Age Differences on a Coincident Anticipation Task

Two experiments were performed as an initial attempt to explain age related limitations in response accuracy on a coincident anticipation task. Five- to 9-year-old boys and adult males participated in each experiment. They made horizontal arm movements in response to stimuli from a Bassin Anticipation Timer. The results of Experiment I confirmed the findings of previous studies, which showed that young children respond early to slow moving stimuli. They were most accurate at intermediate speeds; their responses deteriorated as speed was increased. Older children and adults were more accurate at slow to intermediate speeds; their performances also declined at fast stimulus velocities. Experiment II examined use of a stereotypic or default movement speed as an explanation for these results, particularly for young children. A most comfortable movement pace was determined for each subject and was used as a baseline speed for a subsequent timing task. Four other stimuli were selected in 0.8 mph increments from the baseline speed (two faster, two slower). In addition, selected trials for 6 subjects at each age were filmed at 32 fps. X-coordinates for these trials were obtained and smoothed at 5 Hz. Movement time data suggested that 5-year-olds used a preferred or stereotypic speed, since they were accurate only when responding to their baseline speed. Older subjects matched stimuli up to and including their baselines. Kinematic characteristics confirmed the general notion of preferred speed for 5-year-olds. These same measures demonstrated that older subjects were increasingly adaptable in their responses, despite a failure to respond more accurately. Consequently, the term “preferred speed” lacks generality as an explanatory concept. Age-related shifts in the ability to modify components of a response, like average movement velocity and number of corrections, were used to explain accuracy differences.     

Age difference on a coincident anticipation task: influence of stereotypic or "preferred" movement speed

Two experiments were performed as an initial attempt to explain age related limitations in response accuracy on a coincident anticipation task. Five- to 9-year-old boys and adult males participated in each experiment. They made horizontal arm movements in response to stimuli from a Bassin Anticipation Timer. The results of Experiment l confirmed the findings of previous studies, which showed that young children respond early to slow moving stimuli. They were most accurate at intermediate speeds; their responses deteriorated as speed was increased. older children and adults were more accurate at slow to intermediate speeds; their performances also declined at fast stimulus velocities. Experiment ll examined use of a stereotypic or default movement speed as an explanation for these results, particularly for young children. A most comfortable movement pace was determined for each subject and was used as a baseline speed for a subsequent timing task. Four other stimuli were selected in 0.8 mph increments from the baseline speed (two faster, two slower). In addition, selected trials for 6 subjects at each age were filmed at 32 fps. X-coordinates for these trials were obtained and smoothed at 5 Hz. Movement time data suggested that 5-year-olds used a preferred or stereotypic speed, since they were accurate only when responding to their baseline speed. older subjects matched stimuli up to and including their baselines. Kinematic characteristics confirmed the general notion of preferred speed for 5-year-olds. These same measures demonstrated that older subjects were increasingly adaptable in their responses, despite a failure to respond more accurately. Consequently, the term "preferred speed" lacks generality as an explanatory concept. Age-related shifts in the ability to modify components of a response, like average movement velocity and number of corrections, were used to explain accuracy differences.     

Static balance and developmental coordination disorder

The development of static balance is a basic characteristic of normal motor development. Most of the developmental motor tests include a measure of static balance. Children with a developmental coordination disorder (DCD) often fail this item. Twenty-four children at risk for DCD with balance problems (DCD-BP) and 24 matched control children in the age range of 6-12 years participated in a detailed study of balance control. Additional groups of children (6-7 years, N=25; 10-11 years, n=16; with M-ABC scores >15th percentile) were selected randomly to study developmental changes in balance control in the age range of interest. Three experiments were conducted to examine developmental and clinical differences in the control of static balance. In the first, we measured the excursion of the centre of pressure (force-plate) in conditions with and without vision while standing still on one or two legs for 20 s. In the second experiment, EMGs were measured while standing on one leg. In the third experiment, in which only a subgroup of the DCD-BP and matched control children participated, a short unexpected force in the back lightly perturbed normal standing and EMG and force-plate responses were measured during balance recovery. In conditions of one-leg stance, children were not always able to maintain balance. Only epochs of stable postural control (7.5-20 s) were analysed. The results showed improvement of static balance with age, but only subtle differences between the DCD and control groups. Centre of pressure measures differed in the more difficult conditions. DCD-BP children had more difficulty standing on one leg with eyes closed. While standing on the non-preferred leg the EMGs of the DCD-BP children showed slightly more co-activation of the muscles of lower and upper leg. Perturbation of standing resulted in longer duration of recovery in the first trial in this group. Apparently DCD children learn to compensate for the perturbation within a few trials as well as control children do. The clear improvement with age shows that our measures of balance control are sensitive to detect changes. The general conclusion that may be drawn from this study is that under normal conditions static balance control is not a problem for children with DCD. Only in difficult or novel situations they seem to suffer from increased postural sway as a result of non-optimal balance control.     

