Kinematic Measures of Imitation Fidelity in Primary School Children

We sought to develop a method for measuring imitation accuracy objectively in primary school children. Children imitated a model drawing shapes on the same computer-tablet interface they saw used in video clips, allowing kinematics of model and observers' actions to be directly compared. Imitation accuracy was reported as a correlation reflecting the statistical dependency between values of the model's and participant's sets of actions, or as a mean absolute difference between them. Children showed consistent improvement in imitation accuracy across middle childhood. They appeared to rationalize the demands of the task by remembering duration and size of action, which enabled them to reenact speed through motor-planning mechanisms. Kinematic measures may provide a window into the cognitive mechanisms involved in imitation

Alkali extraction of archaeological and geological charcoal: evidence for diagenetic degradation and formation of humic acids

Charcoal forms a crucial source of archaeological and palaeoenvironmental data, providing a record of cultural activities, past climatic conditions and a means of chronological control via radiocarbon (<sup>14</sup>C) dating. Key to this is the perceived resistance of charcoal to post-depositional alteration, however recent research has highlighted the possibility for alteration and degradation of charcoal in the environment. An important aspect of such diagenesis is the potential for addition of exogenous 'humic acids' (HAs), to affect the accuracy of archaeological and palaeoenvironmental reconstructions based upon chemical analyses of HA-containing charcoal. However the release of significant quantities of HA from apparently pristine charcoals raises the question whether some HA could be derived via diagenetic alteration of charcoal itself. Here we address this question through comparison of freshly produced charcoal with samples from archaeological and geological sites exposed to environmental conditions for millennia using elemental (C/H/O) and isotopic (δ<sup>13</sup>C) measurements, Fourier Transform Infrared Spectroscopy (FTIR) and proton Liquid-State Nuclear Magnetic Resonance (<sup>1</sup>H NMR). The results of analyses show that the presence of highly carboxylated and aromatic alkali-extractable HA in charcoal from depositional environments can often be attributable to the effects of post-depositional processes, and that these substances can represent the products of post-depositional diagenetic alteration in charcoal

Isotopes in pyrogenic carbon: a review

Pyrogenic carbon (PC; also known as biochar, charcoal, black carbon and soot) derived from natural and anthropogenic burning plays a major, but poorly quantified, role in the global carbon cycle. Isotopes provide a fundamental fingerprint of the source of PC and a powerful tracer of interactions between PC and the environment. Radiocarbon and stable carbon isotope techniques have been widely applied to studies of PC in aerosols, soils, sediments and archaeological sequences, with the use of other isotopes currently less developed. This paper reviews the current state of knowledge regarding (i) techniques for isolating PC for isotope analysis and (ii) processes controlling the carbon (<sup>13</sup>C and <sup>14</sup>C), nitrogen, oxygen, hydrogen and sulfur isotope composition of PC during formation and after deposition. It also reviews the current and potential future applications of isotope based studies to better understand the role of PC in the modern environment and to the development of records of past environmental change

A kinematic examination of dual-route processing for action imitation

The dual-route model of imitation suggests that meaningful and meaningless actions are processed through either an indirect or direct route, respectively. Evidence indicates that the direct route is more cognitively demanding, since it relies on mapping visuospatial properties of the observed action on to a performed one. These cognitive demands might negatively influence reaction time and accuracy for actions performed following a meaningless action under time constraints. However, how meaningful and meaningless action imitation processing is reflected in movement kinematics is not yet clear. We wanted to confirm whether meaningless action performance incurs a reaction time cost, whether the cost is reflected in kinematics, and, more generally, to examine kinematic markers of emblematic meaningful and meaningless action imitation. We examined participants’ reaction time and wrist movements when they imitated emblematic meaningful or matched meaningless gestures in either blocks of the same action type, or mixed blocks. Meaningless actions were associated with a greater correction period at the end of the movement, possibly reflecting a strategy designed to ensure accurate completion for less familiar actions under time constraints. Furthermore, in mixed blocks, trials following meaningless actions had a significantly increased reaction time, supporting previous claims that route selection for action imitation may be stimulus-driven. However, there was only convincing evidence for this effect with an interval of ~2948ms, but not ~3573ms or ~2553ms, between movements. Future work motion-tracking the entire hand to assess imitation accuracy, and more closely examining the influence of duration between movements, may help to explain these effects

