1,721,167 research outputs found
The use of viewing posture to control visual processing by lateralised mechanisms
No full textChicks were trained and tested to run to a dish and feed from it under one of four conditions. In three of these, the dish was covered by a light lid that the chicks readily learned to remove. The square lid (SL) had slightly protruding corners, so that it could be removed by a blow of the bill at a range of positions. A round lid (UL), which fitted snugly, could best be removed by inserting the bill into a medial U-shaped indentation. A round lid (STR), which fitted all the way round to the edge of the dish, could be removed by grasping and tugging a centrally placed piece of string. The final dish had no lid (NOL). The dish and the layout of the arena were otherwise identical under all conditions. Chicks trained and tested with lids predominantly fixated the dish during approach with the right eye and showed leftward deviation from the direct line of approach (which facilitated right eye use). NOL chicks fixated with the left eye and deviated rightwards. The right eye is thus used when a motor plan has to be set up and sustained. The use of the left eye is expected when topographical information has to be used. Here, the approach was so simple and practised that the assumption of left eye viewing is likely to be a default condition. It would facilitate detection of any change in layout. A standard set of head positions were used, particularly by SL and NOL chicks, showing that the head was aligned with some reference point, perhaps the centre of the dish. These fell into two series (used by both eyes), and in both the peaks of frequent use were 10° apart. One (20°, 10°) was probably generated by head saccades ending with the bill pointing directly at the dish (0°). The other (35°, 25°, 15°) is best explained by slight divergence of the optic axes. The 25° right eye position was consistently used by STR chicks at the beginning of approach. The STR condition requires the most difficult manipulation, and the manipulandum is most obvious from a distance. This is consistent with right eye use during establishment of a motor plan. Head postures consistent with divergence were also used when close to the dish under conditions where choice between targets was necessary. This was clear in the NOL condition, where the chick could see the food grains as it approached. Here, it is likely that both eyes are used in independent search. If so, it may be that divergence is used as a strategy during establishment of a motor plan (as in STR chicks) to increase the independence of the right eye system
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
Eye use in search is determined by the nature of task in the domestic chick (Gallus gallus)
No full textIn Experiments 1-3 chicks were trained to find, using both eyes, food covered by a cap, using wide-angle search so as to involve lateral and frontal visual fields, with either local or positional cues, or both, identifying the baited site. At test they used right, left or both eyes (RE, LE, Bin). When both types of cue were relevant, LE made greater use of positional cues than the other two groups, as has been previously found, whereas RE made greater use of local (colour) cues. However, when only one type of cue was relevant, RE and LE were equally able to use positional or local cues. Right/left differences emerge when RE and LE can be used in different ways during training. In Experiments 4-5 Bin chicks were shown to turn preferentially to the right during wide-angle search, when relying on local, and to the left when relying on positional cues. In search, parallel processing of RE and LE inputs appears to allow competition which is usually won by the eye system more suited to the task, which then initiates targeting to objects which are visible to its eye
Motor control by vision and the evolution of cerebral lateralisation
No full textChicks (4 or 5 days old), which are able to use either eye freely, use the right eye (RE) preferentially in approach to a food dish when a lid, which has to be removed, is visible during approach. They use the left eye (LE) instead when no manipulation is required, but the same dish is similarly visible. The RE is also used preferentially in selecting food grains scattered over the floor; RE use in these two contexts is thus associated with visual control which brings the bill in planned contact with a visible target rather than with approach to a site where it is anticipated that feeding will occur. Zebrafish also use the RE preferentially when preparing to bite a target; during purely visual examination of the same target, this preference disappears. This evidence is used together with evolutionary evidence to support a new hypothesis for the origin of cerebral lateralization: paired anterior eyes evolved in filter-feeding ancestors of the vertebrates as part of the acquisition of prey catching. A key use for early vision was to predict likely contact with prey so as to inhibit reflexes of rejection and avoidance normally elicitated by tactile input to the mouth and so to allow ingestion. Innervation of mouth structures by the left side of the CNS caused control of mouth reflexes to become predominantly a left CNS affair. As visual abilities developed this starting condition meant that control of manipulation (which is by the mouth for most vertebrates) remained predominantly with the left side of the CNS
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
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