Space-time invariance in handwriting: Contrasts between primary school children displaying advanced or retarded handwriting acquisition

Previous research into the handwriting of adult subjects has highlighted the possible roles of ‘relative timing’ (Viviani and Terzuolo 1980) and simple oscillations (Hollerbach 1981) in controlling movement. Both of these factors provide interesting perspectives with which to view the development of fine motor control in children. The spatio-temporal structure of writing movements was examined between children with refined handwriting skills and those exhibiting unusually poor writing for their age. The analysis concentrated on three sites of temporal variability: absolute timing, temporal patterning, and rhythmic content of the writing movements. The results supported the notion that the relative timing of segments within a movement sequence acts as a major constraint on motor output variability. It is suggested, however, that previous simplistic views of ‘relative timing’ be expanded, and that such timing may be dictated by optimisation strategies. Differences in the stability of the graphic product between groups could not be accounted for by differences in the rhythmic content of the movements. In the absolute timing of writing tasks, the results suggest that variability in writing time from trial to trial, and duration of intra-task pauses, are better indicators of writing difficulties than total writing time or the number of pauses.     

Gait characteristics of children during free ascent climbing performances

The purpose of this study was to examine the characteristics of children's climbing performances with an emphasis placed on determining the appropriate dimensions of climbing apparatus as shown by the gait patterns adopted by the users. Seventy-two male and female children were selected and assigned to one of eight groups according to their age. The population comprised children whose ages ranged between 1.5 and 5.5 years with groups designated every 6 months (total eight groups). Each subject performed three trials consisting of an ascent of a 1.83 X 1.83 m climbing structure. The wooden climbing frame incorporated a regular matrix of handholds/footholds with a between rung difference of 0.15 meters. On command, the subjects climbed from a target area centered at the bottom of the frame to the top where the parent or guardian was located to offer encouragement. all trials were filmed using one 16 mm motion-picture camera. A large mirror placed in the field of vision permitted the recording of both the rear and lateral views. The temporal and displacement characteristics of a representative gait cycle for each subject were analyzed. The results provided little evidence to indicate either an age related or overall preferred consistent climbing gait. However, the most common method of ascent (38.92%) involved an order of peripheral segment movement of the right leg followed by right arm then left leg followed by left arm. A statistical analysis utilizing analysis of variance procedures with Newman Keuls post-hoc evaluation (p<0.05) conducted on the temporal characteristics of a gait cycle during a trial by each subject revealed: (1) that both the absolute contact and airborne times for the upper and lower limb segments were greater for the subjects between 1.5 and 2.5 years than for the subjects between 4.5 and 5.5 years, (2) that there existed an age dependent systematic decrease in the relative contact times for the lower limb segments, (3) that the age dependent decreases in the absolute lower limb airborne times were relatively greater than the corresponding decreases in the contact times with a significant linear trend being recorded. While the preferred horizontal spacing was found to be approximately 0.15 meters for all subjects, the preferred inclined spacing between consecutive handholds/footholds was found to be age dependent.     

Action Interrupted: Movement and Breakpoints in the Processing of Motion Violations in Toddlers and Adults

From early in development, segmenting events unfolding in the world in meaningful ways renders input more manageable and facilitates interpretation and prediction. Yet, little is known about how children process action structure in events composed of multiple coarse-grained actions. More importantly, little is known about the time course of action processing in young children or about the specific features that recruit attention. This is particularly true when we consider action that pauses unexpectedly—as actions sometimes do—thereby violating the expectation of a continuous unfolding of motion. We assessed visual preference to intact and disrupted actions embedded within a multiaction event in toddlers and adults. In 1 condition, pauses were inserted at intact action boundaries, whereas in the other condition, they disrupted action. Attention in both groups was recruited to the disrupted relative to intact events. Time-course analyses, however, revealed developmental differences in sensitivity to the movement features (e.g., motion, pauses, and transitions) of disrupted events.     

