DO INFANTS SHOW GENERALIZED IMITATION OF GESTURES?

Two experiments were conducted to investigate generalized imitation of manual gestures in 1- to 2-year-old infants. In Experiment 1, 6 infants were first trained four baseline matching relations (e.g., when instructed "Do this", to raise their arms after they saw the experimenter do so). Next, four novel gestures that the infants did not match in probe trials were selected as target behaviors during generalized imitation Test 1; models of these gestures were presented on unreinforced matching trials interspersed with intermittently reinforced baseline matching trials. None of the infants matched the target behaviors. To ensure that these behaviors were in the infants' motor skills repertoires, the infants were next trained to produce them, at least once, under stimulus control that did not include an antecedent model of the target behavior. In repeat generalized imitation trials (Test 2), the infants again failed to match the target behaviors. Five infants (3 from Experiment 1) participated in Experiment 2, which was identical to Experiment 1 except that, following generalized imitation Test 1, the motor-skills training was implemented to a higher criterion (21 responses per target behavior), and in a multiple-baseline, across-target-behaviors procedure. In the final generalized imitation test, 1 infant matched one, and another infant matched two target behaviors; the remaining 17 target behaviors still were not matched. The results did not provide convincing evidence of generalized imitation, even though baseline matching was well maintained and the target behaviors were in the infants' motor skills repertoires, raising the question of what are the conditions that reliably give rise to generalized imitation.     

USE OF CHAINING TO INCREASE COMPLEXITY OF ECHOICS IN CHILDREN WITH AUTISM

Echoics are a critical target of language intervention for children with autism, because a well‐established echoic repertoire on the part of the child allows the clinician to use vocal modeling as a flexible, low‐effort prompting procedure during teaching. In this study, we implemented a chaining procedure to increase the complexity of echoics in 2 children with autism and 1 child with developmental delay. The procedure was effective for all 3 participants, and gains were maintained after treatment was withdrawn in most cases.     

THE INFLUENCE OF MATCHING AND MOTOR‐IMITATION ABILITIES ON RAPID ACQUISITION OF MANUAL SIGNS AND EXCHANGE‐BASED COMMUNICATIVE RESPONSES

Establishing a relation between existing skills and acquisition of communicative responses may be useful in guiding selection of alternative communication systems. Matching and motor‐imitation skills were assessed for 6 children with developmental disabilities, followed by training to request the same set of preferred items using exchange‐based communication and manual signs. Three participants displayed both skills and rapidly acquired both communicative response forms. Three others displayed neither skill; 1 mastered exchange‐based responses but not manual signs, and neither of the other 2 easily acquired either response form.     

Imitation of transitive and intransitive actions in healthy individuals

A handful of patients have been described as being impaired in performing transitive gestures, despite being still able to perform intransitive gestures. This impairment need not be explained by assuming different mechanisms; rather, it can be due to transitive actions being more difficult. In this study we tested whether neurologically healthy participants had greater difficulties in imitating transitive actions with respect to intransitive actions. Consistent with the prediction, subjects imitated intransitive better than transitive gestures. The ease of imitation of intransitive actions supports the complexity account of apraxic impairments.     

Patterns of brain-electrical activity during declarative memory performance in 10-month-old infants

This study of infant declarative memory concurrently examined brain-electrical activity and deferred imitation performance in 10-month-old infants. Continuous electroencephalogram (EEG) measures were collected throughout the activity-matched baseline, encoding (modeling) and retrieval (delayed test) phases of a within-subjects deferred imitation task. Infants were divided into two memory performance groups based on the exhibition of ordered-recall after a 24-h delay. Whereas no group differences were found in EEG collected during encoding, performance-group differences in EEG were present during retrieval. Infants who successfully displayed ordered-recall showed a pattern of increasing EEG from baseline to task at anterior temporal scalp locations, whereas infants showing no ordered-recall displayed no changes in EEG from baseline to task. These findings are discussed with respect to the biobehavioral developments underlying declarative memory abilities.     

Gender‐related differences in neonatal imitation

Socio‐emotional behaviour is in part sex‐related in humans, although the contribution of the biological and socio‐cultural factors is not yet known. This study explores sex‐related differences during the earliest communicative exchange, the neonatal imitation in 43 newborn infants (3–96 hours old) using an index finger extension imitative gesture. Results showed that although the experimenter presented comparable stimuli to both sexes, and the total number of movements was similar in boys and girls, girls showed more fine motor movements, a higher number of specific imitative gestures, responded faster during the imitation and showed a higher baseline heart rate during the experiment. Newborn girls, with their faster and more accurate imitative abilities, may create a more responsive and interactive social environment, which in turn may lead to differences in socio‐emotional and cognitive development between girls and boys. Copyright © 2007 John Wiley & Sons, Ltd.     

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.     

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。     

The relationship between Fisher's exact test and Pearson's chi-square test: A bayesian perspective

It is demonstrated in this paper that two major tests for 2 × 2 talbes are highly related from a Bayesian perspective. Although it is well-known that Fisher's exact and Pearson's chi-square tests are asymptotically equivalent, the present analysis shows that a formal similarity also exists in small samples. The key assumption that leads to the resemblance is the presence of a continuous parameter measuring association. In particular, it is shown that Pearson's probability can be obtained by integrating a two-moment approximation to the posterior distribution of the log-odds ratio. Furthermore, Pearson's chi-square test gave an excellent approximation to the actual Bayes probability in all 2×2 tables examined, except for those with extremely disproportionate marginal frequencies.