Concurrent visual feedback and spatial accuracy in continuous aiming movements

The effect of concurrent visual feedback (CVF) on continuous aiming movements was investigated in the preferred hand of participants of college age (ns = 12 men, 8 women). Participants made continuous rapid reversal movements with a lightweight lever in the sagittal plane. Participants attempted to reach a short target (20 degrees) and a long target (60 degrees) in separate constant practice conditions, but alternated between the two targets in a variable practice condition. Four blocks of practice trials were provided in each condition, with 40 movements made in each. CVF of the position-time trace was provided for the first 20 movements of each block, but was removed for the remaining 20 movements in each block. Movements were more accurate and consistent during constant practice compared to variable practice where the short target was overshot and the long target was undershot. CVF reduced errors in all conditions, compared to movements without CVF, particularly for the short target during variable practice. The results suggest that the interference generated by alternating targets can be modulated by providing visual feedback, but once the visual feedback was removed, errors increased markedly.     

Investigating individual differences in children's real-time sentence comprehension using language-mediated eye movements

Individual differences in children's online language processing were explored by monitoring their eye movements to objects in a visual scene as they listened to spoken sentences. Eleven skilled and 11 less-skilled comprehenders were presented with sentences containing verbs that were either neutral with respect to the visual context (e.g., Jane watched her mother choose the cake, where all of the objects in the scene were choosable) or supportive (e.g., Jane watched her mother eat the cake, where the cake was the only edible object). On hearing the supportive verb, the children made fast anticipatory eye movements to the target object (e.g., the cake), suggesting that children extract information from the language they hear and use this to direct ongoing processing. Less-skilled comprehenders did not differ from controls in the speed of their anticipatory eye movements, suggesting normal sensitivity to linguistic constraints. However, less-skilled comprehenders made a greater number of fixations to target objects, and these fixations were of a duration shorter than those observed in the skilled comprehenders, especially in the supportive condition. This pattern of results is discussed in terms of possible processing limitations, including difficulties with memory, attention, or suppressing irrelevant information.     

Preferential looking: A sudden shift in visual fixation pattern at 32 months of age

Observations of eye movements of young children in a modified preferential looking task suggest a change in the visual looking pattern taking place during a very brief time between 32 and 33 months of age. In the younger children, a grating stimulus elicited eye movements towards the target followed by a few seconds of focused attention; in the older children a visual avoidance behavior was observed where subjects looked consistently in the opposite direction of the target. An analysis of video recordings suggests that this avoidance pattern was a composite of a very brief initial target-directed eyemovement which was quickly arrested, and followed by eye movements in the opposite direction, initiating a search of the visual scene.     

中文阅读中词汇视觉编码的年龄特征：来自眼动研究的证据

研究以小学三年级、小学五年级、大学生和老年读者为对象,采用消失文本范式,通过操作注视词消失的延迟时间,考察了不同年龄阶段读者对注视词进行视觉编码的过程.结果发现:(1)注视词延迟消失严重影响小学三年级和老年人的总阅读时间,但对小学五年级和大学生读者总阅读时间的影响不显著;(2)注视词消失不影响小学五年级、大学生和老年读者基于词的平均凝视时间,但影响小学三年级读者的平均凝视时间;(3)所有消失条件都不影响大学生被试的基于词的回视次数,但严重影响小学三年级、小学五年级和老年读者的回视次数.这些结果表明,中文阅读过程中,对注视词的视觉编码能力在小学五年级阶段已趋于成熟,但进入老年阶段出现老化;视觉编码的保持在儿童词汇识别的中后期加工阶段中仍起到一定作用.     

阅读障碍儿童与其年龄和能力匹配儿童阅读空格文本的注视位置效应

采用EyeLink II眼动仪, 选取阅读障碍儿童及与其年龄相同、阅读能力水平相同的儿童为被试, 要求他们阅读正常无空格和词间空格句子。结果发现, 在阅读正常无空格和词间空格句子时, 阅读障碍儿童与年龄匹配组和能力匹配组儿童一样, 单次注视时往往将首次注视定位于词的中心, 多次注视时首次注视往往落在词的开头; 当首次注视落在词的开头时再注视该词的概率增加, 而且再注视往往落在词的结尾部分。我们认为, 中国儿童在阅读过程中采用的是“战略-战术”策略。     

Development of eye-hand coordination in typically developing children and adolescents assessed using a reach-to-grasp sequencing task

