Showing papers by "Florida Atlantic University published in 1992"

Evolution of behavioral attractors with learning: nonequilibrium phase transitions.

Abstract: Learning a bimanual coordination task (synchronization to a visually specified phasing relation) was studied as a dynamical process over 5 days of practicing a required phasing pattern. Systematic probes of the attractor layout of the 5 Ss' coordination dynamics (expressed through a collective variable, relative phase) were conducted before, during, and after practice. Depending on the relationship between the initial coordination dynamics (so-called intrinsic dynamics) and the pattern to be learned (termed behavioral information, which acts as an attractor of the coordination dynamics toward the required phasing), qualitative changes in the phase diagram occurred with learning, accompanied by quantitative evidence for loss of stability (phase transitions). Such effects persisted beyond 1 week. The nature of change due to learning (e.g., abrupt vs. gradual) is shown to arise from the cooperative or competitive interplay between behavioral information and the intrinsic dynamics.

Symmetry breaking dynamics of human multilimb coordination.

Abstract: The dynamics of pattern formation and change are studied in a complex multicomponent system, specifically the arms and legs of human Ss. Among the novel features observed are differential stability of coordinative modes produced by limbs moving in the same versus different directions (Experiment 1); transitions between coordinative modes preceded by a slow drift in relative phase (Experiments 1 and 2); bifurcations or phase transitions from 1 four-limb pattern to another (Experiment 2); and spontaneous emergence of non-1:1-frequency- and phase-locked patterns, in addition to periods of relative coordination (Experiment 3). All observed relative phasing patterns and their dynamics (stability, loss of stability, intermittency) are shown to arise from the same underlying nonlinear dynamical structure, an important feature of which is broken symmetry.

The lived experience of postpartum depression: a phenomenological study.

Abstract: The purpose of this phenomenological study was to describe the essential structure of the lived experience of postpartum depression. Seven mothers who had suffered from postpartum depression were interviewed regarding their subjective experiences. Data were analyzed using Colaizzi's (1978) method of phenomenology. Forty-five significant statements were extracted and clustered into 11 themes. These results were integrated into the essential structure of postpartum depression. Postpartum depression was a living nightmare filled with uncontrollable anxiety attacks, consuming guilt, and obsessive thinking. Mothers contemplated not only harming themselves but also their infants. The mothers were enveloped in loneliness and the quality of their lives was further compromised by a lack of emotions and all previous interests. Fear that their lives would never return to normal was all-encompassing.

Learning as change of coordination dynamics: theory and experiment.

Abstract: Learning of coordination patterns was investigated theoretically from the point of view of a dynamic theory of biological coordination and with reference to recent experiments on the learning of relative timing patterns. The theory is based on theoretical and experimental work showing that coordinated movement is characterized not only by the actually performed pattern of coordination but by an entire dynamics of coordination. Theoretically, such dynamics are captured as equations of motion of relevant collective variables. Experimentally, signatures of these underlying dynamics can be found in the temporal stability of coordination patterns, which can be assessed through various stability measures as well as through processes of pattern change. We argue that not only intrinsic coordination tendencies, but also specific behavioral requirements, be they perceived, memorized, or intended, must be expressed in terms of such dynamics. The concept of behavioral information captures such requirements a...

PHA-L analysis of projections from the supramammillary nucleus in the rat.

