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PubMed2002

Generalized imitation within three response classes in typically developing infants.

Effects of modeling and contingent praise on infant imitation of three different responses was analyzed. Generalization to nonreinforced probe models was assessed both within and across response types. Three 12- to 14-month-old infants and their mothers participated in this study. During baseline the mothers provided models only. During treatment mothers modeled and also praised contingent upon infant matching of the training models. During interspersed probe trials the mothers modeled different responses, which, if matched by the infant, produced no praise. The three responses modeled were motor-with-toy, motor-without-toy, and vocal responses. The dependent measure was the percentage of maternal models that were matched by the infant within 6 s. Nonmatching responses of the same response type were also measured. Results showed a systematic increase in the percentages of training and probe models matched by the three infants following the introduction of the model-and-praise treatment condition. Nonmatching responses did not systematically increase. Thus, imitation generalized within response class, but not across response classes.

Child Development↗
PubMed2001

Selective imitation for a private sign system.

A distinctive feature of all human languages is the diverse and arbitrary nature of the sign (signifier). This can be interpreted as stating that the mapping between signals and referents is established by convention rather than by functional constraints. This property of the sign provides for a great deal of linguistic flexibility and is a key component of symbolic communication. Game theoretic models to describe signal imitation are investigated with a view to understanding how non-arbitrary (indexical) animal-style signals might 'evolve' culturally into diverse, arbitrary signs. I explore the evolutionary hypothesis that private, arbitrary signs emerge as a result of selective imitation within a socially structured population. Once arbitrary signs have emerged, they contribute towards greater assortative interactions among individuals using a shared sign system. In natural populations, the models for imitation will very often be close kin. Hence, kinship provides one mechanism for the creation of true symbols. An imitation-structured population can support many more sign systems than an equivalent non-structured population and is one in which symbols become the dominant force in assortative interactions.

Animal Communication↗
PubMed2001

Cortical correlates of gesture processing: clues to the cerebral mechanisms underlying apraxia during the imitation of meaningless gestures.

The clinical test of imitation of meaningless gestures is highly sensitive in revealing limb apraxia after dominant left brain damage. To relate lesion locations in apraxic patients to functional brain activation and to reveal the neuronal network subserving gesture representation, repeated H2(15O)-PET measurements were made in seven healthy subjects during a gesture discrimination task. Observing paired images of either meaningless hand or meaningless finger gestures, subjects had to indicate whether they were identical or different. As a control condition subjects simply had to indicate whether two portrayed persons were identical or not. Brain activity during the discrimination of hand gestures was strongly lateralized to the left hemisphere, a prominent peak activation being localized within the inferior parietal cortex (BA40). The discrimination of finger gestures induced a more symmetrical activation and rCBF peaks in the right intraparietal sulcus and in medial visual association areas (BA18/19). Two additional foci of prominent rCBF increase were found. One focus was located at the left lateral occipitotemporal junction (BA 19/37) and was related to both tasks; the other in the pre-SMA was particularly related to hand gestures. The pattern of task-dependent activation corresponds closely to the predictions made from the clinical findings, and underlines the left brain dominance for meaningless hand gestures and the critical involvement of the parietal cortex. The lateral visual association areas appear to support first stages of gesture representation, and the parietal cortex is part of the dorsal action stream. Finger gestures may require in addition precise visual analysis and spatial attention enabled by occipital and right intraparietal activity. Pre-SMA activity during the perception of hand gestures may reflect engagement of a network that is intimately related to gesture execution.

Adult↗
PubMed2001

Imitation and matching of hand and finger postures.

Converging evidence from patients with unilateral brain lesions, from a patient with callosal disconnection, and from functional imaging in healthy subjects suggests different competencies of both hemispheres for imitation and matching of hand and finger postures. Whereas the left hemisphere is fully competent for processing hand postures, an additional right hemisphere contribution is needed for finger postures. I propose that the left hemisphere is responsible for coding gestures with reference to knowledge about the structure of the human body, whereas a right hemisphere contribution is needed for visuospatial exploration and analysis of gestures. Single case studies of patients with visuoimitative apraxia and results of functional imaging suggest a prominent role for left area 40 for body-part coding. Additional activation of left MT/V5 in the functional neuroimaging study may be related to processing of the motion implied by the gesture which is presented as a static image.

Attention↗
PubMed2002

A PET exploration of the neural mechanisms involved in reciprocal imitation.

Imitation is a natural mechanism involving perception-action coupling which plays a central role in the development of understanding that other people, like the self, are mental agents. PET was used to examine the hemodynamic changes occurring in a reciprocal imitation paradigm. Eighteen subjects (a) imitated the actions of the experimenter, (b) had their actions imitated by the experimenter, (c) freely produced actions, or (d) freely produced actions while watching different actions made by the experimenter. In a baseline condition, subjects simply watched the experimenter's actions. Specific increases were detected in the left STS and in the inferior parietal cortex in conditions involving imitation. The left inferior parietal is specifically involved in producing imitation, whereas the right homologous region is more activated when one's own actions are imitated by another person. This pattern of results suggests that these regions play a specific role in distinguishing internally produced actions from those generated by others.

Adult↗
PubMed2001

The inhibition of imitative response tendencies.

