共查询到20条相似文献，搜索用时 31 毫秒
1.
Learning to Crawl 总被引：3，自引：0，他引：3
The effects of infants' age, body dimensions, and experience on the development of crawling was examined by observing 28 infants longitudinally, from children's first attempts at crawling until they began walking. Although most infants displayed multiple crawling postures en route to walking, development did not adhere to a strict progression of obligatory, discrete stages. In particular, 15 infants crawled on their bellies prior to crawling on hands and knees, but the other 13 infants skipped the belly-crawling period and proceeded directly to crawling on hands and knees. Duration of experience with earlier forms of crawling predicted the speed and efficiency of later, quite different forms of crawling. Most important, infants who had formerly belly crawled were more proficient crawling on hands and knees than infants who had skipped the belly-crawling period. Transfer could not be explained by differences in infants' age or body dimensions alone. Rather, experience using earlier crawling patterns may have exerted beneficial effects on hands-and-knees crawling by shoring up underlying constituents common to all forms of crawling postures. 相似文献
2.
This study compared the relative contributions of growing body dimensions, age, and walking experience in the development of walking skill in 9- to 17-month-old infants (N = 210), 5-6-year old kindergartners (N = 15), and college students (N = 13). Kinematic measures derived from participants' footprints showed characteristic improvements in walking skill. As children became bigger, older, and more experienced, their steps became longer, narrower, straighter, and more consistent. Improvements reflected a narrowing base of support and increasing control over the path of progression. Although both infants' age and the duration of their walking experience contributed to improvements in walking skill, experience was the stronger predictor. This finding suggests that practice is the more important developmental factor for helping infants to conquer their weak muscles and precarious balance. 相似文献
3.
Developmental transitions of complex systems may be studied by selecting (collective) variables that constrain the degrees of freedom for each developmental state. In a dynamical systems approach, the transitions from state to state are engendered through the scaling of contributing subsystems (control parameters). In this study, the locomotor skills of walking and running were compared in newly running infants by observing several likely collective variables including relative stance, estimated pathway of center of mass, and segmental/joint action. 4 children were filmed longitudinally at 5.5, 7.5, and 9.5 months of independent walking and then at 3 years of age. 3 trials per gait were selected for single stride analysis and compared with data from 4 adults. In general, the proposed collective variables showed transitional forms over the first few months of running, indicating a relatively continuous change between the 2 gait forms. Coordination of the knee joint was very similar between gaits and across age, but the ankle joint was less consistent for both gaits in the infants. Relative stance and stride length data indicated that the children could not generate vertical and horizontal displacement. These findings echo those found in newly walking infants and suggest that similar rate-limiting parameters are present for both gaits. 相似文献
4.
The development of infant sensitivity to biomechanical motions 总被引：1，自引：0，他引：1
3 experiments were conducted to examine infant sensitivity at 20, 30, and 36 weeks of age to the 3-dimensional structure of a human form specified through biomechanical motions. All 3 experiments manipulated occlusion information in computer-generated arrays of point-lights moving as if attached to the major joints and head of a person walking. These displays are readily recognized as persons by adults when occlusion information is present, but not when it is absent or inconsistent with the implicit structure of the human body. Converging findings from Experiments 1 and 2 suggested that 36-week-old infants were sensitive to the presence of occlusion information in point-light walker displays; neither 20- nor 30-week-old infants showed any sensitivity to this information. The results of Experiment 3 revealed further that 36-week-old infants were sensitive to whether or not the pattern of occlusion was consistent with the implicit form of the human body, but only when the displays were presented in an upright orientation. These findings are interpreted as suggesting that infants, by 36 weeks of age, are extracting fundamental properties necessary for interpreting a point-light display as a person. 相似文献
5.
