Crossing the midline: limits of early eye-hand behavior.

The development of the ability to extend the hand across the body midline to contact a visually presented object was examined in 48 normal, full-term, 9--20-week infants. One of the infant's arms was restrained while the behavior of the contralateral, unrestrained arm was observed. Results indicate that infants can first contact objects placed in front of the ipsilateral shoulder, then at the body midline, and later in front of the contralateral shoulder. Between 9 and 17 weeks, success at contacting objects at the midline progressed from 33% to 93%. During this interval, the success in contacting objects presented in front of the contralateral shoulder increased from 0% to 71%. By 18--20 weeks, all infants contacted objects in all three positions. These findings indicate that visually directed hand extension and reaching skills progress from the ipsilateral to include the bilateral and later the contralateral domains. The results are considered in regard to the development of bilateral coordination and complementarity.     

On Wooden Pillows: Multiple Classification and Children''s Category-based Inductions

Previous research has indicated that preschoolers do not distinguish between properties that are generalizable within a given category and those that are not. 2 possible general constraints on children's cognition are proposed to account for these findings. 3 studies are reported that argue against the presence of such general constraints. We examine preschoolers' understanding of the properties associated with material (e.g., wood, cotton) and object (e.g., chair, pillow) categories. In Study 1, subjects consistently made inductions based on the material compositions of items when asked to predict texture and fragility. In Study 2, the same subjects judged that items that shared material would share an unfamiliar dispositional property (e.g., gets sodden in water), but items that shared object kind would share a novel functional property (e.g., used for accelerating). Study 3 tested a younger sample of 3-year-olds and found the same sensitivity to category type, albeit with larger individual differences. By age 3, children use different modes of categorization to generalize different kinds of phenomena. These results argue against general limitations on children's abilities to use categories to make inductions. Even when children lack specific theoretical knowledge, the ability to organize phenomena into domains allows children to recognize which categories are relevant in different situations. This understanding can provide a basis for the development of more specific theories.     

Anticipatory Reaching by Infants and Adults: The Effect of Object Features and Apertures in Opaque and Transparent Screens

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.     

Preschool Children's Symbolic Representation of Objects through Gestures

To investigate the symbolic quality of preschoolers' gestural representations in the absence of real objects, 48 children (16 3-, 4-, and 5-year-olds) performed 2 tasks. In the first task, they were asked to pretend to use 8 common objects (e.g., "pretend to brush your teeth with a toothbrush"). There was an age-related progression in the symbolic quality of gestural representations. 3- and 4-year-olds used mostly body part gestures (e.g., using an extended finger as the toothbrush), whereas 5-year-olds used imaginary object gestures (e.g., pretending to hold an imaginary toothbrush). To determine if children's symbolic skill is sufficiently flexible to allow them to use gestures other than those spontaneously produced in the first task, in the second task children were asked to imitate, for each object, a gesture modeled by an experimenter. The modeled gesture was different from the one the child performed on the first task (e.g., if the child used a body part gesture to represent a particular object, the experimenter modeled an imaginary object gesture for that object). Ability to imitate modeled gestures was positively related to age but was also influenced by the symbolic mode of gesture. 3-year-olds could not imitate imaginary object gestures as well as body part gestures, suggesting that young preschoolers have difficulty performing symbolic acts that exceed their symbolic level even when the acts are modeled. Results from both tasks provide strong evidence for a developmental progression from concrete body part to more abstract imaginary object gestural representations during the preschool years.     

The development of infants' reaches for stationary and moving targets

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.     

Ideational border crossings: rethinking the politics of knowledge within and across disciplines

This article explores the merits, possibilities and difficulties of making intra and trans-disciplinary ‘border crossings’ essentially of an ideational kind. Drawing ideas from complexity literature, the article lauds the potential of ‘concept studies’ as means of making such crossings and addressing enduring issues (e.g., of equity and health) within education, Physical Education (PE) and Health. The article suggests, however, that the culture of neoliberalism and extant power relations may prohibit rather than nurture and encourage any willing exchange of ideas or sharing of resource, presaging border closure rather than ‘border crossing’. Talk of the latter in periods of austerity may become shorthand for ‘rationalisation’, offering new language for a newly invigorated politics of erasure, rather than announcing desire to nurture and actualise new voices and new ways of sharing ideas towards investigating and dismantling enduring social hierarchies and trends.     

