Perceiving
Reference through Dynamic Gesture during Early Lexical Developent
How do infants
unlock the puzzle of reference, the mundane fact that words refer to objects,
actions, attributes, and more? That is, how do infants learn the relation
between the stream of speech and the unceasing flow of events? While this
sounds like a simple question, its answer remains elusive.
Overview of Other Views.
The preponderance of research investigating lexical
development has tested hypotheses proposing that innate predispositions (Markman,
1992), cognitive prerequisites (Clark, 1993; Golinkoff, Mervis, & Hirsh-Pasek,
1994), and/or social abilities (Tomasello,
1988, 2001)
underlie lexical development, usually from 15 months onward. Some six
months earlier, however, infants begin to display comprehension and production
of their first words. A large body of work documents which types of words
and their tokens emerge when and in what order (Fenson et al., 1994). However, little experimental
work examining underlying development has focused on the time frame from 9
through 14 months in which infants learn these first words. Our research seeks
to add to knowledge of this developmental process by testing a hypothesis
derived from a perceptually based theory of early lexical development.
Our Perceptually-Based, Social Interactive Approach
We propose that attention to movement and synchrony
facilitates infants' detection of the correspondence between two fundamentally
different kinds of things: words and aspects of ongoing events (Zukow-Goldring,
1997; Zukow-Goldring & Rader, 2001). This research focused on early language development,
documenting that caregivers' gestures educate their children's
attention to engender a shared perspective of the world.Ê Understanding the perceptual abilities and
caregiver practices underlying the emergence of infants' first words is key,
because language development without words cannot go forward.
Attention is a topic
that permeates the early lexical development literature. However, the relationship
found between attentional style and early lexical development brings us no
closer to understanding how lexical development does, in fact, occur. We believe
that J. Gibsonâs theory of direct perception (1966, 1979) provides a basis
for explaining why perceptual processes hold the key to understanding early
lexical development. Gibsonâs theory describes perceptual input in terms of
invariant information in a dynamic array over time and argues that these invariants
specify meaningful aspects of the environment.Ê Attention is embodied as an individual orients
to and explores the environment. During cycles of perceiving and acting, a
person detects the perceptual structure in light, sound, odor, touch, and
taste; such discovery informs further action. According to E. Gibson's (1969,
1997) view of perceptual learning, what changes with learning is the detection
of this information. With practice, perceiving becomes more differentiated
and appropriate to the task at hand (Gibson & Rader, 1979).
Theory of Amodal Referring through Gesture and
Speech
We briefly present
four postulates that delineate developmentally important processes and caregivers'
methods of educating attention. (For a more complete account, see Zukow-Goldring
& Rader, 2001).
Postulate 1: A general perceptual process (namely,
detecting amodal invariants) allows infants to perceive the correspondence
between word and referent.Ê Amodal invariants perceivable in the synchronous
and dynamic coupling of gesture and speech may clip for the infant the relevant
segment of the speech stream and of the ongoing event, making detectable the
relation between a word and what it represents.
Postulate 2: Infants can and do detect amodal regularities
prior to the comprehension of
Specifically, we propose that infants learn to comprehend words initially
through the pick-up of the amodal invariance expressed in vision, sound, touch,
and so on by the caregiver while gesturing and speaking.
Postulate 3: Caregivers present amodal regularities
as they gesture and speak to infants from 6 months. "An equivalence in gestural
and prosodic contour suggests a means by which infants might detect an invariant
relation between object and word" (Zukow, 1990: 718). She argued that "caregivers make amodal invariant
relations (timing, tempo, intensity, and rhythmicity) prominent as they gather
and direct attention to animate beings, objects, and actions. Infants pick
up these regularities in their speech and action" (Zukow-Goldring, 1997:
240).
Postulate 4: Temporal synchrony of action and word,
not temporal contiguity, is of crucial importance to lexical development. Naturalistic evidence
supports this position: asynchronous, but temporally contiguous, presentation
of word and action did not lead to word learning, whereas temporal synchrony
did (Zukow-Goldring, 1997, pp. 237-239).
Research
Hypothesis
In this study we focus on a hypothesis derived from
the first postulate by comparing the efficacy of dynamic show versus static held gestures for the learning of new lexical items. show gestures, in which objects are loomed and waggled, occur most frequently
during the prelinguistic period when caregivers display objects. (Zukow-Goldring
& Ferko, 1994; Zukow-Goldring, 1997; Gogate et al., 2000). In waggling,
caregivers routinely display the entire object by turning it back and forth.
held gestures display a much
smaller proportion of the object's surface and do not dynamically set off
the object from the background. We hypothesize that dynamic show gestures accompanied by attention-directing speech
will facilitate early lexical development more than held gestures correlated with the same verbal script.