Abstract: The projections of the supramammillary nucleus (SUM) were examined in the rat by the anterograde anatomical tracer Phaseolus vulgaris leucoagglutinin (PHA-L). The majority of labeled fibers from SUM ascended through the forebrain within the medial forebrain bundle. SUM fibers were found to terminate heavily in the hippocampal formation, specifically within the granule cell layer and immediately adjoining molecular layer of the dentate gyrus. In addition, SUM fibers were shown to distribute densely to several structures with strong connections with the hippocampus, namely, the nucleus reuniens of the thalamus, the medial and lateral septum, the entorhinal cortex, and the endopiriform nucleus. SUM fibers were also shown to project significantly to several additional subcortical and cortical sites. The subcortical sites were the dorsal raphe nucleus, the midbrain central gray, the fields of Forel/zona incerta, the dorsomedial hypothalamic area, midline/intralaminar nuclei of the thalamus (posterior paraventricular, rhomboid, central medial, intermediodorsal, and mediodorsal), the medial and lateral preoptic areas, the bed nucleus of the stria terminalis, the substantia innominata, the vertical limb of the diagonal band nucleus, and the claustrum. The cortical sites were the occipital, temporal, parietal, and frontal cortices. Some notable differences were observed in projections from the lateral as compared to the medial SUM. For example, fibers originating from the lateral SUM distributed heavily to the hippocampal formation and parts of the cortex, whereas those from the medial SUM projected sparsely to these two regions. The SUM projections to the hippocampal formation and associated structures may serve as the substrate for a SUM involvement in the generation of the theta rhythm of the hippocampus and the gating of information flow through the hippocampal formation. © 1992 Wiley-Liss, Inc.

Statistical mechanics of social impact.

Abstract: We discuss the mean-field theory for a class of probabilistic cellular automata that can describe the dynamics of social impact. The models exhibit complex intermittent behavior.

Phase Transitions in the Human Brain: Spatial Mode Dynamics

Abstract: Pattern formation and switching between self-organized states are often associated with instabilities in open, nonequilibrium systems We describe an experiment which shows that systematically changing a control parameter induces qualitative changes in sensorimotor coordination and brain activity, as registered by a 37-SQUID (Superconducting Quantum Interference Device) array Near the instability point, predicted features of nonequilibrium phase transitions (critical slowing down, fluctuation enhancement) are observed in both the psychophysical data and the brain signals obtained from single SQUID sensors Further analysis reveals that activity from the entire array displays spatial patterns evolving in time Such spatiotemporal patterns are characterized by the dynamics of only a few coherent spatial modes

Imaging the ocean with ambient noise

Abstract: FOR many years, the principal means of probing the ocean using sound has been through the use of 'active' or 'passive' techniques. With an active system, an object is illuminated by a pulse of sound and its presence inferred from the echo it produces, whereas the passive approach involves simply listening for the sound that the object itself emits. Here we report a new method of using sound in the ocean, which is neither passive nor active. It relies on the naturally occurring, incoherent ambient noise field in the ocean— which can be thought of as 'acoustic daylight'—as the sole source of acoustic illumination. By focusing the sound scattered by an object immersed in the noise field, it should be possible to produce a visual image of the object on a television monitor. We have tested this concept by conducting a simple experiment in the ocean, with a parabolic reflector acting as an acoustic lens, and our results confirm that objects illuminated only by ambient noise can indeed be 'seen' at frequencies between 5 and 50 kHz

Mechanisms for anoxic survival in the vertebrate brain.

Abstract: When energy supplies to the mammalian brain are significantly reduced by anoxia, for a very short time energy requirements are curtailed by such routes as the suppression of synaptic transmission, while energy supply is enhanced by an increase in cerebral blood flow and an increase in glycolysis. The reduction of ATP consumption is insufficient to match the greatly curtailed supply of ATP coming from anaerobic glycolysis and the hydrolysis of PCr, and within minutes ATP falls, there is a loss of ion homeostasis with depolarization, and cell death occurs. The anoxia-tolerant species, like the turtle, appear to employ similar mechanisms to reduce energy expenditure, but in addition to such means as increases in inhibitory neurotransmitters and the manipulation of ion channel activities, they are able to reduce the energy costs to a level that can be met by a greatly reduced supply from anaerobic glycolysis. In this way ATP levels are maintained for many hours, and anoxic depolarization, with its concomitant consequences such as an uncontrolled release of excitatory amino acids are avoided. The greater anoxic tolerance of the mammalian neonate brain is due in part to intrinsic lower metabolic requirements and, perhaps through mechanisms similar to those in the turtle, to suppress metabolic demand. Studies of the survival mechanisms of anoxia-tolerant brains of such species as the turtle and crucian carp are not only of value for investigating a remarkable neuronal adaptation, but they promise to provide a valuable model for the study of the etiology of hypoxic damage and survival strategies in the mammal.

