cortex expansion that resulted in the pars
ww> triangularis and parsopercularis of
ww> the inferior frontal convolution was coupled with the parietal
ww> sensory association cortex expansion that resulted in the
ww> enhancement of the angular and supramarginal gyri and the shift
ww> of the lunate sulcus to its inferior medial, nonpongid position.
ww> These simultaneously evolving
ww> cortices, Broca's area and the POT, are reciprocally connected by a
ww> major axon tract,remote from connection to the body, and highly
ww> intrinsically connected, as would be expected of neocortical areas
ww> subserving cognitive functions.We suggest that the configuration of
ww> the association cortex,derived from primary motor and sensory
ww> cortices and motivated via selection
ww> for neural control of the evolving hand, provided afoothold for the
ww> operations involved in linguistic processing.This does not imply
ww> that the respective roles of the POT or of Broca's area
ww> in language were in any sense predetermined.Rather, functional
ww> changes in parietal and frontal
ww> structures proceeded even as did changes in the structures
ww> themselves (for general discussion of
ww> relevant principles, see Bock, 1959;Futuyma, 1986, p. 424). It is
ww> our contention that, as a consequence of the configurational
ww> compatibility, these parietaland frontal substrates were
ww> subsequently reappropriated for language and, ultimately, for
ww> linguistically formatted communication. The shift in placement of
ww> the lunate sulcus as a result of the motor-sensory expansion was
ww> illustrated schematically in Figure 4.Recall that at the same time
ww> that the manual
ww> behaviors under selection were developing and becoming more
ww> complex, so too was brain function becoming lateralized (as
ww> indicated by the development of right-handedness among the
ww> habilines). This phenomenon derives from the nature of the
ww> behaviors for which we are claiming selective advantage. As noted,
ww> in throwing, a two-handed release allows neither sufficient force
ww> nor acceleration for an advantageous weapon trajectory. In flaking
ww> stones, one
ww> hand is used to steady the target (or core) stone while the skilled
ww> movement is executed by the
ww> other. With selection operating for behaviors associated with
ww> unilateral performance,the stage
ww> may be set for preferential handedness and cerebrallateralization.
Comment: I feel a little dissatisfied with this argumentation. As the
title of this subsection, and most importantly the main subject of the
paper would suggest, the authors should show how language develops.
What we get instead, however, is (I) the description of how the
anatomical possibility of language evolved, and (ii) how cognitive
processes in general (and conceptualization in particular) might have
evolved. This however gives no account of language. If we accept that
communicational needs constituted no driving force (as the authors have
suggested earlier, they argued that communication could be done in ways
other than language), then we have still no clue as to why and how
language appeared.With the above given scenario, we might as well have
ended up having a rich conceptual structure, some mimicing or gesturing
for communication, but no language at all.
ww> Conceptual Structure
ww> If our account proves valid, by the time of H. habilis the marked
ww> sulcal division between the parietal and occipital lobeshad
ww> "disappeared." In addition, there were other significant
ww> evolutionary changes affecting the hominid brain. These include the
ww> expansion of visual cortex
ww> and of the temporal lobe. The close proximity and resultant
ww> junction of the three posterior lobes culminated in a situation in
ww> which information was readily available for processing in an
ww> overlap of the three related association areas and which could
ww> result in amodal representation.It
ww> is important to note at this point that, in light of the size of
ww> axon tracts between neural structures, geographical proximity is
ww> not necessary for processing connections. It is the case,
ww> however, that proximal location and organization is oftenthe rule
ww> for related functions. This can
ww> be exemplified by a consideration of the organization of motor and
ww> somatosensory functions on
ww> either side of the central sulcus. In the POT area,close proximity
ww> of the association areas for
ww> sight, audition, andthe tactile sense results in the facilitated
ww> integration of sensory information.The POT allows for a particular
ww> way of organizing perceptual information that we
ww> believe to be necessary for the typicallyhuman amodal
ww> representation of abstract features. Recall that humans, but
ww> apparently neither monkeys nor apes, can abstract distinctive properties
ww> from sensory input and apply those properties in the processing of
ww> sensory information from various modalities or, in other words,
ww> accomplish what was called metaphorical matching (see
ww> Section 4.3.1). We suggest that this is the substance associated
ww> with the process Jerison (1976)