The expressive behaviors of full-term and preterm infants and their mothers were examined during face-to-face interaction when the infants were approximately 2 1/2, 5, and 7 1/2 months old. Videotapes of the sessions were coded on a second-to-second basis using Izard's discrete emotion coding system. Overall, infants showed a linear increase in positive effect, especially interest and joy, and a corresponding decrease in negative affect, especially pain and knit brow, with age; decrease in negative affect was accounted for largely by the preterm infants. In terms of maternal responses, there was an increase in contingent responding to infant interest expressions and a decrease in contingent responding to infant pain expressions over time, especially in the case of the preterm infant. The data set as a whole was examined further to establish the directionality of influence between mothers and infants in change patterns over time. There was evidence of learning effects in infants as a function of maternal modeling and contingency patterns. Anomalies in maternal responses to preterm infant affect expressions were observed. Mothers of these infants displayed significantly less matching or imitation of their infant's facial expressions, showed random rather than contingent responsiveness to sadness, and a significant ignoring response to infant anger. These differences were attributed to differences in gazing patterns and negative emotion expression in preterm infants. The results are discussed within a framework of emotion socialization that recognizes bidirectionality of influence in the emotional patterns of mothers and infants. 相似文献
6.
为改善脑卒中患者穿戴下肢外骨骼机器人进行步行康复训练时,步行平衡稳定性不足的问题,提出髋关节内收/外展自由度控制机理和设计方法,通过基于零力矩点理论的步行平衡稳定性分析,研究髋关节内收/外展主动运动对人机系统平衡的作用。通过设定欠驱动髋关节内收/外展运动自由度,改善人机系统步行平衡,并利用单电机驱动单元实现左右两侧髋关节内收/外展运动的协调控制,从而在运动安全的前提下提升步行平衡安全性。通过MATLAB与ADAMS仿真分析,分别验证步行平衡稳定性和欠驱动方案的有效节能性。仿真结果显示,欠驱动方案相比传统每个关节分别安装驱动的方案,扭矩降低了32.52%。该步行平衡解决方案与欠驱动设计方法对促进康复外骨骼机器人应用推广具有重要意义。 相似文献
7.
This study examined whether 16-month-old walking infants take the material composition of a handrail into account when assessing its effectiveness as a tool to augment balance. Infants were encouraged to cross from one platform to another via bridges of various widths (10, 20, 40 cm) with either a "wobbly" (foam or latex) or a wooden handrail available for assistance. Infants attempted to walk over wider bridges more often than narrow ones, and attempts were more frequent when the sturdy wooden handrail was available. Infants tailored their exploratory behaviors, bridge-crossing strategies, and handrail-use strategies to the material properties of the rail. 相似文献
8.
A Longitudinal Study of Intralimb Coordination in the First Year of Independent Walking: A Dynamical Systems Analysis 总被引：1，自引：0，他引：1
Using a dynamical systems approach, we examined the development of intralimb coordination over the first year of independent walking. The segmental motion of the thigh and shank and their intralimb coordinative relationship were modeled dynamically as a system of coupled limit cycles. To test the predictions of such a dynamic model in the development of intralimb coordination, 3 infants were filmed from the onset of their first upright independent walking steps, and weekly for the next month and then every month thereafter until they had been walking for 1 year. 3 adults also were included for comparison. Analysis of the kinematics data derived from the film revealed that at the emergence of walking, the limit cycle system displayed instability in several aspects. With walking experience, however, the limit cycle regime became more attractive, such that by 3 months of walking the infants appeared to have found an adult-like stable coordinative relationship between the 2 segments. This pattern of instability followed by stability is consisted with the transitional behaviors of dynamical systems. Several potential control parameters are discussed that might contribute to the stabilization of the walking behavior. The utility of employing a dynamical systems approach for understanding developing behavioral systems is discussed. 相似文献
9.
Russell A. Isabella 《Child development》1993,64(2):605-621
This study built on attachment theory and previous research in examining the interactional origins of the secure, insecure-resistant, and insecureavoidant patterns of attachment. Maternal sensitive responsivity, rejection, and activity were the focus of repeated naturalistic observations when infants were 1, 4, and 9 months of age; quality of attachment was assessed at 1 year. Mothers of secure 1-year-olds were observed to be more sensitively responsive at 1 and 4 months and less rejecting at 1 and 9 months than mothers of insecure infants. Mothers of insecure-avoidant infants were more rejecting at 9 months, whereas mothers of insecure-resistant infants were least sensitively responsive and most rejecting at 1 month; the insecure groups were also differentiated on the basis of patterns of change from 1 to 9 months, with mothers of resistant infants becoming less rejecting and mothers of avoidant infants becoming more rejecting relative to other mothers. 相似文献
10.
