Poster group
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poster
In infants, the developmental course of haptic perception is constrained bythedevelopment of attention to object properties and by the development of theability to execute various movements with the hands. The purpose of this studyis to consider how infants become able to use the hands to assess qualities ofobjects such as hardness/softness, between 4 to 6 months, during thedevelopment of the prehension. The stimulus object was divided into 4 equalparts alternatively hard and soft : It was tactually heterogeneous butvisuallyhomogeneous. Three aspects of exploration in relation with the hand used, leftor right were considered : The mode of touch - contact, pressure and taping- ,the means used for exploring - whole hand or fingers -, and the substancetouched - hard, soft or mixed parts -. Results show that infants adjust theirmovements to the objects' qualities tested, that is the infant varies thedistribution of investigative and manipulative behaviors, according to thenature of the specific object being explored : Pressure movements appear aspredominant exploratory procedure for the soft consistence, where as tapingmovements appear as predominant movements for the hard parts. Concerning themanual laterality, results show that the left hand is more used for contactingobject than the right one, whereas the right hand is more devoted to press thesoft part and tap the hard part. Final conclusion concern the discussion abouta manual specialization in very early ages of the life.
poster
The skill of reaching and grasping for objects during infancy has longbeen recognized as a bench mark for early intellectual development. Early theoretical discussion by Piaget and Gesell, followed by animportant array of experimental observations by Ashmead, Bower,Bushnell, Bullinger, Thelen, von Hofsten, and others across the past 3decades have demonstrated the scale and complexity of how early motorskill is organized and contextualized within the infant's cognitivearchitecture. More specifically, we now have a very sophisticatedunderstanding of how the infant coordinates the many degrees ofmovement freedom to hand-match the target object under numerousconfigurations of space, time, and location. What is far lessunderstood, though, is the manner in which the infant's intentions orthoughts for action (e.g., what they will do with the object) aremanifested in the skilled actions themselves.While our earlier studies have investigated the complex interactionbetween motor development and volition in means-ends tasks, thiscurrent (in-progress) study is designed to investigate how infantscoordinate perceptual-motor skills (i.e., reaching and grasping) inorder to act purposefully on their environment. More specifically,this study experimentally examines how thinking and the precursor tothinking, intention, are mapped and expressed on the developing bodyof the human infant. The fundamental question posed here is:how does thought or intention for action become manifested within thedynamics of body movement?Thus far we have observed 15 infants between the ages of 9.5 and 12.5 months. Infants were given16 30-second reaching trials counterbalanced by object type and function (8 familiar-function [FF]objects and 8 unfamiliar-function [UF] objects ). Objects in the FFcondition include items such as a spoon, a hair brush, a baby bottle;objects in the UF condition include such items as a lego-stick, around cylinder, and a plastic mallet. The experimenter modelled thekey-use aspect of the FF objects (e.g., bringing bottle to mouth); UFobjects were also modelled but with an arbitrary, non-familiarend-point act. Time of modelling and presentation length werestandardized for both object types and functions.The video records of each reach were analysed for time and movement parameters including time-to-contact and grasp, reaching and grasping accuracy, and the quality of the end-pointimitative act. Preliminary findings with this current sample aremixed. While functionally or 'ecologically relevant' goal-objects leadmore often to modelled actions, they do not elicit better qualitymovements compared with those goal-objects deprived of functionalrelevance. Potentially relevant comparisons to similar adult-basedresearch (e.g., Lin et al. 1997) are incongruent, for adultsdemonstrate more 'movement efficiency' for function-based objects.Within the context of an attention-competition model, however, theseresults are important for they at least in part suggest that theinfant's intentions of object use interfere with the movement plan andexecution. Within this competition model, then, the results begin toillustrate that the developing body can 'carry' or map the thoughts orintentions of the agent.
poster
Infants' ability to fit objects through openings was studied. Such a taskreflects abilities related to spatial perception, as well as motorcompetence and knowledge of means-end relationship. The number of possibleways in which an object can be fitted into an opening is constrained by thesymmetry axes of its shape. While a sphere could be oriented in anyarbitrary way and still be fitted into a circular hole, a non-symmetricprism has to be oriented in a unique way in order to fit into a triangularopening corresponding to its transversal dimensions. The focus of interestwas not limited to whether infants succeeded in performing the task, butalso how the task was performed. This was measured in terms of motorperformance (such as hand(s) used, grips employed, and whether the objectwas oriented in an anticipatory way to fit the opening).The apparatus consisted of a lid with an opening corresponding to one ofthe transverse sections of the object to be fitted. A sphere and a cylinderwere fitted into a circular opening, a cube and a rod with a squarecross-section were fitted into a square opening, a rod with a rectangularcross-section was fitted into a rectangular opening, and a triangular prismwas fitted into a triangular opening. Four groups of infants were studied(12, 16, 20 and 24 month-olds). The orientation in which the objects werepresented was manipulated too. Altogether, each child performed 16 trials.The infants were able to fit a sphere and a cylinder into a circularopening at 12 months of age, a cube into a square opening at 16 months,rods with square and rectangular cross-sections into corresponding openingsat 20 months, and a prism into a triangular opening at 24 months. Thepresentation mode affected the children's performance. In the modes ofpresentation that required more adjustments of the object orientationbefore it could be fitted into the opening, orienting the block in theappropriate orientation was mastered at a later age. Although youngerinfants roughly adjusted the object into the aperture, older infants couldanticipate the act of fitting the block into the aperture well before thehand reached the lid.
