Continuous visual control of interception

People generally try to keep their eyes on a moving target that they intend to catch or hit. In the present study we first examined how important it is to do so. We did this by designing two interception tasks that promote different eye movements. In both tasks it was important to be accurate relative to both the moving target and the static environment. We found that performance was more variable in relation to the structure that was not fixated. This suggests that the resolution of visual information that is gathered during the movement is important for continuously improving predictions about critical aspects of the task, such as anticipating where the target will be at some time in the future. If so, variability in performance should increase if the target briefly disappears from view just before being hit, even if the target moves completely predictably. We demonstrate that it does, indicating that new visual information is used to improve precision throughout the movement.     

Knowing when to move on: cognitive and perceptual decisions in time

We investigated people's ability to decide how much time to spend on the task at hand. To make such decisions well, one must take into account, among other things, the cost of failing and how one's task performance changes as a function of time. We first investigated timing decisions when the underlying task was perceptual. Decisions were highly efficient and suggested that people can make good use of perceptual knowledge and abstract reward information. Previous studies have found that perceptual decisions are generally optimal, but that cognitive decisions are generally suboptimal--a perception-cognition gap. Does a similar gap exist for timing decisions? We compared timing decisions for a perceptual task with timing decisions for more cognitive tasks. Performance was highly similar across the tasks, which suggests that knowledge can be acquired, and used to make timing decisions, in an equally efficient way regardless of whether that knowledge is derived through perceptual or cognitive experience.     

Bodily self and schizophrenia: The loss of implicit self-body knowledge

Schizophrenia spectrum has been associated with a disruption of the basic sense of self, which pertains, among others, the representation of one's own body. We investigated the impact of either implicit or explicit access to the representation of one's own body-effectors on bodily self-awareness, in first-episode schizophrenia (FES) patients and healthy controls (HCs). We contrasted their performance in an implicit self-recognition task (visual matching) and in an explicit self/other discrimination task. Both tasks employed participant's own and others' body-effectors. Concerning the implicit task, HCs were more accurate with their own than with others' body-effectors, whereas patients did not show such self-advantage. Regarding the explicit task, both groups did not exhibit a self-advantage, and patients showed a higher percentage of self-misattribution errors. Neither self/other nor implicit/explicit effects were found in both groups when processing inanimate-objects. We propose that FES patients suffer of a disturbed implicit sense of bodily self.     

相对到达时间任务中飞行员对客体特征与运动特征的分离

相对到达时间任务(RAT)是判断两个运动客体哪个先到达指定目标, 可用来评估个体动态空间能力。采用RAT任务对飞行员与普通被试进行对照研究, 寻求发现两组在运动客体特征和视觉空间运动特征及其相互关系上的处理差异。设计了3个实验分别考察客体颜色、客体大小、运动方向、速率大小、视线方向以及背景特征对判断的影响。结果显示：(1)客体颜色不影响运动客体的相对时间判断, 客体大小、运动方向、速率大小、视线方向以及背景特征影响判断; (2)控制组对显示屏上从左到右的运动客体的相对时间判断好于从右到左任务, 大速率任务判断更好, 对大客体快速行驶而小客体低速行驶时的相对到达时间更易区分, 且与两眼视线方向不一致的运动方向会使控制组判断更难, 运动背景中的目标线特征改变使控制组判断绩效降低; (3)和控制组比, 飞行员反应快正确率高, 其快速判断优势集中体现在从右到左运动以及小速率任务上, 且在不同运动方向和不同速率上的反应时均无差异, 飞行员的处理优势还表现在不受客体大小、视线方向改变和目标线特征改变的影响。结论：飞行员能在变化的空间中准确处理相对速度、相对距离、相对时间等运动信息, 能分离客体大小、背景、运动方向等因素对相对到达时间判断的影响, 在运动空间中飞行员具有较高场独立性认知特征和动态空间处理能力。     

On the role of peripheral visual afferent information for the control of rapid video-aiming movements

It has been shown that, even for very fast and short duration movements, seeing one's hand in peripheral vision, or a cursor representing it on a video screen, resulted in a better direction accuracy of a manual aiming movement than when the task was performed while only the target was visible. However, it is still unclear whether this was caused by on-line or off-line processes. Through a novel series of analyses, the goal of the present study was to shed some light on this issue. We replicated previous results showing that the visual information concerning one's movement, which is available between 40 degrees and 25 degrees of visual angle, is not useful to ensure direction accuracy of video-aiming movements, whereas visual afferent information available between 40 degrees and 15 degrees of visual angle improved direction accuracy over a target-only condition. In addition, endpoint variability on the direction component of the task was scaled to direction variability observed at peak movement velocity. Similar observations were made in a second experiment when the position of the cursor was translated to the left or to the right as soon as it left the starting base. Further, the data showed no evidence of on-line correction to the direction dimension of the task for the translated trials. Taken together, the results of the two experiments strongly suggest that, for fast video-aiming movements, the information concerning one's movement that is available in peripheral vision is used off-line.     

