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Based on a variational approach, we propose that there are two kinds of low-energy states in the t-J-type models at low doping. In a quasiparticle state an unpaired spin bound to a hole with a well-defined momentum can be excited with spin waves. The resulting state shows a suppression of antiferromagnetic order around the hole with the profile of a spin bag. These spin-bag states with spin and charge or hole separated form a continuum of low-energy excitations. Very different properties predicted by these two kinds of states explain a number of anomalous results observed in the exact diagonalization studies on small clusters up to 32 sites.

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This study aimed at testing whether there were different types of dysfunctional schemas and cognitive distortions that could help to differentiate three emotional/behavioural problems, i.e., anxiety, depression, and aggression, from each other. Five hundred and eighty-one Chinese adolescents from five mainstream high schools in Hong Kong were recruited and completed several self-report questionnaires. Bivariate correlation showed an indiscriminate pattern of association between dysfunctional schemas, cognitive distortions, and the three emotional/behavioural problems. However, when the effects of the confounding correlated emotional/behavioural problems were controlled in regression analysis, different problems did show some specific association with different types of dysfunctional schemas and/or cognitive distortions. Despite some inconsistency, these findings generally supported a specificity hypothesis. Cognitive variables were thus not only relevant in understanding psychopathology, but their different patterns of association with anxiety, depression, and aggression also supported the separability of these three emotional/behavioural problems, despite their significant correlation.

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This study examined the prevalence and risk of psychiatric disturbances and suicidal behaviours among the peers of suicide attempters and completers. The subjects were selected from high schools with and without history of student suicides in the past 3 years. The psychiatric disturbances (as measured by the YSR and CBCL), suicidal behaviours, drug use, and a wide range of potential risk factors were measured. About a quarter of the peers of suicide completers and attempters were probable psychiatric cases and 15-21% of them reported suicidal acts. The increased risk of psychiatric disturbances and suicidal behaviours were still evident after controlling for age, sex, and potential risk factors. The presence of psychiatric disturbances could not wholly account for the increased odds of suicidal behaviours. Peers of suicide attempters carried a higher risk than peers of suicide completers. The close friends of suicide completers were particularly at risk of internalising problems, whereas the close friends of suicide attempters were at high risk of externalising problems. The peers of suicide completers and attempters represent a high-risk group for psychiatric disturbances and suicidal behaviours. The specific association of different types of psychiatric disturbances in the peers of suicide completers and attempters suggested that different risk mechanisms might be in operation within these peer groups.

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Hyperactive children have been described as motorically clumsy. To explore the validity of this assertion, an experiment using the additive factor method was designed to examine motor organization and execution in hyperactive children. Four groups of boys aged 7 to 8 years took part in the study: (1) a pure hyperactive (HA) group, N=20; (2) a pure conduct-disordered (CD) group, N=18; (3) a mixed hyperactive/conduct-disordered (HA+CD) group, N=12; (4) a normal (N) control group, N=22. While the small sample size precluded a definitive conclusion, the results indicated that neither HA nor CD children showed any motor organization or execution deficit in a simple sequential key-tapping task. Given previous findings indicating that hyperactive children show deficits in more complex motor coordination skills, the generalizability of our negative results needs to be examined on other more complex tasks.

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A community sample of 405 adolescents were given the Youth Self-Report Form (YSR) and the Children's Negative Cognitive Errors Questionnaire (CNCEQ). Both regression and group comparison analyses, using the full sample and a subset of extreme scorers, respectively, indicated that internalising problems were specifically associated with the various forms of cognitive distortions assessed, namely, selective abstraction, personalising, overgeneralisation, and catastrophising. Furthermore, they displayed a curvilinear relationship; as the severity of internalising problems increased, the magnitude of cognitive distortions grew positively at a quadratic rate, displaying a U-shaped upward curve. However, in view of the potential measurement bias of CNCEQ toward internalising problems, the conclusion was qualified. Although our results found some specific event/schema-linked cognitive distortions that distinguished internalising from externalising problems, we could not conclude that the latter were free from any other event/schemalinked cognitive distortions that the CNCEQ might have failed to elicit.

