Development and maintenance of choice in a dynamic environment

Four pigeons were exposed to a concurrent procedure similar to that used by Davison, Baum, and colleagues (e.g., Davison & Baum, 2000, 2006) in which seven components were arranged in a mixed schedule, and each programmed a different left∶right reinforcer ratio (1∶27, 1∶9, 1∶3, 1∶1, 3∶1, 9∶1, 27∶1). Components within each session were presented randomly, lasted for 10 reinforcers each, and were separated by 10-s blackouts. These conditions were in effect for 100 sessions. When data were aggregated over Sessions 16-50, the present results were similar to those reported by Davison, Baum, and colleagues: (a) preference adjusted rapidly (i.e., sensitivity to reinforcement increased) within components; (b) preference for a given alternative increased with successive reinforcers delivered via that alternative (continuations), but was substantially attenuated following a reinforcer on the other alternative (a discontinuation); and (c) food deliveries produced preference pulses (immediate, local, increases in preference for the just-reinforced alternative). The same analyses were conducted across 10-session blocks for Sessions 1-100. In general, the basic structure of choice revealed by analyses of data from Sessions 16-50 was preserved at a smaller level of aggregation (10 sessions), and it developed rapidly (within the first 10 sessions). Some characteristics of choice, however, changed systematically across sessions. For example, effects of successive reinforcers within a component tended to increase across sessions, as did the magnitude and length of the preference pulses. Thus, models of choice under these conditions may need to take into account variations in behavior allocation that are not captured completely when data are aggregated over large numbers of sessions.     

THE DYNAMICS OF THE LAW OF EFFECT: A COMPARISON OF MODELS

Dynamical models based on three steady‐state equations for the law of effect were constructed under the assumption that behavior changes in proportion to the difference between current behavior and the equilibrium implied by current reinforcer rates. A comparison of dynamical models showed that a model based on Navakatikyan's (2007) two‐component functions law‐of‐effect equations performed better than models based on Herrnstein's (1970) and Davison and Hunter's (1976) equations. Navakatikyan's model successfully described the behavioral dynamics in schedules with negative‐slope feedback functions, concurrent variable‐ratio schedules, Vaughan's (1981) melioration experiment, and experiments that arranged equal, and constant‐ratio unequal, local reinforcer rates.     

Measures of dynamic stability: Detecting differences between walking overground and on a compliant surface

Numerous measures of dynamic stability have been proposed to gauge fall risk in the elderly, including stride interval variability and variability of the center of mass. However, these measures have been deemed inadequate because they do not take into account temporal information. Therefore, research on the measurement of dynamic stability has turned to other analysis methods such as stride interval dynamics and the maximum Lyapunov exponent. Stride interval dynamics reflect the statistical persistence of an individual’s stride interval time series and the Lyapunov exponent quantifies local dynamic stability – the sensitivity of the system to infinitesimal perturbations. In this study, we compare the ability of these measurement tools to detect changes between overground and compliant-surface walking, a condition known to affect stability, to determine their aptness as measures of dynamic stability. Fourteen able-bodied participants completed three 15 min walks, two overground and one on a compliant surface. Our results show that the Lyapunov exponent may be more sensitive to gait changes than stride interval dynamics and gait variability measures.     

The effects of perpetrator age and abuse disclosure on the relationship between feelings provoked by child sexual abuse and posttraumatic stress

Abstract

The present study examined the relationship between feelings provoked by child sexual abuse (CSA) and posttraumatic stress disorder (PTSD) symptom scores in a sample of 163 female survivors of CSA. Finkelhor and Browne's traumagenic dynamics model was applied. The interactive effects of provoked feelings with perpetrator age and the existence of abuse disclosure were also studied. Results showed an overall relationship between feelings provoked by CSA and PTSD symptom scores. Feelings of stigma, betrayal, and powerlessness as a result of CSA were associated with PTSD symptom score when the entire group of CSA victims was analyzed. The role of traumatic sexualization was relevant only when analyzed in interaction with the age of the perpetrator and disclosure. The relationship between traumatic sexualization and PTSD symptom scores was only significant when the abuse was committed by an adult perpetrator and when a disclosure was made during the time of abuse, or a short time after the abuse had occurred.     