Perceiving verbal and vocal emotions in a second language

Emotional inferences from speech require the integration of verbal and vocal emotional expressions. We asked whether this integration is comparable when listeners are exposed to their native language and when they listen to a language learned later in life. To this end, we presented native and non-native listeners with positive, neutral and negative words that were spoken with a happy, neutral or sad tone of voice. In two separate tasks, participants judged word valence and ignored tone of voice or judged emotional tone of voice and ignored word valence. While native listeners outperformed non-native listeners in the word valence task, performance was comparable in the voice task. More importantly, both native and non-native listeners responded faster and more accurately when verbal and vocal emotional expressions were congruent as compared to when they were incongruent. Given that the size of the latter effect did not differ as a function of language proficiency, one can conclude that the integration of verbal and vocal emotional expressions occurs as readily in one's second language as it does in one's native language.     

Comparison of patients with Parkinson's disease or cerebellar lesions in the production of periodic movements involving event-based or emergent timing

We have hypothesized a distinction between the processes required to control the timing of different classes of periodic movements. In one class, salient events mark successive cycles. For these movements, we hypothesize that the temporal goal is a requisite component of the task representation, what we refer to as event-based timing. In the other class, the successive cycles are produced continuously. For these movements, alternative control strategies can optimize performance, allowing timing to be emergent. In a previous study, patients with cerebellar lesions were found to be selectively impaired on event-based timing tasks; they were unimpaired on a continuously produced task. In the present study, patients with Parkinson's disease were tested on repetitive movement tasks in which timing was either event-based or emergent. Temporal variability on either type of task did not differ between on- and off-medication sessions for the Parkinson's patients nor did patient performance differ from that of controls. These results suggest that the basal ganglia play a minimal role in movement timing and that impairments on event-based timing tasks are specific to cerebellar damage.     

Saccades predict and synchronize to visual rhythms irrespective of musical beats

ABSTRACT

Music has been shown to entrain movement. One of the body’s most frequent movements, saccades, are arguably subject to a timer that may also be susceptible to musical entrainment. We developed a continuous and highly-controlled visual search task and varied the timing of the search target presentation, it was either gaze-contingent, tap-contingent, or visually-timed. We found: (1) explicit control of saccadic timing is limited to gross duration variations and imprecisely synchronized; (2) saccadic timing does not implicitly entrain to musical beats, even when closely aligned in phase; (3) eye movements predict visual onsets produced by motor-movements (finger-taps) and externally-timed sequences, beginning fixation prior to visual onset; (4) eye movement timing can be rhythmic, synchronizing to both motor-produced and externally timed visual sequences; each unaffected by musical beats. These results provide evidence that saccadic timing is sensitive to the temporal demands of visual tasks and impervious to influence from musical beats.     

Self-motion impairs multiple-object tracking

Investigations of multiple-object tracking aim to further our understanding of how people perform common activities such as driving in traffic. However, tracking tasks in the laboratory have overlooked a crucial component of much real-world object tracking: self-motion. We investigated the hypothesis that keeping track of one’s own movement impairs the ability to keep track of other moving objects. Participants attempted to track multiple targets while either moving around the tracking area or remaining in a fixed location. Participants’ tracking performance was impaired when they moved to a new location during tracking, even when they were passively moved and when they did not see a shift in viewpoint. Self-motion impaired multiple-object tracking in both an immersive virtual environment and a real-world analog, but did not interfere with a difficult non-spatial tracking task. These results suggest that people use a common mechanism to track changes both to the location of moving objects around them and to keep track of their own location.     

