Taxometrics in Psychopathology Research: An Introduction to Some of the Procedures and Related Methodological Issues.

This article introduces a special section on the use of taxometrics to examine the categorical versus the dimensional structure of various forms of psychopathology. Paving the way into the special section, this introduction briefly describes 3 taxometric methods--mean above minus below a sliding cut (MAMBAC), maximum covariation (MAXCOV), and maximum eigenvalue (MAXEIG)--and discusses possible threats to statistical conclusion validity that often emerge when such techniques are applied in psychopathology research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

冲击噪声背景下的近场源二维参数估计方法

本文针对背景噪声为冲击噪声的情况,提出了一种新的近场源二维参数估计方法.本方法利用协变异(或协变异系数)构造矩阵,并通过求根的方法估计近场源的方向角和距离参数.该算法可以抑制冲击噪声对估计性能的影响,同时具有无需谱峰搜索的优点.仿真实验证明了该算法的有效性.     

分数低阶α稳定分布的功率谱估计新方法

传统的α稳定分布噪声下信号功率谱估计方法有两种,分别为共变谱估计与协方差谱估计。这两种谱估计方法都是以自相关这个二阶矩作为频域分析对象,而自相关是个损失了信号中相位的信息,不能用于时频域分析。针对这一问题,提出了一种新的分数低阶功率谱估计方法,计算机仿真结果表明,与现有方法相比,该新方法不仅在进行分数低阶功率谱估计时具有更优良的性能,而且可进一步应用于时频域分析,具有更广泛的应用价值。     

Assessing Interactive Causal Influence.

The discovery of conjunctive causes--factors that act in concert to produce or prevent an effect--has been explained by purely covariational theories. Such theories assume that concomitant variations in observable events directly license causal inferences, without postulating the existence of unobservable causal relations. This article discusses problems with these theories, proposes a causal-power theory that overcomes the problems, and reports empirical evidence favoring the new theory. Unlike earlier models, the new theory derives (a) the conditions under which covariation implies conjunctive causation and (b) functions relating observable events to unobservable conjunctive causal strength. This psychological theory, which concerns simple cases involving 2 binary candidate causes and a binary effect, raises questions about normative statistics for testing causal hypotheses regarding categorical data resulting from discrete variables. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Variability, covariation, and invariance with respect to coordinate systems in motor control: Reply to Smeets and Louw (2007).

In their comment on the tolerance-noise covariation (TNC) method for decomposing variability by H. Müller and D. Sternad (2003, 2004b), J. B. J. Smeets and S. Louw (see record 2007-01135-017) show that covariation (C), as defined within the TNC method, is not invariant with respect to coordinate transformations and contend that it is, therefore, meaningless. Although the observation is correct, their interpretation is misleading in the following ways: (a) They equate covariation C with the known statistical quantity covariance and noise (N) with standard deviations. The two quantities C and N are conceptually different statistical measures. (b) Dependency on the reference frame is not only a feature of C but of all 3 components. However, such dependency is ubiquitous in motor control. (c) As the frame of reference in biological systems is poorly understood, the TNC method may afford evaluation of different coordinates for control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intraindividual variability is related to cognitive change in older adults: Evidence for within-person coupling.

In this study, the authors addressed the longitudinal nature of intraindividual variability over 3 years. A sample of 304 community-dwelling older adults, initially between the ages of 64 and 92 years, completed 4 waves of annual testing on a battery of accuracy- and latency-based tests covering a wide range of cognitive complexity. Increases in response-time inconsistency on moderately and highly complex tasks were associated with increasing age, but there were significant individual differences in change across the entire sample. The time-varying covariation between cognition and inconsistency was significant across the 1-year intervals and remained stable across both time and age. On occasions when intraindividual variability was high, participants' cognitive performance was correspondingly low. The strength of the coupling relationship was greater for more fluid cognitive domains such as memory, reasoning, and processing speed than for more crystallized domains such as verbal ability. Variability based on moderately and highly complex tasks provided the strongest prediction. These results suggest that intraindividual variability is highly sensitive to even subtle changes in cognitive ability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sources of covariation among attention-deficit/hyperactivity disorder, oppositional defiant disorder, and conduct disorder: The importance of shared environment.

Research has documented high levels of covariation among childhood externalizing disorders, but the etiology of this covariation is unclear. To unravel the sources of covariation among attention-deficit/hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), and conduct disorder (CD), the authors studied 11-year-old twins (N/&=/&1,506) from the Minnesota Twin Family Study. Symptom counts for each of these disorders were obtained from interviews administered to the twins and their mothers. A model was fit that allowed the parsing of genetic, shared environmental (factors that make family members similar to each other), and nonshared environmental (factors that make family members different from each other) contributions to covariation. The results revealed that although each disorder was influenced by genetic and environmental factors, a single shared environmental factor made the largest contribution to the covariation among ADHD, ODD, and CD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Implicit task sets in task switching?

In 2 experiments, the authors compare stimulus-based versus task-rule-based task performance. Participants practiced 8 stimulus-response mappings either with or without knowledge about 2 underlying task sets. After practice, 2 transfer blocks with 8 new stimuli were presented. Results show that rule knowledge leads to significant switch and transfer costs, whereas without rule knowledge neither switch nor transfer costs occur. However, significant Task Type × Response Type interactions occurred in both conditions. In a second experiment including only the no rule condition, half of the stimulus-response mappings in the transfer blocks were incongruent to the underlying task rule. Slower response times for these incongruent stimuli as compared with congruent stimuli and the absence of switch costs suggest that participants acquired (presumably implicit) knowledge about 4 different stimulus-response categories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

水下目标分数低阶统计特性分析

大量的理论与实验检验表明,多数情况下舰船辐射噪声和海洋环境噪声等水声信号通常具有脉冲特性,服从稳定分布,二阶统计量不再稳定收敛,传统的水下目标噪声信号调制谱分析方法在这种环境下性能可能会下降。针对上述问题,为提高分析方法的稳健性,采用共变谱代替传统调制谱分析方法中的功率谱,提出基于分数低阶统计量的目标信号调制谱分析方法...     

基于分数阶谱的频域广义白化滤波方法

在简要介绍稳定分布统计特性的基础上,描述了稳定分布的谱表示,提出了一种不同于二阶过程功率谱的共变谱密度概念及基于共变函数与共变谱密度的稳定分布白噪声的概念及其判断标准,对传统意义上的白噪声进行了广义化,并依据稳定分布的参数模型,论述了一种基于α谱的频域广义白化滤波方法。仿真实验表明,这种算法是一种在高斯和分数低阶α稳定分布噪声条件下具有良好韧性的白化滤波方法,是对传统的二阶统计量基础上的白化滤波方法的改造与推广。