Eye-hand coordination is required to accurately perform daily activities that involve reaching, grasping and manipulating objects. Studies using aiming, grasping or sequencing tasks have shown a stereotypical temporal coupling pattern where the eyes are directed to the object in advance of the hand movement, which may facilitate the planning and execution required for reaching. While the temporal coordination between the ocular and manual systems has been extensively investigated in adults, relatively little is known about the typical development of eye-hand coordination. Therefore, the current study addressed an important knowledge gap by characterizing the profile of eye-hand coupling in typically developing school-age children (n = 57) and in a cohort of adults (n = 30). Eye and hand movements were recorded concurrently during the performance of a bead threading task which consists of four distinct movements: reach to bead, grasp, reach to needle, and thread. Results showed a moderate to high correlation between eye and hand latencies in children and adults, supporting that both movements were planned in parallel. Eye and reach latencies, latency differences, and dwell time during grasping and threading, showed significant age-related differences, suggesting eye-hand coupling becomes more efficient in adolescence. Furthermore, visual acuity, stereoacuity and accommodative facility were also found to be associated with the efficiency of eye-hand coordination in children. Results from this study can serve as reference values when examining eye and hand movement during the performance of fine motor skills in children with neurodevelopmental disorders.     

Development of the coordination between posture and manual control

Studies have suggested that proper postural control is essential for the development of reaching. However, little research has examined the development of the coordination between posture and manual control throughout childhood. We investigated the coordination between posture and manual control in children (7- and 10-year-olds) and adults during a precision fitting task as task constraints became more difficult. Participants fit a block through an opening as arm kinematics, trunk kinematics, and center of pressure data were collected. During the fitting task, the precision, postural, and visual constraints of the task were manipulated. Young children adopted a strategy where they first move their trunk toward the opening and then stabilize their trunk (freeze degrees of freedom) as the precision manual task is being performed. In contrast, adults and older children make compensatory trunk movements as the task is being performed. The 10-year-olds were similar to adults under the less constrained task conditions, but they resembled the 7-year-olds under the more challenging tasks. The ability to either suppress or allow postural fluctuations based on the constraints of a suprapostural task begins to develop at around 10 years of age. This ability, once developed, allows children to learn specific segmental movements required to complete a task within an environmental context.     

Modality differences in timing and temporal memory throughout the lifespan

The perception of time is heavily influenced by attention and memory, both of which change over the lifespan. In the current study, children (8 yrs), young adults (18–25 yrs), and older adults (60–75 yrs) were tested on a duration bisection procedure using 3 and 6-s auditory and visual signals as anchor durations. During test, participants were exposed to a range of intermediate durations, and the task was to indicate whether test durations were closer to the “short” or “long” anchor. All groups reproduced the classic finding that “sounds are judged longer than lights”. This effect was greater for older adults and children than for young adults, but for different reasons. Replicating previous results, older adults made similar auditory judgments as young adults, but underestimated the duration of visual test stimuli. Children showed the opposite pattern, with similar visual judgments as young adults but overestimation of auditory stimuli. Psychometric functions were analyzed using the Sample Known Exactly-Mixed Memory quantitative model of the Scalar Timing Theory of interval timing. Results indicate that children show an auditory-specific deficit in reference memory for the anchors, rather than a general bias to overestimate time and that aged adults show an exaggerated tendency to judge visual stimuli as “short” due to a reduction in the availability of controlled attention.     

Visual scanning during pattern recognition in children and adults

Eye movement and fixation responses of 3- to 6-year-old children and adults were recorded during a pattern recognition task. During familiarization, fixations were more repetitive and less extensive for older subjects. The fixation patterns of older children who were consistently able to solve the recognition problems were like those of the adults. Unsuccessful 4- to 6-year-olds spent more time fixating the modified area of the nonstandard pattern presented in paired comparison with the standard, even though their final decision was false. Thus, preschool children were able to locate relevant visual information even when they did not use this information to solve tasks. The results suggest that visual fixations do not always reflect active attention, and that direct fixations of visual information are clearly not sufficient and may not be necessary for problem solving.     

Memory representations guide targeting eye movements in a natural task

The change blindness phenomenon suggests that visual representations retained across saccades are very limited. In this paper we sought to specify the kind of information that is in fact retained. We investigated targeting performance for saccadic eye movements, since one need for visual representations across eye and body positions may be to guide coordinated movements. We examined saccades in the context of an ongoing sensory motor task in order to make stronger generalizations about natural visual functioning and deployment of attention. Human subjects copied random patterns of coloured blocks on a computer display. Their eye movement pattern was consistent from block to block, including a precise saccade to a previously-placed, neighbouring block during each additional block placement. This natural, consistent eye movement allowed the previously-placed, neighbouring block to serve as an implicit target without instructions to the subject. On random trials, we removed the target object from the display during a preceding saccade, so that observers were required to make the targeting saccade without a currently visible target. Targeting performance was excellent, and appeared to be influenced by spatial information that was not visible during the preceding fixation. Subjects were generally unaware of the disappearance and reappearance of the target. We conclude that spatial information about visual targets is retained across eye movements and used to guide subsequent movements.     