Catching of balls unexpectedly thrown or fired by cannon

Although learned actions can be automatically elicited in response to expected stimuli for which they have been prepared, little is known about whether learned actions can be automatically initiated by unexpected stimuli. Responses of unwitting participants to balls unexpectedly thrown by an experimenter (n=10) or propelled by a hidden ball cannon (n=22) were recorded by motion capture. Experience of ball catching correlated negatively with hand movement distance, indicating most responses were defensive, but successful catches were made in response to both thrown and fired balls. Although reaction time was faster in response to fired balls, interception was more frequent in response to thrown balls, indicating that movement cues by the thrower facilitated unexpected ball catching. The latency to begin a catching action by the only successful catcher of an unexpectedly fired ball was 296 msec. Given current knowledge of reaction time tasks and latencies of neural substrates of conscious perception and deliberation, it is probable that there was insufficient time available for conscious preparation of catch attempts. Ball catching may represent an example of a learned response which can be rapidly and unconsciously initiated without contextual priming or expectation of the stimulus.     

自由拦截启动策略与信息利用

手的启动方向自由, 伸手拦截不同速度的运动小球。本研究通过考察手启动时的运动参数, 研究自由启动的情况下的信息利用和拦截策略, 并且考察了人的启动模式。结果发现, 自由拦截时手的拦截区域相对固定, 在物体快速运动情景下启动晚, 而在慢速下启动早, 可能综合利用了接触时间和距离信息, 存在速度伴随效应, 手的拦截启动策略为启动有相对稳定的角度和加速度, 并不随物体运动速度和物体大小的改变而改变。     

Temporal coordination of alternative and simultaneous aiming movements of constrained timing structure

Two experiments are reported addressing the preparation and initiation of movements with equal or unequal timing properties for both hands. Temporal coordination was examined in two movement tasks: one in which both hands performed the movements simultaneously (simultaneous aiming task) and one in which only one alternative of two possible movements was executed (choice aiming task). For each task a different group of subjects was used. Besides the timing relationships between both movements, the effects of preparation interval (1, 3, and 5 s), the average velocity (7, 14, 17.5, and 70 cm/s), the presence of advance information about the required velocity of the movement(s), and practice were investigated. Based on the common- and the specific-timing notions, distinct hypotheses were tested as to the effects of the variables on the temporal coordination as revealed by reaction time. A main result was that the effects of timing differences between the hands was task specific. For the choice task the data are in agreement with the common-timing notion of coordination, i. e., only one timing demand at a time can be prepared, whereas in the simultaneous task evidence was obtained for the specific-timing notion, i. e., independent preparation and initiation of different timing properties for the hands. However, it is argued that the results of the choice task probably do not reflect a general inability to prepare movements of different timing requirements for both hands, but is related to a task-specific strategy of selective preparation.     

Upper and lower limb reciprocal tapping: evidence for gender biases

According to D. Kimura's (2000) interpretation of the hunter-gatherer hypothesis, men are better at targeting tasks and women are better at fine-motor tasks because of their evolutionary experiences. The author applied that hypothesis to a lower limb pointing task, a task uninfluenced by hunting and gathering experience throughout history. Participants (39 women, 35 men) completed the P. M. Fitts (1954) task by using both their dominant right hand and foot. Results suggested that for both the upper and lower limbs, men move faster, particularly for the more difficult tasks. The hunter-gatherer hypothesis does not predict those data; rather, linear regression data suggest that gender differences in movement strategies affect motor performance. The author proposes that men and women preferentially adopt distinct strategies emphasizing speed for men and accuracy for women.     

Boundary Distance Effects on Overshooting

Experiments with a subject-paced pursuit tracking task show that overshoot rate is dependent upon the distance between the target and the display boundary measured in the direction of movement, and that a previously noted inverse relationship with distance to the target is artifactual. The effect held for tasks with direct and reverse control-display relations, and for tasks with constant and variable target distances. The findings were consistent with Wetford’s (1968) hypothesis that a pursuit response is initiated with a ballistic, distance-covering, movement. Ralph Leonardo carried out extensive work in collecting data, Fred Hyde maintained the apparatus, and Georgie Green assisted in data analysis.     