Motor signatures of emotional reactivity in frontotemporal dementia

Automatic motor mimicry is essential to the normal processing of perceived emotion, and disrupted automatic imitation might underpin socio-emotional deficits in neurodegenerative diseases, particularly the frontotemporal dementias. However, the pathophysiology of emotional reactivity in these diseases has not been elucidated. We studied facial electromyographic responses during emotion identification on viewing videos of dynamic facial expressions in 37 patients representing canonical frontotemporal dementia syndromes versus 21 healthy older individuals. Neuroanatomical associations of emotional expression identification accuracy and facial muscle reactivity were assessed using voxel-based morphometry. Controls showed characteristic profiles of automatic imitation, and this response predicted correct emotion identification. Automatic imitation was reduced in the behavioural and right temporal variant groups, while the normal coupling between imitation and correct identification was lost in the right temporal and semantic variant groups. Grey matter correlates of emotion identification and imitation were delineated within a distributed network including primary visual and motor, prefrontal, insular, anterior temporal and temporo-occipital junctional areas, with common involvement of supplementary motor cortex across syndromes. Impaired emotional mimesis may be a core mechanism of disordered emotional signal understanding and reactivity in frontotemporal dementia, with implications for the development of novel physiological biomarkers of socio-emotional dysfunction in these diseases

Combusted bone: Physical and chemical changes of bone during laboratory simulated heating under oxidising conditions and their relevance for the study of ancient fire use.

Human Origin

Heating histories and taphonomy of ancient fireplaces: A multi-proxy case study from the Upper Palaeolithic sequence of Abri Pataud (Les Eyzies-de-Tayac, France)

While the use of fire has long been recognised as a crucial innovation in the cultural evolution of humankind, much research has focused on the (debated) chronology of its earliest use and control, and less on the ways in which fire was used in the deep past. At its latest by the Upper Palaeolithic, hunter-gatherers routinely used fire to heat a wide range of materials, adjusting parameters like temperature, exposure time and fuel type to the specific requirements of the treated materials, for instance in food preparation or tool production. Comparing analyses of the chemical and physical properties of modern materials, heated under a range of controlled conditions in a laboratory, to archaeological ones might allow the reconstruction of the “heating history” of excavated materials and hence to infer the function of particular fires in the past - provided changes affecting the properties of the heated archaeological material during burial time are taken into consideration. To investigate the feasibility of such an approach, heated materials sampled from ~40,000 to 25,000 year old fireplaces (hearths) and their sedimentary matrices from the Upper Palaeolithic Abri Pataud rock shelter in South-Western France are used here to study (1) the fuel type(s) used by the site's occupants, (2) the temperatures reached in fireplaces and (3) the potential changes in human activities related to fireplaces over time, with the influence of post-depositional processes taken into explicit consideration throughout. For this purpose, we used a range of methods to analyse macroscopically visible as well as “invisible” (microscopic and molecular) heat-altered materials. The results suggest that charred organic materials (COM) encountered in the samples predominantly result from the fuel used in fireplaces, including the earliest reported use of dung as fuel. Earlier suggestions about the use of bone as fuel at the Abri Pataud are not supported by this study. The heating temperature of COM increased gradually from 350 °C in the Aurignacian to 450 °C in Gravettian levels. Py-GC–MS studies identified a range of organic compounds, biomolecules derived from plant as well as animal sources, still preserved in the sediments after exposure to heat and burial in the rock shelter more than 20,000 years ago. Mammalian mtDNA was identified in sediment samples retrieved from the fireplaces, including ancient mtDNA fragments that originated from one or more modern human-like mitochondrial genome(s). This makes the Abri Pataud the first archaeological site for which ancient modern human mtDNA has been retrieved from sediment samples. The absence of specific organic compounds (furans) in the Aurignacian levels and their presence in the Gravettian ones, the changes in temperatures reached through the Aurignacian-Gravettian sequence as well as changes in the character of the fireplaces (presence/absence of lining river pebbles) suggest that the functions of hearths changed through time. These results highlight the potential of multi-proxy analyses of macro- and microscopic traces of ancient fireplaces, and especially of a shift in focus towards molecular traces of such activities. Systematic sampling of fireplaces and their sedimentary matrix should become a standard part of the excavation protocol of such features, to improve our understanding of the activities of humans in the deep past