Method
Participants
In this within-in subject study, participants were
ten infants, four males and six females, between the ages of 10 and
14 months with a mean age of 12
months. A criterion
for participation was the ability to look towards mommy or daddy when asked
to do so.Ê Each infant participated
in both gesture
conditions,
but was randomly assigned to word-object pairings and orderings.
Materials
Nonce words. The monosyllabic stimuli
(hork, smiff) adhered to the phonological rules of English (Ladefoged,
1975).
Objects. The two objects we
constructed were
distinct in color and form, mildly attractive to infants and novel for any
infants tested.Ê (Object 1: blue and yellow jumbo
Lego blocks arranged in a tower format with cantilevered segments, Object
2: green and
organgeorange circular modules.)
Learning and Testing Trials
Apparatus. Infants were seated
in an adjustable infant high chair positioned 21” away from a 20” television
monitor. To avoid subtle influences from the caregiver, he/she was seated
behind the infant, but was not in physical contact with her/him. A small video camera mounted
on the wall recorded the infants' behavior. ÊThe
VCRs for presenting the stimuli during training trials and for recording the
infant throughout training and testing were located in an observation room
to avoid distraction.
Video Learning Trials
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To insure consistency, videotaped scenarios were used. Utilizing infant-directed speech, the presenter said, This is a hork/smiff. Look it's a hork/smiff.Ê See the hork/smiff.Ê Look at the hork/smiff.Ê See, hork/smiff. A complete repetition of the script followed for a total of ten utterances. For the dynamic show gesture, the objects were loomed and waggled. This gesturing occurred synchronously with word articulation. In the static held gesture scenario, the object was held in front of the speaker but was not moved as she talked.The particular combination of word and gesture was randomly determined for each infant.
Comprehension Trial.
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Following the learning
phase of the testing, word comprehension was assessed, using an adaptation of
the preferential
looking task (Hirsh-Pasek & Golinkoff, 1996). Two videotaped scenarios
were created, one for each object, in which a different female speaker asked
the infant to look at the hork or the smiff. The speakerâs face
appeared in a central monitor while the referent choice objects sat on small
tables to the right and left of the infant. The speaker said, Do you see
the hork/smiff?Ê Look at the hork/smiff.Ê
Are you looking at the hork/smiff?Ê I want you to look at the hork/smiff.Ê Look at the hork/smiff.Ê The order of the requests and the positioning
of the choices were counterbalanced.
Results
Because we were interested
in the degree of attention during the learning trials, we coded for looking
duration for each condition during this phase of the study. Coding was done
without knowledge of the gesture condition.Ê
Inter-rater reliabilities were r=.99 for the static-gesture
scenarios and r=.98 for the dynamic-gesture scenarios. Infants did not spend more time looking at the dynamic
show gesture scenario than
at the static held gesture scenario, F(1,7)=.09,
p=.77.Ê
For the comprehension
trials, we were interested in whether the infant had learned the relationship
between the nonce word and the objects.Ê Therefore,
for this phase of the study the dependent variable was the proportion of correct
looks to
the total number of looks.
Inter-rater reliability was r=1.0 for the condition in which the object
had been presented with a dynamic gesture and r=.96 for the condition
in which the object had been presented with a static gesture. The effect of gesture
was significant, F(1,9)=5.73, p=.04, with infants making
more correct looks to the object presented using the dynamic SHOW gesture.
Discussion
This experimental study
was designed to test the effects of dynamic show
gestures
caregivers have been observed to use during early word learning.Ê The results support the hypothesis that a dynamic
show gesture leads to better
comprehension than a static held gesture.Ê We suggest that amodal invariants make
word and referent "stand in" relation to each other and "stand
out" from other possibilities. Furthermore, these practices/methods may be more important
in the
visually crowded
environments of daily life than in the very spare lab environment that
has few distractions
Trochaic stress patterns in word final
position (strong-weak) may assist the child to detect a word in the speech
stream and enhance comprehension. However, trochaic stress alone cannot explain
our results, because trochaic stress occurs in both our experimental conditions.
In the condition in which movement was synchronous with this pattern, we found
improved comprehension.
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