The Effects of Object Weight on the Kinematics of Prehension

The purpose of these experiments was to determine the effects of object weight and condition of weight presentation on the kinematics of human prehension. Subjects performed reaching and grasping movements to metal dowels whose visible characteristics were similar but whose weight varied (20, 55, 150, 410 g). Movements were performed under two conditions of weight presentation, random (weight unknown) and blocked (weight known). Three-dimensional movements of the thumb, index finger, and wrist were recorded, using a WATSMART system to obtain information regarding the grasp and transport components. The results of the first experiment indicated that object weight and condition of presentation affected the temporal and kinematic measures for both the grasp and transport components. In conjunction with the results of a second experiment, in which time in contact with the dowel was measured, it was shown that the free-motion phase of prehension (i.e., up to object contact) was invariant over the different conditions, however. The changes were observed in the finger-object interaction phase (when subjects applied forces after contact with the dowel), prior to lift-off. These results were interpreted as indicating (a) object weight does not influence the planning and execution of the free-motion phase of prehension and (b) there are at least two motor control phases involved in prehension, one for making contact with the object and the other for finger-object interaction. The changing contributions of visual, kinesthetic, and haptic information during these two phases is discussed.     

Lateralization of the Approach Movement and the Prehension Movement in Infants from 4 to 7 Months

The aim of the study was to analyse lateralized preferences during reaching and grasping in infants relative to changes in manual actions from 4 to 7 months of age. Reaching and grasping movements with visual fixation were studied with objects placed in one of three places on a table: to the left, to the right and in the midline of the infant. Although the two lateralized objects were approached and grasped with ipsilateral hand, movements towards the object in the midline were most often performed with a preferential hand. There was preferential use of the left hand for reaching around the fourth month, then a preferential use of the right hand for grasping from the sixth month. The shape of the left hand during reaching movements terminated in the vicinity of the object. The slower the speed, the closer the hand came to the object. The onset of the prehension was associated with a preferential use of the right hand, which performed grasping, more finely than the left hand. Thus, manual specialization is already present in early infancy: the left hand appears to be dedicated to spatial calibration and the right hand to the task of prehension.     

Effects of Auditory Feedback on Movement Time in a Fitts Task

The purpose of the present experiment was to investigate the role of auditory feedback and its impact on movement time in a standard Fitts task. Feedback was given at the moment of target acquisition. A 2-way analysis of variance found significant differences between feedback groups at all three indexes of difficulty (F(2, 40) = 156.02, p < .001). Results from a mixed-model multivariate analysis of variance for kinematic factors show significant differences in peak velocity and the location of peak velocity when comparing feedback groups. In general, the addition of auditory feedback decreased the task ID by .5.     

Temporal Orientation,Human Movement Responses and Time Estimation

The relationship between temporal orientation, human movement (M) responses on the Barron inkblots, and brief time estimates was investigated. Knapp's Time Metaphor Test and the Barron inkblots were administered to 110 Ss. 40 Ss were selected on the basis of their scores on the Time Metaphor Test to participate in an individual time estimation experiment This produced two criterion groups: 20 Dynamic-Hasty (D-H) Ss and 20 Naturalist-Passive (N-P) Ss. Results indicated that N-P Ss had a lower M threshold, perceived more M and overestimated the passage of time. Discussion focused on the relationship between temporal orientation, fantasy behavior, and impulse control.     

遮挡范式下运动速度和方向对碰撞时间估计绩效指标的影响

为探索运动速度和方向对碰撞时间（TTC）估计的影响,采用3运动速度×4运动方向的双因素设计开展了实验研究。结果发现,在相对慢速条件下,受试者TTC估计的准确性显著差于相对中速和相对快速条件;仅在相对慢速条件下受试者对竖直方向的TTC估计准确度显著差于水平方向、低估TTC的比例显著高于高估TTC的比例。结果表明,运动速度对TTC估计绩效指标的影响相对较强,运动方向对其影响相对较弱;两个因素的影响存在交互作用。     

Effects of S-R Compatibility and Task Difficulty on Unimaimual Movement Time

Using a system in which S controlled a cursor on an oscilloscope screen by moving a lever, the S-R relationship on either hand could be reversed. This system was used in two experiments designed to investigate the effect on unimanual movement time of varying S-R compatibility, and task difficulty as defined by Fitts (1954). The results indicated the necessity of specifying task difficulty in an investigation of S-R compatibility. Further, it was found that as task difficulty increased the difference in performance between the right and left hands became more marked.     

