From: joedees@bellsouth.net
Date: Sat 09 Aug 2003 - 01:41:09 GMT
The Ontogenesis of the Gurwitschian Perceptual Structure: A
Model for its Investigation in Preverbal Infants
by Joe E. Dees
ABSTRACT
The experimental methodology of genetic epistemology is
discussed. Difficulties in its use to investigate the ontogenesis of
perceptual structure arising from the maturation of the
sensorimotor stage prior to verbal facility are discussed. Kraft's
evidence for a physical substrate for Piaget's developmental stages
is reviewed. Gurwitch's theme - thematic field - margin structure
is outlined. It is conjectured that Kraft's evidence also supports the
ontogenesis of Gurwitsch's structure. The use of semiotics to
extend Piaget's methodology to preverbal infants is proposed, and
a prior study be Lewis and Brooks-Gunn is outlined as an example
of such an extension. Two experiments are proposed to
investigate the development of visuospatial and auditory structure
in preverbal infants. Possibilities for the use of phenomenology,
genetic epistemology and semiotics as aids to the investigations of
cognitive science are explored, and the interrelations of the
disciplines are discussed.
THE ADVANTAGES AND DISADVANTAGES OF
PIAGETIAN METHODOLOGY
A plethora of studies have been conducted on the development of
child cognition, with the main influence in the field being the
French structuralist Jean Piaget. His work on genetic
epistemology and the equilibration of cognitive structures has
largely framed the context within which subsequent explorations
have been formulated. The reason for this pervasive influence is
that the investigative methodology of genetic epistemology is one
of observation of verbal and manipulative behavior, and thus has
been well received by behavioristically oriented psychologists.
This is true in spite of the fact that Piaget himself may fairly be
characterized as a cognitivist of the emergent mentalist stripe. In
Piagetian-type studies, the evolution of child cognition is inferred
from the frequiency and types of mistakes children of diverse ages
make during responses to questions and the performance of
various tasks.
If Piaget was correct, however, concrning the order of succession
of his developmental stages, the ontogenesis and development of
perceptual structures would of necessity be much more difficult to
ascertain, since it would occur prior to the development of
symbolic verbal facility. Perception, unlike manipulative or
communicative action, is not open to direct outside observation.
Furthermore, even the verbal child lacks the experience of adult
perception, and thus cannot compare his or her own with it in
order to report observed differences.
Ut is highly likely that Piaget was indeed correct. In an important
review, R. Harner Kraft (1985) has provided, via the correlations
of the work of others, evidence of a physical substrate for Piaget's
developmental stages by perusing a number of studies of the
cerebra of children who died at various ages. The myelination of
different structures and connections within the developing brain at
certain critical periods seems to parallel the appearance of new
Piagetian cognitive capacities within the child at those periods,
and the structures (and their connections) so myelinated are areas
of the brain commonly associated with these capacities.
Myelination both canalizes and increases the efficiency of axonal
impulse transmission. According to Kraft, the visual and primary
sensorimotor cortices, as well as the subcortical acoustic fibers
from the cochlear nerve to the medial geniculate nucleus in the
thalamus, complete their myelinogenetic cycle prior to the major
myelination of the corpus callosum and the projections from the
medial geniculate nucleus to the temporal lobe cortical analyzer.
The intrahemispheric association and supralimbic cortical fibers
mature later, and the fibers interconnecting the nonspecific
associational cortices later still. At this point the nonferal child is
developmentally capable of verbally describing his/her perceptual
structures to others, but they will have already completed their
developmental cycle.
Seeing and hearing mature prior to the ability to abstractly say
how one sees or hears, and thus the develoment of the child's
visuospatiol and auditory structures is verbally indescribable by
the child.
THE PHENOMENOLOGICAL STRUCTURE OF PERCEPTION
The theme - thematic field - margin structure was proposed by the
phenomenologist Aron Gurwitsch (1957). According to
Gurwitsch, within every perceptual or conceptual field there is
always a theme, or focus of intention, surrounded by a thematic
field, or context, which is in turn bounded by a margin, or fringe.
Visually, this structure is primarilyspatial; in audition it is mainly
temporal, and if our focus is an internally grasped concept, its
thematic field consists of other concepts relevant to it. The focus
can be narrowed or widened at will with an adjustment of one's
scope of attention, but one loses in intensity what one gains in
extension. The demarcation between the theme and its field is
neither smoothly sloped nor radically discontinuous, and the
margin fades into nonawareness at the limits of the structure.
If this seems both Gestaltist and somewhat Piagetian, it must be
remembered that both Piaget and phenomenology were influenced
by Gestalt theory. In fact, a perusal of Piaget's development of
child cognition from syncretism (combining elements that do not
belong together) and juxtaposition (bifurcating elements that do
belong together) to correct discrimination and synthesis supports
the view that, in cognition at least, Piaget has approximately
described the ontogenesis of Gurwitsch's theme - thematic field -
margin structure.
Kraft's data can also be read to indicate the perceptual ontogenesis
of Gurwitsch's theme thematic field - margin structure. From
primarily unorganized visuo-spatial and auditory fields subserved
by relatively isolated and nonspecialized cerebral hemispheres, by
the age of two years one might expect such structures to emerge in
the visual and auditory systems consequent upon visual, acoustic
and sensorimotor myelination. In addition, Kraft notes that the
development of specific capacities in a cerebral hemisphere
occurs in parallel with the increase of interhemispheric
connection and communication, and tends to inhibit the
duplication of these functions and abilities within the other
hemisphere. Interhemispheric co-operation and interhemispheric
specialization seem to mutually reinforce, avoiding redundancy.
Would the appearance of such a structure have to follow the
myelination of the corpus callosum, or could both hemispheres,
the left in audition and the right visually, manifest it prior to
efficient interconnection? Or is such a perceptual structure hard-
wired? Up until recently, it has been impossible, for the reasons
previously stated, to discern.
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