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The present study represents a cross-cultural study of animal fears in which subjects from seven Western and Asian countries were asked to rate their fear of a range of familiar animals. Factor analyses of these ratings in all samples revealed a coherent three factor solution in which animals fell into a fear-irrelevant, fear-relevant (fierce) or disgust-relevant category. The core group of animals making up the disgust-relevant category were similar across cultures. Some views on how a universal disgust-relevant category of feared animals may have developed are discussed.

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The nature of impulsivity in hyperactive and conduct-disordered children was examined in two experiments, one involving a priming task, the other a delayed reaction time task. Four groups of children, aged 7 to 8 years and with IQs in the normal range, were recruited for study: (1) a pure hyperactive group (HA), (2) a hyperactive/conduct-disordered group (HA+CD), (3) a pure conduct-disordered group (CD), and (4) a normal control group (N). When the stimulus configuration and presentation were simple and well organized, none of the three clinical groups displayed any sign of impulsivity at the input/perceptual stage; there was no tendency to rush responding before adequate consideration of the relevant stimuli, i.e. a trading of accuracy for speed. Instead, the HA children were found to be disinhibited at the output/motor stage, i.e. failing to temporarily withhold activated responses. This deficit was found to be specific to the HA children; it was not observed in the CD and HA+CD children.

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Calcitonin gene-related peptide (CGRP), a neuropeptide may play a role in the formation of neuromuscular junctions is synthesized by the motor neurons and is able to stimulate the expression of acetylcholine receptor (AChR) in cultured myotubes. By using antibody and DNA probe that are specific for acetyl cholinesterase (AChE), we reported the expression of AChE could also be stimulated by CGRP in cultured chick myotubes. After CGRP application, the amount of AChE protein, that showed a molecular weight of approximately 105 kDa as recognized by the anti-AChE monoclonal antibody, was increased by approximately 1.7-fold. Two transcripts encoding AChE, approximately 4.8 and approximately 6.0 kb, were identified and their levels of expression were increased to approximately 3-fold after treatment with CGRP. However, the total AChE enzymatic activity in the CGRP-treated myotubes was unchanged. These evidences suggest that most of the CGRP-induced AChE proteins in the cultured chick myotubes are the inactive pool of enzyme.

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In a two-stage community study of 3069 Chinese schoolboys in Hong Kong, those entering stage 2 were classified by scores on Rutter's teacher and parent questionnaires into: (1) a mixed hyperactive/conduct-disturbed (HA-CD) group; (2) a pure hyperactive (HA) group; (3) a pure conduct-disturbed (CD) group; and (4) a normal control group. The four groups of children were compared on a series of psychosocial, cognitive and neurodevelopmental measures. This was followed by a regression analysis to examine the specificity of the differential patterns of associations between HA and CD. There was a mix of negative and positive findings defying a simple, definitive conclusion. However, the positive findings that did emerge supported a growing body of recent literature which favoured a separation of HA from CD and their cross-cultural validity: the former was associated with neurodevelopmental impairments, the latter with family disharmony. The mixed condition, HA-CD, was a hybrid of its two constituent conditions, displaying the attributes of both.

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An increasing number of students in a secondary convent girls school developed syncope attacks over a time course of about two months. Fourteen students who suffered from syncope and 12 other students from the same class with no symptoms were assessed by a team of psychologists and paediatricians with the aim of identifying the cause of the problem and to formulate possible remedial action. Psychological assessments included a mental state examination, developmental, personal and psychological history, state-trait anxiety, self-esteem, hypnotic suggestibility, and students' beliefs about the cause and nature of the syncope attacks. Physical investigations included physical examination, blood pressure and electrocardiogram. The results indicated that most participants and controls had no physical or psychological pathologies. The two groups were not different on the physical and psychological measures. Analyses of the interview data, however, indicated that all the syncope sufferers belonged to a cohesive and exclusive social network. Social psychological circumstances rather than individual psychopathology were noted to be primarily responsible for the spread and maintenance of the mass hysterical influence. Intervention consisted of health education, authoritative reassurance and back-up support. Follow-up assessment after three and 12 months indicated no further syncope episodes.

