Bounded stability of the quiet standing posture: an intermittent control model

The paper presents a control model of body sway in quiet standing, which aims at achieving bounded stability by means of an intermittent control mechanism. Control bursts are generated when the current state vector exits an area of uncertainty around the reference point in the phase plane. This area is determined by the limited resolution of proprioceptive signals and the burst generation mechanism is predictive in the sense that it incorporates a rough, but working knowledge (internal model) of the biomechanics of the human inverted pendulum. We show that such a model, in spite of its simplicity and of the fact that it relies on very noisy measurements, is robust and can explain in a detailed way the measured sway patterns.     

Superiority of variable to repeated practice in transfer on anagram solution

Previous research in motor learning shows that practicing variations of a task (variable practice) leads to better transfer than does repeatedly practicing the exact same task (repeated practice). In contrast, research on priming using verbal materials shows that performance on a test improves to the extent that the material at learning and test overlap. We tested whether variability in practice conditions can lead to improved performance with the verbal priming task of anagram solution. Participants practiced solving anagrams, either repeatedly solving the same anagram that was later tested, repeatedly solving a different anagram from the one that was later tested, or solving different variations of the anagram that was later tested. We found that this last condition-variable practice on different versions of an anagram-led to improved test performance in relation to repeated practice, even when the test anagram was the one that had been repeatedly practiced. This finding aligns results from the motor learning literature with a higher level cognitive task: anagram solution. Shea and Kohl's (1991) hypothesis, arguing that varied practice may lead to greater elaborative processing than does repeated practice, provides one account of the results.     

Adherence to antiretroviral therapy: an empirical test of the information-motivation-behavioral skills model.

Consistent and nearly perfect adherence is considered an essential requirement for HIV-positive patients on antiretroviral therapy (ART) to fully realize its life-extending benefits. The current study evaluated a comprehensive model of ART adherence--the information-motivation-behavioral skills (IMB) model. This model views adherence behavior as a function of the interrelations between adherence-related information, motivation, and behavioral skills. It hypothesizes that adherence-related information and motivation work through adherence-related behavioral skills to affect the initiation and maintenance of optimal ART adherence. In a series of structural equation models, the IMB model's critical constructs and assumptions were evaluated with a sample of 100 HIV-positive patients in clinical care. Across all analyses, the authors found support for the assumptions of the IMB model of ART adherence. Consistent with the model, adherence-related information and motivation related significantly to adherence-related behavioral skills, and behavioral skills related significantly to self-reported optimal adherence. Further, as predicted, the effects of information and motivation on self-reported adherence were mediated by adherence-related behavioral skills. Current study results are explored, and implications for adherence promotion interventions based on the model are discussed.     

Friendship stability and change in childhood and adolescence

The objective of this review is to focus on a neglected aspect of children’s and adolescents’ friendships: the level of temporal stability. First, a rationale for examining stability as a distinct friendship dimension is presented. Next, the different levels of friendship experiences are distinguished. Friendship stability is also discussed across developmental periods. Factors affecting friendships stability and individual correlates associated with friendship stability are then covered. Finally, the methodological issues pertaining to the study of friendship stability are addressed. The authors conclude by emphasizing the importance of pursuing future research that aims to demonstrate the pertinence of the friendship stability construct as an individual difference variable. Further, on a methodological level, the assessment of stability needs to be based on longitudinal designs that include multiple measurement waves. Ultimately, such detailed analysis of stability will allow a better understanding of the dynamic processes by which friendships change over time and affect children’s and adolescents’ psychosocial development.     

Aging and implicit memory: Examining the contribution of test awareness

The study examined whether test awareness contributes to age effects in priming. Younger and older adults were given two priming tests (word-stem completion and category production). Awareness was assessed using both a standard post-test questionnaire and an on-line measure. Results from the on-line awareness condition showed that, relative to older adults, younger adults showed higher levels of priming and awareness, and a stronger relationship between the two, suggesting that awareness could account for age differences in priming. In contrast, in the post-test questionnaire condition, there was no age effect in word-stem completion or category production priming, despite the fact that awareness was greater in younger than older adults in the word-stem completion test and that category production priming was dependent on awareness in both age groups. These results suggest that awareness may mediate age effects in priming, but only under conditions of relatively high levels of awareness.     

An order of pure decision: growing up in a virtual world and the adolescent's experience of being-in-a-body

Technological advances and the dominant values of contemporary culture make it possible and acceptable to alter, extend, or altogether bypass the body and its functions in actuality and in virtual space. This has contributed to a split between the body and the self, leading to a disembodied subjectivity that may encourage a neglect of the body's unconscious meaning for the individual. Due to the psychic requirement during adolescence to accommodate the reality of the changing body, some vulnerable adolescents are especially primed for the seductions of virtual space--a "space" that is nowadays not only culturally sanctioned, but also idealized. The use of cyberspace can become a psychic refuge from the challenge of integrating the reality and meaning of the sexual body into the image of the self. Two case examples illustrate how for some vulnerable adolescents it is through the use of cyberspace that confusion about the real body can be denied or disavowed; for them the integrity of the self is sustained through pseudorepresentations of the body defensively experienced in terms of "play" rather than pathology.