Preschool children's learning proclivities: When the ritual stance trumps the instrumental stance

Previous research has demonstrated an efficiency bias in social learning whereby young children preferentially imitate the functional actions of a successful individual over an unsuccessful group member. Our aim in the current research was to examine whether this bias remains when actions are presented as conventional rather than instrumental. Preschool children watched videos of an individual and a group member. The individual always demonstrated a successful instrumental action and the group member an unsuccessful action that was either causally transparent or opaque. Highlighting the selective nature of social learning, children copied the group at higher rates when the demonstrated actions were causally opaque than when they were causally transparent. This research draws attention to the influence of conventional/ritual‐like actions on young children's learning choices and emphasizes the role of this orientation in the development of human‐specific cumulative culture.     

Development of rule-based eye-hand-decoupling in children and adolescents

In the present study, we characterize how the ability to decouple guiding visual information from a motor action emerges during childhood and adolescence. Sixty-two participants (age range 8–15 yrs.) completed two eye-hand coordination tasks. In a direct interaction task, vision and motor action were in alignment, and participants slid their finger along a vertical touch screen to move a cursor from a central target to one of four peripheral targets. In an eye-hand-decoupled task, eye and hand movements were made in different planes and cursor feedback was 180° reversed. We analyzed whether movement planning, timing and trajectory variables differed across age in both task conditions. There were no significant relationships between age and any movement planning, timing, or execution variables in the direct interaction task. In contrast, in the eye-hand-decoupled task, we found a relationship between age and several movement planning and timing variables. In adolescents (13–15 yrs.), movement planning and timing was significantly shorter than that of young children (8–10 yrs.). Eye-hand-decoupled maturation emerged mainly during late childhood (11–12 yrs.). Notably, we detected performance differences between young children and adolescents exclusively during the eye-hand decoupling task which required the integration of rule-based cognitive information into the motor action. Differences were not observed during the direct interaction task. Our results quantify an important milestone for eye-hand-decoupling development in late childhood, leading to improved rule-based motor performance in early adolescence. This eye-hand-decoupling development may be due to frontal lobe development linked to rule-based behavior and the strengthening of fronto-parietal networks.     

Parenting young children with challenging behaviour

Previous research has established the link between harsh parenting and poor outcomes in children, although little attention has been paid to the concurrent protective factors which may exist. The relationship between parenting behaviours and childhood externalizing behaviours was investigated in a sample of 60 parents of young children (ages 2–5 years). Thirty families were selected for participation based on teacher‐reported externalizing behaviour in their young child which exceeded normal limits and matched with a sample of 30 parents of children without externalizing behaviour problems. Results found that parents of young children with externalizing behaviours tended to use more frequent verbal and corporal punishment with their young children, and reported more behaviour problems with their young children when compared with a control group. However, no significant differences were found between groups with respect to positive, nurturing behaviours, or utilizing appropriate developmental expectations. Implications for prevention are discussed. Copyright © 2005 John Wiley & Sons, Ltd.     

Visual variability affects early verb learning

Research demonstrates that within‐category visual variability facilitates noun learning; however, the effect of visual variability on verb learning is unknown. We habituated 24‐month‐old children to a novel verb paired with an animated star‐shaped actor. Across multiple trials, children saw either a single action from an action category (identical actions condition, for example, travelling while repeatedly changing into a circle shape) or multiple actions from that action category (variable actions condition, for example, travelling while changing into a circle shape, then a square shape, then a triangle shape). Four test trials followed habituation. One paired the habituated verb with a new action from the habituated category (e.g., ‘dacking’ + pentagon shape) and one with a completely novel action (e.g., ‘dacking’ + leg movement). The others paired a new verb with a new same‐category action (e.g., ‘keefing’ + pentagon shape), or a completely novel category action (e.g., ‘keefing’ + leg movement). Although all children discriminated novel verb/action pairs, children in the identical actions condition discriminated trials that included the completely novel verb, while children in the variable actions condition discriminated the out‐of‐category action. These data suggest that – as in noun learning – visual variability affects verb learning and children's ability to form action categories.     