Comparison and Contrast Between Belief System Theory and Cognitive Theory

This article contrasts how belief system theory and specific cognitive theories view the process of stability and change in the human organism, comparing the writings of major theorists in the fields of psychology and sociology. With a focus on cognitive structure, and particularly the relation of such structure to the emotional disorders, each theory is presented along with coinciding techniques for behavior change. The theories are compared and it is clear that similarities far outweigh differences; both could grow through an integration of thinking and focus.     

Trauma and the transference‐countertransference: working with the bad object and the wounded self

This paper focuses on the transference‐countertransference dynamics that manifest in work with those individuals who experienced severe early relational trauma and, in particular, childhood sexual abuse. The literature is surveyed from Davies and Frawley's (1992a) seminal paper through to more current trauma‐related and sensorimotor approaches, which deepen our understanding greatly. The rapidly shifting, powerful, conflicting and kaleidoscopic transference‐countertransference dynamics are explored in the light of these views and in relation to a lengthy clinical example. The author elucidates the dual‐aspect of the traumatic complex, whereby the abuser figure, which is disavowed by the patient, becomes manifest in prosecuting the analyst for the ‘wounds’ that the analysis evokes. The paper also explores the particular nature of the splitting processes, whereby pressure is put on the analyst to adopt an idealized role, in particular to act as a self‐object, in order to enable the patient to safely express and ‘be’ themselves in an attempt to make up for what was not possible in childhood; the analyst will necessarily fail in this task. In the context of powerful masochisto‐sadistic dynamics, the analyst's masochism is likely to be called up in the spirit of caring ‘humanity’ (another inevitable enactment), which can impede the progress of the analysis if not addressed. The extreme woundedness, intense affect and moral outrage associated with these dynamics are characteristic and compelling. Issues relating to disclosure, enactment and analytic attitude are also discussed.     

Development of Force Adaptation During Childhood

Humans learn to make reaching movements in novel dynamic environments by acquiring an internal motor model of their limb dynamics. Here, the authors investigated how 4- to 11-year-old children (N = 39) and adults (N = 7) adapted to changes in arm dynamics, and they examined whether those data support the view that the human brain acquires inverse dynamics models (IDM) during development. While external damping forces were applied, the children learned to perform goal-directed forearm flexion movements. After changes in damping, all children showed kinematic aftereffects indicative of a neural controller that still attempted to compensate the no longer existing damping force. With increasing age, the number of trials toward complete adaptation decreased. When damping was present, forearm paths were most perturbed and most variable in the youngest children but were improved in the older children. The findings indicate that the neural representations of limb dynamics are less precise in children and less stable in time than those of adults. Such controller instability might be a primary cause of the high kinematic variability observed in many motor tasks during childhood. Finally, the young children were not able to update those models at the same rate as the older children, who, in turn, adapted more slowly than adults. In conclusion, the ability to adapt to unknown forces is a developmental achievement. The present results are consistent with the view that the acquisition and modification of internal models of the limb dynamics form the basis of that adaptive process.     

Strength Recovery Patterns Following Isometric and Isotonic Exercise

In 3 experiments, the author tested the hypothesis that coordination dynamics is the content of a generalized motor program (GMP) for rhythmic interlimb coordination. In Experiment 1, learners (N = 14) practiced a ?90° movement with either identically timed or differently timed limbs. Both acquisition and transfer to novel (effector and pattern) timings were unaffected by the learning condition and were suggestive of the intrinsic dynamics for in-phase and antiphase. In Experiment 2, learners' (N = 13) acquisition of 2 different phase relations (?90° and ?45°) was qualitatively identical. Attractor reconstruction revealed an increase in the predictability of individual movement trajectories and a decrease in attractor dimensionality over learning. Transfer for both ?90° and ?45° was again suggestive of the intrinsic dynamics. In Experiment 3, learning altered participants' (N = 8) performance of in-phase and antiphase relations. Together, the results suggested a single continuum of phase relations, called an attractor landscape, that produces similar patterns of CE and VE for both previously stable and learned coordinations.     

Influence of Response Similarity on Interference in Perceptual Motor Learning

Motor interference was measured in terms of average response time in sorting 15 pairs of cards, each pair containing words which were either unrelated or identical but printed in different colors. The two words of each pair were used in labeling two cubicles in such a way that they were apart by 0, 1, 2, or 3 intervening cubicles in quasirandomly chosen directions. