Building an identifiable latent class model with covariate effects on underlying and measured variables

In recent years, latent class models have proven useful for analyzing relationships between measured multiple indicators and covariates of interest. Such models summarize shared features of the multiple indicators as an underlying categorical variable, and the indicators' substantive associations with predictors are built directly and indirectly in unique model parameters. In this paper, we provide a detailed study on the theory and application of building models that allow mediated relationships between primary predictors and latent class membership, but that also allow direct effects of secondary covariates on the indicators themselves. Theory for model identification is developed. We detail an Expectation-Maximization algorithm for parameter estimation, standard error calculation, and convergent properties. Comparison of the proposed model with models underlying existing latent class modeling software is provided. A detailed analysis of how visual impairments affect older persons' functioning requiring distance vision is used for illustration.This work was supported by National Institute on Aging (NIA) Program Project P01-AG-10184-03 and National Institutes of Mental Health grant R01-MH-56639-01A1. Dr. Bandeen-Roche is a Brookdale National Fellow. The authors wish to thank Drs. Gary Rubin and Sheila West for kindly making the Salisbury Eye Evaluation data available. We also thank the Editor, the Associate Editor, and three referees for their valuable comments.     

Visuo‐spatial abilities in autism: A review

Individuals with autism show various signs of heightened abilities in visuo‐spatial functioning. First, it is long‐established that they excel on embedded figures and block design tests relative to comparison participants. Second, some evidence suggests that processing global features is affected by inappropriate processing of the constituent elements of a stimulus. Third, they are more accurate than comparison participants in judging the shape of a slanted circle in a context in which ambient visual cues are eliminated. This suggests that their perception of the shape is less influenced by prior knowledge. Fourth, they are fast at searching for feature and conjunctive targets in a visual array. Contrary to earlier reports, however, they are susceptible to visual illusions. Also, they do show evidence of utilising prior knowledge when pairing a colour with an atypically coloured target. Accordingly, we conclude that there is something distinctive about autistic visuo‐spatial functioning, but not necessarily in ways that are predicted by the ‘weak central coherence’ hypothesis. Copyright © 2004 John Wiley & Sons, Ltd.     

Location of a missing object and detection of its absence by infants: Contribution of an eye‐tracking system to the understanding of infants' strategies

Previous research has demonstrated infants' capacity to discriminate between situations in which all the objects successively hidden behind a screen are present, or not, after the removal of the screen. Two types of interpretation have been proposed: counting capacity or object memorization capacity. In the usual paradigm, the missing object in the impossible event is usually the last object which is placed behind the screen. Following this, a third interpretation can be offered: infants' exploration is first directed to this object's location, and its presence or absence is noticed. Two experiments using Wynn's (Nature 1992; 358 :749) paradigm were performed to test the third hypothesis. The first experiment involved four objects (teddy bears) placed in four squares. Infants looked longer at the impossible event (3 objects, the last one missing) than at the possible event (4 objects) when the impossible event was presented first. No difference in looking duration was observed for the opposite order. In the second experiment, the four objects were disposed in a line and an eye‐tracking system was used. No difference in the number of looks was observed between the impossible event (3 objects, the second one missing) and the possible event (4 objects). Therefore, it appears that at least in this complex situation (4 objects used instead of 2 usually), the location of the missing object is a key factor for event discrimination. Eye‐tracking also indicated in the second experiment that infants looked less at the second location during an impossible event (object missing) than during the possible event (object present), indicating that the impossibility of the event was not a determining factor for looking durations. Altogether, the data indicate the potential usefulness of eye‐tracking analysis in this type of situation. Copyright © 2004 John Wiley & Sons, Ltd.     

小学生字词识别与语言技能、工作记忆关系研究

本研究采用注音任务、语言任务、再认方法探讨了小学生字词识别与语言技能、工作记忆的关系和影响小学生字词识别的因素。发现：(1)字词识别与语言技能、工作记忆在2、4年级相关均显著;6年级学生字词识别与语言技能的形旁及工作记忆相关不显著,但与语言技能其它维度相关显著(2)预测小学生字词识别发展的主要因素随年级升高而变化。预测2年级学生字词识别的重要指标是语音的音节、字形的形旁与工作记忆;4年级是语音的音节、字形的声旁、句法与工作记忆;6年级是语音的声韵、字形的声旁与语义。     