EDI Adoption and Implementation: A Focus on Interorganizational Linkages

Abstract: This paper explores the role of interorganizational distributions of power in EDI adoption. It reports findings of a vendor survey of a Fortune 1000 company that wants to adopt EDI. As hypothesized, perceived costs are negatively and significantly related to EDI adoption. However, perceived benefits, trust in trading partners, and net dependency do not significantly affect the intent to adopt EDI. Implications of the findings are discussed.

A curriculum strategy that expands time for in-depth elementary science instruction by using science-based reading strategies: Effects of a year-long study in grade four

Abstract: An integrative curriculum strategy emphasizing science process skills and hands-on activities expanded the time allocated for in-depth science instruction by replacing a district-adopted basal reading program with science-content reading designed to facilitate applied comprehension skills. This study investigated the combined effect of these curricular components (i.e., in-depth science, science-content-based reading) upon student achievement, attitudes, and self-confidence in both science and reading over the school year. In doing so, teachers in three fourth-grade classrooms each incorporated applied reading (and language arts) objectives into science reading activities as part of a daily, expanded, in-depth science teaching block that encompassed the total instructional time originally allocated to reading and science. Using multivariate covariance analysis, results showed that the students in the experimental group, compared to demographically similar controls, not only displayed significantly greater standardized test achievement as measured by the Iowa Tests of Basic Skills reading subtest and the Metropolitan Achievement Test science subtest, but also displayed a more positive attitude toward science and reading and greater self-confidence in learning science. Implications of the strategy for future curriculum research in science education are discussed.

Other Figures in Other Places: On Feminism, Postmodernism and Geography

Abstract: In a recent paper entitled "Travels in the postmodern", Elspcth Probyn uses the metaphors of local, locale, and location to open up a political dialogue between feminism and postmodernism, providing a particularly explicit example of a more general use of spatial figures in contemporary theoretical debate. These spatial references arc not entirely figurative, but allude to our positioning within particular contexts, which both frame and are constructed by our texts. Thus, Probyn's dialogue inevitably raises geographical questions. Moreover, geography is not merely a passive, unnamed party through which Probyn's dialogue is conducted; it is not immune from or in any way 'outside* the situatedness its terminology is employed to articulate. In this context, the metaphorical maps Probyn uses to find her way between the differing terrains of feminism and postmodernism are far from neutral, truthful, transparent representations. In this paper an extension of Probyn\s travels at the boundaries between feminism and postmodernism is sought by introducing a more active, self-critical geographical voice. The often hidden tensions underlying the linkages between geography, postmodernism, and feminism arc explored, and key issues at the interface between critical human geography and feminist deconstruction arc brought to the fore. "The subaltern's situation is not that of an exotic to be saved. Rather, her position is 'naturalized' and reinscribed over and over again through the practices of locale and location. In order for her to ask questions, the ground constructed by these practices must be rearranged .... In rearticulatin g the ground that is locally built around us, we give feminist answers that show up the ideological conditions of certain postmodernist questions."

Dorsal raphe neurons: synchronous discharge with the theta rhythm of the hippocampus in the freely behaving rat.