婴儿如何认识他心：“似我”假说述评

Meltzoff的“似我”假说认为,婴儿借助“我他对等”认识解读他人行为和心理状态,通过他人间的互动信息推断和调整自身行为。“似我”认识以动作表征为基础,借助第一人称体验建立双向映射,对“似我”之人进行因果推理,由此构成发展路径引导婴儿认识他心。注视追随与模仿两种初级社会学习机制进一步丰富了婴儿对社交关系的理解,使人类学习的渠道突破了自我体验的局限而变得更加多元。     

Paradoxical decrease of imitation performance with age in children

Imitation development was studied in a cross-sectional design involving 174 primary-school children (aged 6–10), focusing on the effect of actions' complexity and error analysis to infer the underlying cognitive processes. Participants had to imitate the model's actions as if they were in front of a mirror (‘specularly’). Complexity varied across three levels: movements of a single limb; arm and leg of the same body side; or arm and leg of opposite body sides. While the overall error rate decreased with age, this was not true of all error categories. The rate of ‘side’ errors (using a limb of the wrong body side) paradoxically increased with age (from 9 years). However, with increasing age, the error rate also became less sensitive to the complexity of the action. This pattern is consistent with the hypothesis that older children have the working memory (WM) resources and the body knowledge necessary to imitate ‘anatomically’, which leads to additional side errors. Younger children might be paradoxically free from such interference because their WM and/or body knowledge are insufficient for anatomical imitation. Yet, their limited WM resources would prevent them from successfully managing the conflict between spatial codes involved in complex actions (e.g. moving the left arm and the right leg). We also found evidence that action side and content might be stored in separate short-term memory (STM) systems: increasing the number of sides to be encoded only affected side retrieval, but not content retrieval; symmetrically, increasing the content (number of movements) of the action only affected content retrieval, but not side retrieval. In conclusion, results suggest that anatomical imitation might interfere with specular imitation at age 9 and that STM storages for side and content of actions are separate.     

Imitation and social responsiveness in autistic children

Fifteen autistic children, ages 4–6 years, participated in the present study. Imitation and object permanence skills were assessed. Language and social behaviors were observed during free play. Children were also exposed to three interactive procedures that differed in developmental sophistication. The experimenter either (1) simultaneously imitated the child's actions, (2) modeled a familiar action, or (3) modeled a novel action. It was found that the autistic children who had a low level of imitative ability (Piaget's Stages 2–3) were more socially responsive, showed more eye contact, and played with toys in a less perseverative manner when the experimenter imitated their behavior than when the experimenter modeled either a familiar or a novel action. When the experimenter modeled a familiar as opposed to a novel action, these children were more likely to spontaneously imitate the experimenter. The autistic children with more highly developed imitation skills, however, responded similarly to all conditions. They also were generally more socially and verbally responsive. These results suggest that developmental status is an important variable in designing intervention programs for severely impaired children.We would like to express our appreciation to the autistic children who participated in the study, and to their parents, and to the staff of the T.E.A.C.C.H. Division, University of North Carolina for their help and cooperation. We would also like to thank Karen Cotten, Pete Giordano, Vickie Hall, Lee Hendrix, Shari Jernigan, Kevin Lumley, Cindy Seagroves, Sheryl Solomon, Kathy Stetson, and Jeannie Teasley for their assistance in data collection and coding, and Mary Lynn Eckert and Anne Stanford for their secretarial assistance. Cathy Dent provided helpful suggestions on earlier drafts of the paper. Support was provided by UNC Research Council.     

Effects of short-term retrieval on adult age differences in long-term recall of actions.

In Experiment 1 young and elderly subjects either recalled or repeated after every block of 4 actions, whereas control subjects received neither interpolated short-term recall nor action repetition. On a later long-term memory test, experimental subjects, regardless of age or condition, recalled slightly more actions than control subjects. In Experiment 2 young adult and elderly subjects received 12 short-term memory trials in which 2 actions were performed on each trial, but only 1 was cued for recall after a brief retention interval filled with a distracting activity. On a later long-term memory test for the actions performed on the short-term trials, both young and elderly subjects recalled significantly more previously cued than noncued actions. The Age X Cuing Condition interaction was negligible. Prior retrieval of actions appears to enhance later recall regardless of age but seemingly only when prior retrieval requires considerable cognitive effort (as in Experiment 2).     

Multiple information sources in interceptive timing

This study was designed to explore the limitations of tau (τ) as an explanatory construct for the timing of interceptive action. This was achieved by examining the effects of environmental structure and binocular vision on the timing of the grasp in a simple one-handed catch. In two experiments, subjects were required to catch luminous balls of different diameters (4, 6, 8 and 10 cm) in a completely darkened room. In the first experiment the influence of the presence vs. absence of an environmental background structure (both under monocular viewing) was tested, and in the second experiment the influence of monocular vs. binocular vision was examined. It was found that irrespective of the presence of environmental structure, an effect of ball size occurred in the monocular viewing conditions. That is, in monocular viewing conditions the grasp was initiated and completed earlier for the larger balls as compared to the smaller ones, while in the binocular viewing condition subjects behaved in accordance with a constant time to contact strategy: no effects of ball size were found. It is concluded that under binocular viewing a binocular information source is used, while in the monocular viewing condition a lower order information source like image size or image velocity is probably involved.     