Children's use of nonegocentric standards in judgments of functional size

Dimensional adjectives are inherently relative in meaning, and so provide a test of children's ability to apply nonegocentric standards. The present research investigates children's ability to apply one kind of relative standard assessing the size of an object with regard to its intended use (a functional interpretation). In 3 experiments, children 3-5 years of age were asked to judge objects as "big" or "little" according to their function (e.g., a hat for a doll; a key for a door). Contrary to previous claims, the ability to use nonegocentric functional standards was present by age 3. However, 3-year-olds performed above chance only when their attention was directed to the relevant function, either by means of action (when actually shown how the objects fit together) or by means of language. In contrast, 4-year-olds performed well without additional action-based or linguistic cues. It is suggested that children have an implicit ordering in their interpretations of big and little, such that functional judgments are lower in priority than 2 other standards: normative (the size of an object is compared to a stored mental standard, e.g., a chihuahua is small for a dog) and perceptual (the size of an object is compared to another physically present object of the same type, e.g., a chihuahua 6 inches tall is big compared to a chihuahua 4 inches tall). Even 3-year-olds can make nonegocentric functional judgments of relative size, but the basis of the judgment must be unambiguous.     

Inability of five-month-old infants to retrieve a contiguous object: a failure of conceptual understanding or of control of action?

Infants of 5 to 6 months of age can retrieve a free-standing object, but fail to retrieve the same object from atop a slightly larger object. The accepted explanation has been that the infants do not understand that an object continues to exist independently when placed upon another. Predictions based on that explanation were tested against the hypothesis that infants' problem consists of lack of precision in visually guided reaching and lack of ability to inhibit reflexive reactions to touch. Twelve infants each at 5 and 7 months of age were tested on 16 trials. More 5-month-olds succeeded, in less time, and with fewer touches to an edge of the base, on trials more forgiving of an imprecise reach than on less forgiving trials. Success in retrieving objects close in size and fully contiguous with their bases was seen even at 5 months when the demands on skill in reaching were reduced. It is proposed that when 5-month-old infants fail to retrieve one object placed upon another, it is not because of a lack of conceptual understanding, but because they lack the skill to reach to the top object without accidentally touching an edge of the base en route.     

Perceiving the Affordance of Contact in Fourand Five-Month-Old Infants

The focus of this study was on the ability of infants to perceive whether an object is positioned at a distance that would make contact possible. As a toy was presented, sometimes within and sometimes beyond reach, the initiation of reaching and leaning forward was scored. Infants were divided into leaning and nonleaning groups. Both leaning and nonleaning 5-month-olds changed their behavior dramatically when the object was placed beyond, as opposed to within, reach. The nonleaners showed a decline in reaching when this boundary for contact was crossed. The "leaners" did not; rather, they began to lean forward. These results suggest that 5-month-olds use information for the affordance of contact. 4-month-olds provided less evidence that arm length regulates reaching. 5-month-old infants acted as if they not only had some sensitivity to the absolute distance of an object but also to the effect that leaning forward has on their ability to make contact with a distant object.     

