1,720,972 research outputs found
Recognising a hand by grasp
No full textThe present study aimed to demonstrate that motor representations are used to recognise biological stimuli. In three experiments subjects were required to judge laterality of hands and forearms presented by pictures. The postures of the hands were those assumed when holding a small, medium and large sphere. In experiment 1, the sphere held in hand was presented, whereas in experiment 2 it was absent. In experiment 3, the same images, showing holding-a-sphere hands, as in experiment 1 were presented, but without forearm. In all experiments one finger of each hand could be absent. In experiment 1 recognition time was longer for those hand postures for which the corresponding grasping motor acts required more accuracy. This was confirmed by a control experiment (experiment 4), in which subjects actually grasped the spheres. Absence of fingers did not influence right-left hand recognition. However, the absence of target object in experiment 2, and of forearm in experiment 3 reduced the effects of the type of holding on hand laterality recognition. The results of the present study indicate that grasp representations are used to recognise hand laterality. In particular, the visual description of how hand and object interact in space (the opposition space [M.A. Arbib, Programs, schemas and neural networks for control of hand movement: beyond the RS frameworks, in: M. Jeannerod (Ed.), Attention and Performance XIII: Motor Representation and Control, Lawrence Erlbaum, Hillsdale, NJ, 1990, 111-138; M.A. Arbib, T. Iberall, D. Lyons, Coordinated control programs for movements of the hand, in: A.W. Goodman, I. Darian-Smith (Eds.), Hand function and the neocortex, Springer, Berlin, 1985, pp. 135-170]) and the anchoring of the hand to the agent are the features of the grasp representations used in hand-recognition processes. The data are discussed according to the more general notion that motor representations are automatically extracted in the process of intuiting situations, or people's intentions. These motor representations, which are compared with those of other people, contain concrete information on the actions (the motor program) by which a situation is created and on the aim of the agents executing those actions. © 2000 Elsevier Science B.V
Language and motor control
No full textWe investigated the possible influence of automatic word reading on processes of visuo-motor transformation. Subjects reached and grasped an object on which the following Italian words were printed: 'VICINO' (near) or 'LONTAN' (far) on an object either near or far from the agent (experiments 1, 2); PICCOLO (small) or 'GRANDE' (large) on either a small or a large object (experiment 4); and 'ALTO' (high) or 'BASSO' (low) on either a high or a low object (experiment 5). The kinematics of the initial phase of reaching-grasping was affected by the meaning of the printed words. Namely, subjects automatically associated the meaning of the word with the corresponding property of the object and activated a reach and/or a grasp motor program influenced by the word. No effect on initial reach kinematics was observed for words related to object properties not directly involved in reach control (experiment 3). Moreover, in all the experiments, the presented words poorly influenced perceptual judgement of object properties. In experiments 5-7, the effects of the Italian adjectives 'ALTO' (high) and 'BASSO' (low) on reaching-grasping control were compared with those of the Italian adverbs 'SOPRA' (up) and 'SOTTO' (down). Adjectives influenced visual analysis of target-object properties, whereas adverbs more directly influenced the control of the action. We suggest that these effects resemble the structure of a sentence, where adjectives are commonly referred to nouns, and adverbs to verbs. In other words, class of words and, in a broad sense, grammar influenced motor control. The results of the present study show that cognitive functions such as language can affect visuo-motor transformation. They are discussed according to the notion that a strict relation between language and motor control exists, and that the frontal cortex can be involved in interactions between automatic word reading and visuo-motor transformation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Visual illusions and the control of children arm movements
No full textThe aim of the present study was to determine whether children like adults (Gentilucci M, Chieffi S, Daprati E, Saetti MC, Toni
I. Visual illusion and action. Neuropsychologia 1996;34:369–76; Gentilucci M, Daprati E, Gangitano M, Toni I. Eye position
tunes the contribution of allocentric and egocentric information to target localisation in human goal directed arm movements.
Neurosci Lett 1997;222:123–6) are influenced by visual illusions when they transform visual information in motor command.
Children and adults pointed to a shaft extremity of the Mu ̈ ller-Lyer configurations, as well as to an extremity of a control
configuration. Movements were executed in two experimental conditions. In the vision condition subjects saw both the stimulus
and their hand before and during movement. In the no vision (memory) condition subjects saw the stimulus and their hand before, but not during movement. Movement started 5 s after vision was precluded. The Mu ̈ ller-Lyer illusion affected pointing kinematics of both children and adults. As found previously (Gentilucci M, Chieffi S, Daprati E, Saetti MC, Toni I. Visual illusion and action. Neuropsychologia 1996;34:369–76; Gentilucci M, Daprati E, Gangitano M, Toni I. Eye position tunes the contribution
of allocentric and egocentric information to target localisation in human goal directed arm movements. Neurosci Lett
1997;222:123–6), subjects undershot and overshot the shaft extremity of the closed and of the open configuration, respectively.
The illusion effect was greater in the no vision than in the vision condition. These results show that in children like in adults the
system underlying visual perception in an object-centered frame of reference and that involved in motor control functionally
interact with each other. Although the processes of target localisation were the same, the transformation of target position
information in a sequence of motor patterns was different in children from that in adults. Even if both children and adults
lengthened duration of the deceleration phase in the vision condition, only adults shortened duration of the acceleration phase in order to maintain constant movement time (Viviani P, Schneider R. A developmental study of the relationship between geometry
and kinematics in drawing movements. J Exp Psychol 1991;17:198–218). This result suggests that children are yet unable to co-ordinate temporally acceleration with deceleration phase
The influence of stimulus color on the control of reaching-grasping movements
No full textThis kinematic study aimed to determine
whether color is a stimulus property involved in the control
of reaching-grasping movements. Subjects reached
and grasped a target-object, located either on the right or
on the left of the subject’s midline. A distractor, placed
along the subject’s midline, could be randomly presented.
The colors, i.e., both chromaticity (red and green
stimuli were presented) and lightness, of the target and
distractor were varied in experiment 1. Only stimulus
lightness and only stimulus chromaticity were varied in
experiments 2 and 3, respectively. In experiment 4 subjects
matched with their thumb and index finger the size
of the target-stimuli presented in experiment 1. Chromaticity
(experiments 1 and 3) of the target and distractor
influenced grasp, but not reach. Maximal finger aperture
was larger during grasping the red than the green target.
Data collected in the matching task (experiment 4) confirmed
a trend to overestimate the red target and to underestimate
the green one. During grasp, hand shaping
was influenced by distractor chromaticity when it was
different from target chromaticity. Distractor lightness
affected reach, but not grasp (experiments 1 and 2).
Reach was slower when the distractor was lighter and
arm trajectory veered away from it. The results of the
present study suggest that color, that is the ensemble of
chromaticity and lightness, is a stimulus property involved
in the control of reaching-grasping. The different
effects of target color on reach and grasp support the notion
that intrinsic object properties, such as color, affect
grasp more than reach. In addition, the different effects
of distractor chromaticity and lightness on reach and
grasp confirm that target-objects are visually extracted
from surrounding cues by means of different processes,
according to the required motor response
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