执行困难理论 (Executive Dysfunction)
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什么是「执行困难」？(Hughes, Russell, & Robins, 1994)
最简单来说，是不能从目前的处境中抽离，也不能跟随个人的思考模式来行动。在想法解读 (Theory of Mind) 的错误想法 (false belief) 测试中，它指知觉上不能摆脱对象在当眼位置的影响，因而选择了一个最明显但也是错的答案。
什么和执行职能 (executive functioning) 有关？
目前对执行职能所包括的能力并无定论，一般认为应有下列：
1. 组成抽象概念；
2. 订立具弹性的行动方案；
3. 维持集中的注意力和思考力；
4. 快速地抽取有关资料；
5. 进行某项工作当中的自我监控和修正；
6. 抑制冲动的反应。
参考Hughes & Russell (1993) 的测试内容，可有更好的了解：
小窗测试
在这项测试中，小孩可从一个小窗观看两个箱子的内部，他需要指向他挑选的那个箱子。假如他指向那个没有放糖的箱子，就可赢得一粒糖。如他指向有糖的箱子，就不会有糖的奖赏。另一种测试是加进一位对手，对手会打开小孩曾经指向的箱子，如果里面有糖，就归对手所有。这项测试的关键是要小孩骗倒对手，他方可得到奖赏。测试结果显示自闭症儿童不管有没有对手，他的成绩都很差。
(以上见于Happ F. (1994). Autism. Massachusetts: Harvard University Press P.54)
威斯康辛卡片分类测试 - 「执行困难」理论的最有力测试
这项测试目的是量度接受测试人士随?口头指示改变分类基准的灵活性。先让接受测试人士看4张分为不同颜色、外形、或号码的卡片，然后请他开始为128张卡片分类。测试员不会告诉他怎样分，只在他每迭好一张卡片后告诉他做得正确不正确。他?对10张卡片后，测试员会告诉他改用另一种分类基准，如此类推，直至迭完128张卡片为止。这个测试统计三项分数：
1. 完成分类的数目；
2. 正确的分类卡数；
3. 因为用上一个分类基准而错误的卡片数目。
自闭症人士的第三项分数比一般人都低。
(Heaton, Chelune, Talley, Kay, & Curtis, 1993)
学者 (Fein, D. et.al. Executive Functioning in High-functioning Children with autism. Journal of Child Psychology and Psychiatry Vol.42, Bo.2, pp.261-270, 2001) 对「执行困难」理论的研究结果：
1. 自闭症人士只有某些执行职能受损，最明显的是重复地犯同样的错误，在一些困难的作业尤其常见。自闭症人士特别倾向于知道错还是继续错下去，遇到困难的作业，很难改变思考模式。
2. 计划能力有问题。「执行困难」与重复犯错不清楚是否存在?因果关系，也许重复犯错反映了自闭症的基本问题。
「执行困难」与前额叶受损的关系
(以下见于Ozonoff, S. (1995) Executive Functions in Autism. Learning and Cognition in Autism. New York: Plenum Press)
脑前额叶受伤病人的表现：
1. 重复、无意义的行为或说话；
2. 难以抑制某些熟习或易有的反应；
3. 不适当地重复某些旧的想法或行动；
4. 编订计划能力不足；
5. 在处理数据方面，只注意数据的某个单一部分、或难以?合零星数据、或不能同时兼顾来自不同渠道的数据、或不能适当地运用已知的数据。
自闭症人士相似的行为：
1. 僵化、欠缺弹性的行为；
2. 因环境的轻微改变而感到不安；
3. 坚持完全遵循惯例的每个细节；
4. 只对某偏狭嗜好有兴趣或不停重复某个刻板的行为；
5. 行为冲动、难以抑制实时的反应；
6. 难以运用大量储存的数据；
7. 只能针对细节而不顾及整体。
脑前额叶包括的能力：
1. 构思一个想法 (如计划、大纲、反应模式)，并用之来完成某项工作。在一个策略不适用时，可以转换其它反应模式；
2. 调校社交行为、情绪反应和社交谈话。
由于后者，脑前额叶受损因而可解释自闭症社交方面的障碍。
以脑前额叶受损解释自闭症的局限：
1. 为什么前额叶早期受损的儿童没有自闭症？前额叶功能不足只是一个必须条件，而不是造成自闭症的充分条件，加入了其它认知的障碍或神经的功能不足才会引发自闭症的征状。
2. 有些由想法指导行动的能力，见于譬如‘对象恒在’ (object permanence: Morgan, Cutrer, Coplin, & Rodrigue, 1989)‘错的照片’(false photographs tasks: Leslie & Thaiss, 1992) 等等测试，测试员以为它们会因前额叶受损而受到影响 可是并不如此。
3. 因前额叶引致的认知能力受损，也见于过度活跃症，行为失调问题等。执行困难障碍和自闭症究竟有什么特别的关连？
「执行困难」理论的内容有很多争议性的地方，如
l 有自闭症人士并无抑制能力方面的问题；
l 有自闭症人士并无短期记忆 (working memory) 的问题；
l 有自闭症人士并非不明白曾经存在的事物 (比对目前的现实较不明显)；
l 「执行困难」理论作为失调症的界准不够明显，因其它如过度活跃症、精神分裂、妄想强迫症也有这问题；
l 它始终不足以解释社交障碍不存在其它有执行困难问题的失调症而只存在于自闭症。
学者Simon Baron-Cohen 对「执行困难」理论的意见
Baron-Cohen, S. (draft 4th May 2001). The exact mind: Empathising and systemizing in autism spectrum conditions? To appear in Goswami, U, (ed) Handbook of Cognitive Development. Blackwell:Oxford (in press)
直至目前为止，从认知角度去解释自闭症的重复性行为、喜欢遵循惯例与坚持一成不变等习性，只有「执行困难」理论。(Ozonoff, Rogers, Farnham & Pennington, 1994; Pennington et al., 1997: Russell, 1997b)
虽然「执行困难」理论有可能导致刻板行为，但也有亚士保加症 (Asperger Syndrome)人士并无执行困难征状，他们对系统有良好的概念，却在感情代入方面能力不足。由此可见，「执行困难」不可能是自闭症的主要征状。
「执行困难」理论亦向来忽略了重复性行为的内容。相对来说，感情代入(empathizing)/系统建立(systemizing)理论却指出自闭症儿童对机械或其它系统的沉迷，是基于它们拥有一些可知的规律，它可能显示自闭症儿童完整甚或发展良好的普通物理常识。 Executive Functioning
以下采自Fein, D. et.al.(2001) Executive Functioning in High-functioning Children with autism. Journal of Child Psychology and Psychiatry Vol.42, Bo.2, pp.261-270, 2001
Autistic disorder and other pervasive developmental disorders are generally associated with weaknesses on tasks involving cognitive flexibility, verbal reasoning, complex or verbal memory, and complex language. It has been proposed, accordingly, that cognitive deficits, specifically executive functioning deficits, are a primary cause of autistic behavior (Ozonoff, Pennington, & Rogers, 1991; Pennington et al., 1997: Russell, 1997)
What is Executive Functioning (EF) or Executive Dysfunction?
Although there is no consensus about the components of executive functioning, it is thought to include such processes as
- forming abstract concepts,
- having a flexible sequenced plan of action,
- focusing and sustaining attention and mental effort,
- rapidly retrieving relevant information
- being able to self-monitor and self-correct as a task is performed
- being able to inhibit impulsive responses
Executive functioning can also be described as the ability to disengage from the current situation and guide behavior by referring to mental models (Hughes, Russell, & Robins, 1994)
最简单来说，是不能将自己从某些对象脱离，在ToM的错误想法(false belief)测试中，它指知觉上不能摆脱对象在实际位置的明显性，因而选择了一个最明显但也是错的答案。
参考Hughes & Russell (1993) 的测试内容，可有更好的了解：
“windows task”
In this task the child simply had to point to one of two boxes, into which he/she alone could see via a small window. On each trial a sweet was placed in one of the boxes, and if the child indicated the empty box(versus the second, baited box), he won the sweet. In the competitor version, an ignorant second player searched in the indicated box, and kept any sweets thus found – so that the child was effectively rewarded for “deceiving” the competitor.
It was found that autistic subjects did badly at the “windows task’ with or without a competitor.
(以上见于Happ F. (1994). Autism. Massachusetts: Harvard University Press P.54)
The most Robust Test in EF – Wisconsin card Sorting Test (WCST) and what is it?
This test involves the ability to change sorting categories flexibly in response to verbal feedback. Subjects are shown 4 cards that vary on three dimensions (color, form, and number). They are then told that they must sort a stack of 128 cards but are not told how to sort them. They must respond to examiner feedback (they are told correct or incorrect after each trial). After a subject sorts 10 cards correctly, the sorting principle changes (from color to form to number). Several scores are calculated during this test. Total categories indicates the total number of complete sorting categories achieved (the maximum is 6). Total number correct indicates how many correct cards were sorted. Number of perseverative errors indicates how many times the subject sorted to a previously reinforced category, thus ignoring the negative feedback.
(Heaton, Chelune, Talley, Kay, & Curtis, 1993)
Temple Grandin’s explanation of ‘Perseveration’ (1995):
People with autism may be using a different selective attention mechanism than normal people (Ciesielski, Courchesne, & Elmasian, 1990) Their research has shown that people with autism take much longer to shift between visual and auditory stimuli. Attention shifting may explain some socially inappropriate behavior. Donna Williams explained that it is difficult to look for social rules in her memory at the moment an event is occurring. In some cases, perseveration may be an extreme dysfunction of attention shifting.
Findings of Fein’s paper:
1. Only certain executive functions are affected in autism, most notably perseveration (知道错但继续错下去). Perseveration occurs most often on tasks of greater difficulty. Individuals with autism tend to make perseverative errors and have difficulty changing cognitive set on challenging tasks.
2. There are deficits on planning tasks.
It is unclear whether the relationship between EF and perseverative behavior is causal or whether perserveration is a reflection of how autism was defined in the first place.
Relationship between Executive Dysfunction and Frontal Lesion
(以下见于Ozonoff, S. (1995) Executive Functions in Autism. Learning and Cognition in Autism. New York: Plenum Press)
脑前额叶受伤病人的表现：
The deficits incurred have been richly described by Luria (1966) and more recently, by Duncan (1986) and Stuss and Benson (1986); they include
l Repetitive, aimless movements or speech
l Difficulty inhibiting familiar or obvious responses
l Inappropriate repetition of previous thoughts or actions
l Diminished capacity for planning
Stuss (1987,cited in Mateer 7 Williams, 1991) described several additional information-processing deficits :
l A tendency to focus on one aspect of information
l Difficulty relating or integrating isolated details
l Problems managing simultaneous or multiple sources of information
l Impaired ability to act on or apply knowledge in a meaningful manner
自闭症人士相似的行为：
l rigid and inflexible behavior
l becoming distressed over trivial changes in the environment
l insistence on following routines in precise detail
l focusing on one narrow interest or repetitively engaging in one stereotyped behavior
l impulsiveness, having trouble delaying or inhibiting responses
l having trouble applying or using their large store of knowledge
l focusing on details and having difficulty in seeing the big picture
脑前额叶包括的能力：
l the ability to form a mental representation (e.g. a plan, schema or response set) that must be held on-line to successfully complete the task and flexibility in shifting response set when a strategy is no longer correct
l regulation of social behavior, emotional reactions (Stuss & Benson, 1986) and social discourse (Dennis, 1991)
由于后者，脑前额叶受伤因而可解释自闭症社交方面的障碍。
以脑前额叶受伤解释自闭症的局限：
1.Why do children with early frontal lesions not appear autistic?
Prefrontal dysfunction may be a necessary, but not a sufficient, criterion for the development of autism; perhaps other cognitive deficits, or neurological dysfunction, must also be present to produce the full-blown syndrome.
2. There are some abilities that a deficit in using mental representations to guide behaviors would predict to be impaired are in actual circumstances not impaired, e.g. object permanence (Morgan, Cutrer, Coplin, & Rodrigue, 1989); false photograph tasks (Leslie & thaiss, 1992) Is it because they rely on external clues or these tasks are not highly abstract or novel? Thus, a number of factors may be important in determining whether individuals with autism can use internal models, rather than external context, to guide behavior.
3. frontal lobe cognitive dysfunction is not specific to autism, also seen in ADHD, conduct disorder etc. The question is : how executive function deficits might be related to autism in a way that differentiates it from other disorders.
EF的理论内容有很多争议性的地方，如
- 有自闭症人士并无inhibition 的问题
- 有自闭症人士并无working memory 的问题
- 有自闭症人士并非不明白曾经存在的事物 (比对目前的现实较不明显)
- EF作为失调症的界定性不够明显，因其它如ADHD, 精神分裂, obsessive-compulsive disorder 也有这问题
- Bishop (1993) : It is insufficient to account for documented deficits in social cognition, because such deficits are not shown by other clinical groups with impaired executive system functions, and because autistic children fail to show comparable difficulty when second-order representations do not involve social material.
What does Simon Baron-Cohen say about EF?
Baron-Cohen, S. (draft 4th May 2001). The exact mind: Empathising and systemizing in autism spectrum conditions? To appear in Goswami, U, (ed) Handbook of Cognitive Development. Blackwell:Oxford (in press)
To date, the only cognitive account to attempt to explain “repetitive behavior”, a strong desire for routines, and a “need for sameness” is the executive dysfunction theory (Ozonoff, Rogers, Farnham & Pennington, 1994; Pennington et al., 1997: Russell, 1997b)
While ‘stereotypies’ are likely to be due to executive deficits, the fact that it is possible for people with Asperger Syndrome to exist who have no demonstrable executive dysfunction whilst still have deficits in empathizing and talents in systemizing suggests that executive dysfunction cannot be a core feature of autism spectrum conditions.
The executive account has also traditionally ignored the content of “repetitive behavior”. The empathizing-systemising theory in contrast draws attention to the fact that much repetitive behavior involves the child’s ‘obsessional’ or strong interests with mechanical systems or other systems that can be understood in terms of rules and regularities. This may reflect the child’s intact or even superior development of their folk physics |