Abstract: 1. Single-unit activity of 30 dorsal raphe (DR) neurons was recorded along with the cortical and hippocampal electroencephalogram and neck muscle electromyogram in freely behaving rats during sleep-waking states. 2. On the basis of firing rates, DR cells were divided into slow-firing (S-cells), fast firing (F-cells), and very fast firing (FF-cells) units. The S-cells (8 units) fired at rates of < 10 Hz, the F-cells (11 units) at 10-40 Hz, and the FF-cells (11 units) at 55-70 Hz. 3. The activity of 17 of 30 DR units was correlated with the theta rhythm of the hippocampus. They included both slow and rapidly firing DR neurons. These cells typically fired irregularly (single spikes or short-duration bursts of activity) during non-theta states of quiet waking and slow-wave sleep. With the change of behavioral state to awake-moving or rapid eye movement sleep, the activity of these units switched to a regular bursting pattern synchronous with the hippocampal theta rhythm. Seven of these 17 units were classified as theta-rhythmic cells on the basis of the tight phase-locking of their discharge to the hippocampal theta rhythm. The remaining 10 units were classified as theta-modulated cells on the basis of a smaller but significant coherence between unit discharge and the theta rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)

On-line learning control of autonomous underwater vehicles using feedforward neural networks

Abstract: A neural-network-based learning control scheme for the motion control of autonomous underwater vehicles (AUV) is described. The scheme has a number of advantages over the classical control schemes and conventional adaptive control techniques. The dynamics of the controlled vehicle need not be fully known. The controller with the aid of a gain layer learns the dynamics and adapts fast to give the correct control action. The dynamic response and tracking performance could be accurately controlled by adjusting the network learning rate. A modified direct control scheme using multilayered neural network architecture is used in the studies with backpropagation as the learning algorithm. Results of simulation studies using nonlinear AUV dynamics are described in detail. The robustness of the control system to sudden and slow varying disturbances in the dynamics is studied and the results are presented. >

Maternity blues and postpartum depression.

Abstract: Objective To investigate the relationship between maternity blues and postpartum depression in mothers discharged early from the hospital and those discharged after the customary length of hospital stay. Design A descriptive correlation design. Setting 550‐bed community and teaching hospital in the midwestern United States. Participants 49 privately paying, primiparous, American‐born women, 18 years of age or older, with uncomplicated pregnancies and vaginal deliveries of healthy neonates weighing 2,600‐4,000 g. Measures Stein Maternity Blues Scale and Beck Depression Inventory were used to collect data. Results No significant differences found between the two groups of mothers; significant relationships found between maternity blues at 1 week after delivery and postpartum depression at 6 and 12 weeks after delivery. Conclusions Early discharge appears to pose no threat to psychologic well‐being. Primiparas experiencing more severe maternity blues are at increased risk for postpartum depression.

