"白痴学者"之谜的哲学思考

提出解释白痴学者之谜的"左右脑发育不平衡假说".假说认为,白痴学者的独特思维特征源于左右脑的不平衡发育--白痴学者的左脑发育不全,偿补性地促使右脑得到充足发育,在一定环境条件下,诱发产生了白痴学者这一异常思维现象.根据假说,文章对白痴学者所表现的种种事实特征逐一加以解析说明.     

The structured representation of information in long-term memory: A possible explanation for the accomplishments of “idiots savants”

Traditional accounts of the “idiot savant”—the development of a superior skill in otherwise subnormal individuals—are challenged through the examination of two cases, a pair of twins with extraordinary numerical ability but otherwise moronic, and Nadia, an autistic girl with extraordinary drawing ability. It is suggested that these phenomenal but particular skills are due to the functional reallocation of representational space in long-term memory. The hierarchical schematic organization of the mnemonic space, normally used for a range of conventional skills such as language, is employed instead for the hypertrophy of one-particular skill. What may appear to be feats of rapid calculation or artistic creativity actually represent automatic routings through long-term memory and translation into motor activity, possibly attributable to an unorthodox context of socialisation and social interaction. Evidence from such cases therefore proves to be inconclusive with regard to determining the nature of intelligence.     

Parity still isn't a generalisation problem

Clark & Thornton take issue with my claim that parity is not a generalisation problem, and that nothing can be inferred about back-propagation in particular, or learning in general, from failures of parity generalisation. They advance arguments to support their contention that generalisation is a relevant issue. In this continuing commentary, I examine generalisation more closely in order to refute these arguments. Different learning algorithms will have different patterns of failure: back-propagation has no special status in this respect. This is not to deny that a particular algorithm might fortuitously happen to produce the "intended" function in an (oxymoronic) parity-generalisation task.     

The development of calendrical skills

Calendrical calculation is the unusual ability to name days of the week for dates in the past and sometimes the future. Previous investigations of this skill have concerned savants, people with pervasive developmental disorders or general intellectual impairment. This research has yielded a hypothesis about how calendrical skills develop but no direct evidence. This study attempts to learn about the development of savant skills by investigating the development of calendrical skills in two boys (aged 5 and 6 years) along with more general cognitive and social assessments. Consistent with the hypothesis, they initially demonstrated knowledge of regularities but limited range and accuracy in answering date questions and they were slower than many adult savants. At follow up, neither had improved their calendrical skills and they were less willing to answer date questions. Possibly this is because, unlike savants, they had developed interests more commonly shared by their peers and they now received praise for more conventional achievements.     

Local and global processing in savant artists with autism

We explored the hypothesis that an enhanced local processing style is characteristic of both art and autism spectrum disorder (ASD) by examining local and global processing in savant artists with ASD. Specifically, savant artists were compared against non-talented individuals with ASD or mild/moderate learning difficulties (MLD), as well as artistically talented or nontalented students, on the block-design task and meaningful and abstract versions of the embedded figures test (EFT). Results demonstrated that there were no significant differences between the meaningful and abstract versions of the EFT, in any of the groups. This suggests that the primary process governing performance on this task was perceptual (local), rather than conceptual (global). More interestingly, the savant artists performed above the level of the ASD and MLD groups on the block-design test, but not the EFT. Despite both the block-design task and the EFT measuring local processing abilities, we suggest that this result is due to the block-design task being an active construction task (requiring the conversion of a visual input into a motor output), whereas the EFT is a passive recognition task. Therefore, although an enhanced local processing style is an important aspect of savant artistic talent, motor control also appears to be a necessary skill.     

The day of the week when you were born in 700 ms: calendar computation in an Autistic savant

Some individuals are able to determine the weekday of a given date in a few seconds (finding for instance that June 12, 1900, was a Tuesday). This ability has fascinated scientists for many years because it is predominantly observed in people with limited intelligence and may appear very early in life. Exceptional visual memory, exceptional concentration abilities, or privileged access to lower levels of information not normally available through introspection have been advanced to explain such phenomena. In the present article, the authors show that a simple cognitive model can explain all aspects of the performance of Donny, a young autistic savant who is possibly the fastest and most accurate calendar prodigy ever described.     