Rapid discrimination of visual patterns in children and adults

Rapid visual discrimination in children (9 to 11 yr.) and adults was investigated using two tasks in which the subject had to search for a target pattern embedded in 35 background patterns. The time available for inspecting the search arrays was altered by varying the stimulus duration. In one task, there was a large difference in the feature or 'texton' content of patterns between the target and the background; in the other, this difference was small. In the first task, the children could detect the target pattern in a briefly flashed search array with high accuracy, because the target 'popped out' perceptually from the array, but in the second task the same detection rate was not reached until the stimulus duration was much longer, since a serial searching strategy was required. Results achieved by children and adults were similar. It seems that serial visual search is as efficient in children as in adults.     

The utilization of external and movement cues in simple spatial tasks by blind and sighted children.

The role of visual experience in coding spatial position by movements or by external cues was examined in simple (nonrotational) shift tasks with blind and sighted children. Age and the salience of external cues were also of interest. Results showed that the congenitally totally blind used movement cues significantly more even when external cues were present and prominent. The blind with minimal visual experience coded by external cues, but made errors beyond the age by which blindfolded sighted children performed correctly. It was argued that visual experience affects coding by drawing attention to external cues, and by providing more adequate spatial information than other sources usually available to the blind. In its absence, movement coding and self-reference can become preferred strategies.     

Search performance without eye movements

Visual search performance (with sets chosen to elicit both serial and parallel search patterns) under two conditions that precluded saccades was compared to the typical situation in which visual inspection of the array is possible. In one condition, the display duration was so brief that any saccades that were executed would be too late to bring the targeted portion of the array into the fovea. In the other, the display remained present until the subject's response, but eye position was monitored and trials with shifts in fixation were excluded from analysis. The latter condition produced search latencies that were nearly identical to those with free inspection. Brief exposure, in contrast, did not produce the pattern typical of serial search, presumably because of strategies induced to deal with the rapid decay of the visual array. It is concluded that saccadic eye movements play little role in the patterns of performance used to infer serial and parallel search, and that brief exposure is not a satisfactory technique for exploring the role of saccadic eye movements in visual search.     

Grammatical aspect and event recognition in children’s online sentence comprehension

This study investigated whether or not the temporal information encoded in aspectual morphemes can be used immediately by young children to facilitate event recognition during online sentence comprehension. We focused on the contrast between two grammatical aspectual morphemes in Mandarin Chinese, the perfective morpheme –le and the (imperfective) durative morpheme –zhe. The perfective morpheme –le is often used to indicate that an event has been completed, whereas the durative morpheme –zhe indicates that an event is still in progress or continuing. We were interested to see whether young children are able to use the temporal reference encoded in the two aspectual morphemes (i.e., completed versus ongoing) as rapidly as adults to facilitate event recognition during online sentence comprehension. Using the visual world eye-tracking paradigm, we tested 34 Mandarin-speaking adults and 99 Mandarin-speaking children (35 three-year-olds, 32 four-year-olds and 32 five-year-olds). On each trial, participants were presented with spoken sentences containing either of the two aspectual morphemes while viewing a visual image containing two pictures, one representing a completed event and one representing an ongoing event. Participants’ eye movements were recorded from the onset of the spoken sentences. The results show that both the adults and the three age groups of children exhibited a facilitatory effect trigged by the aspectual morpheme: hearing the perfective morpheme –le triggered more eye movements to the completed event area, whereas hearing the durative morpheme –zhe triggered more eye movements to the ongoing event area. This effect occurred immediately after the onset of the aspectual morpheme, both for the adults and the three groups of children. This is evidence that young children are able to use the temporal information encoded in aspectual morphemes as rapidly as adults to facilitate event recognition. Children’s eye movement patterns reflect a rapid mapping of grammatical aspect onto the temporal structures of events depicted in the visual scene.     

The size illusion: visual and kinaesthetic information in size perception

Earlier studies have shown the size of kinaesthetically presented two-dimensional movement patterns to be significantly overestimated. Whether this size overestimation is characteristic of the kinaesthetic system alone has not been established. Two experiments are reported which were designed to investigate size judgment made after kinaesthetic and visual pattern presentation and the effect of environmental cues on the perception of movement patterns. In experiment 1 patterns were presented kinaesthetically (experimenter guided hand movements around the outline of the pattern) or in combination with visual information given by a moving light (pinpoint light attached to the stylus which was moved around the pattern); visual and kinaesthetic cues were either congruent or conflicting with each other; and environmental cues were either present or absent. In experiment 2 static visual display was compared with visually traced pattern presentation, again with or without environmental cues. Overall the results showed that, regardless of experimental manipulation, in all cases where the information was given over time the subject perceived the pattern larger than reality. After static visual display, overestimation of size did not occur.     

