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1.
The present study assessed the development of reaching for objects positioned in front of the contralateral shoulder. In particular, it examined how the development of crossing the midline is related to the development of bimanual reaching. Twenty infants were observed longitudinally at 12, 18, and 26 weeks of age while reaching for two balls (3 cm and 8 cm in diameter) located at three positions (ispsilateral, midline, and contralateral). The reaches were analyzed from video recordings. With age, the infants increasingly adapted the number of hands used to the size of the object. The number of reaches crossing the body midline increased with age. Furthermore, the majority of the midline crossings were part of two-handed reaches for the large ball and occurred at or after onset of bimanual reaching. Together, these findings strongly suggest that the development of crossing the body midline emerges in the context of bimanual reaching. It was concluded that the need to grasp a large ball positioned contralaterally with two hands induces midline crossing. Hence, the development of midline crossings is not exclusively dependent on organismic constraints (e.g., the maturation of hemispheric connections), but rather on their interaction with environmental constraints (e.g., object size).  相似文献   

2.
Is Visually Guided Reaching in Early Infancy a Myth?   总被引：4，自引：0，他引：4  
The issue examined was whether infants require sight of their hand when first beginning to reach for, contact, and grasp objects. 7 infants were repeatedly tested between 6 and 25 weeks of age. Each session consisted of 8 trials of objects presented in the light and 8 trials of glowing or sounding objects in complete darkness. Infants first contacted the object in both conditions at comparable ages (mean age for light, 12.3 weeks, and for dark, 11.9 weeks). Infants first grasped the object in the light at 16.0 weeks and in the dark at 14.7 weeks, a nonsignificant difference. Once contact was observed, infants continued to touch and grasp the objects in both light and dark throughout all sessions. Because infants could not see their hand or arm in the dark, their early success in contacting the glowing and sounding objects indicates that proprioceptive cues, not sight of the limb, guided their early reaching. Reaching in the light developed in parallel with reaching in the dark, suggesting that visual guidance of the hand is not necessary to achieve object contact either at the onset of successful reaching or in the succeeding weeks.  相似文献   

3.
The ability of infants aged 8–12 months to coordinate their arm and trunk movements to contact an object located in different positions was investigated in 2 experiments. In the first, 8- and 10-month-old infants reached for near objects but both reached and leaned for more distant ones indicating that they perceived that forward leaning extends the range of contact beyond that of reaching alone. In addition, arm and trunk movements were initiated simultaneously; visual information concerning object distance was sufficient to activate an integrated reaching-and-leaning response. Object distances were increased and a mechanical aid was provided on half the trials in the second experiment with 10- and 12-month-old infants. For both age groups the degree of leaning was reduced for objects that were out of reach without the aid. Only older infants were able to use the aid to extend partially their range of contact. Overall the results support the conclusions that, by at least 8 months, infants perceive that leaning extends their effective reaching space; by 10 months they perceive the limits within which reaching together with leaning is likely to be effective; and by 12 months they begin to perceive how this space may be extended by a mechanical aid.  相似文献   

4.
Infants with Down syndrome (DS) represent a population in which new behaviors are acquired significantly more slowly than in nondisabled infants. We propose that infants' spontaneous movements hold a key to understanding the process of development—of integrating intrinsic dynamics and function. In this investigation, we compared the spontaneous leg movements of 10 infants with DS and 2 groups of nondisabled (ND) infants matched for chronological age and motor age. In contrast to common perceptions, we did not observe a significant difference in the frequency of movements between infants with DS and ND infants. But, infants with DS demonstrated significantly fewer of the most complex patterned leg movements, that is, kicking patterns. Further, the frequency with which both DS and ND infants kicked was significantly correlated with the age at which they began to walk. Biomechanical variables were identified, as well, that related to their emergent movement patterns. These data are consistent with Edelman's proposal that spontaneous movements that occur repeatedly in regions of the organism's functional work space facilitate the development of stable behavioral patterns and emphasize the role of the interaction of multiple subsystems in the emergence of new behaviors.  相似文献   

5.
Although recent behavioral and neural research indicates that infants represent the body’s structure, how they engage self-representations for action is little understood. This study addressed how the human face becomes a reaching space. Infants (N = 24; 2–11 months) were tested longitudinally approximately every 3 weeks on their ability to reach to a vibrating target placed at different locations on the face. Successful reaches required coordinating skin- and body-based codes for location, a problem known as tactile remapping. Findings suggest that a functional representation of the face is initially fragmented. Infants localized targets in the perioral region before other areas (ears/temples). Additionally, infants predominantly reached ipsilaterally to targets. Collectively, the findings illuminate how the face becomes an integrated sensorimotor space for self-reaching.  相似文献   

6.
Ontogeny of infantile oral reflexes and emerging chewing   总被引：1，自引：0，他引：1  
The ontogeny of rooting, lip, lateral tongue, mouth opening, biting, and Babkin reflexes and emerging chewing behaviors were observed in 2 normal infants from 1 week to 35 weeks of age. These behaviors were videotaped at 9 monthly test sessions, and their movement patterns analyzed during slow-motion playback. The reflex responses were elicited in both infants through 35 weeks of age. They consisted of those characteristic movements described in the literature plus additional movements that elaborated the characteristic pattern. The complexity of the reflexes and the quality of movement changed with age. Components of chewing, which emerged sequentially from 1 week of age, were cyclical mandibular elevation and depression, lateral tongue movements, transport of the bolus from lateral to medial oral position, mandible retrusion, lateralization and protrusion movements in association with mandibular elevation and depression, increase in speed of rhythmical chewing movements to the mature speed of 1 cycle per second, and mastication. Chewing and oral reflexes contained similar movements but differed in the relative frequency of certain characteristic movements and in the stimulus response relationship.  相似文献   

7.
Six- to 8-year-olds, 10- to 12-year-olds, and adults (N = 108) performed the Simon task by reaching to targets on a digital display. The spatial and temporal characteristics of their movements were used to assess how two key processes underlying cognitive control—a threshold adjustment process and a controlled selection process—unfold over the course of a response (within-trial dynamics), are modulated by recent experience (cross-trial dynamics), and contribute to age-related gains in control (developmental dynamics). The results indicate that the controlled selection process undergoes a more protracted development than the threshold adjustment process. The results also shed light on a prominent debate concerning the cross-trial dynamics of control by supporting the feature integration account over the conflict adaptation account.  相似文献   

8.
By applying the principles and methods of mechanics to the musculoskeletal system, new insights can be discovered about control of human limb dynamics both in adults and infants. Here, we first provide a basic primer about biomechanics—its historical context, terminology, and analytical techniques. Next we review research with animals and human adults that illustrates how limb dynamics provides a window for examining the physical mechanisms underlying neuromotor control. Finally, we elaborate on how our research group has adapted dynamics techniques to investigate how infants gain control of their limbs and learn to reach in the first year of life.  相似文献   

9.
The claim that very young infants can imitate rests largely on reports that infants match adult displays of mouth opening (MO) and tongue protrusion (TP). Recent reviews suggest that only tongue protruding is reliably matched by young infants. This study tests the proposal that infants' "imitation" of tongue protruding reflects a coincidental match between a sight that infants find interesting and a behavior by which infants express interest. In Study 1, 4-week-old infants who looked longer at a nonsocial light display also produced TPs at higher rates than infants showing less interest. In Study 2, 4-week-old infants showed more interest in (looked longer at) a tongue-protruding adult face than a mouth-opening face. Study 3 tracked 2 infants' responses to interesting objects for several weeks before and after the onset of manual reaching. Both infants produced tongue protrusions in response to objects within reach before but not after reaching developed. Together, the results of the 3 studies suggest that infants' tongue protrusions in response to a tongue-protruding adult reflect very early attempts at oral exploration of interesting objects.  相似文献   

10.
The organization of infants' reaching skill for stationary and moving targets was examined. While 58 term, healthy infants at 5.5, 8.5, and 11.5 months of age reached for and grasped a cloth-covered dowel, their reaches were videotaped for later slow-motion analysis. Analyses addressed infants' anticipatory adjustment of hand alignment, use of information from spinning and oscillating targets to update ongoing reaches, and ability to capture targets moving in depth. Infants at all ages made anticipatory adjustments of hand alignment, although the effectiveness of these adjustments improved with age. Regardless of age, infants also used dynamic information from spinning and oscillating targets to update ongoing reaches, but the way infants used this information was related to age. Developmental constancy characterized infants' reaches for approaching targets. By observing infants' reaches for stationary, spinning, and approaching targets, the study expands the range of conditions under which adaptive reaching skill has been examined and provides insight into the roles of anticipation and updating in the development of early manual skill.  相似文献   

