Abstract: Abstract Autism Spectrum Disorder (ASD) is a developmental disorder characterized by impairments in social communication and repetitive or restricted behaviors. Atypical attention, while not a diagnostic feature, has usually been considered to be associated with ASD. Recent studies have suggested that attentional abnormalities play a primary role in the etiology of autism. Visual orienting is comprised of three successive attentional processes which are disengagement, shifting and engagement. When individuals orientate themselves to other stimulus, disengagement is needed firstly from the currently fixated object, which is evidenced usually by the time taken to initiate their saccades to the next target. Then, shifting means the movement process of visual attention. After this process, individuals fixate on the new object to engage their attention to the new stimulus. The gap-overlap paradigm is a classic experimental paradigm aimed to study attentional processes. In 1967, Saslow created this paradigm for the first time, in which two or three task conditions were included. On gap task, the central stimulus appears in the center for a variable duration. After 200-250ms temporal gap, a target appears in the peripheral field. On overlap task, the central stimulus remains on the screen throughout the trials. On null task, the central stimulus disappears at the onset of the target without a temporal gap. In all of the three tasks, time needed to move the saccade to the target after its onset is analyzed. Thus, gap task or null task reveals the process of attentional shift, and the overlap task reflects the process of both attentional disengagement and shift. Attention is our window to the world, an early-developing disorder of attention might have a far-reaching effect on cognitive development(Fischer et al., 2014). Attentional disengagement is one of the most widely discussed attentional components in autism. In most cases, the gap-overlap paradigm reveals the abnormality of attentional disengagement in autism compared to the control group. More importantly, in several prospective studies, attentional disengagement deficits are amongst the earliest markers in infants or toddlers at-risk of autism, and are predictive of their later diagnosis. The developmental changes are most pronounced in individuals later diagnosed with ASD who need longer saccadic reaction time (SRT) to disengage from the central stmulus. This disengagement difficulties tend to exist in children or adults with autism, as evidenced by longer SRT compared to the typically developing . The prospective study in autism using the paradigm is particularly extensive abroad. As apparently indicated by the previous studies, gap-overlap paradigm is very appropriate to examine the attentional processes in autism and thus predict the development of ASD in early life. In future studies, investigating how the atypical disengagement results in the autistic symptom during development is a crucial question. Only based on this, can the effective intervention be applied to prevent the occurrence of ASD. However, domestic research focuses peculiarly less on this issue. In order to promote the application of gap-overlap paradigm in the study of autistic children in China, this paper systematically introduces the principles, measures and design of this paradigm, as well as its application in attentional research in autism. Some important methodological questions are also discussed in the end of this paper. In future studies, more attention should be paid to the use of gap-overlap paradigm for predicting infants with ASD. By combining eye tracking and electrophysiological or brain imaging techniques, it is hoped that the deeper causes of autism in terms of the attentional process will be revealed. The gap-overlap paradigm is a common experimental paradigm to study the visual attentional characteristics. In 1967, Saslow used the paradigm in his study for the first time. A typical trial of the paradigm includes two tasks: gap tasks and overlap tasks. In gap tasks, the central stimulus appears in the center of a visual display for a variable duration. The central stimulus then disappeared is followed by a 200-250ms temporal gap before a target appears in the peripheral fields. In overlap tasks, the central stimulus remains on the screen during the presentation of the peripheral target. A modified gap-overlap paradigm also includes two tasks: overlap tasks and null tasks. In null tasks the central stimulus disappear at the onset time of the peripheral target without a temporal gap. Overlap tasks are the same as the above. Some studies also use all three tasks to reveal attention characteristics of ASD. Visual orienting is comprised of three successive components of spatial attention. Firstly, disengagement of attention is the breaking of visual attention from a fixated stimulus; Secondly, shifting attention is the movement of visual attention from a previously fixated stimulus to a new target; Thirdly, engagement of attention refers to visual fixation on the new target. Gap tasks or null tasks reveal the process of attentional shift, and the overlap tasks reveal the