Performance of dyslexic children on speech perception tests

Several researchers who have compared the performance of dyslexic and normal-reading children on a variety of different tasks have suggested that dyslexic children may have subtle deficits in the phonemic analysis of spoken as well as written language. Thus it is of interest to know how children who have extraordinary difficulty learning to read can perform explicity auditory-phonetic tasks. Seventeen dyslexic children (10 years of age) and a group of 17 controls were administered tests of identification and discrimination of synthesized voiced stop consonants differing in place of articulation. These were tests of the type used to study categorical perception in adults, adapted for use with young children. Significant differences between dyslexics and controls were found in both kinds of tasks; the pattern of identification and discrimination differences suggests an inconsistency in the dyslexics' phonetic classification of auditory cues. A significant relationship was found between reading level and speech discrimination.     

Projective drawings and children who stutter

Five young stutterers (aged 5–10 yr) and a matched group of five nonstuttering children completed five projective drawings and a scale for assessing communication attitudes of children at the beginning and at the end of a 3-mo treatment period. While the attitude scale failed to indicate differences between stuttering and nonstuttering children, performances on selected drawings did distinguish between experimental and control subjects. In addition, significant changes were observed in selected drawings over the treatment period for the young stutterers.     

Plasticity of the human auditory cortex induced by discrimination learning of non-native,mora-timed contrasts of the Japanese language

In this magnetoencephalographic (MEG) study, we examined with high temporal resolution the traces of learning in the speech-dominant left-hemispheric auditory cortex as a function of newly trained mora-timing. In Japanese, the “mora” is a temporal unit that divides words into almost isochronous segments (e.g., na-ka-mu-ra and to-o-kyo-o each comprises four mora). Changes in the brain responses of a group of German and Japanese subjects to differences in the mora structure of Japanese words were compared. German subjects performed a discrimination training in 10 sessions of 1.5 h each day. They learned to discriminate Japanese pairs of words (in a consonant, anni–ani; and a vowel, kiyo–kyo, condition), where the second word was shortened by one mora in eight steps of 15 msec each. A significant increase in learning performance, as reflected by behavioral measures, was observed, accompanied by a significant increase of the amplitude of the Mismatch Negativity Field (MMF). The German subjects' hit rate for detecting durational deviants increased by up to 35%. Reaction times and MMF latencies decreased significantly across training sessions. Japanese subjects showed a more sensitive MMF to smaller differences. Thus, even in young adults, perceptual learning of non-native mora-timing occurs rapidly and deeply. The enhanced behavioral and neurophysiological sensitivity found after training indicates a strong relationship between learning and (plastic) changes in the cortical substrate.     

An Energetic Comparison of Symmetrical and Asymmetrical Human Gait

This article contrasts the mechanical energy profiles of asymmetrical galloping with those of symmetrical running in adult humans. Seven female subjects were filmed while performing overground running and galloping at their preferred velocities. A previous study (Whitall & Caldwell, 1992) showed that kinematic differences between these gait modes included higher preferred velocity for running than galloping, with distinct differences in interlimb coordination but surprisingly similar intralimb patterns. Energetically, in the present study the whole body center of mass during galloping was found to behave much as it does in walking; kinetic and potential energy profiles were out of phase, as compared with running, which exhibited in-phase fluctuations of kinetic and potential energies. The primary reason for these center of mass differences was found in the energetics of the back leg of galloping, which demonstrated alterations in timing of its energy fluctuations and less energy generation than the front leg. Analysis of the power sources underlying the segmental energies during swing phase showed that the back leg's energy changes were accomplished mainly through reduced use of the hip muscles and less interlimb energy transfer. The back leg's energetics during swing also displayed a shift toward greater reliance on nonmuscular energy sources. A pattern of energy inflow during early swing and energy outflow during late swing was common to both running and galloping, although the galloping legs both demonstrated more abrupt transitions between these phases. The possibility is raised that the 67/33 interlimb phasing ratio used in galloping is selected to reduce mechanical energy variations of the total body center of mass. These data suggest that models of asymmetric gait in humans must account for more than merely phase alteration.