Deterministic Chaos and Computational Complexity: the Case of Methodological Complexity Reductions

Some problems rarely discussed in traditional philosophy of science are mentioned: The empirical sciences using mathematico-quantitative theoretical models are frequently confronted with several types of computational problems posing primarily methodological limitations on explanatory and prognostic matters. Such limitations may arise from the appearances of deterministic chaos and (too) high computational complexity in general. In many cases, however, scientists circumvent such limitations by utilizing reductional approximations or complexity reductions for intractable problem formulations, thus constructing new models which are computationally tractable. Such activities are compared with reduction types (more) established in philosophy of science. This revised version was published online in August 2006 with corrections to the Cover Date.     

The effects of age and cue-action reminders on event-based prospective memory performance in preschoolers

The present study investigated event-based prospective memory in five age groups of preschoolers (i.e., 2-, 3-, 4-, 5-, and 6-year-olds). Applying a laboratory-controlled prospective memory procedure, the data showed that event-based prospective memory performance improves across the preschool years, at least between 3 and 6 years of age. However, our findings do not confirm early speculations that 2-year-olds may have attained reliable skills to carry out future intentions on their own. By contrast, there were first signs of prospective memory abilities among the 3-year-olds. The present study also revealed that children as young as 3 years can use external memory aids in the form of cue-action reminders to improve their event-based prospective remembering. Finally, the findings suggest that parents or caregivers can adequately estimate their preschool children's prospective memory abilities, as revealed by applying a modified version of the Prospective and Retrospective Memory Questionnaire (PRMQ).     

Swimming constraints and arm coordination

Following Newell's concept of constraint (1986), we sought to identify the constraints (organismic, environmental and task) on front crawl performance, focusing on arm coordination adaptations over increasing race paces. Forty-two swimmers (15 elite men, 15 mid-level men and 12 elite women) performed seven self-paced swim trials (race paces: as if competitively swimming 1500m, 800m, 400m, 200m, 100m, 50m, and maximal velocity, respectively) using the front crawl stroke. The paces were race simulations over 25m to avoid fatigue effects. Swim velocity, stroke rate, stroke length, and various arm stroke phases were calculated from video analysis. Arm coordination was quantified in terms of an index of coordination (IdC) based on the lag time between the propulsive phases of each arm. This measure quantified three possible coordination modes in the front crawl: opposition (continuity between the two arm propulsions), catch-up (a time gap between the two arm propulsions) and superposition (an overlap of the two arm propulsions). With increasing race paces, swim velocity, stroke rate, and stroke length, the three groups showed a similar transition in arm coordination mode at the critical 200m pace, which separated the long- and mid-pace pattern from the sprint pace pattern. The 200m pace was also characterized by a stroke rate close to 40strokemin(-1). The finding that all three groups showed a similar adaptation of arm coordination suggested that race paces, swim velocity, stroke rate and stroke length reflect task constraints that can be manipulated as control parameters, with race paces (R(2)=.28) and stroke rate (R(2)=.36) being the best predictors of IdC changes. On the other hand, only the elite men reached a velocity greater than 1.8ms(-1) and a stroke rate of 50strokemin(-1). They did so using superposition of the propulsion phases of the two arms, which occurred because of the great forward resistance created when these swimmers achieved high velocity, i.e., an environmental constraint. Conversely, the elite women and mid-level men had shorter stroke lengths and maintained a time gap between the propulsions of the two arms throughout the increase in paces, with gender and expertise explaining 9% and 8.3% of the IdC changes, respectively. These results indicate that arm coordination cannot be interpreted solely from the IdC value but should be considered from the perspective of task, environmental, and organismic constraints. These constraints can serve as control parameters in experiments aimed at gaining insight into changes in arm coordination during the front crawl. In this context, catch-up coordination, which is often considered as a mistake, was seen to be an adaptation to a relative constraint.     

Opportunism in Memory: Preparing for Chance Encounters

Recognizing opportunities to achieve pending goals is an important cognitive ability. But when and how do we recognize that a current situation is especially suited to resuming a past goal? The predictive encoding model suggests pending goals are encoded into memory in association with anticipated environmental features. Optimally, these features are (a) necessary for successful goal satisfaction, (b) distinctive preconditions for expecting a plan to achieve the goal, and (c) described so as to be readily identified in the environment. Later, ordinary perception of features in the environment leads to automatic recognition of opportunities already prepared in memory. Evidence from experimental studies supports this theory, and demonstrates that general preparation can produce apparently novel opportunism. These findings suggest ways to facilitate the recognition of opportunities to satisfy pending goals.     

Effects of multisource feedback and a feedback facilitator on the influence behavior of managers toward subordinates

The authors compared a feedback workshop with both a no-feedback control group and a comparison group of managers who received a feedback report but no feedback workshop. The multisource feedback was based on ratings of a manager's influence behavior by subordinates, peers, and bosses. Managers in the feedback workshop increased their use of some core influence tactics with subordinates, whereas there was no change in behavior for the control group or for the comparison group. The feedback was perceived to be more useful by managers who received it in a workshop with a facilitator than by managers who received only a printed feedback report.     

The duration component of the stress effect in stuttering

The purpose of the present study was to investigate whether there is a relationship between stuttering on stressed syllables and the duration of these syllables. Sixteen adults who stutter read a text consisting of 226 syllables. The relative stress of each syllable was rated, and syllables were categorized into long- and short-stressed syllables, unstressed syllables and intermediate syllables lying in-between. In order to isolate effects caused by within-word position from those caused by linguistic stress, syllables in initial and in subsequent positions were analyzed separately. In both word position categories stressed syllables were stuttered more often than unstressed syllables. Stuttering frequency of intermediate syllables seems to be in-between stressed and unstressed syllables, just as their stress level is rated in-between. Results regarding the duration of stressed syllables do not allow final conclusions.

Educational objectives: The reader will learn about and be able to describe (1) language factors related with stuttering events, (2) the stress effect in adults who stutter, and (3) methods to control for its confounding variables.