Nonlinear Random-Effects Mixture Models for Repeated Measures

A mixture model for repeated measures based on nonlinear functions with random effects is reviewed. The model can include individual schedules of measurement, data missing at random, nonlinear functions of the random effects, of covariates and of residuals. Individual group membership probabilities and individual random effects are obtained as empirical Bayes predictions. Although this is a complicated model that combines a mixture of populations, nonlinear regression, and hierarchical models, it is straightforward to estimate by maximum likelihood using SAS PROC NLMIXED. Many different models can be studied with this procedure. The model is more general than those that can be estimated with most special purpose computer programs currently available because the response function is essentially any form of nonlinear regression. Examples and sample code are included to illustrate the method.     

Defining reward value by cross-modal scaling

Researchers in comparative psychology often use different food rewards in their studies, with food values defined by a pre-experimental preference test. While this technique rank orders food values, it provides limited information about value differences because preferences may reflect not only value differences, but also the degree to which one good may “substitute” for another (e.g., one food may substitute well for another food, but neither substitutes well for water). We propose scaling the value of food pairs by a third food that is less substitutable for either food offered in preference tests (cross-modal scaling). Here, Cebus monkeys chose between four pairwise alternatives: fruits A versus B; cereal amount X versus fruit A and cereal amount Y versus fruit B where X and Y were adjusted to produce indifference between each cereal amount and each fruit; and cereal amounts X versus Y. When choice was between perfect substitutes (different cereal amounts), preferences were nearly absolute; so too when choice was between close substitutes (fruits); however, when choice was between fruits and cereal amounts, preferences were more modest and less likely due to substitutability. These results suggest that scaling between-good value differences in terms of a third, less-substitutable good may be better than simple preference tests in defining between-good value differences.     

Does anxiety sensitivity correlate with startle habituation? An examination in two independent samples

Individuals with anxiety disorders have previously demonstrated abnormal habituation to aversiveness over time. As anxiety sensitivity (AS), or an individuals' propensity to fear of anxiety-related sensations, has been shown to be a risk factor for anxiety disorders (particularly panic disorder), the present study examined whether AS was also associated with abnormal habituation. This association was examined in two independent samples of undergraduates (N_total=178). Habituation was operationalised as the reduction in startle response to multiple startle probes presented over 2.5 minutes and three definitions of this reduction were employed. Results indicated that individuals with higher levels of AS evidenced deficits in startle habituation, but the strength of this relationship was somewhat dependent on the definition of startle habituation, with the most robust definition being an analysis of participants' individual slopes across all nine blinks. The present findings suggest that startle habituation is a key mechanism underlying AS, and may help elucidate the role this risk factor plays in the pathogenesis of anxiety disorders.     

Books Briefly Noted

Political Freedom By George G. Brenkert Routledge, 1991. Pp. 278. ISBN 0–415–03372–1. £35 hbk.

Wittgenstein: A Bibliographical Guide By Guido Frongia and Brian McGuinness Basil Blackwell, 1990. Pp. x + 438. ISBN 00631–13765–3. £60.00.

Metaphysics By Peter van Inwagen Oxford University Press, 1993. Pp. xiii + 222. ISBN 0–19–8751400. £11.95 pbk.

The Nature of Moral Thinking By Francis Snare Routledge, 1992. Pp. 187. ISBN 0–415–04709–9. £9.99 pbk.

Filosofía analitica hoy: Encuentro de tradiciones Edited by Mercedes Torrevejano Servicio de Publications Universidade de Santiago de Compostela, 1991. Pp. 284. ISBN 84–7191–722‐X. $15.5 pbk.

The Puzzle of Experience By J.J. Valberg Clarendon Press, 1992. Pp. 227. ISBN 0–19–824291–3. £25.

Religion and Philosophy Edited by Martin Warner Royal Institute of Philosophy Supplement: 31 Cambridge University Press, 1992. Pp. vi + 155. ISBN 0–521–42951‐X. £10.95 pbk.

The Uses of Philosophy By Mary Warnock Blackwell, 1992. Pp. 256. ISBN 0–631–18038–9. £35.00 hbk. £11.95 pbk.

The Disappearance of Time: Kurt Godel and the Idealistic Tradition in Philosophy By Palle Yourgrau Cambridge University Press, 1991. Pp. x + 182. ISBN 0–521–41012–6. £27.50     

The Influence of Confirmation Bias on Memory and Source Monitoring

Two experiments were conducted to examine whether recognition memory for information and/or its source are influenced by confirmation bias. During Phase 1, subjects were shown a summary about the issue of gun control and asked to indicate a position on the issue. During Phase 2, 12 abstracts (Experiment 1) or social media posts (Experiment 2) were shown, one at a time. Posts in Experiment 2 were associated with either friends or strangers. Participants indicated whether they wanted to read a more extensive version of each abstract (Experiment 1) or post (Experiment 2). Phase 3 was the memory phase. Thirty-two abstract titles (Experiment 1) or posts (Experiment 2) were shown one at a time. Participants indicated yes or no, and whether they recognized the titles/posts from the last phase. Recognition memory for information that supported the participants' viewpoint was higher than that for opposing information.     