视知觉无意识加工中的形状优势效应

研究了视知觉无意识加工中是否存在形状优势效应。被试为天津师范大学本科生60名。仪器为pentium lll高分辨率计算机．程序用E-prime心理实验软件系统编制而成。在实验1中,用信号检测论技术发现．当启动图形呈现时间为20ms时．被试是不能觉知到该图形的。在实验2和3中．被试的任务分别是判断图形的形状和颜色,用MANOVA分析启动图形对靶图形的启动效应时发现．启动图形的颜色线索不会影响靶图形的形状判断,但启动图形的形状线索却能抑制或促进靶图形的颜色判断。实验证据提示．在判断物体整体特征时,无意识知觉具有形状优势效应。     

What Eye Movements Tell About Identifying Compound Words in Reading and Top-Down Effects in Reading Long Texts

InthisarticleIsummarizetwolinesofeyemovementresearchthatwehaveconductedoverthepastseveralyearsinFinland.Onelineofre鄄searchdealswithhowcompetentadultreadersi鄄dentifycompoundwordsduringreading.Theotherlineofresearchdealswithhowaspecificreadinggoal(wecallitthereadingperspective)influencesthewayalongexpositorytextisreadandwhatisrememberedofthetext*.Inbothlinesofresearchwehaveappliedtheeyemovementtechniquebyregisteringreaders'eyemovementswhentheyreadsilentlysinglesentencesorlongertextsforcom鄄pr…     

Future Directions for Eye Movement Research

Eyemovementdatahaveproventobeex鄄tremelyusefulinthestudyofmanytopicsrelatedtocognitiveprocessing.Indeed,theymaybethebeston-linemeasureofmoment-to-momentcogni鄄tiveprocesses.Thisisnottosaythateyemove鄄mentswillproveusefulineveryaspectofcognitiveprocessing.Forexample,itisdifficulttoseehoweyemovementsmayrevealagreatdealaboutbasicmemoryprocesses(but,evenhere,theycouldbeusefulindeterminingexactlywhatpeoplerememberfromasceneorvisualdisplay).Inthisarticle,Iwillbrieflysummarizesomeimportantfindingsth…     

The role of state self‐esteem in positive mood effects on person impression: When does a positive mood lead to a favorable view of others?

Subjects in a positive or a neutral mood were engaged in an impression formation task (Experiment 1), and in a word fragment completion task (Experiment 2). A self‐referent versus other‐referent sentence completion task was used to induce a positive mood state. As a result, the subjects exhibited mood congruent effects on impression ratings in the self‐referent but not in the other‐referent mood induction condition. Word completion data, however, indicated that relevant traits (i.e., friendly traits) had been equally activated across the two mood induction conditions. It was also demonstrated that the self‐referent induction procedure was effective in enhancing the level of self‐esteem, whereas the other‐referent one was not. The results converged to suggest that the enhancement in state self‐esteem accompanying the self‐referent procedure might be relevant to positive mood effects on person impression. This indicates the limitation of the mood priming model.     

注意视觉搜索研究的新进展

一个时期以来有关注意视觉搜索的研究认为,注意是以系列搜索或平行搜索方式进行的.而Wolfe(1998)通过对10多年有关研究数据整理画出的坡度曲线图则表明,注意视觉搜索坡度的整体分布是没有波峰的,表明系列搜索或平行搜索理论是错误的.而且,他新近研究又表明注意视觉搜索同样遵循认知经济原则:自由无序扫描是比系统扫描更快发现项目的方式.     

Posture,muscular tone and visual attention in 5 month‐old infants

The present paper aims at studying the relationships between posture, muscle tone and visual attention in 5 month‐old infants. To this end, a specially designed seating arrangement made it possible to vary posture while keeping constant the spatial relationship between eyes and stimuli. Five month‐olds were placed in the reclining position (30°) or in a more erect position (60°). The more erect the posture, the more difficult it should be for the infant to maintain a straight body axis. Muscle tone was evaluated, and infants distinguished in terms of whether they were hypertonic or hypotonic. It was hypothesised that in a more erect position hypotonic children, who experience more difficulties in maintaining posture, should organise their visual exploration in ways different from those considered to be hypertonic. To test it, pairs of three‐dimensional stimuli were presented in the distal visual field for one group (N=48) and in the proximal visual field in another group (N=32) for 2 min in each posture. The dynamical organisation of attention was evaluated through the number and duration of fixations on each target, the number of shifts from one target to the other (alternations) and the number of repetitions (back to the previous target). Results showed that visual behaviour was significantly affected by the distance at which stimuli were presented. Infants spent more time in visual exploration when the object was within reach than when it was out of reach. Although posture was shown to play a role in the organisation of visual exploration, no link with muscle tone was found, a surprising result which is discussed. Copyright © 2002 John Wiley & Sons, Ltd.