process of attentional disengagement. Attention is our window to the world, an early-developing disorder of attention might have a far-reaching impact on development. Attentional disengagement is one of the most widely discussed attentional components of autism. Impaired attentional disengagement is a prime suspect in the etiology of autism which can explain many symptoms of ASD. The gap- overlap paradigm reveals the abnormality of autism in the attentional disengagement. Attentional disengagement deficits are amongst the earliest markers in at-risk siblings of children with autism (high-risk by virtue of having an elder sibling diagnosed with ASD) , and are predictive of a later diagnosis. The developmental changes were most pronounced in the group later diagnosed with ASD who have longer saccadic reaction time. In numerous studies, Compared with those of normal children, the attentional disengagment of the autistic children are abnormal. The prospective study of attentional disengagement in autism using the gap-overlap paradigm is particularly extensive abroad. However, our country has?peculiarly little research in this area. In order to promote the application of gap-overlap paradigm in the study of autistic children in China，this paper systematically introduces the program, the principle, the main use index and other contents of gap-overlap paradigm. The function of the gap-overlap paradigm in the prediction of infants with autism and the methodological problems in use are also discussed. In future studies, we should pay attention to the use of gap-overlap paradigm for predicting infants with autism; By the combination of eye movement research and electrophysiological or brain imaging techniques, it is hoped that the deeper causes of autism will be revealed. The gap-overlap paradigm is a common experimental paradigm to study the visual attentional characteristics. In 1967, Saslow used the paradigm in his study for the first time. A typical trial of the paradigm includes two tasks: gap tasks and overlap tasks. In gap tasks, the central stimulus appears in the center of a visual display for a variable duration. The central stimulus then disappeared is followed by a 200-250ms temporal gap before a target appears in the peripheral fields. In overlap tasks, the central stimulus remains on the screen during the presentation of the peripheral target. A modified gap-overlap paradigm also includes two tasks: overlap tasks and null tasks. In null tasks the central stimulus disappear at the onset time of the peripheral target without a temporal gap. Overlap tasks are the same as the above. Visual orienting is comprised of three successive components of spatial attention. Firstly, disengagement of attention is the breaking of visual attention from a fixated stimulus; Secondly, shifting attention is the movement of visual attention from a previously fixated stimulus to a new target; Thirdly, engagement of attention refers to visual fixation on the new target. Gap tasks or null tasks reveal the process of attentional shift, and the overlap tasks reveal the process of attentional disengagement. Attention is our window to the world, an early-developing disorder of attention might have a far-reaching impact on development. Attentional disengagement is one of the most widely discussed attentional components of autism. Impaired attentional disengagement is a prime suspect in the etiology of autism which can explain many symptoms of ASD. The gap- overlap paradigm reveals the abnormality of autism in the attentional disengagement. Attentional disengagement deficits are amongst the earliest markers in at-risk siblings of children with autism (high-risk by virtue of having an elder sibling diagnosed with ASD) , and are predictive of a later diagnosis. The developmental changes were most pronounced in the group later diagnosed with ASD who have longer saccadic reaction time. In numerous studies, Compared with those of normal children, the attentional disengagment of the autistic children are abnormal. The prospective study of attentional disengagement in autism using the gap-overlap paradigm is particularly extensive abroad. However, our country has?peculiarly little research in this area. In order to promote the application of gap-overlap paradigm in the study of autistic children in China，this paper systematically introduces the program, the principle, the main use index and other contents of gap-overlap paradigm. The function of the gap-overlap paradigm in the prediction of infants with autism and the methodological problems in use are also discussed. In future studies, we should pay attention to the use of gap-overlap paradigm for predicting infants with autism; By the combination of eye movement research and electrophysiological or brain imaging techniques, it is hoped that the deeper causes of autism will be revealed.

Key words: autism, gap-overlap paradigm, visual attention, attentional disengagement

摘要： 摘 要 空白重叠范式是研究视觉注意特征常用的实验范式。自闭症儿童普遍存在注意解离缺陷，空白重叠范式揭示出该群体注意解离存在异常。国外开始重视将该范式用于自闭症的预测，而我国在这方面的研究很少。本文对空白重叠范式的操作程序、基本原理和数据分析等内容进行了系统地介绍，并就空白重叠范式在自闭症婴幼儿预测中的作用、使用时需注意的方法论等问题进行了展望，以期促进空白重叠范式在我国自闭症早期预测中的运用。

关键词: 自闭症, 空白重叠范式, 视觉注意, 注意解离