On the determination of appropriate dimensionality in data with error

The study deals with the problem of determining true dimensionality of data-with-error scaled by Kruskal's multidimensional scaling technique. Artificial data was constructed for 6, 8, 12, 16, and 30 point configurations of 1, 2, or 3 true dimensions by adding varying amounts of error to the true distances. Results show how stress is affected by error, number of points, and number of dimensions, and indicate that stress and the elbow criterion are inadequate for purposes of identifying true dimensionality when there is error in the data. The Wagenaar-Padmos procedure for identifying true dimensionality and error level is discussed. A simplified technique, involving a measure calledConstraint, is suggested.The authors wish to thank Dr. J. B. Kruskal for his valuable help and suggestions.Computer time for this research was supplied by the Instruction and Research Computer Center, The Ohio State University.     

Conditions necessary for sand digging in laboratory rats

Continuous availability of a sand blocked tube elicited intense and persistent digging by laboratory rats. Neither training nor prior exposure to the apparatus were necessary for response initiation. Continuous presence of an open pile of sand would not elicit digging. No theoretical explanation is offered.     

On the form of psychometric functions for taste

Psychometric functions were determined for the discrimination of weak solutions of quinine hydrochloride or of hydrochloric acid from distilled water. The slopes of these functions were compared with those of some functions previously determined for sodium chloride and for sucrose. In general, the functions for QHCl were the least steep and those for NaCl were the most steep, but the differences were not great. Thus, it appears that the psychometric functions for these different taste qualities have substantially the same form, even though absolute sensitivity varies over several orders of magnitude.     

Modulation of Taste Aversions by a Pentobarbital Drug State: An Assessment of Its Transfer Properties

In a drug-discrimination procedure using conditioned taste aversions, a pentobarbital injection signaled a taste–toxin pairing while the vehicle injection signaled the same taste in the absence of the toxin. In transfer tests, drug states transferred control over consumption to other targets. If the training target was a fluid (saccharin), then transfer occurred to other fluids (both novel and familiar) but not to solid food. If the training target was food, then some transfer occurred to novel targets (both fluids and solid food) but not to familiar targets. Control rats revealed that the differential consumption seen during acquisition and during transfer tests was not due to the summation of two simple associations (i.e., drug–toxin and flavor–toxin) but rather reflected conditional control over consumption by the drug state.     

Application of chaos theory to biology and medicine

The application of “chaos theory” to the physical and chemical sciences has resolved some long-standing problems, such as how to calculate a turbulent event in fluid dynamics or how to quantify the pathway of a molecule during Brownian motion. Biology and medicine also have unresolved problems, such as how to predict the occurrence of lethal arrhythmias or epileptic seizures. The quantification of a chaotic system, such as the nervous system, can occur by calculating the correlation dimension (D2) of a sample of the data that the system generates. For biological systems, the point correlation dimension (PD2) has an advantage in that it does not presume stationarity of the data, as the D2 algorithm must, and thus can track the transient non-stationarities that occur when the systems changes state. Such non-stationarities arise during normal functioning (e.g., during an event-related potential) or in pathology (e.g., in epilepsy or cardiac arrhythmogenesis). When stochastic analyses, such as the standard deviation or power spectrum, are performed on the same data they often have a reduced sensitivity and specifity compared to the dimensional measures. For example, a reduced standard deviation of heartbeat intervals can predict increased mortality in a group of cardiac subjects, each of which has a reduced standard deviation, but it cannot specify which individuals will or will not manifest lethal arrhythmogenesis; in contrast, the PD2 of the very same data can specify which patients will manifest sudden death. The explanation for the greater sensitivity and specificity of the dimensional measures is that they aredeterministic, and thus are moreaccurate in quantifying the time-series. This accuracy appears to be significant in detecting pathology in biological systems, and thus the use of deterministic measures may lead to breakthroughs in the diagnosis and treatment of some medical disorders.     

Perirhinal cortex lesions impair context aversion learning

Rats with perirhinal cortex lesions were compared with sham controls on a conditional discrimination in which saccharin was paired with LiCl in context 1, but paired with saline in context 2. Perirhinal-lesioned rats were slightly slower to acquire the discrimination but reached control levels by the end of acquisition. Both groups showed transfer to familiar tap water, consuming less in context 1 than in context 2. Unlike sham rats, perirhinal rats failed to show an aversion to context 1 on a place choice test. These data provide neuroanatomical support for the postulated difference between Pavlovian conditioning and conditional learning.     

Chaos,danger, and maternal parenting in families: Links with adolescent adjustment in low‐ and middle‐income countries

The current longitudinal study is the first comparative investigation across low‐ and middle‐income countries (LMICs) to test the hypothesis that harsher and less affectionate maternal parenting (child age 14 years, on average) statistically mediates the prediction from prior household chaos and neighborhood danger (at 13 years) to subsequent adolescent maladjustment (externalizing, internalizing, and school performance problems at 15 years). The sample included 511 urban families in six LMICs: China, Colombia, Jordan, Kenya, the Philippines, and Thailand. Multigroup structural equation modeling showed consistent associations between chaos, danger, affectionate and harsh parenting, and adolescent adjustment problems. There was some support for the hypothesis, with nearly all countries showing a modest indirect effect of maternal hostility (but not affection) for adolescent externalizing, internalizing, and scholastic problems. Results provide further evidence that chaotic home and dangerous neighborhood environments increase risk for adolescent maladjustment in LMIC contexts, via harsher maternal parenting.     

An Examination of Alcohol Use Disorder Symptoms and Neighborhood Disorganization from Age 21 to 39

Living in disorganized neighborhoods characterized by high levels of poverty, crime, violence, and deteriorating buildings has been associated with increased alcohol consumption and mental health problems. Data drawn from the Seattle Social Development Project (N = 790), a theory‐driven longitudinal study originating in Seattle, WA, were used to estimate trajectories of Alcohol Use Disorder (AUD) symptoms from age 21 to 39. Time‐varying measures of neighborhood disorganization, psychological distress, and sociodemographic factors were associated with deviations from average AUD symptoms at each wave. Results indicated that, on average, AUD symptoms decreased as individuals got older. Living in more disorganized neighborhoods and experiencing psychological distress was associated with increased AUD symptoms after accounting for average reductions from AUD symptoms over time and time‐varying measures of relevant sociodemographic factors. Results of mediation analysis suggested that psychological distress is a mechanism by which disorganized neighborhoods increased risk of AUD from age 21 to 39.