Fluctuations and phase symmetry in coordinated rhythmic movements

Pendular, clocking movements typify mammalian terrestrial locomotion. They can be investigated with a procedure in which people swing hand-held pendulums at the wrists, comfortably and rhythmically. Pendular, clocking behavior was examined for in-phase and out-of-phase coordinations. The periodic timing and powering of rhythmic movements in the comfort state follow from different laws (Kugler & Turvey, 1986). One law guides the assembling of the reference frame for "clocking." Another law guides the assembling of the muscular, escapement processes determining the cycle energy. Wing and Kristofferson's (1973) method for parsing periodic-timing variance into independent "clock" and "motor" sources was applied. Mean periodicity was unaffected by phase. "Clock" fluctuations, however, were larger out of phase than in phase. "Motor" fluctuations were indifferent to phase but reflected the departures of individual wrist-pendulum systems from their preferred periods. It appears that an intended phase relation is realized as a constraint on "clock" states. These states are more stable under the in-phase constraint than under the out-of-phase constraint.     

Inquiry into intentional systems I: Issues in ecological physics

Summary The role of intention in guiding the behavior of goal-directed systems is a problem that continues to challenge behavioral science. While it is generally agreed that intentional systems must be consistent with the laws of physics, there are many obvious differences between inanimate, physical systems and sentient, intentional systems. This suggests that there must be constraints over and above those of physics that govern goal-directed behavior. In this paper it is suggested that generic properties of self-organizing mechanisms may play a central role in the origin and evolution of intentional constraints. The properties of self-organizing systems are first introduced in the context of simple physical systems and then extended to a complex (biological) system. Whereas behavior of an inanimate physical system is lawfully determined by force fields, behavior of an animate biological system is lawfully specified by information fields. Biological systems are distinguished from simple physical systems in terms of their ubiquitous use of information fields as special (biological and psychological, social, etc.) boundary conditions on classical laws. Unlike classical constraints (boundary conditions), informational constraints can vary with time and state of the system. Because of the nonstationarity of the boundary conditions, the dynamic of the system can follow a complex trajectory that is organized by a set of spatially and temporally distributed equilibrium points or regions. It is suggested that this equilibrium set and the laws that govern its transformation define a minimal requirement for an intentional system. One of the benefits of such an approach is that it suggests a realist account for the origin of semantic predicates, thereby providing a basis for the development of a theory of symbolic dynamics. Therefore, the principles of self-organization provide a comprehensive basis for investigating intentional systems by suggesting how it is that intentions arise, and by providing a lawful basis for intentional behavior that reveals how organisms become and remain lawfully informed in the pursuit of their goals.     

Competent and incompetent criminal defendants: a quantitative review of comparative research

Thirty studies comparing competent and incompetent criminal defendants (N = 8,170) were quantitatively reviewed to identify variables associated with judgments about defendants' competency to stand trial. Effect sizes reflecting the magnitude of the relationship between competency status and defendant characteristics were derived and averaged across studies. The characteristics most strongly related to incompetency were (a) poor performance on psychological tests or interviews specifically designed to assess defendants' legally relevant functional abilities, (b) a psychotic diagnosis, and (c) psychiatric symptoms reflective of severe psychopathology. To a lesser degree, traditional psychological tests, previous psychiatric hospitalization, previous legal involvement, marital resources, and demographic characteristics were also related to competency status. Although these results are generally consistent with the legal standard for competency to stand trial, some of the correlates of competency may reflect potential biases in the decision-making process. Limitations of existing research and directions for future inquiry are discussed.     