ww> refers to as the uniquely human "construction of reality."This
ww> human manner of building reality,
ww> utilizing the integration of information from the various
ww> modalities is derived directly from the
ww> facts of neurology. It would not seem unreasonable, then, to expect
ww> a theory of cognition (a higherlevel of abstraction) to be
ww> responsible to similar considerations. Cognition must, of course,
ww> ultimately be instantiated in the brain. The proposed cognitive
ww> construct (relevant to language) most apparently compatible with
ww> this viewof neurology is Jackendoff's Conceptual
ww> Structure (1983, 1987,and elsewhere).Conceptual Structure
ww> (henceforth CS) is the central conceptin a theory of semantics that
ww> integrates meaning as relevant tolanguage with meaning as
ww> relevant to other cognitive domains. CS is explicitly developed in
ww> order to serve not only the
ww> concernsof linguistic theory but also those of theories of vision,
ww> music,motor systems, etc. It is
ww> to be seen, in fact, as the level of structure relevant to all
ww> cognitive domains. Jackendoff says: "There is a single level of
ww> mental representation,conceptual structure, at which linguistic,
ww> sensory, and motor information are compatible." CS, as conceived of
ww> here, and based
ww> on Jackendoff, is made up of basic ontological categories and
ww> constituents put together according to CS-specific rules of
ww> combination. The basic categories generalize across semantic
ww> fields and across conceptual modalities. The rules of combination
ww> construct higher-level constituents, such as STATES and EVENTS, out
ww> of the basic categories, such as THINGS and
ww> PATHS. For example, a sentence involving the verb throw (e.g. Ben
ww> threw the ball to the dog)
ww> would include a representation of an EVENT in which a THING(a ball)
ww> goes along a PATH
ww> from THING (Ben) to a different THING(the dog). Because this is a
ww> causal EVENT, one THING (Ben) CAUSEs the ACT in which the THING
ww> (ball) is acted upon. (This isdiscussed
ww> in more formal terms in Section 8.1.)Importantly, CS is not part of
ww> the linguistic system per se.
ww> Rather, the linguistic system is related to CS through a set of
ww> correspondence rules. The theory
ww> of CS is a theory of mental representation, and to the extent to
ww> which CS can be shown to provide for a successful linguistic
ww> semantics, semantics will notbe part of the strictly linguistic
ww> domain. From this point ofview, the theory of grammar deals with
ww> syntax and phonology; semantics falls under the theory of CS.To
ww> relate the discussion of CS more directly to what we
ww> have said regarding neuroanatomical structure, we suggest that CS
ww> is the cognitive construct that is produced by the POT through its
ww> interaction with Broca's area. By virtue of the POT,
ww> human sensory input is highly processed in association cortex and
ww> losesits modality-specific character; by virtue of Broca's area's
ww> influence on the POT, the amodal representations are subject to
ww> hierarchical structuring. Structured modality-neutral
ww> representation, we suggest, is
ww> the essence of CS. (Further,amodality and hierarchical structure
ww> are necessary for feature abstraction, to which we return shortly.)
Comment 1: Here again, it is quite visible ("CS is not part of the
linguistic system per se.") that what the authors propose is not the
development of language, but that of the conceptual system.
(This related to the previous comment.)
Comment 2: Jackendoff's model (in his The Architecture of the Language
Faculty, 1997) is a complex architecture built up of the modules of
many cognitive functions. Language itself consists of more modules.
Conceptual structure is only a part of the whole model. The authors
should indicate how modules other than CS are mapped into brain anatomy
or brain evolution. However, they don't say much about it. They even
ignore the purely linguistic modules. (Though elsewhere in the
article, they make the (unmotivated) claim that syntax evolved later
and gradually. )
Comment 3: They say that CS is hierarchical, and because it is in a way
the representation of the world, there should be relations between the
stored items. Some kind of "syntax" should exist even within CS (a
language of thought), but where does it come from? In the authors'
view, the syntax of language is only a development posterior to CS. And
even if we somehow accept their arguments about CS, how is CS
"syntax"/hierarchy mapped into the syntax of natural language. In
linguistics, it is usually assumed that the link (one of the links)
between syntax and semantics (that is CS) is assured by thematic roles
(Agent, Patient, Goal, etc.). In the model described by the authors
(later in the article), these roles and even some grammatical
information (category, e.g. N, V etc. and subcategorisation) are
included in CS (just like in Jackendoff), but no mention is made of how
these categories and grammatical structures are created and put into
CS.
Gervain Judit
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