孤独症群体的孤岛能力

孤岛能力是个体在一般能力普遍落后的情况下某一个或几个领域表现出来的与其整体能力极不匹配的超常能力。令人惊讶的是,人类近一半的孤岛能力产自于孤独症谱系障碍。本文系统回顾了孤独症孤岛能力的特征、传统的各种心理学解释和当前最有力的认知神经科学发现:脑病理性优势假说和孤独症特质假说。在此基础上,本文认为脑优势中心的转移和混乱的大脑连接可能是孤岛能力产生的前提,而特定技能的遗传和后天的反复练习则是孤岛能力得以强化和巩固的重要因素。     

A specific calculating ability

We report two experiments that investigate the calculating strategy used by a low IQ savant to identify prime numbers. Hermelin and O'Connor (1990) had suggested previously that this subject may use a procedure first described by Eratosthenes to detect a prime number, namely, dividing a target number by all primes up to the square root of the target number and testing for a remainder. In the first experiment, we compare the reaction times of the savant to decide whether a number is prime with those of a control subject proficient in mathematical calculation. In addition, we measured the savant's speed of information processing using an inspection time task. We found that the reaction times of the savant, although generally faster, followed the same pattern of the control subject who reported using the Eratosthenes procedure. The savant's inspection time indicated that his speed of processing was far superior to that expected from someone of his IQ. In the second experiment, we measured the time it takes mathematics students to divide by different prime numbers and we also tested them on the prime identification task. We used their division times to simulate their performance on the prime number identification task under the assumption that they used the Eratosthenes procedure. We also simulated the reaction times that would result from a simple memory-based procedure for identifying primes. We found that the Eratosthenes simulation, in contrast to the memory simulation, provided a good fit to both the students' and the savant's reaction times. We conclude that the savant is using a complex computational algorithm to identify primes and suggest two explanations of how the apparent contradiction between his low general intelligence and his superior numerical ability might be resolved.     

The savant syndrome and autistic disorder

Savant syndrome, characterized by remarkable islands of mental ability in otherwise mentally handicapped persons, may occur in autistic as well as nonautistic individuals. Overall, approximately 10% of autistic persons exhibit savant abilities; roughly 50% of those with savant syndrome have autism, and the remaining 50% have other forms of developmental disability. Most commonly, savant syndrome takes the form of extraordinary musical abilities, but may also include calendar-calculation, artistic, mathematical, spatial, mechanical, and memory skills. While savant syndrome was first described more than a century ago, only recently have researchers begun to employ a more uniform nomenclature and more standardized testing in an effort to compare the abilities of savants with those of normal persons. Males show signs of savant syndrome approximately four times more often than females. Along with imaging study findings, this fact suggests the presence of a developmental disorder involving left-brain damage with right-brain compensation.     

Exceptional calendar calculation ability after early left hemispherectomy

An 18-year-old male subject who had had his left hemisphere removed at age eight was better than chance at calculating the day of the week upon which dates in the past and future fell. He was able to describe his method of calculation, which relied upon both visual memory and serial calculations. The use of a serial calculation method was supported by evidence that both response time and accuracy were related to the distance in years from the current year. The use of both visual and verbal "working" memory was supported by interference effects from calendar calculations and delayed visual and verbal memory tasks. The case is discussed in terms of theories regarding similar calculation skills in idiot savants.     

Implementations are not conceptualizations: revising the verb learning model.