11.
10 preterm and 10 full-term infants were tested longitudinally from 28 to 60 weeks of age on a modified version of the AB task, a nonreaching AB task, a Barrier Detour task, a Means-End task, and Perseveration in the Means-End task. Results show that age-corrected (age since conception) premature infants tolerated longer delays than full-term infants on the modified and nonreaching AB tasks. However, when compared by chronological age (age since birth), there were no group differences on either the reaching or nonreaching AB task. No group differences were found on Barrier Detour, Means-End, or Perseveration in either the age-corrected or chronological age comparisons. The results suggest that the function that mediates modified AB performance is one of memory and not of perseveration or means-end ability. Further, these findings suggest that current proposals about brain development based on single samples of infants may be tenuous. Finally, the results of this study suggest that development of the brain structure(s) that mediate modified AB performance is strongly influenced by experience in the postnatal environment.  相似文献   

12.
The present research used a preferential‐reaching task to examine whether 9‐ and 11‐month‐olds (n = 144) could infer the relative weights of two objects resting on a soft, compressible platform. Experiment 1 established that infants reached preferentially for the lighter of 2 boxes. In Experiments 2–4, infants saw 2 boxes identical except in weight resting on a cotton wool platform. Infants reached prospectively for the lighter box, but only when their initial exploratory activities provided critical information. At 11 months, infants succeeded as long as they first determined that the platform was compressible; at 9 months, infants succeeded only if they also explored the boxes and thus had advance knowledge that they differed in weight.  相似文献   

13.
The development of detour ability during infancy   总被引：1，自引：0，他引：1  
3 longitudinal studies were conducted to examine the generalization of detour ability across motor responses and barrier types and the relationship between the development of object permanence and detour ability. In Experiment 1, 12 8-month-olds were tested every 3 weeks for 4 months on 4 different detour problems and Stage 4 and 6 object permanence tasks. In the detour problems, infants had to reach or move around a transparent or opaque barrier to obtain an object. The results indicated that infants made reaching detours before corresponding locomotor ones and generally made detours around opaque barriers before transparent ones. Infants also solved the Stage 4 task before the detour problems but failed to solve the Stage 6 task before testing ended. The results of Experiments 2 and 3 suggested that the difference in reaching and locomotor detour performance was not an artifact of barrier length or the infant's position relative to the barrier. The overall results are discussed in relation to issues of developmental synchrony and Piaget's theory of infant spatial development.  相似文献   

14.
The relations between changes in the scalp-recorded electroencephalogram (EEG) and the development of the ability to perform successfully 2 cognitive tasks attributed to frontal lobe functioning were examined in 13 infants from 7 to 12 months of age. Infants successful in performing the A-not-B task with increasingly longer delays across the second half of the first year of life showed changes in power in scalp-recorded brain electrical activity in the frontal region and an increase in anterior/posterior EEG coherence. Infants with rapid mastery of object retrieval did not differ in frontal EEG development from infants who exhibited the normal developmental progression in object retrieval performance. In a task examining inhibition of reaching to a novel toy, there were no differences in frontal EEG as a function of performance. Results from a cross-sectional sample revealed similar findings. These data confirm work with nonhuman primates on the importance of maturation of frontal cortex in the successful performance on certain tasks (A-not-B), but do not confirm nonhuman primate data on the importance of frontal cortex for other tasks (object retrieval). The data also suggest that the electroencephalogram may be useful as a noninvasive measure of central nervous system development during the first year of life.  相似文献   

15.
Treadmill-elicited stepping in seven-month-old infants   总被引：4，自引：0，他引：4  
E Thelen 《Child development》1986,57(6):1498-1506
When infants begin to walk independently, their step patterns, while not fully mature, are different in kinematic details from those of newborn stepping and supine kicking. 6 7-month-old infants, who performed little or no stepping movements, were supported over a small, motorized treadmill. All showed immediate alternating stepping. These movements were more similar to adult-like steps than newborn steps. The implications of eliciting a more mature pattern by the treadmill are discussed. Although infants normally perform few steps at this age, the underlying mechanism has not "disappeared."  相似文献   