Associations between infants' transition to walking and object activities were examined. Fifty infants were observed longitudinally during home observations. At 11 months, all infants were crawlers; at 13 months, half became walkers. Over age, infants increased their total time with objects and frequency of sharing objects with mothers. Bidirectional influences between locomotion and object actions were found. Walking was associated with new forms of object behaviors: Walkers accessed distant objects, carried objects, and approached mothers to share objects; crawlers preferred objects close at hand and shared objects while remaining stationary. Earlier object activities predicted walking status: Crawlers who accessed distant objects, carried objects, and shared objects over distances at 11 months were more likely to walk by 13 months. 相似文献
11.
为了解青岛市3-6岁幼儿的体质状况,探讨幼儿体质发展变化的规律及完善国民体质监测网络,对青岛市七区和五市的805名幼儿进行了测试与分析。结果表明：青岛市3-6岁幼儿体质总体状况良好,身体形态方面,男幼儿好于女幼儿,城市幼儿好于农村幼儿,但身体素质发展不平衡,下肢力量和平衡能力有所提高,而上肢力量出现下降。对此,幼儿教师和家长应转变观念,树立＂健康第一＂和教育始于体育的思想,合理安排幼儿的体育活动。 相似文献
12.
Lana B. Karasik Karen E. Adolph Sara N. Fernandes Scott R. Robinson Catherine S. Tamis-LeMonda 《Child development》2023,94(4):1049-1067
In Tajikistan, infants are bound supine in a “gahvora” cradle that severely restricts movement. Does cradling affect motor development and body growth? In three studies (2013–2018), we investigated associations between time in the gahvora (within days and across age) and motor skills and flattened head dimensions in 8–24-month-old Tajik infants (N = 269, 133 girls, 136 boys)) and 4.3–5.1-year-old children (N = 91, 53 girls, 38 boys). Infants had later motor onset ages relative to World Health Organization standards and pronounced brachycephaly; cradling predicted walk onset age and the proficiency of sitting, crawling, and walking. By 4–5 years, children's motor skills were comparable with US norms. Cultural differences in early experiences offer a unique lens onto developmental processes and equifinality in development. 相似文献
13.
In actual engineering practice, the stress increment within a composite foundation caused by external loads may vary simultaneously
with depth and time. In addition, column installation always leads to a decay of soil permeability towards the column. However,
almost none of the consolidation theories for composite foundation comprehensively consider these factors until now. For this
reason, a stress increment due to external loads changing simultaneously with time and depth was incorporated into the analysis,
and three possible variation patterns of soil’s horizontal permeability coefficient were considered to account for the detrimental
influence of column installation. These three patterns included a constant distribution pattern (Pattern I), a linear distribution
pattern (Pattern II), and a parabolic distribution pattern (Pattern III). Solutions were obtained for the average excess pore
water pressures and the average degree of consolidation respectively. Then several special cases were discussed in detail
based on the general solution obtained. Finally, comparisons were made, and the results show that the present solution is
the most general rigorous solution in the literature, and it can be broken down into a number of previous solutions. The consolidation
rate is accelerated with the increase in the value of the top to the bottom stress ratio. The consolidation rate calculated
by the solution for Pattern I is less than that for Pattern II, which in turn is less than that for Pattern III. 相似文献
14.