Influential Factors in Artist's Lives and Themes in Their Artwork

ABSTRACT: The purpose of this study was to investigate the relations among influential factors in artists' lives, the process of creativity, and themes in the resulting artwork. Both qualitative and quantitative methods were used. In Phase I of the research, 6 contemporary artists identified themes, influences, feelings, thoughts, and representations about 5 pieces of their own art. They also completed a 50-item survey about influential factors. Two judges also were asked to identify themes, influences, feelings, thoughts, and representations in Phase 2 of the research. The judges relied on 30 slides depicting the work of the 6 artists. The same 50-item survey concerning influential factors was completed by each of the judges while examining the slides a 2nd time. Hypothesis 1, which predicted that artists would articulate the events, experiences, and memories that have influenced their lives, was supported. Hypothesis 2, which predicted that artists would be aware of the relations between influential factors in their lives and specific themes, images, expressions, and representations in their paintings, also was supported. Hypothesis 3, which predicted that potentially influential factors would be communicated in the themes, images, expressions, and representations in artists' paintings, and that objective viewers can identify them, was supported partially. The judges responded similarly to at least 2 of the 5 pieces of art for each participant. Hypothesis 4, which predicted that influential themes would be similar across all participants ' paintings, also was supported partially. One hundred percent agreement was found for the strongest influences (e.g., loss and culture) when the men and the women were evaluated separately.     

E‐readers,Computer Screens,or Paper: Does Reading Comprehension Change Across Media Platforms?

The present research examined the impact of technology on reading comprehension. While previous research has examined memory for text, and yielded mixed results of the impact technology has on one's ability to remember what they have read, the reading literature has not yet examined comprehension. In comparing paper, computers, and e‐readers, results from this study indicated that these three different presentation modes do not differentially affect comprehension of narrative or expository text. Additionally, readers were not consistently compensating for difficulties with comprehension by engaging in different reading behaviors when presented with text in different formats. These results suggest that reading can happen effectively in a variety of presentation formats. Copyright © 2013 John Wiley & Sons, Ltd.     

Subtypes of Psychopathology in Children Referred for Neuropsychological Assessment

The validity of a Personality Inventory for Children-Revised edition (PIC-R) typology was examined in a sample of 323 children aged 6–16 years. These children had been referred to a children's mental health centre for neuropsychological assessment. In study 1, K-means cluster analysis (k = 12) was applied to the PIC clinical scales in an attempt to replicate the 12 clusters identified by Gdowski, Lachar, and Kline (1985). Partial cluster replication was achieved. Examination of the obtained clusters revealed significant overlap, suggesting that fewer clusters would represent an optimal solution. In study 2, a two-stage cluster analysis yielded a seven-cluster solution consistent with several key forms of psychopathology previously reported in the literature using specific neuropsychological populations. Identified subtypes included profiles characterized as: normal, cognitive deficit, cognitive deficit with internalized psychopathology, cognitive deficit with social impairment, cognitive deficit with hyperactivity, cognitive deficit with both internalized and externalized psychopathology, and combined internalized and externalized psychopathology without a cognitive deficit component.     

Depression and heart rate variability in cardiac rehabilitation patients: exploring the roles of physical activity and fitness

Cardiac patients with depression have shown altered autonomic nervous system functioning, expressed as reduced heart rate variability. This may be associated with poorer physical fitness and less physical activity among depressed patients. These relationships were explored among patients enrolled in outpatient cardiac rehabilitation. 22 depressed and 22 nondepressed patients, matched for sex and age, were assessed at enrollment. The Beck Depression Inventory and structured interviews were used to measure depression. Patients completed ambulatory monitoring of ECG (i.e., Holter) and physical activity, as well as a treadmill stress test. Depression was associated with several measures of heart rate variability. Activity and fitness were lower among the depressed patients. Although exploratory, accounting for activity and fitness attenuated the relationship between depression and heart rate variability. This suggests that altered fitness and activity may help explain altered autonomic tone that characterizes patients with cardiovascular diseases who are psychologically depressed.     

A time of change: Behavioral and neural correlates of adolescent sensitivity to appetitive and aversive environmental cues

Adolescence is a developmental period that entails substantial changes in affective and incentive-seeking behavior relative to both childhood and adulthood, including a heightened propensity to engage in risky behaviors and experience persistent negative and labile mood states. This review discusses the emotional and incentive-driven behavioral changes in adolescents and their associated neural mechanisms, focusing on the dynamic interactions between the amygdala, ventral striatum, and prefrontal cortex. Common behavioral changes during adolescence may be associated with a heightened responsiveness to incentives and emotional cues while the capacity to effectively engage in cognitive and emotion regulation is still relatively immature. We highlight empirical work in humans and animals that addresses the interactions between these neural systems in adolescents relative to children and adults, and propose a neurobiological model that may account for the nonlinear changes in adolescent behavior. Finally, we discuss other influences that may contribute to exaggerated reward and emotion processing associated with adolescence, including hormonal fluctuations and the role of the social environment.