poster
Bernstein (1967) proposed that skill acquisition involves learning toorchestrate degrees of freedom (e.g. muscles or segments of the body). Heproposed that individuals (a) initially freeze out degrees of freedom,decreasing task complexity, (b) release degrees of freedom and (c) settleinto economical preferred movement strategies. In a previous study we(Haehl et al., 1999) examined changes in the coordination between thesegments of the trunk from the onset of cruising sideways through walkingonset to test Bernstein's hypotheses. We found that infants did notinitially freeze out degrees of freedom of the trunk. Instead, infantsdemonstrated a 'wobble phase' in which movements of the thorax and pelviswere relatively uncoupled with many reversals in direction. Gradually,infants decreased the degrees of freedom, and eventually reached a plateauin the number of movement reversals prior to walking onset. The purposeof this study was to extend previous work by eliciting cruising forward inorder to make the task of cruising and walking more homogeneous, and toexamine the changes in coordination of multiple segments involved in thetransition from forward cruising to walking. We videotaped seven infants weekly, who had 3 weeks of cruisingexperience, through walking onset and one month following walking onset.We placed markers on infants' arms, legs, thorax and pelvis. Infantscruised forward between two support surfaces and were videotaped frombehind. We calculated marker position in 2-D and analyzed frontal planemotion. Cross correlations of segment pairs were used to reflect changesin coordination among the segments. Standard deviations of correlationcoefficients and phase lags measured changes in the variability ofcoordination. Overall, infants demonstrated freezing out the degrees of freedom amongmultiple segments at the onset of walking. There was a shift in the crosscorrelation coefficients towards 1, and the phase lags towards 0 among thefollowing segment pairs: right arm/left arm, arm/thorax, andpelvis/thorax. Some also demonstrated a shift in the cross correlationcoefficients towards 1, and the phase lags towards 0 between theleg/pelvis pair, though this finding was less consistent. Standarddeviations decreased among the pelvis/thorax segment pair, and in some ofthe other highly correlated segment pairs. Overall, one month followingthe onset of walking most of the correlations among segments decreased andphase lags dispersed from 0. Standard deviations increased. Infants in this study demonstrated freezing degrees of freedom betweenmultiple segments of the body at walking onset. Infants did not freezedegrees of freedom at the onset of cruising (Haehl et al., 1999). Onepossible explanation for the different results is that the constraints forcruising are few compared to the task constraints for new walkers, whichare numerous. Thus, there is no compelling reason for infants to freezethe degrees of freedom at the onset of cruising. Another possible reasonis that at the onset of cruising, infants are unable to control themovements sufficiently to freeze degrees of freedom. Cruising mayprovide opportunities for movement exploration required for acquiring theskill of walking.
poster
Handedness is considered to be an important variable associating with individual differences in language cognitive development, because of its association with cerebral speech lateralization (Annett, 1975; Lebrun & Zangwill, 1981; Geschwind & Galaburda, 1986). The present study designed a test to measure LQ (lateral quotient) below 2 years of age, with a parent's report and by observation, and ascertained whether there are signs of a link between emergence of handedness and beginnings of language. The sample consisted of 36 children (19 male, 17 female) aged 18 months and 36 children (18 male, 18 female) aged 30 months. The interview consisted of a parent's judgment on general hand preference and specifically addressed hand preferences in seven manual activities; i.e., while writing, throwing, using a spoon, etc., commonly used items in questionnaires for mature individuals (Crovitz & Zener, 1962; Annett, 1970; Oldfield, 1971). In observation session, thirteen activities including above seven were observed directly. Parents responded to a questionnaire consisting of Mental Development Inventory and additional items relating to language development. Are the results of a parent's report of usual handedness and a brief observation consistent? There was a strong significant correlation between the two methods with regard to number of 'right-handed' items (r0.762; p<0.0001). There was also a strong significant correlation regarding 'left-handed' (r0.712; p<0.0001). And there was a strong correlation between the two kinds of calculated LQ values ; i.e., LQ by interview and LQ by observation (r0.812; p<0.0001). These high correlations validate the measurement of handedness below 2 years of age. A parent's simple report on general hand preference was consistent with LQ by both measures when individuals were divided into two groups (right- and non-right-handed) with a cut-off LQ value of 60. The present study ascertained a possible relationship between handedness and language development. Based on the parent's responses, each child was assigned to a language developmental stage, using an 8-rank scoring system. At 30 months, there was no significant correlation between rank scores of language and LQ by both measures. However, at 18 months, rank scores of language were significantly correlated with both LQ by observation (r0.693; p<0.0001) and LQ by interview (r0.606; p<0.0001). In a comparison of mean language scores according to sex and handedness (based on a criterion of LQ 60 by observation) by ANOVA, both handedness(p<0.05) and sex (p<0.05) had significant effects at 18 months. Scheffe's test revealed that mean for right-handed (n15) was significantly greater than that for non-right-handed (n15) , and mean for females (n12) was significantly higher than that for males (n18). Non-right-handed males were the most delayed group.
poster
Tool use involves establishing systematic relations between a tool and surface. Although tool use in children has been attributed to the onset of symbolic thinking, little is known about how infants begin to use common tools and establish systematic tool-surface relations. Information about how infants establish such relations may provide insights into the origins of tool use