Maternal interactional behavior with nonorganic failure-to-thrive infants: a case comparison study 总被引：1，自引：0，他引：1
Mothers of 47 6-month-old infants with early histories of nonorganic failure to thrive (NOFT) infants and a matched comparison group of physically healthy infants were observed in interactions with their infants in their homes one month following hospitalization. Mothers of NOFT infants were observed to have less adaptive social interactional behavior, less positive affective behavior, and demonstrated more arbitrary termination of feedings. No group differences were found in flexibility or sensitivity of maternal feeding, or in environmental circumstances such as number of persons present, noise level, or level of activity. These salient deficiencies in maternal interactional behavior may continue to disrupt the NOFT child's physical growth and psychological development following initial diagnosis and hospitalization. Additional studies are needed to identify patterns of maternal interactional behavior which influence psychological prognosis and to assess the responsiveness of maternal interactional behavior to intervention. 相似文献
15.
《Early childhood research quarterly》1995,10(3):261-275
Ninety nine infants were observed at entry into child care and at 3-month intervals during the first 6 months. We examined changes in relations among indices of adjustment and caregiver behaviors and which entry variables predict patterns of 6-month adjustment. Toy play shows no systematic relation with infant affective behavior at entry, yet 6 months later it is associated with positive affect and reduced social involvement. Caregiver interaction also changes; after 6 months expressive children receive more and different forms of attention than do nonexpressive children. Bowlby's (1969) account of institutionalized infants was used to identify different patterns of adjustment. Despair-like infants were distressed, immobilized, and self-soothing at entry. Infants who were detachment-like (i.e., object centered, happy, and socially unengaged after 6 months) received less attention from caregivers at entry. Some 6-month patterns have their roots in temperament dispositions, with differential outcomes determined largely by caregiver responsiveness. 相似文献
16.
Attachment research has shown the emergence of individual differences in the security of infant-mother attachment during the first year of life as well as their importance for later social-emotional development. A biobehavioral perspective may help settle disagreements about the validity and interpretation of 12-month-old infants' different behavioral patterns of attachment assessed by Ainsworth's Strange Situation. It was shown that, despite less overt distress in insecure-avoidant infants after short separations from the mother, overall cardiac measures indicate arousal patterns similar to the secure infants during separation. However, differences in cardiac response emerged with regard to object versus person orientation during reunion. Additionally, findings of increased cortisol in both insecure-avoidant and disorganized infants support the theoretical interpretation that these infants, in contrast to secure infants, lack an appropriate coping strategy. 相似文献
17.
18.
冷菊丽 《辽宁科技学院学报》2017,19(1)
为了风洞试验天平在高马赫数试验中免受冲击载荷所产生的破坏,设计了一套全新的试验天平保护装置,该套装置安装与模型支杆内部,而不是安装于风洞上.采用改变受力形式的原理,将模型冲击载荷由单支点支撑改为双支点支撑.在保护装置设计中,采用传统丝杠传动与新式压电陶瓷驱动器相结合的方式,实现了轴向与法向两个方向的运动.新设计的机构具有尺寸小,承载能力大,定位精度高、成本低的特点.该套装置能够降低天平感受到的模型冲击载荷,减少天平所受应力,使天平免受破坏. 相似文献
19.
Prematurity stereotyping: effects on mother-infant interaction 总被引：1，自引：0，他引：1
The possibility that the self-fulfilling prophecy process can adversely affect the caregiving environment of premature infants was explored in this study. A portion of this process was investigated experimentally by assessing cognitive and behavioral reactions of 27 mothers to unfamiliar full-term infants who were labeled either full-term or premature. Infants who were described as premature were touched less and given a more immature toy to play with, were rated as smaller, finer-featured, and less cute, and were liked less than infants who were labeled full-term. In turn, infants labeled premature were less active during the interaction than infants labeled full-term. College students who later observed the videotapes made of the mother-infant interactions were able to accurately guess which label was assigned to the infants. The results of this study further support the existence of a prematurity stereotype and the impact of expectations on perceptions and behavior. 相似文献
20.
George P. Rice Jr. 《Quarterly Journal of Speech》2013,99(1):21-25
The perspective from which a less powerful social group views a “dominant” group—either as another culture or as a co‐culture —influences the structure and function of its strategies for communicating with the “dominant” group. Four recurring patterns of communication between groups with asymmetrical power relationships are analyzed using the theory of the coordinated management of meaning. 相似文献