1,720,991 research outputs found
Performance in rapid sequential visually-guided pointing movements.
No full textPurpose: We investigated how directional change, distance, and reward affected the speed and accuracy of rapid pointing movements to multiple targets.
Method: On each trial subjects saw two targets presented on a horizontal LCD touch screen. They attempted to hit both targets in a specified order within 400 ms after they initiated movement. Successful hits resulted in monetary rewards. Subjects were first trained to perform the task (640 trials) without reward. In the experimental session, subjects were rewarded for hits. Four subjects participated, three naïve.
We varied direction: the two movements required a change of 0, 90, 180, or 270 degrees in direction; distance: The two movement distances were equal (7.5cm) or the second was increased by a factor of 1.375; and reward structure: In one reward condition, both targets had the same value. In the other reward condition, the second target was worth 5 times more than the first target. Subjects performed 16 blocks (4 directions x 2 distances x 2 rewards) of 50 trials each for a total of 800 experimental trials per subject.
Results: When distance and reward were equal, all subjects spent considerably more time transiting to the first target (mean 148±15ms) than to the second (mean 106±9ms) and the likelihood of hitting the first was correspondingly higher (87±1%) than for the second (63±2%). When the distance to the second target was greater subjects spent only 13±2ms more on the second movement. When reward was unequal, subjects spent more time in transiting from first to second target but with only a slight increase in probability (7.6%) of hitting the second. We found no significant influence of hitting one target on the probability of hitting the other. This lack of interaction and the overall tendenc
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
Trajectory planning in sequential pointing movements. Bridging the gap between sensation and motor control: from computation to behavior
No full textMovement planning under risk differs from decision making under risk in how subjects make use of probability information.
No full textTrommershäuser, Maloney & Landy (JOSA, 2003) studied performance in tasks that were formally equivalent to decision making under risk. They found that subjects' planned movements nearly maximized expected gain, a result inconsistent with the decision making literature. Here we replicated a decision making experiment (Wu & Gonzalez, Management Science,1996) that tested whether subjects correctly use probability information in choosing between lotteries. We replicate the original experiment with the probabilities of outcomes explicitly given in the lotteries and we also replicated the experiment with each lottery translated into an equivalent motor task (“motor lottery”) where the probability of each outcome is implicit in movement uncertainty. We will describe how we measured subjects' movement uncertainty and designed an equivalent motor lottery for any given lottery. Each subject ran the implicit and explicit conditions in counterbalanced order. Task: On each trial in both conditions subjects indicated which lottery/motor lottery they preferred (2AFC). They knew that, at the end of the experiment, they would be allowed to attempt only one of their preferred explicit lotteries and one of their preferred implicit motor lotteries chosen at random and receive the outcome. Results: All subjects failed to correctly use probability information or maximize expected gain in the explicit condition, consistent with Wu & Gonzalez. Five out of eight of these subjects made choices consistent with maximizing expected gain in the implicit (motor lottery) condition. The results indicate that planning rapid movements differs qualitatively from classical decision making in how subjects make use of probability information
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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