In a recent issue of this journal, Pinker and Prince (1988) and Lachter and Bever (1988) presented detailed critiques of Rumelhart and McClelland's (1986) connectionist model of the child's learning of the phonological form of the English past tense. In order to address these criticisms, a new connectionist model was constructed using the back-propagation algorithm, a larger input corpus, a fuller paradigm, and a new phonological representation. This new implementation successfully addressed the criticisms of the phonological representation used by Rumelhart and McClelland. It did a much better job of learning the past tense using a fuller input set with realistic frequencies of occurrence. Ancillary simulations using the same network were able to deal with the homonymy problem and the generation of forms like "ated" from "ate". The one feature not provided by the new model was a way of modeling early correct production of irregular forms. The success of the new model can be used to help clarify the extent to which the published critiques apply to a particular connectionist implementation as opposed to fundamental principles underlying the broader connectionist conceptualization.     

Six principles for biologically based computational models of cortical cognition

This review describes and motivates six principles for computational cognitive neuroscience models: biological realism, distributed representations, inhibitory competition, bidirectional activation propagation, error-driven task learning, and Hebbian model learning. Although these principles are supported by a number of cognitive, computational and biological motivations, the prototypical neural-network model (a feedforward back-propagation network) incorporates only two of them, and no widely used model incorporates all of them. It is argued here that these principles should be integrated into a coherent overall framework, and some potential synergies and conflicts in doing so are discussed.     

Locally Bayesian learning with applications to retrospective revaluation and highlighting

A scheme is described for locally Bayesian parameter updating in models structured as successions of component functions. The essential idea is to back-propagate the target data to interior modules, such that an interior component's target is the input to the next component that maximizes the probability of the next component's target. Each layer then does locally Bayesian learning. The approach assumes online trial-by-trial learning. The resulting parameter updating is not globally Bayesian but can better capture human behavior. The approach is implemented for an associative learning model that first maps inputs to attentionally filtered inputs and then maps attentionally filtered inputs to outputs. The Bayesian updating allows the associative model to exhibit retrospective revaluation effects such as backward blocking and unovershadowing, which have been challenging for associative learning models. The back-propagation of target values to attention allows the model to show trial-order effects, including highlighting and differences in magnitude of forward and backward blocking, which have been challenging for Bayesian learning models.     

Savant-like numerosity skills revealed in normal people by magnetic pulses

Oliver Sacks observed autistic twins who instantly guessed the exact number of matchsticks that had just fallen on the floor, saying in unison "111". To test the suggestion that normal individuals have the capacity for savant numerosity, we temporarily simulated the savant condition in normal people by inhibiting the left anterior temporal lobe of twelve participants with repetitive transcranial magnetic stimulation (rTMS). This site has been implicated in the savant condition. Ten participants improved their ability to accurately guess the number of discrete items immediately following rTMS and, of these, eight became worse at guessing as the effects of the pulses receded. The probability of as many as eight out of twelve people doing best just after rTMS and not after sham stimulation by chance alone is less than one in one thousand.     

A distributed, developmental model of word recognition and naming

A parallel distributed processing model of visual word recognition and pronunciation is described. The model consists of sets of orthographic and phonological units and an interlevel of hidden units. Weights on connections between units were modified during a training phase using the back-propagation learning algorithm. The model simulates many aspects of human performance, including (a) differences between words in terms of processing difficulty, (b) pronunciation of novel items, (c) differences between readers in terms of word recognition skill, (d) transitions from beginning to skilled reading, and (e) differences in performance on lexical decision and naming tasks. The model's behavior early in the learning phase corresponds to that of children acquiring word recognition skills. Training with a smaller number of hidden units produces output characteristic of many dyslexic readers. Naming is simulated without pronunciation rules, and lexical decisions are simulated without accessing word-level representations. The performance of the model is largely determined by three factors: the nature of the input, a significant fragment of written English; the learning rule, which encodes the implicit structure of the orthography in the weights on connections; and the architecture of the system, which influences the scope of what can be learned.     

Atypical memory performance in an autistic savant.