Recent neurocognitive studies show that perception and execution of actions are intimately linked. The mere observation of an action seems to evoke a tendency to execute that action. Since such imitative response tendencies are not adaptive in many everyday situations imitative response tendencies usually have to be inhibited. These inhibitory processes have never been investigated using brain imaging techniques. Former work on response inhibition and interference control has focused on paradigms such as the Stroop task or the go/no-go task. We have carried out an event-related functional magnetic resonance imaging study in order to investigate the cortical mechanisms underlying the inhibition of imitative responses. The experiment employs a simple response task in which subjects were instructed to execute predefined finger movements (tapping or lifting of the index finger) in response to an observed congruent or incongruent finger movement (tapping or lifting). A comparison of brain activation in incongruent and congruent trials revealed strong activation in the dorsolateral prefrontal cortex (middle frontal gyrus) and activation in the right frontopolar cortex and the right anterior parietal cortex, as well as in the precuneus. These results support the assumption of prefrontal involvement in response inhibition and extend this assumption to a "new" class of prepotent responses, namely, to imitative actions.

Adult↗
PubMed2000

Differences in the complexity of song tutoring cause differences in the amount learned and in dendritic spine density in a songbird telencephalic song control nucleus.

In our search for relations between vocal learning and neuron structure in the song control nuclei of songbird forebrains, we tested whether differential experience that leads to differences in adult song repertoire would affect dendritic spine density in HVc (also called high vocal center) and RA (robustus archistriatalis). We tape-tutored juvenile Eastern marsh wrens (Cistothorus palustris) with either 5 or 45 song types. As adults, the small repertoire group had learned mostly 5 or 6 song types, and the large repertoire group had learned 36 to 47. Wrens that learned the large song repertoires had a greater dendritic spine density for the most spiny neurons present in HVc (mean difference, 36%), but not in RA. Recent physiological evidence describes HVc as a premotor area coding syllables, motifs, and higher-order song patterns, and our data now clearly reveal that differences in the size of the song repertoire that is experienced lead to differences both in song learning and in the density of dendritic spines in HVc. In the forebrain song nuclei of these songbirds, as in some other vertebrate systems, differences in learning and performance are associated with differences in synaptic anatomy specifically in the region that organizes the learned pattern.

Animals↗
PubMed1989

Perceptual and motor factors in the imitation of simple temporal patterns.

This study investigated the relative importance of perceptual and motor factors in the imitation of simple temporal patterns. Previous research in which subjects tap out interval sequences using one finger has suggested that perceptual factors play an important role in response timing. Studies of bimanual tapping, in contrast, stress the importance of motor interactions between the two hands. In this experiment we compared the ability of subjects to tap out two-interval sequences using one finger, two fingers on one hand, and two fingers on opposite hands. The results showed almost identical performance under the three response conditions. It is suggested that the perceptual relations between intervals in a pattern were the main determinant of performance in this experiment.

Adult↗
PubMed1990

A reanalysis of the impact of non celebrity suicides. A research note.

Previous work on suicide and the media has neglected theoretical issues. Some work has implied that only celebrity suicides can be expected to trigger additional suicides in the real world. The present study focuses on non celebrity suicides. Correcting coding errors in a previous work, it finds that the suicides of non celebrities are associated with increases in the national suicide rate. An index of publicized celebrity suicide stories was, however, more closely associated to increases in suicide than the publicized non celebrity stories. The model explains 90 percent of the variance in monthly suicide rates.

Cross-Sectional Studies↗
PubMed1983

Learning through observation: the effects of peer modeling on acquisition and generalization in autistic children.

The purpose of this study was to systematically determine whether low-functioning autistic children [MA of approximately half of their CA or less] could learn through observation by the use of a peer modeling procedure. Since modeling is less structured than traditional one-on-one procedures, it was also thought that modeling might facilitate subsequent generalization of tasks learned through observation. Four autistic children were taught two receptive labeling tasks. One task was taught by a traditional trial-and-error procedure, while the other task was taught by a modeling procedure wherein the models were other autistic children. Results indicated that all four children learned through observation of their peer model. Additionally, generalization and maintenance of correct responding were superior when the children learned through observation rather than by trial and error. These results are discussed in terms of the modeling literature, generalization issues, and implications for designing teaching settings for autistic children.

Adolescent↗
PubMed1975

Control of echolalic speech in psychotic children.

Immediate echolalia, a common language disorder in psychotic children, was studied in a series of replicated single-subject designs across six schizophrenic and five normal children. In Experiment 1, each child was presented with several questions and commands, some of which set the occasion for specific, appropriate responses and some of which did not. The former were referred to as discriminative stimuli and the latter, as neutral stimuli. The psychotic children tended to echo the neutral stimuli while responding appropriately to the discriminative stimuli; the normal children, in contrast, typically echoed neither type of stimulus. In Experiment 2, three psychotic children were taught appropriate responses to each of several neutral stimuli. Following this training, the children generally responded appropriately to these stimuli without echoing. A plausible interpretation of these results is that the neutral stimuli were initially incomprehensible or meaningless to the children (whereas the discriminative stimuli were comprehensible or meaningful) and that verbal incomprehensibility may be one important determinant of immediate echolalia. Finally, the results are noteworthy in that they isolate a sufficient treatment variable (i.e., the reinforcement of alternative, nonecholalic responses) for eliminating instances of this language anomaly.

Adolescent↗
PubMed1979

Cognitive abilities and disabilities in infantile autism: a review.

The literature on various aspects of learning and performance in autistic children is reviewed and interpreted as indicating very little that is specific to autism. Inadequate and inconsistent methodology precludes generalizations concerning the nature of the disorder. It is suggested that future research should be particularly concerned with controlling for developmental influences on performance, and with investigation of the higher functioning autistic children who are less governed by retardation factors. The current evidence is considered to support a hypothesis concerning abnormal hemisphere functioning in this group of children.

Autistic Disorder↗