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121.
Unimanual left-right responses to up-down stimuli show a stimulus-response compatibility (SRC) effect for which the preferred mapping varies as a function of response eccentricity. Responses made in the right hemispace and, to a lesser extent, at a midline position, are faster with the up-right/down-left mapping than with the up-left/down-right mapping, but responses made in the left hemispace are faster with the up-left/down-right mapping. Also, for responses at the midline position, the preferred mapping switches when the hand is placed in a supine posture instead of the more usual prone posture. The response eccentricity effect can be explained in terms of correspondence of asymmetrically coded stimulus and response features, but it is not obvious whether the hand posture effect can be explained in a similar manner. The present study tested the implications of a hypothesis that the body of the hand provides a frame of reference with respect to which the response switch is coded as left or right. As was predicted by this hand referent hypothesis, Experiment 1 showed that the influence of hand posture (prone and supine) on orthogonal SRC was additive with that of response location. In Experiment 2, the location of the switch relative to the hand was varied by having subjects use either a normal grip in which the switch was held between the thumb and the index finger or a grip in which it was held between the little and the ring fingers. The magnitudes of the mapping preferences varied as a function of the grip and hand posture in a manner consistent with the hand referent hypothesis. 相似文献
122.
Is visual short-term memory object based? Rejection of the "strong-object" hypothesis 总被引:6,自引:0,他引:6
Is the capacity of visual short-term memory (VSTM) limited by the number of objects or by the number of features? VSTM for objects with either one feature or two color features was tested. Results show that capacity was limited primarily by the number of colors to be memorized, not by the number of objects. This result held up with variations in color saturation, blocked or mixed conditions, duration of memory image, and absence or presence of verbal load. However, conjoining features into objects improved VSTM capacity when size-orientation and color-orientation conjunctions were tested. Nevertheless, the number of features still mattered. When feature heterogeneity was controlled, VSTM for conjoined objects was worse than VSTM for objects made of single features. Our results support a weak-object hypothesis of VSTM capacity that suggests that VSTM is limited by both the number of objects and the feature composition of those objects. 相似文献
123.
The question of independently controlled components in the act of reaching and grasping has attracted interest experimentally and theoretically. Data from 35 studies were recently found consistent with simulated kinematic finger and thumb trajectories optimised for minimum jerk. The present study closely reproduces those trajectories using a discrete-time model based on minimum acceleration. That model was further used to generate two-dimensional trajectories for finger and thumb to reach and grasp an elliptical object with varying position and/or orientation. Orthogonalisation of these four trajectories revealed one degree of freedom when direction of reach was constant and two degrees of freedom when direction of reach varied, irrespective of object distance and orientation. These simulations indicate that reach and grasp movements contain redundancy that is removable by formation of task-dependent synergies. As skilled movement can be planned and executed in a low dimension workspace, control of these independent components lessens central workload. 相似文献
124.
The motion of objects that are both translating and rotating can be decomposed into an infinite number of translational and rotational combinations. How, then, do such stimuli routinely elicit specific percepts and behavioral responses that are usually appropriate? A possible answer is that motion percepts are fully determined by the probability distributions of all the possible correspondences and differences in the stimulus sequence. To test the merits of this conceptual framework, we investigated the perceived motion elicited by a line that is both translating and rotating behind an aperture. When stimuli are presented such that a particular sequence of appearance and disappearance occurs at the aperture boundary, subjects report that the line is rotating only; furthermore, the perceived centers of rotation appear to describe a cycloidal trajectory, even when one aperture shape is replaced by another. These and other perceptual effects elicited by translating and rotating stimuli are all accurately predicted by the probability distribution of the possible sources of the physical movements, supporting the conclusion that motion perception is indeed generated by a wholly probabilistic strategy. 相似文献
125.
We extended perceptual studies of the Brodatz set of textured materials. In the experiments, texture perception for different texture sets, viewing distances, or lighting intensities was examined. Subjects compared one pair of textures at a time. The main task was to rapidly rate all of the texture pairs on a number scale for their overall dissimilarities first and then for their dissimilarities according to six specified attributes (e.g., texture contrast). The implied dimensionality of perceptual texture space was usually at least four, rather than three. All six attributes proved to be useful predictors of overall dissimilarity, especially coarseness and regularity. The novel attribute texture lightness, an assessment of mean surface reflectance, was important when viewing conditions were wide-ranging. We were impressed by the general validity of texture judgments across subject, texture set, and comfortable viewing distances or lighting intensities. The attributes are nonorthogonal directions in four-dimensional perceptual space and are probably not narrow linear axes. In a supplementary experiment, we studied a completely different task: identifying textures from a distance. The dimensionality for this more refined task is similar to that for rating judgments, so our findings may have general application. 相似文献
126.
A common research problem is the estimation of the population correlation between x and y from an observed correlation rxy obtained from a sample that has been restricted because of some sample selection process. Methods of correcting sample correlations for range restriction in a limited set of conditions are well-known. An expanded classification scheme for range-restriction scenarios is developed that conceptualizes range-restriction scenarios from various combinations of the following facets: (a) the variable(s) on which selection occurs (x, y and/or a 3rd variable z), (b) whether unrestricted variances for the relevant variables are known, and (c) whether a 3rd variable, if involved, is measured or unmeasured. On the basis of these facets, the authors describe potential solutions for 11 different range-restriction scenarios and summarize research to date on these techniques. 相似文献
127.
In a sample of 18 industrialized nations, measures of national character did not improve the power of socioeconomic variables in predicting unemployment rates. 相似文献
128.
Humans conduct visual search more efficiently when the same display is presented for a second time, showing learning of repeated spatial contexts. In this study, we investigate spatial context learning in two tasks: visual search and change detection. In both tasks, we ask whether subjects learn to associate the target with the entire spatial layout of a repeated display (configural learning) or with individual distractor locations (nonconfigural learning). We show that nonconfigural learning results from visual search tasks, but not from change detection tasks. Furthermore, a spatial layout acquired in visual search tasks does not enhance change detection on the same display, whereas a spatial layout acquired in change detection tasks moderately enhances visual search. We suggest that although spatial context learning occurs in multiple tasks, the content of learning is, in part, task specific. 相似文献
129.
130.
自我面孔识别的独特性 总被引:4,自引:1,他引:3
与识别他人的面孔相比,自我面孔识别在行为反应、种系发生、个体发展以及脑机制等方面都具有很大的独特性。行为指标方面,自我面孔识别在速度上快于识别他人的面孔;种系发生方面,只有人类和大猩猩等高级灵长类动物才具有识别自己面孔的能力;个体发展方面,儿童出生后不久即能识别他人面孔,但要在18个月左右才能表现出自我面孔识别能力;脑机制方面,神经心理学和脑成像研究结果表明自我面孔识别可能主要是右脑的功能。该领域的研究进展将为深入了解自我的形成机理提供一个新的探视“窗口”。 相似文献