This study explored the mechanisms underlying the hypermnesia of an autistic savant (NM) through three experiments. The first two served to assess whether absence of interference was responsible for NM's exceptional list memory. The third investigated the type of cues used in recall. Results indicated absence of retroactive interference but presence of slight proactive interference in list recall of proper names. Normal interference effects were found, however, in list recall of common nouns. Exceptional performance was also demonstrated in a missing-name task involving spatial and verbal recall cues. The findings suggest that the outstanding episodic memory presented by some savant persons with autism might be related to an abnormally high resistance to interference.     

Atypical Memory Performance in an Autistic Savant

This study explored the mechanisms underlying the hypermnesia of an autistic savant (NM) through three experiments. The first two served to assess whether absence of interference was responsible for NM's exceptional list memory. The third investigated the type of cues used in recall. Results indicated absence of retroactive interference but presence of slight proactive interference in list recall of proper names. Normal interference effects were found, however, in list recall of common nouns. Exceptional performance was also demonstrated in a missingname task involving spatial and verbal recall cues. The findings suggest that the outstanding episodic memory presented by some savant persons with autism might be related to an abnormally high resistance to interference.     

Restructuring partitioned knowledge: the role of recoordination in category learning

Knowledge restructuring refers to changes in the strategy with which people solve a given problem. Two types of knowledge restructuring are supported by existing category learning models. The first is a relearning process, which involves incremental updating of knowledge as learning progresses. The second is a recoordination process, which involves novel changes in the way existing knowledge is applied to the task. Whereas relearning is supported by both single- and multiple-module models of category learning, only multiple-module models support recoordination. To date, only relearning has been directly supported empirically. We report two category learning experiments that provide direct evidence of recoordination. People can fluidly alternate between different categorization strategies, and moreover, can reinstate an old strategy even after prolonged use of an alternative. The knowledge restructuring data are not well fit by a single-module model (ALCOVE). By contrast, a multiple-module model (ATRIUM) quantitatively accounts for recoordination. Low-level changes in the distribution of dimensional attention are shown to subsequently affect how ATRIUM coordinates its modular knowledge. We argue that learning about complex tasks occurs at the level of the partial knowledge elements used to generate a response strategy.     

Expressive drawing ability in children with autism

The autistic impairments in emotional and social competence, imagination and generating ideas predict qualitative differences in expressive drawings by children with autism beyond that accounted by any general learning difficulties. In a sample of 60 5–19‐year‐olds, happy and sad drawings were requested from 15 participants with non‐savant autism and compared with those drawn by three control groups matched on either degree of learning difficulty (MLD), mental age (MA) or chronological age (CA). All drawings were rated by two artists on a 7‐point quality of expression scale. Contrary to our predictions, the drawings from the autistic group were rated similar to those of the MA and MLD groups. Analysis of the people and social content of the drawings revealed that although children with autism did not draw fewer people, they did draw more immature forms than mental age controls. Furthermore, there was tentative evidence that fewer social scenes were produced by the autism sample. We conclude that the overall merit of expressive drawing in autism is commensurate with their general learning difficulties, but the social/emotional impairment in autism affects their drawings of people and social scenes.     

A Study of Perceptual Analysis in a High-Level Autistic Subject with Exceptional Graphic Abilities

We report here the case study of a patient (E.C.) with an Asperger syndrome, or autism with quasinormal intelligence, who shows an outstanding ability for three-dimensional drawing of inanimate objects (savant syndrome). An assessment of the subsystems proposed in recent models of object recognition evidenced intact perceptual analysis and identification. The initial (or primal sketch), viewer-centered (or 2-1/2-D). or object-centered (3-D) representations and the recognition and name levels were functional. In contrast. E.C.′s pattern of performance in three different types of tasks converge to suggest an anomaly in the hierarchical organization of the local and global parts of a figure: a local interference effect in incongruent hierarchical visual stimuli, a deficit in relating local parts to global form information in impossible figures, and an absence of feature-grouping in graphic recall. The results are discussed in relation to normal visual perception and to current accounts of the savant syndrome in autism.