Developmental differences in drawing performance of the dominant and non-dominant hand in right-handed boys and girls

This paper addresses the development of fine motor skills in the dominant and non-dominant hand. A total of 60 right-handed children, aged 4-12 years old, were divided in five groups of 12 children, with six girls and six boys in each group. The children were presented with drawing tasks that had to be performed with the dominant and non-dominant hand. Small or large targets had to be connected by lines making either a zigzag (discrete) or slalom (continuous) movement. For each task, effects of age group, gender, hand, and target size were examined for drawing time, percentage of stop time, drawing distance, velocity, and errors. Comparison of stop times in both tasks showed that the zigzag task was performed in a discrete way while the slalom task was performed more continuously, except in the youngest children, who performed both tasks in a discrete manner. With increasing age the children performed the tasks faster, more accurate and with shorter stops. No significant differences were found between boys and girls. While a shorter drawing distance and less errors were observed for the dominant hand in both tasks, drawing time and velocity were not significantly different between both hands. However, the percentage of stop time was higher for the dominant hand. Moving to smaller targets resulted in slower and less accurate performance. A significant interaction of age group and hand was found for errors in both tasks, and for stop time and velocity in the slalom task, suggesting differential maturational changes for both hands in discrete and continuous drawing tasks.     

Auditory-visual interactions in the perception of a ball's path

We carried out two experiments to measure the combined perceptual effect of visual and auditory information on the perception of a moving object's trajectory. All visual stimuli consisted of a perspective rendering of a ball moving in a three-dimensional box. Each video was paired with one of three sound conditions: silence, the sound of a ball rolling, or the sound of a ball hitting the ground. We found that the sound condition influenced whether observers were more likely to perceive the ball as rolling back in depth on the floor of the box or jumping in the frontal plane. In a second experiment we found further evidence that the reported shift in path perception reflects perceptual experience rather than a deliberate decision process. Instead of directly judging the ball's path, observers judged the ball's speed. Speed is an indirect measure of the perceived path because, as a result of the geometry of the box and the viewing angle, a rolling ball would travel a greater distance than a jumping ball in the same time interval. Observers did judge a ball paired with a rolling sound as faster than a ball paired with a jumping sound. This auditory-visual interaction provides an example of a unitary percept arising from multisensory input.     

Is there manual asymmetry in movement preparation?

Manual asymmetry in response preparation was investigated in simple and complex movements by using simple reaction-time tasks. The simple movement consisted of lifting the index finger, while in the complex one subjects reversed direction of movement to hit a switch after reaching for and grasping a tennis ball. Analysis showed that performance with either the right or the left hand was equivalent, with longer latencies for reacting on the complex task in comparison to the simple one. These findings indicate similar capabilities of the right and the left cerebral hemispheres to prepare the motor system for action independently of the spatial requirements of movement.     

Psychophysical investigation of vigilance decrement in jumping spiders: overstimulation or understimulation?

The inability to maintain signal detection performance with time on task, or vigilance decrement, is widely studied in people because of its profound implications on attention-demanding tasks over sustained periods of time (e.g., air-traffic control). According to the resource depletion (overload) theory, a faster decrement is expected in tasks that are cognitively demanding or overstimulating, while the underload theory predicts steeper decrements in tasks that provide too little cognitive load, or understimulation. Using Trite planiceps, a jumping spider which is an active visual hunter, we investigated vigilance decrement to repetitive visual stimuli. Spiders were tethered in front of two stimulus presentation monitors and were given a polystyrene ball to hold. Movement of this ball indicates an attempt to turn towards a visual stimulus presented to a pair of laterally facing (anterior lateral) eyes for closer investigation with high acuity forward-facing (anterior median) eyes. Vigilance decrement is easily measured, as moving visual stimuli trigger clear optokinetic responses. We manipulated task difficulty by varying the contrast of the stimulus and the degree of ‘noise’ displayed on the screen over which the stimulus moved, thus affecting the signal:noise ratio. Additionally, we manipulated motivation by paired testing of hungry and sated spiders. All factors affected the vigilance decrement, but the key variable affecting decrement was stimulus contrast. Spiders exhibited a steeper decrement in the harder tasks, aligning with the resource depletion theory.     

反馈类型和反馈时间对动作技能获得的影响

基于简单直线运动任务和复杂曲线追踪任务,在运动技能获得阶段考察不同反馈类型和反馈时间对操作绩效的影响。结果发现,在复杂曲线轨迹追踪任务中,接受运动轨迹反馈的被试组比接受偏差数值反馈组的成绩更好;即时反馈和延迟反馈组的操作绩效间没有显著差异。在简单直线运动任务中,提供落点偏差的图形反馈组成绩始终优于提供“近/远”信息的文本反馈组;在练习初期,即时反馈组成绩更好。说明,反馈信息的具体-抽象程度影响被试运动技能获得,提供具体直观的轨迹/图形反馈利于运动技能获得;反馈时间对运动技能的影响因任务难度而异。