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The behavioral problems of Chinese children were examined in a questionnaire study of a representative sample of 3,069 seven-year-old Chinese schoolboys in Hong Kong using Rutter's questionnaires for completion by parents and teachers. Separate robust dimensions of hyperactivity, antisocial, and neurotic behaviors were evident. The correlations among different dimensions were similar to those reported in the West. Short-term longitudinal analysis suggested that these dimensions were stable over time and that antisocial behaviors might develop in hyperactive children. The finding highlights the necessity of differentiating the hyperactive domain from the antisocial one. A significant source effect was found in all three dimensions. Chinese schoolboys had nearly two times the level of questionnaire-rated hyperactivity compared with school boys in the West; but it is premature to conclude that hyperactivity is more common in Chinese schoolboys in Hong Kong. Cross-cultural differences in adults' expectations and tolerance remain a plausible explanation.

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BACKGROUND: This study was undertaken to examine the validity of different diagnostic definitions of hyperactivity in a Chinese population. Estimates of the prevalence of hyperactivity were made according to these different diagnostic definitions. METHOD: In a two-stage epidemiological study of hyperactivity in Hong Kong, 3069 Chinese schoolboys were screened by questionnaires; and a stratified sample of 611 of them entered a second stage for more detailed diagnostic assessment. RESULTS: Children with hyperkinetic disorder (ICD-10) or ADDH (DSM-III) both displayed significant hyperactive symptoms, but with somewhat different external correlates; hyperkinetic disorder tended to show more neurodevelopmental impairments, ADDH more cognitive and educational difficulties. These findings raise the possibility of heterogeneity in the disorders present with hyperactivity. The DSM-III-R category of ADHD was more common, and those extra cases, that did not overlap with ADDH or hyperkinetic disorder, included children with no obvious behavioural, cognitive or neurodevelopmental impairments. Hence ADHD may be an over-inclusive category. Prevalence rates for hyperkinetic disorder, ADDH and ADHD were respectively 0.78%, 6.1% and 8.9%. CONCLUSIONS: A disorder of hyperactivity does exist in the Chinese culture, displaying the same kinds of symptomatology and external correlates as in the West. The prevalence rates of hyperkinetic disorder and ADDH in Chinese schoolboys are on the low side when compared to those reported in Western studies.

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Hyperactive children are often said to be inattentive and distractible. However, the results from a number of experimental studies are equivocal. To examine this discrepancy, a Chinese version of the Stroop Test was devised. Four groups of subjects recruited from a community sample of 1479 Chinese boys living in Hong Kong took part in the investigation. These were: (1) a pure hyperactive (HA) group; (2) a mixed hyperactive/conduct-disordered (HA + CD) group; (3) a pure conduct-disordered (CD) group; and (4) a normal (N) control group. The results revealed that HA children were more markedly affected by the introduction of distracting stimuli. This distractibility was probably a function of both stimulus potency and the random order in which stimuli were presented. The specificity of a greater distractibility to HA children indicates its diagnostic value with regard to hyperactivity. The failure to find a similar deficit in HA + CD children raises questions about the clinical identity of this mixed diagnostic group.

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Groups of home and school situational hyperactive primary schoolboys identified from the community were compared with pervasive hyperactive and non-hyperactive controls on a wide range of measures. The hyperactive groups tended to persist in the same category over a half-year period. Both situational hyperactive groups had lower measured activity levels than the pervasive hyperactive group and only the latter differed from non-hyperactive controls. Home hyperactivity was characterized by poor family relationships and was not distinguishable from non-hyperactive home-antisocial controls. School hyperactive boys had specific correlates of low intelligence, motor clumsiness, poor reading and academic abilities. Pervasive hyperactive subjects differed from both situational groups in showing a higher percentage of delayed language development. While home hyperactivity has dubious identity, the distinct pattern of external correlates in school and pervasive hyperactivity speak for the need to regard these as separate entities.