Patterns of Human Interlimb Coordination Emerge from the Properties of Non-Linear,Limit Cycle Oscillatory Processes

The present article represents an initial attempt to offer a principled solution to a fundamental problem of movement identified by Bernstein (1967), namely, how the degrees of freedom of the motor system are regulated. Conventional views of movement control focus on motor programs or closed-loop devices and have little or nothing to say on this matter. As an appropriate conceptual framework we offer Iberall and his colleagues’ physical theory of homeokinetics first elaborated for movement by Kugler, Kelso, and Turvey (1980). Homeokinetic theory characterizes biological systems as ensembles of non-linear, limit cycle oscillatory processes coupled and mutually entrained at all levels of organization. Patterns of interlimb coordination may be predicted from the properties of non-linear, limit cycle oscillators. In a set of experiments and formal demonstrations we show that cyclical, two-handed movements maintain fixed amplitude and frequency (a stable limit cycle organization) under the following conditions: (a) when brief and constantly applied load perturbations are imposed on one hand or the other, (b) regardless of the presence or absence of fixed mechanical constraints, and (c) in the face of a range of external driving frequencies from a visual source. In addition, we observe a tight phasic relationship between the hands before and after perturbations (quantified by cross-correlation techniques), a tendency of one limb to entrain the other (mutual entrainment) and that limbs cycling at different frequencies reveal non-arbitrary, sub-harmonic relationships (small integer, subharmonic entrainment). In short, all the above patterns of interlimb coordination fall out of a non-linear oscillatory design. Discussion focuses on the compatibility of these results with past and present neurobiological work, and the theoretical insights into problems of movement offered by homeokinetic physics. Among these are, we think, the beginnings of a principled solution to the degrees of freedom problem, and the tentative claim that coordination and control are emergent consequences of dynamical interactions among non-linear, limit cycle oscillatory processes.     

Trait-Focused Spin in Presidential Debates: Surviving the Kisses of Death

In the context of presidential debates, 2 experiments explored the impact of “trait-focused spin”—messages interpreting potentially negative personality traits in terms of broader, positive frameworks—in comparison to unfocused spin—messages simply predicting positive performance. Of interest were differences between high and low Need for Cognition (NFC) participants in their willingness to accept these messages. In Experiment 1, high NFC participants responded well to trait-focused spin but found unfocused spin unpersuasive. Low NFC participants responded equally well to both. In Experiment 2, high NFC participants again rated the target candidate more positively after trait-focused but not after unfocused spin, whereas low NFC participants did the opposite. Thus trait-focused spin can influence even those suspicious of unfocused spin.     

Predictors of Differential Responding on a Sentence Completion Task in Traumatized Children

Information-processing theories posit that persons who have experienced trauma may have disturbed emotional processing and therefore exhibit an excess of negative responses to otherwise neutral cues. The role of this mechanism in traumatized children has yet to be fully investigated. This study examined the relationship of varied clinical characteristics and theoretically relevant moderating variables to increased trauma related responding on a non-idiographic sentence completion task. One hundred and eighty-nine children (ages 6–17) residing at a residential home between 1996 and 2011 who had experienced physical, emotional and/or sexual abuse were administered a sentence completion task and the Trauma Symptom Checklist for Children (TSCC) shortly after their admission. Three independent raters determined whether sentence completion responses were trauma related (TRR), non-trauma related, or ambiguous. Trauma related responses were then reviewed for either avoidant/denial style responding or loss related responding. The TSCC posttraumatic stress subscale (PTS) was the only subscale that was uniquely related to TRR. A significant interaction between abuse type and PTS was found with sexual abuse moderating the effect of PTS on TRR. Additionally, age at assessment was positively correlated with both TRR and loss related responding. Time since removal from home was negatively correlated with TRR. Gender differences were found for TRR and loss related responding. These findings highlight the empirical relevance of the sentence completion task in clinical research. Results are discussed in terms of their implications for research, assessment, and intervention.     