点电荷电场能量发散问题初探

从点电荷模型与客体的差异入手,考虑带电体的带电量受带电体大小制约,尝试解决点电荷电场能量发散问题。     

点电荷电场能量发散问题初探

从点电荷模型与客体的差异入手,考虑带电体的带电量受带电体大小制约,尝试解决点电荷电场能量发散问题。     

How Two- and Four-Year-Old Children Interpret Adjectives and Count Nouns

We examined the role of object kind familiarity (i.e., knowledge of a count noun for an object) on preschoolers' sensitivity to the relation between a novel word's form class (adjective or count noun) and its reference (to a material kind-property or to an object kind). We used a forced-choice match-to-target task, in which children learned a word for one object (e.g., a metal cup), and then chose between 2 other objects. One was from the same object kind but a different material kind (with different related properties, such as color and texture; e.g., a white plastic cup); the other was from a different object kind but the same material kind (with the same related properties; e.g., a metal spoon). In Experiment 1, children learned either a count noun (e.g., "This is a zav") or an adjective (e.g., "This is a zav one"). Within each form class, we crossed the familiarity of the referent object kind (familiar and unfamiliar) with the age of the children (2- and 4-year-olds). The principal finding was that in interpreting an adjective, 4-year-olds were more likely to choose the object sharing material kind with the target if the target was familiar than if it was unfamiliar. No such familiarity effect was evident among 2-year-olds. In Experiment 2, we employed a more unambiguously adjectival frame (e.g., "This is a very zav-ish one"), and replicated the results of Experiment 1. We interpret the results in terms of 2 proposed word learning biases: one that learners initially expect any word applied to an unfamiliar object to refer to a (basic-level) kind of object, and a second that learners prefer words to contrast in meaning. We consider several interpretations of the observed age difference.     

Visual Guidance in Infants' Reaching toward Suddenly Displaced Targets

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.     

Learning to Crawl

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.     

浅谈交通灯控制方案的技术改进

我国现行交通灯多为单灯多向式和单灯单向式。其最多车辆同行方向数仅为10,且其中还存在交叉问题。但若将交通灯的安装位置、交叉路口的结构做一下调整,则不仅可使车辆同行方向数成倍增加,而且可使我国道路车辆的调头问题达到进一步解决。     

The use and effectiveness of maternal scaffolding in mother-infant games

Maternal behaviors within mother-infant games were examined to determine the amount, type, and functional value of maternal helping behaviors. 17 mother-infant pairs were videotaped on monthly visits from 8 to 16 months as they played 5 separate games. 2 of these games, roll the ball and peekaboo, were analyzed in terms of "rounds" of each game. Results show that dyads play more rounds of both games in the first months that infants perform game-relevant behaviors (e.g., returning a ball, performing uncovering or covering-uncovering). Maternal attention-getting and physical "stage-setting" behaviors occur in the early rounds of both games. In roll the ball, maternal hands-out and reinforcement behaviors increase in the months after the child begins to return the ball, while the percentage of rounds in which dyads play nonreturn variants decreases. Infants are more likely to return a ball when mother holds out her hands than when she does not. Infants are also able to perform returning or uncovering in game contexts before they perform similar behaviors in cognitive tests. The general similarity of findings in the peekaboo and roll-the-ball games, in spite of differences in the amounts of scaffolding, attention-getting, stage-setting, and reinforcement behaviors between the 2 games, indicates that the types and functions of maternal helping behaviors may be generalizable to other contexts of mother-infant interactions.     

Infants'' Localization of Sounds within Hemifields: Estimates of Minimum Audible Angle

Infants' acuity in localizing sounds within hemifields was examined by determining the smallest sound shift off 60 degrees and along the horizontal axis that infants could discriminate reliably, that is, minimum audible angle (MAA). Infants 6, 12, and 18 months of age were tested using a Go/No-Go conditioned head-turn procedure in which infants received an equal number of no-change (control) trials and sound-shift (experimental) trials. A correct response (i.e., a head turn toward the loud-speakers) on an experimental trial resulted in visual reinforcement. Localization acuity for sounds within hemifields was fairly poor and improved systematically with increasing age. MAA estimates at each age were significantly higher, indicating poorer localization acuity, in comparison to those obtained previously in research examining infants' resolution of auditory space near midline. These findings are consistent with adult data and demonstrate a finer partitioning of auditory space near midline than within hemifields. The implications of these findings for our understanding of the development of auditory processing mechanisms in sound localization are discussed.