Predictors of aggressive behavior

Abstract: A multiple factor approach was used to test additive and multiplicative models as well as to isolate a best predictive model of physical aggression. The variables of aggressive learning history, provocation, sex of target, sex of subject, sex-role orientation, and aggressive tendencies were selected. Eighty-three males and 117 females participated in the experimental session. Multiple regression analyses indicated that multiple predictor models were able to account for significantly more variance than were single predictor models; however, multiplicative models were unable to increase predictive efficacy. A model composed of sex of target, masculinity, and aggressive tendencies was established as the best predictive model for unprovoked aggression; provocation, masculinity, and aggressive tendencies made up the best predictive model of provoked aggression. VioLit summary: OBJECTIVE: The purpose of this study by Hammock and Richardson was to apply a multifactor approach to the study of aggression, in order to produce a more comprehensive understanding of the behavior by isolating a model that could offer the best prediction. The researchers based their work in Bandura's social learning theory of aggression. METHODOLOGY: A quasi-experimental cross-sectional design was employed, with a one-group pretest-posttest format. A non-probability sample of 420 subjects from a large southeastern university participated in the pretest session, with 200 returning for the experimental part of the study (83 males, 117 females). The origin of aggressive behavior was measured by aggressive learning history, sex of the respondent, sex-role orientation and aggressive tendencies. Aggressive learning history was measured with the 14-item Steinmetz Family Problem-Solving Questionnaire concerning family conflict responses ranging from calm to physical violence. Reports were gathered about interactions between parents and from each parent and each sibling to the respondent. Sexual orientation was measured with the 24-item Personal Attributes Questionnaire, with scales for masculinity, femininity, and masculinity-femininity. Aggressive tendencies were measured with the aggressiveness component of the Buss-Durkee Inventory. Other factors included provocation and sex of target, used as measures of instigators of aggression. All of these measures, as well as background questions, were administered to subjects in the first session of the study. For the second session, participants were separated into pairs for an experiment with levels of electric shock and time trials. For each pair, both of the subjects could choose the level of shock to be applied to the other if they were slower on the time trial. Two measures of aggression were the dependent variables - unprovoked and provoked aggression. Unprovoked aggression was operationalized as a combination of the shock setting on the initial trial and the residual of the total score without the effect of provocation. Provoked aggression was measured as an average of the shock settings on the second through thirteenth trials. Analyses included ANOVA and principle components analysis, as well as Pearson product-moment and point-biserial correlations and multiple regression. FINDINGS/DISCUSSION: In an initial analysis, the researchers found no significant differences on the predictor variables between those who attended only the first session, those who returned for the experimental part of the study, and those who were suspicious of the real nature and purpose of the study. Males both delivered and received higher levels of shock than did females, with unprovoked aggression being significantly positively related to masculinity and aggressive tendencies, but negatively related to femininity. A stepwise multiple regression found that unprovoked aggression was best predicted by sex of target, masculinity and aggressive tendencies (R Square=0.17). Provoked aggression was best predicted by provocation, masculinity and aggressive tendencies (R Square=0.56). Significant correlations were found between all of the independent variables and at least one measure of aggression. The authors concluded that aggressive tendencies and masculinity had strong and consistent relationships with aggressive behavior. AUTHORS' RECOMMENDATIONS: The authors recommended the use of a multifactor approach to the study of aggression, rather than a design investigating single variables. EVALUATION: As this study was conducted in the artificiality of a laboratory setting, the generalizability of the results is not very good. Whilst the multifactor approach is certainly useful, more independent variables could have been included, and could have offered alternative explanations for findings. Despite these limitations, the methods of statistical analysis are appropriate, providing a solid base for further research. (CSPV Abstract - Copyright © 1992-2007 by the Center for the Study and Prevention of Violence, Institute of Behavioral Science, Regents of the University of Colorado) KW - College Student Research KW - Adult Aggression KW - Aggression Causes KW - Aggression Predictors KW - Social Learning Theory KW - Adult Female KW - Adult Male KW - Male Aggression KW - Female Aggression KW - Gender Differences VioLit summary:

Predicting software errors, during development, using nonlinear regression models: a comparative study

Abstract: Accurately predicting the number of faults in program modules is a major problem in quality control of a large software system. The authors' technique is to fit a nonlinear regression model to the number of faults in a program module (dependent variable) in terms of appropriate software metrics. This model is to be used at the beginning of the test phase of software development. The aim is not to build a definitive model, but to investigate and evaluate the performance of four estimation techniques used to determine the model parameters. Two empirical examples are presented. Results from average relative error (ARE) values suggest that relative least squares (RLS) and minimum relative error (MRE) procedures possess good properties from the standpoint of predictive capability. Moreover, sufficient conditions are given to ensure that these estimation procedures demonstrate strong consistency in parameter estimation for nonlinear models. Whenever the data are approximately normally distributed, least squares may possess superior predictive quality. However. in most practical applications there are important departures from normality: thus RLS and MRE appear to be more robust. >

Consideration Set Measurement

Abstract: The consideration set is a concept that is both intuitively appealing and practically useful. However, there is no standard operational definition of the construct, little reported research investigating alternative measures for empirically assessing the construct, and only limited investigation of interproduct differences in set characteristics (typically focusing on set size). Results of the experiment reported here indicate that situation-specific operational definitions yield smaller reported consideration sets that exhibit greater correspondence to reported purchases than do situation-neutral definitions, and that semantic variations within definition type have little impact on measured set characteristics. Further, findings indicate that much of the interproduct variation in consideration set size is related to awareness set size.