The role of anxiety sensitivity in the relationship between posttraumatic stress symptoms and negative outcomes in trauma-exposed adults

Background: The development of posttraumatic stress symptoms (PTSs) following a trauma is related to impairment, diminished quality of life, and physical health issues. Yet it is not clear why some trauma-exposed individuals experience negative outcomes while others do not. The purpose of this study was to determine the role of several influential factors related to PTS severity and negative outcomes. Methods: One hundred and twenty-two trauma-exposed adults were administered the following self-report measures: the Posttraumatic Stress Disorder Checklist-Civilian, the Trauma History Questionnaire-Short, the Anxiety Sensitivity Index-3, Depression and Anxiety Stress Scale 21, Sheehan Disability Scale, World Health Organization Quality of Life-BREF, and an abbreviated Patient Health Questionnaire. Primary Results: PTS severity was positively correlated with depressive symptom severity (r = 0.54, p < 0.001), chronicity of the most distressing trauma (r = 0.21, p = 0.017), and number of traumas (r = 0.22, p = 0.012). Main effects were found for PTS severity (β = ?0.38, p < 0.01) and anxiety sensitivity (AS; β = ?0.39, p < 0.01) on quality of life. No interaction was found between PTS severity and AS with any negative outcome. PTS severity mediated the relationship between AS and physical health issues (0.05; 95% CI: 0.02–0.08). Conclusion: This study helps clarify the role of various factors in the relationship between trauma and negative outcomes. Clinical and research implications are discussed.     

Public good provision in inter‐team conflicts: Effects of asymmetry and profit‐sharing rule

A fundamental problem in organizations is designing mechanisms for eliciting voluntary contributions from individual members of a team who are entrapped in a social dilemma. To solve the problem, we utilize a game‐theoretical framework that embeds the traditional within‐team social dilemma in a between‐team competition for an exogenously determined prize. In equilibrium, such competition enhances the incentive to contribute, thereby reducing free‐riding. Extending existing literature, we focus on asymmetric competitions between teams of unequal size, and competitions between more than two teams. Comparing two protocols for sharing the prize—egalitarian and proportional profit‐sharing rules—we find that (i) free‐riding diminishes and (ii) team members contribute more toward their team's effort when they belong to the larger team and when the profit‐sharing rule is proportional. (iii) Additionally, under the egalitarian profit‐sharing rule team members contribute more than predicted by the equilibrium solution. We discuss implications of our findings for eliciting contributions in competitive environments. Copyright © 2009 John Wiley & Sons, Ltd.     

Social Influence on Political Judgments: The Case of Presidential Debates

Four experiments investigated the extent to which judgments of candidate performance in presidential debates could be influenced by the mere knowledge of others' reactions. In Experiments 1 and 2 participants watched an intact version of a debate or an edited version in which either "soundbite" one-liners or the audience reaction to those soundbites were removed. In Experiment 3 participants saw what was supposedly the reaction of their fellow participants on screen during the debate. Participants in Experiment 4 were exposed to the reactions of live confederates as they watched the last debate of an active presidential campaign. In all studies, audience reactions produced large shifts in participants' judgments of performance. The results illustrate the power of social context to strongly influence individuals' judgments of even large amounts of relevant, important information, and they support the categorization of presidential debates as ambiguous stimuli, fertile ground for informational social influence.     

Orthographic structure versus morphological structure: principles of lexical organization in a given language

Most models of visual word recognition in alphabetic orthographies assume that words are lexically organized according to orthographic similarity. Support for this is provided by form-priming experiments that demonstrate robust facilitation when primes and targets share similar sequences of letters. The authors examined form-orthographic priming effects in Hebrew, Arabic, and English. Hebrew and Arabic have an alphabetic writing system but a Semitic morphological structure. Hebrew morphemic units are composed of noncontiguous phonemic (and letter) sequences in a given word. Results demonstrate that form-priming effects in Hebrew or Arabic are unreliable, whereas morphological priming effects with minimal letter overlap are robust. Hebrew bilingual subjects, by contrast, showed robust form-priming effects with English material, suggesting that Semitic words are lexically organized by morphological rather than orthographic principles. The authors conclude that morphology can constrain lexical organization even in alphabetic orthographies and that visual processing of words is first determined by morphological characteristics.