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To investigate the nature of the frames of reference used to control an arm movement aimed at a visual target, we studied the accuracy of movements differing by the initial arm and eye positions. The results support the assumption that in darkness target location is internally represented in an egocentric frame of reference. Furthermore, when movements carried out with and without eye saccade are compared, it appears that foveating the target changes the reference used to generate the reaching arm movements, that is, the oculocentric reference is replaced by a head-trunk reference. An explanation for this phenomenon could be that a steady body-related landmark is needed to insure stable registering of the target location in the surrounding space, despite displacement of the body segments with respect to one another. 相似文献
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Hanser examines Derek Parfit's contention in his treatise on rationalism, Reasons and Persons (Oxford University Press; 1984) that acts that are not reproductive in nature can nonetheless predictably affect the identities of future people, and that this fact has unexpected and important consequences for ethical theory. Hanser argues tht this fact is not as significant as Parfit believes it to be. The arguments of both scholars concern the morality of choices that, while causing future persons to be badly off, do not make them worse off than they would have been if the choices had not been made. Hanser concludes his essay with a discussion of responsibility for acts that will affect the health of future offspring. 相似文献
236.
Levitt M 《Science and engineering ethics》1997,3(3):305-315
Empirical research with young people in Finland, Germany, Spain and Britain was carried out as part of the BIOCULT project
funded by the European Union. The project focused on their attitudes to biotechnology and, in particular, the formation of
arguments about risk and safety. This paper looks at the responses of 14–18 year olds to a story about the so called anti-obesity
gene, in the form of advice to a friend who is taking it. The majority advised against taking it with some differences by
gender and country. Most reservations were on grounds of safety and the feeling that ‘natural’ ways to lose weight are better:
A minority questioned the idea of striving for a ‘perfect’ body. The types of arguments used by the young people reveal underlying
perspectives on the place of human beings in the world and whether they have a right to manipulate nature and their own bodies.
Marie Levitt is a sociologist with research interests in attitudes and values in relation to biotechnology, health and religion. 相似文献
237.
Languages differ in their phonological structure and physcholinguists have begun to explore the conseqence, of this fact for speech perception. We review research documenting that listeners attune their perceptual processes finaly to exploit the phonological regularities of their nativ language. As a consequence, these perceptual process are fill-adapted to listening to languages that do not display such, regularities. Thus, not only do late language-learners have trouble speaking a second language, also they do not hear it as native speakers do; worse, they apply their native language listening prosedures which may actually interfere with successful processing of the non-native input. We also present data from studies on infants showing that the initial attuning occurs early in life; very yong infants are sensitive to the relevant phonological regularities which distinguish different languages, and quickly distinguish the native language of their environment from languages with different regularities. 相似文献
238.
The auditory cortex of the mustached bat shows complex multiple frequency maps, because cortical neurons in several areas are tuned to particular combinations of signal elements. Different types of combination-sensitive neurons form computational maps in which information-bearing parameters for echolocation (biosonar) are represented systematically. Neuronal response properties and multiple-frequency and computational maps were considered to be created solely by divergent-convergent interactions of neurons in the 'ascending' system. However, we have found that the 'corticofugal' system also plays an important role. Neurons in an iso-best frequency (or echo delay) 'minicolumn' of the auditory cortex augment the auditory responses of subcortical neurons tuned to that frequency (or echo delay) and sharpen their tuning. At the same time, they reduce the response and shift the tuning of subcortical neurons tuned to other frequencies (or echo delays) away from the best frequency (or delay) of the cortical neurons. Cortical neurons mediate a highly focused positive feedback, incorporated with widespread lateral inhibition, via corticofugal projections. This 'egocentric selection' is expected to play an important role in self-organizing the central auditory system. 相似文献
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In 2 experiments, the effect of active or passive mobility and active or passive choice experiences on children's memory for locations visited while retrieving puzzle pieces hidden in a large room were examined. In the first experiment, fifty-two 6- and 7-year-old children were randomly assigned to 1 of 4 training conditions: active choice-active movement, active choice-passive movement, passive choice-active movement, and passive choice-passive movement. After 3 training trials, all children were tested in the active choice-active movement condition. A 2 (movement) x 2 (choice) factorial multivariate analysis of variance revealed a significant main effect for movement. Children who had moved actively to find the puzzle pieces in the training trials had (a) a greater percentage correct, (b) more correct visits between errors, and (c) a later visit of first error than children who had been passively pushed in a wheelchair. Making active choices in training did not significantly affect performance. A second experiment used identical procedures but tested 32 children with mobility dif-difficulties who regularly used a wheelchair because of either cerebral palsy or spina bifida. Children from this group who moved actively during training to retrieve the puzzle pieces also performed better on testing. Implications of the results for children with disabilities and for developmental theory are discussed. 相似文献