Seafinding By Hatchling Sea Turtles: Role of Brightness, Silhouette and Beach Slope as Orientation Cues

Abstract: Upon emerging from underground nests, sea turtle hatchlings immediately crawl toward the ocean. The primary cues used in orientation are visual but the nature of the visual cues was a matter of speculation. Hatchlings might also respond to secondary cues, such as beach slope. Experiments were carried out in an arena where specific visual and slope cues, simulating those present at nest sites, could be precisely controlled and manipulated. Subjects were green turtle (Chelonia mydas L.) and loggerhead (Caretta caretta L.) hatchlings. Both species oriented toward the more intensely illuminated sections of the arena. They also oriented away from dark silhouettes which simulated an elevated horizon, typical of the view toward land. Turtles responded primarily to stimuli (both silhouettes and photic differences) at or near eye level. When presented simultaneously with a silhouette and a photic gradient located in different directions, hatchlings oriented away from the silhouette and ignored photic stimuli. Under infrared light, both species oriented down slopes. However in the presence of nocturnal levels of visible light loggerheads ignored slope cues and responses of green turtles to slope were weakened. The data suggest that loggerhead and green turtle hatchlings usually find the sea by orienting away from elevated silhouettes. This is a prominent and reliable cue for species which typically nest on continental beaches.

Predictive modeling techniques of software quality from software measures

Abstract: The objective in the construction of models of software quality is to use measures that may be obtained relatively early in the software development life cycle to provide reasonable initial estimates of the quality of an evolving software system. Measures of software quality and software complexity to be used in this modeling process exhibit systematic departures of the normality assumptions of regression modeling. Two new estimation procedures are introduced, and their performances in the modeling of software quality from software complexity in terms of the predictive quality and the quality of fit are compared with those of the more traditional least squares and least absolute value estimation techniques. The two new estimation techniques did produce regression models with better quality of fit and predictive quality when applied to data obtained from two software development projects. >

A new approximate solution technique for randomly excited non-linear oscillators—II

Abstract: The method of weighted residuals is applied to the reduced Fokker-Planck equation associated with a non-linear oscillator, which is subjected to both additive and multiplicative Gaussian white noise excitations. A set of constraints are deduced for obtaining an approximate stationary probability density for the system response. One of the constraints coincides with the previously proposed criterion of dissipation energy balancing, and the others are useful for calculating the equivalent conservative force. It is shown that these constraints imply certain relationships among certain statistical moments; their imposition guarantees that such moments computed from the approximate probability density satisfy the corresponding exact equations derived from the original equation of motion. Moreover, the well-known procedure of stochastic linearization and its improved version of partial linearization are shown to be special cases of this scheme, and they are less accurate since the approximations are not chosen from the entire set of the solution pool of generalized stationary potential. Applications of the scheme are illustrated by examples, and its accuracy is substantiated by Monte Carlo simulation results.

Expertise, Aptitude, and Strategic Remembering

Abstract: Second- and fourth-grade children were classified according to their knowledge of soccer (experts vs. novices) and IQ (high vs. low), and given 2 sort-recall tasks. One task included items related to the game of soccer and the other included items from familiar natural language categories. Previous research has shown that expertise in a subject can compensate for low levels of performance on text comprehension tasks. Our results, the first examining the effects of both expertise and intelligence on a strategic memory task, were that soccer expert children recalled more items on the soccer list but not on the nonsoccer list than soccer novice children. However, soccer expertise did not modify a significant effect of IQ level, with high-IQ children recalling more than low-IQ children for all contrasts. Interest in soccer was found to be related to expertise but did not contribute to differences in memory performance. The results demonstrate that the knowledge base plays an important role in children's memory, but that domain knowledge cannot fully eliminate the effects of IQ on sort-recall tasks using domain-related materials. That is, although rich domain knowledge seemed to compensate for low aptitude, in that low-aptitude experts performed at the level of high-aptitude novices, its effects were not strong enough to eliminate performance differences between high- and low-aptitude soccer experts.