Distance and Movement Time Effects on the Timing of Agonist and Antagonist Muscles

The experiment examined the effects of movement time (MT) and distance on the timing of electromyographic (EMG) activity from an agonist and antagonist muscle during rapid, discrete elbow movements in the horizontal plane. According to impulse-timing theory (Wallace, 1981) MT, not distance moved, should have a pronounced effect on the timing of EMG activity (duration of initial agonist and antagonist burst and time to onset of initial antagonist burst). The levels of MT were 100 and 160 msec and the levels of distance were 27° and 45° of elbow flexion. In general support of impulse-timing theory, the results of the three EMG timing measures showed that MT had a more pronounced effect on these measures than distance. In addition, the timing of EMG activity in relation to total MT remained fairly consistent across the four MT-distance conditions.     

Evolutionary Constraints on Human Object Perception

Language and culture endow humans with access to conceptual information that far exceeds any which could be accessed by a non‐human animal. Yet, it is possible that, even without language or specific experiences, non‐human animals represent and infer some aspects of similarity relations between objects in the same way as humans. Here, we show that monkeys’ discrimination sensitivity when identifying images of animals is predicted by established measures of semantic similarity derived from human conceptual judgments. We used metrics from computer vision and computational neuroscience to show that monkeys’ and humans’ performance cannot be explained by low‐level visual similarity alone. The results demonstrate that at least some of the underlying structure of object representations in humans is shared with non‐human primates, at an abstract level that extends beyond low‐level visual similarity. Because the monkeys had no experience with the objects we tested, the results suggest that monkeys and humans share a primitive representation of object similarity that is independent of formal knowledge and cultural experience, and likely derived from common evolutionary constraints on object representation.     

Chaos in Human Rhythmic Movement

Rhythmic movements typical of locomotory actions are usually modeled as limit cycle dynamics, and their deviations from pure periodicity are attributed to stochastic physiological noise. In the present study, the dynamics of human rhythmic movements were found to contain more than the 2 dynamically active variables expected from limit cycle dynamics; the number depended upon the size of the limb oscillator. Observed positive Lyapunov exponents and fractal attractor dimensions indicated that the gross variability of human rhythmic movements may stem largely from low-dimensional chaotic motion on strange attractors.     

Internal Forces During Static Prehension: Effects of Age and Grasp Configuration

The authors studied effects of healthy aging on 3 components of the internal force vector during static prehensile tasks. Young and older subjects held an instrumented handle using a 5-digit prismatic grasp under different digit configurations and external torques. Across digit configurations, older subjects showed larger internal normal (grip) and tangential (load-resisting) digit force components and larger internal moment of force. In contrast to earlier reports, safety margin values were not higher in the older subjects. The results show that the increased grip force in older persons is a specific example of a more general age-related problem reflected in the generation of large internal force vectors in prehensile tasks. It is possible that the higher internal forces increase the apparent stiffness of the hand+handle system and, hence, contribute to its stability. This strategy, however, may be maladaptive, energetically wasteful, and inefficient in ensuring safety of hand-held objects.     

Combined Effects of Movement Velocity and Duration on Programming Time: Spijkers (1989) Revisited

The goal of the present study was to determine the combined effects of movement velocity and duration on motor programming. Subjects were submitted to a two-choice reaction time task that could be completed by aiming movements differing in the mean velocity at which they were to be produced as well as by their movement time. The results of the present study indicate that, in each pair of responses used, the responses having the higher mean velocity were initiated faster than those having the lower mean velocity. Contrary to Spijkers' (1989) study, the different movement time pairings did not modify the effect of movement velocity on response programming time. Moreover, the same pattern of results was observed whether or not the subjects were permitted to visually guide their ongoing movement. Thus, Spijkers' proposition, that the type of control one may use to guide an aiming movement needs to be determined before movement initiation can take place, was not confirmed.     

