11—14个月儿童的语言获得——成人的言语教授和儿童的模仿学习

对儿童言语记录个案的分析表明:儿童在11—14个月期间开始获得词。此时儿童所获得的词,主要是与儿童日常生活或动作相联系的名词和动词,其次是象声词。这些词语87.5％来源于成人的言语教授和儿童相应的模仿学习。 成人的言语教授和儿童相应的模仿学习总是由成人结合情景进行的,具有很高的选择性。儿童对成人言语的学习并不是简单地模仿,而是有一定的主动性和创造性,这在一定程度上规定着成人言语教授的作用。由此可见,儿童言语的获得是在人类特有的大脑以及言语器官发育的基础上,在与人们交际过程中,经过成人的言语教授,并经儿童有选择的模仿学习和概括而成的。     

Analysis of discriminative control by social behavioral stimuli

Visual discriminative control of the behavior of one rat by the behavior of another was studied in a two-compartment chamber. Each rat's compartment had a food cup and two response keys arranged vertically next to the clear partition that separated the two rats. Illumination of the leader's key lights signaled a “search” period when a response by the leader on the unsignaled and randomly selected correct key for that trial illuminated the follower's keys. Then, a response by the follower on the corresponding key was reinforced, or a response on the incorrect key terminated the trial without reinforcement. Accuracy of following the leader increased to 85% within 15 sessions. Blocking the view of the leader reduced accuracy but not to chance levels. Apparent control by visual behavioral stimuli was also affected by auditory stimuli and a correction procedure. When white noise eliminated auditory cues, social learning was not acquired as fast nor as completely. A reductionistic position holds that behavioral stimuli are the same as nonsocial stimuli; however, that does not mean that they do not require any separate treatment. Behavioral stimuli are usually more variable than nonsocial stimuli, and further study is required to disentangle behavioral and nonsocial contributions to the stimulus control of social interactions.     

Reaching skills of infants born very preterm predict neurodevelopment at 2.5 years

The purpose was to investigate associations between quality of reaching for moving objects at 8 months corrected age and neurodevelopment at 2.5 years in children born very preterm (gestational age (GA), 24–31 weeks). Thirtysix infants were assessed while reaching for moving objects. The movements were recorded by a 3D motion capture system. Reaching parameters included aiming, relative length of the reach, number of movement units, proportion of bimanual coupled reaches and number of hits. Neurodevelopment was assessed at 2.5 years by the Bayley Scales of Infant Development III. There were strong associations between infant reaching kinematics and neurodevelopment of cognition and language but the patterns differed: in children born extremely preterm (GA < 28 weeks), planning and control of reaching was strongly related to outcome, while in children born very preterm (GA 28–31 weeks) number of hits and bimanual strategies were of greater relevance. In conclusion, for extremely preterm infants, basic problems on how motion information is incorporated with action planning prevail, while in very preterm infants the coordination of bimanual reaches is more at the focus. We conclude that the results reflect GA related differences in neural vulnerability and that early motor coordination deficits have a cascading effect on neurodevelopment.     

Examining the impact of error estimation on the effects of self-controlled feedback

Two experiments were conducted that examined the motivational and informational perspectives concerning learning advantages from self-controlled practice. Three groups were tasked with learning a novel skill; self-controlled (SC), yoked traditional (YT), and yoked with error estimation required during the acquisition phase (YE). Results from the delayed learning measures showed the YE group performed better than the SC and YT groups, for Expt. 1. A similar pattern emerged for Expt. 2, albeit, this was not significant. While there were no motivation differences across the groups in either experiment, a strong correlation in Expt. 2 was shown between error estimation capabilities, which were best for the YE group, and learning. These combined results suggest that informational processes contribute more to the self-controlled feedback learning advantage, relative to motivational contributions.     