16.
When prelocomotor infants are supported on a motorized treadmill, they perform well-coordinated, alternating stepping movements that are kinematically similar to upright bipedal locomotion. This behavior appeared to be a component of independent walking that could not be recognized without the facilitating context of the treadmill. To understand the ontogenetic origins of treadmill stepping and its relation to later locomotion, we conducted a longitudinal study using an experimental strategy explicitly derived from dynamic systems theory. Dynamic systems theory postulates that new forms in behavior emerge from the cooperative interactions of multiple components within a task context. This approach focuses on the transitions, often nonlinear, where one preferred mode of behavior is replaced by a new form. Specific predictions about these transitions help uncover the processes by which development proceeds. Chapters II, III, and IV introduce dynamic principles of pattern formation and their application to development. In our application of these principles, we tested nine normal infants twice each month beginning from month 1 in a task where the treadmill speed was gradually scaled up and in an additional condition where each leg was driven by the treadmill at a different speed. Kinematic variables were derived from computerized movement analysis equipment and videotaped records. We also collected a number of anthropometric measurements, Bayley motor scores, and a behavioral mood scale for each month. Several infants stepped on the treadmill in their first month, but in all infants performance showed a rapidly rising slope from month 3 to month 6. Infants also showed corresponding improvement in adjustments to speed and relative coordination between the legs. In dynamic terminology, we found evidence that alternating stepping on the treadmill became an increasingly stable attractor during the middle months of the first year. Dynamic predictions that transitions would be characterized by increased variability and sensitivity to perturbation were borne out. Identifying the transitions enabled us to suggest a control parameter or variable moving the system into the stable response to the treadmill. This appeared to be the waning of flexor dominance in the legs during posture and movement that allowed the leg to be stretched back on the treadmill and so elicited the bilaterally alternating response. Further studies are needed to test this hypothesis. This dynamic analysis confirmed earlier suggestions that skill in general, and locomotion in particular, develops from the confluence of many participating elements and showed how emergent forms may result from changes in nonspecific components. A dynamic approach may be useful for understanding ontogenetic processes in other domains as well.  相似文献   

17.
Infants’ pointing gestures are a critical predictor of early vocabulary size. However, it remains unknown precisely how pointing relates to word learning. The current study addressed this question in a sample of 108 infants, testing one mechanism by which infants’ pointing may influence their learning. In Study 1, 18‐month‐olds, but not 12‐month‐olds, more readily mapped labels to objects if they had first pointed toward those objects than if they had referenced those objects via other communicative behaviors, such as reaching or gaze alternations. In Study 2, when an experimenter labeled a not pointed‐to‐object, 18‐month‐olds’ pointing was no longer related to enhanced fast mapping. These findings suggest that infants’ pointing gestures reflect a readiness and, potentially, a desire to learn.  相似文献   

18.
This experiment evaluated the role of visual input about the location of a target object and the location of the hand in reaching by infants and adults. 5- and 9-month-old infants were presented with illuminated toys to reach for in a dark room. On no-switch trials, the toy remained illuminated throughout the infant's reach, whereas on switch trials the first-lit toy was replaced during the reach by a second-lit toy at a different position. On approximately half of the trials of each type a luminescent marker was attached to the reaching hand. Adult subjects (tested without the hand marker) fully compensated to the second-lit toy on switch trials, during a second reaching segment. On switch trials, 9-month-olds partially adjusted to the second-lit toy when wearing the hand marker and did not adjust without it. On no-switch trials, 9-month-olds reached just as accurately with or without the hand marker. 5-month-olds were generally inaccurate in their reaching and were unaffected by the presence or absence of the hand marker. The findings suggest that during the development of reaching there is an increase in visual guidance during the approach phase of reaches.  相似文献   

19.
Perception of the manner in which objects may be grasped was examined in a series of experiments with adults and 10-month-old infants; visuomotor adjustment in hand orientation before making contact with objects served as the index throughout. In the first experiment, infants modified their hand orientation to match more closely the long axis of an object. They did so even though the target object could have been grasped by either end with hands oriented orthogonally to the long axis of the object. In two subsequent experiments involving reaching through narrow apertures to grasp the target, anticipatory adjustments in hand posture were evident for adults but not for infants. However, anticipatory adjustments by infants, sometimes appropriate and sometimes inappropriate, were made when the object was of such a size that it could neither be grasped nor retrieved through the aperture. In the final experiment, infants directed their hands first toward a handle, the only graspable part of an object, and oriented their hands so as to be nearly parallel with it prior to contact. This was the only orientation in which a grasp was possible. It was concluded that infants at 10 months respond more appropriately to object properties than to surface apertures that place limitations on how an object may be grasped.  相似文献   

20.
The roles of person familiarity and parental involvement in 3.5-month-old infants' sensitivity to the dynamic emotion expressions of others were explored. In the home, parental facial/vocal expressions (happy, sad, angry) were videotaped, and measures of parent-infant involvement were obtained. In the laboratory, 32 infants alternately viewed their mother and father and an unfamiliar woman and man portraying expressions in an intermodal preference task. Infants looked differentially at mothers' expressions but not at those of fathers or unfamiliar adults. Examination of parent-child involvement patterns revealed significant relations with infants' sensitivity to expressions. Results suggest that person familiarity may facilitate infants' developing understanding of others' emotion expressions, and that individual differences in family dynamics may be relevant to infants' patterns of responding.  相似文献   

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