客体工作记忆的保持对时距知觉的影响

初步探讨毫秒范围内,客体信息保持对时间知觉的影响。实验一发现,知觉到的时间不受记忆负荷的影响,但当保持时间短时,低负荷的反应时低于高负荷的反应时;实验二仅要求被试完成时间知觉任务,发现知觉负荷异于记忆负荷对时间知觉的影响。结果说明,客体工作记忆保持对时间知觉的影响受到工作记忆资源的调节。     

The Development of Infants' Perception of Object Movement Along Inclines

Three experiments investigated 10- and 16-month-old infants' perceptions of events involving a computer-generated ball rolling up or down an incline. Experiment 1 demonstrated that infants do not have a priori preferences for either impossible or possible events. In Experiments 2 and 3, infants were habituated to either a possible or an impossible event and then shown three novel events that involved changes in individual features that may or may not correspond to changes in possibility. Ten-month-old infants responded to changes in individual features when habituated to downward movement and did not discriminate among any changes when habituated to upward movement. Sixteen-month-old infants responded to possibility changes that were accompanied by a change in direction when habituated to downward movement, and responded to changes in individual features when habituated to upward movement. These findings are discussed in terms of a framework by which infants first attend to individual features in events and later respond on basis of the combination of those features.     

Prehension and perception of size in left visual neglect

Right hemisphere damaged patients with and without left visual neglect, and age-matched controls had objects of various sizes presented within left or right body hemispace. Subjects were asked to estimate the objects' sizes or to reach out and grasp them, in order to assess visual size processing in perceptual-experiential and action-based contexts respectively. No impairments of size processing were detected in the prehension performance of the neglect patients but a generalised slowing of movement was observed, associated with an extended deceleration phase. Additionally both patient groups reached maximum grip aperture relatively later in the movement than did controls. For the estimation task it was predicted that the left visual neglect group would systematically underestimate the sizes of objects presented within left hemispace but no such abnormalities were observed. Possible reasons for this unexpected null finding are discussed.     

The Effect of Movement Amplitude and Target Diameter on Reaction Time

Siegel’s (1977) interpretation that his reaction time results were solely a function of response factors (movement amplitude and target diameter) was discussed and criticized. It was argued that Siegel’s interpretation was inappropriate because stimulus factors (eccentric and visual angle) and response factors were confounded. It was also argued that the surprising U-shaped relation between reaction time and movement amplitude was probably the result of the confounding between stimulus and response factors.     

学习时间分配机制的眼动研究

本研究采用被试内的实验设计,以无意义词对为实验材料,利用眼动记录技术,通过分析在有无时间压力时,个体对不同难度词对的学习时间分配,检验学习时间分配的差距缩减模型和最近学习区模型.研究发现:(1)在总注视时间上,难度和时间压力的影响都是显著的,并且存在交互作用.(2)个体的学习次序是由易到难的.研究结果支持了最近学习区模型.     

文字与图片呈现形成想象空间记忆的比较

学习通过文字或图片方式显示的空间布局材料之后,采用空间定位任务．分别检验在不同朝向和相对位置的条件下,对想象空间方位判断的差异。结果表明,使用图片进行空间布局的学习,记忆后再各自以同样显示形式进行空间定位任务时,判断的速度比使用文字的反应时要快;同时,无论是文字还是图片形式呈现．在进行想象转向时．都会呈现朝向效应和相对位置效应。     

真实物体搜索中的视角依赖效应:来自眼动的证据

已有研究发现物体识别存在视角依赖效应,那么在真实物体搜索中是否也存在视角依赖效应呢?本研究采用物体阵列搜索任务,通过眼动技术探讨真实物体搜索中的视角依赖效应及其来源。结果发现:(1)图片提示的搜索绩效优于名称提示;(2)以名称提示时,常规视角的搜索绩效高于新异视角,与新异视角相比,以常规视角呈现的目标物体在扫描和确认阶段的注视点数较少且持续时间较短,表现出视角依赖效应;(3)以图片为提示时,搜索绩效与视角无关。由此可见,在以名称提示的物体搜索中,常规视角比新异视角条件下的注意引导更高效,对目标物体的确认也更快,扫描和确认阶段均存在视角依赖效应,支持目标模板的双功能理论。