Fronto-parietal mirror neuron system modeling: Visuospatial transformations support imitation learning independently of imitator perspective

Although the human mirror neuron system (MNS) is critical for action observation and imitation, most MNS investigations overlook the visuospatial transformation processes that allow individuals to interpret and imitate actions observed from differing perspectives. This problem is not trivial since accurately reaching for and grasping an object requires a visuospatial transformation mechanism capable of precisely remapping fine motor skills where the observer’s and imitator’s arms and hands may have quite different orientations and sizes. Accordingly, here we describe a novel neural model to investigate the dynamics between the fronto-parietal MNS and visuospatial processes during observation and imitation of a reaching and grasping action. Our model encompasses i) the inferior frontal gyrus (IFG) and inferior parietal lobule (IPL), regions that are postulated to produce neural drive and sensory predictions, respectively; ii) the middle temporal (MT) and middle superior temporal (MST) regions that are postulated to process visual motion of a particular action; and iii) the superior parietal lobule (SPL) and intra-parietal sulcus (IPS) that are hypothesized to encode the visuospatial transformations enabling action observation/imitation based on different visuospatial viewpoints. The results reveal that when a demonstrator executes an action, an imitator can reproduce it with similar kinematics, independently of differences in anthropometry, distance, and viewpoint. As with prior empirical findings, similar model synaptic activity was observed during both action observation and execution along with the existence of both view-independent and view-dependent neural populations in the frontal MNS. Importantly, this work generates testable behavioral and neurophysiological predictions. Namely, the model predicts that i) during observation/imitation the response time increases linearly as the rotation angle of the observed action increases but remain similar when performing both clockwise and counterclockwise rotation and ii) IPL embeds essentially view-independent neurons while SPL/IPS includes both view-independent and view-dependent neurons. Overall, this work suggests that MT/MST visuomotion processes combined with the SPL/IPS allow the MNS to observe and imitate actions independently of demonstrator-imitator spatial relationships.     

Coordination and control of posture and ball release in basketball free-throw shooting

The objective of this study was to investigate the coordination of a whole-body task (basketball free-throw) in which success in performance outcome can be achieved through a manifold of combinations of postural and movement trajectory configurations. Participants were healthy men (19–24 years) with a range of skill levels that were tested for the accuracy of 50 basketball free-throws with both their dominant and non-dominant hand. The trial-to-trial variance in release parameters as well as postural stability of the shooter and synchronization of postural movement and ball release were strong predictors of performance, with non-elite shooters having a higher mean and variability of center-of-mass (COM) speed at the time of ball release. The synchronization between the time of peak COM and the time of ball release increased as a function of skill level and hand dominance, with the better performers releasing the ball more closely to the time of COM peak height. These findings reveal how, in addition to successfully controlling the trial-to-trial variability along the solution manifold of release parameters, the relative importance of the coordination of postural control and ball release properties on shooting success changes as a function of skill level.     

A systematic review on perceptual-motor calibration to changes in action capabilities

Perceptual-motor calibration has been described as a mapping between perception and action, which is relevant to distinguish possible from impossible opportunities for action. To avoid movement errors, it is relevant to rapidly calibrate to immediate changes in capabilities and therefore this study sought to explain in what conditions calibration is most efficient. A systematic search of seven databases was conducted to identify literature concerning changes in calibration in response to changes in action capabilities. Twenty-three papers satisfied the inclusion criteria. Data revealed that calibration occurs rapidly if there is a good match between the task that requires calibration and the sources of perceptual-motor information available for exploration (e.g. when exploring maximal braking capabilities by experiencing braking). Calibration can take more time when the perceptual-motor information that is available is less relevant. The current study identified a number of limitations in the field of perceptual-motor research. Most notably, the mean participant age in the included studies was between 18 and 33 years of age, limiting the generalizability of the results to other age groups. Also, due to inconsistent terminology used in the field of perceptual-motor research, we argue that investigating calibration in older cohorts should be a focus of future research because of the possible implications of impaired calibration in an aging society.