自然阅读中儿童和成人新词学习能力的差异比较:基于眼动的证据

从读者重复学习新词时眼动行为经历的变化,揭示儿童和成人自然阅读中新词学习能力的差异。构造双字假词作为新词,将其嵌在五个语境中,记录儿童和成人阅读时的眼动轨迹。结果发现:随着新词学习次数的递增,儿童和成人在新词上的首次注视时间呈相同变化;在对新词的凝视时间和再注视概率上,成人在第二次阅读时就大幅下降,而小学生在第四次阅读时才开始下降。表明成人新词学习能力高于儿童体现在词汇加工的相对晚期阶段。     

Roles of Visual Information for Control of Reaching Movements in Children

What visual information do children normally require for the control of reaching movements? How is performance affected when children do not have access to the preferred mode of perceptual information? These questions were studied in 28 children who were tested on 3 occasions: at 6, 7, and 8 years of age. The task was to pick beads, 1 at a time, from 1 cup and carry them to another cup. With the aid of a mirror arrangement and a curtain, the amount of visual information was manipulated with regard to both the target and the performing hand. The movements were monitored with an optoelectronic device (SELSPOT II) and analyzed in terms of transport and object-handling phases. Results showed that object handling required visual information on both hand and target. For the transport phase of the movement, visual information on the spatial location of the target was sufficient, and sight of the hand did not improve performance. In contrast to adult subjects, when children did not have access to the required visual information, their performances deteriorated markedly. These results indicate that from the age of 6, children use visual information for control of arm movements in a manner like that of adults, although with less accuracy and speed. However, even 8-year-old children are limited in their ability to use alternative perceptual strategies for movement control, and they therefore become less flexible and more dependent on visual information.     

Effects of collicular lesions in the hamster during visual discrimination. An analysis from computer-video actograms

Recent reports have suggested that lesions of the superior colliculus may impair the orienting or scanning movements of the head that are thought to serve a key function in visual discrimination. In the present investigation computer-video “actograms” were used to quantify the head movements of freely moving hamsters performing a simultaneous visual discrimination. Hamsters with collicular lesions did not differ from the controls in their head movement spectra, but there was a significant reduction in the incidence of the pauses in locomotion during which these movements are made. Intact animals showed slower and irregular progression interspersed with pauses during which they made scanning movements, whereas collicular hamsters made straighter runs. Although the rate of learning of lesioned hamsters was not impaired, our data strongly suggest that they used different orienting and learning strategies. When tested for the effects of novel stimuli, unrelated to the task, normal hamsters reacted strongly with active exploratory scanning movements, but collicular animals did not, although qualitative changes in their behaviour suggested that the novel stimuli were not being ignored.     

Perspective taking in children and adults: Equivalent egocentrism but differential correction

Children generally behave more egocentrically than adults when assessing another's perspective. We argue that this difference does not, however, indicate that adults process information less egocentrically than children, but rather that adults are better able to subsequently correct an initial egocentric interpretation. An experiment tracking participants' eye movements during a referential communication task indicated that children and adults were equally quick to interpret a spoken instruction egocentrically but differed in the speed with which they corrected that interpretation and looked at the intended (i.e., non-egocentric) object. The existing differences in egocentrism between children and adults therefore seems less a product of where people start in their perspective taking process than where they stop, with lingering egocentric biases among adults produced by insufficient correction of an automatic moment of egocentrism. We suggest that this pattern of similarity in automatic, but not controlled, processes may explain between-group differences in a variety of dual-process judgments.     

Coincidence anticipation of young normal and handicapped children

Two coincident-timing experiments examined the role of three different target velocities and display extents and three age levels of normal and retarded children. Subjects made a ballistic response to a target moving horizontally across their visual field. In the first experiment there were generally no clear differences between normal and retarded children on the task, with subjects having difficulty for both the slow and fast target speeds. In the second experiment, with target velocity held constant, no significant differences were reported between normal and handicapped children, although the longer the subjects were allowed to view the target the more accurate they were. The data were discussed in terms of the response strategies to perform anticipatory ballistic movements. An ecological issue was raised which suggested that children as well as adults make their most accurate anticipations when confronted with velocity problems that have been experienced in their everyday world.