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A random population sample of 1479 Chinese boys from Hong Kong was screened and diagnosed in a two-stage epidemiological study. Four groups, age 7-8, were distinguished: (1) a pure hyperactive group (HA), (2) a mixed hyperactive/conduct-disordered group (HA+CD), (3) a pure conduct-disordered group (CD), and (4) a normal control group (N). On a visual search task, only the HA children showed a specific processing deficit in performance. This confirms the diagnostic value of such a deficit for hyperactivity, differentiating it from conduct disorder. The failure to find a similar deficit in the HA+CD group raises questions concerning the clinical identity of these children. Each group showed a performance decrement over time in the visual search task but the decrement did not differ between the four groups. This observation is not congruent with the reports of a short attention span in hyperactive children; explanations of this apparent contradiction are considered.

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The incidence of language delay in Chinese preschool children was studied by a stratified proportional sampling of all 3 year olds in Hong Kong. The Developmental Language Screening Scale (DLSS) devised for use with Cantonese speaking children was used to identify children with language delay. Of 855 children sampled in the stage I screening procedure, 4%, 2.8% and 3.3% were identified as having delay in verbal comprehension, expression or both respectively. The stage II clinical diagnostic study included a randomly selected group of children screened in stage I with or without any associated behavioural problem. Among these, 3.4% were identified as having a language delay using the Reynell Language Developmental Scale (RDLS) with a criterion of language age of less than or equal to two-thirds of the chronological age; 3% had specific language delay using the criteria of language age less than or equal to two-thirds the chronological age and developmental age more than or equal to two-thirds the chronological age. More boys were found to have language delay, although this was not statistically significant.

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Sixty-one boys, 6-12 years old, met both the diagnostic criteria of ADHD of DSM-III-R and hyperkinetic syndrome of ICD-9. They could be subdivided into two groups: 43 showed hyperactive symptoms in the clinic situation and 18 did not. The former group were younger and showed significantly poorer performance in measures of general intelligence, attention, cognitive styles, motor clumsiness and minor neurological deficits. Controlling for age and intelligence attenuated the differences, but significant differences remained in activity level, attention, and minor neurological deficits. This result suggests that direct observation is important in the assessment of pervasiveness of childhood hyperactivity.

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Nearly all 3-year-old Chinese children in Hong Kong attend preschool facilities, making it possible to study their behavior in a group learning situation based upon teachers' perception. The Preschool Behavior Checklist (PBCL), a teacher's questionnaire, was applied to a random sample of 851 Chinese children, ages 36 to 48 months. The factor structure of the PBCL was very similar to that obtained from its original British study, supporting its usage cross-culturally. Prevalence of behavior disorder was high as defined by the PBCL. This reflected specific cultural demands at school settings. Significant sex differences were also found in the overall rate of behavior disorder and symptom patterns. As in other studies, boys had more hyperactive, conduct, and speech problems. The results suggested a certain degree of universality of symptomatology for children at the preschool level.

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A representative sample of 855 Hong-Kong Chinese children aged 36-48 months were assessed using the BSQ and the PBCL. Good reliability for both instruments were found. For the BSQ and PBCL, 12.75% and 27.5% were above the cut-off points of 10+ and 12+ respectively and 5.9% were above both cut-off points. In the second stage, 234 subjects were recruited by stratified random sampling according to the results of the screening state. A clinician interviewed the parent, child and teacher before making a diagnosis. The prevalence of behaviour disorder was: nil, 53.7%; dubious, 23.1%; mild, 18.0%; moderate, 4.5%; and severe, 0.7%. There were significantly more boys in the categories mild, moderate and severe.

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