Effects of practice and task constraints on stiffness and friction functions in biological movements

A dynamical model of the movements of the platform of a ski-simulator was derived from experimental data, using the graphical and statistical methods developed by Beek and Beek (Beek, P. J., & Beek, W. J. (1988). Human Movement Science, 7, 301–342). The data were collected in an experiment in which both amplitude and practice were manipulated. The data were filtered and further reduced to normalised cycles that were averaged within and across subjects. Graphical methods were applied to these averaged normalised cycles to determine the stiffness and friction terms to be included in the model. The relative contribution of each term was assessed by means of multiple regression. The model, which included cubic and quintic Duffing terms and one or two dissipative Van der Pol terms, accounted on average for 99.2% of the variance. The exact parameter setting of the model differed considerably across subjects. For one subject, a qualitatively different model, including Rayleigh instead of Van der Pol terms, provided a better account of the data. Systematic changes of the coefficients in the model, related to amplitude and the duration of practice, were evident.     

Age-related deficits in generation and manipulation of mental images: I. The role of sensorimotor speed and working memory.

The authors investigated age-related slowing of information processing in mental imagery tasks. Eighty-five healthy adults (ages 18 to 77) performed a visual, sensorimotor, reaction-time task; a visual-perceptual choice reaction task; and 3 mental imagery tasks that varied in apparent difficulty and involved stimuli at 2 levels of graphic complexity. Age was associated with prolongation of response time across all tasks and both levels of stimulus complexity. Accuracy of response was adversely affected by increase in stimulus complexity in all tasks, whereas it was negatively related to age only on the tasks with substantial mental imagery requirements. Slowing of information processing and reduction in accuracy were mediated by declines in working memory but not by decrease of sensorimotor speed.     

The attentional demands of encoding and retrieval in younger and older adults: 2. Evidence from secondary task reaction time distributions

Three studies examined the effects of encoding or retrieval on properties of secondary task reaction time (RT) distributions in younger and older adults. Relative to full attention conditions, encoding and retrieval increased secondary task RT medians and standard deviations more for older adults than for younger adults, and the age-related RT increase was most pronounced among the slowest RTs. Hierarchical regression analyses revealed two age-related mechanisms underlying these effects, which were interpreted as cognitive slowing and reductions in attentional resources. Cognitive slowing affects the entire RT distribution regardless of the memory task. By contrast, reduced attentional resources result in very long RTs, especially when the tasks require self-initiated encoding or retrieval operations.     

On the rationality of positive mysterianism

In Paradox in Christian Theology (2007) I argued that the Christian doctrines of the Trinity and the Incarnation are paradoxical—that is, they appear to involve implicit contradictions—yet Christians can still be rational in affirming and believing those doctrines. Dale Tuggy has characterized my theory of theological paradox as a form of “positive mysterianism” and argues that the theory “faces steep epistemic problems, and is at best a temporarily reasonable but ultimately unsustainable stance.” After summarizing my proposed model for the rational affirmation of theological paradox and considering whether my proposal is indeed a form of “positive mysterianism” as Tuggy defines the term, I address the two main criticisms raised in Tuggy’s paper: first, that the doctrine of divine incomprehensibility cannot bear the weight required by my defense of paradox; and second, that my proposed model is afflicted with epistemic instability. I conclude that Tuggy has failed to show that a mysterian stance with respect to paradoxical Christian doctrines is in principle unreasonable, unnatural, or unsustainable.     

“We want the world and we want it now”: Materialism,time perspectives and problem spending tendency of Chinese

Chinese consumers' spending has been expanding rapidly in the past decade, and along with it household and credit card debt. The present research collected evidence to triangulate the contention that materialism is positively related with Chinese's problem spending tendency (PST), and that present‐time‐perspective (PTP) and future‐time perspectives (FTP) interact systematically with materialism to affect PST. A survey of the general population in Macao, China (Study 1; N = 239) confirmed that materialism was positively correlated with PST. An interaction between materialism and PTP intensified the relationship, whereas an interaction with FTP weakened the relationship. Another survey with a sample of university students (Study 2; N = 223) again found positive relationships among PST, materialism, and PTP, as measured by temporal discount rate. But further exploration showed that PST was only related with temporal discounting among high materialists, but not among low materialists. Study 3 experimentally examined the causal effects of materialism and FTP on PST. When being primed of an orientation towards materialism (n = 33), the participants' planned consumption doubled that of the control group (n = 31). A FTP prime interacted with materialism prime and put a “damper” on participants' planned spending (n = 29), compared to their counterparts who were not primed of such a time perspective.     

Compensating for an Inattentive Audience

The common ground that conversational partners share is thought to form the basic context for language use. According to the classic view, inferences about common ground, or mutual knowledge, are guided by beliefs about the physical, cognitive, and attentional states of one's communicative partners. Here, we provide a first test of the attention assumption for common ground, the proposal that common ground for a co‐present entity—such as an object or an utterance—can only be formed if a person has evidence that his or her partner has also attended to it. In three experiments, a participant speaker and two partners learned names for novel monster pictures as a group. The speaker was then asked to describe the monsters to each partner separately in a referential communication task. The critical manipulation was the (in)attentiveness of one partner at different points in the study. Analysis of the speaker's referring expressions revealed that speakers assumed their partner shared common ground for the monster names only when that partner exhibited engaged attention as the names were learned. These findings provide key and novel support for the classic proposal that formation of common ground critically depends on assumptions about the attentional state of one's conversational partner.     

Sequenced neurocognitive and behavioral parent training for the treatment of ADHD in school-age children

The present study examines the potential of sequencing a neurocognitive intervention with behavioral parent training (BPT) to improve executive functions (EFs), psychiatric symptoms, and multiple indices of functional impairment in school-age children aged 7 to 11 years who have been diagnosed with attention-deficit/hyperactivity disorder (ADHD). Specifically, in a randomized controlled trial design, 85 children were assigned to either Cogmed Working Memory Training (CWMT) followed by an empirically supported, manualized BPT intervention, or to a placebo version of CWMT followed by the same BPT intervention. Working memory maintenance (i.e., attention control/short-term memory), working memory processing and manipulation, ADHD and oppositional defiant disorder (ODD) symptoms, impairment in parent–child dynamics, familial impairment, and overall functional compromise were evaluated as outcomes. The results suggest specific effects of the combined CWMT and BPT program on verbal and nonverbal working memory storage and nonverbal working memory processing and manipulation but no incremental benefits in regard to ADHD symptoms, ODD symptoms, and functional outcomes. The present findings do not support the hypothesis regarding the complementary and augmentative benefits of sequenced neurocognitive and BPT interventions for the treatment of ADHD. These results, the study’s limitations, and future directions for research are further discussed.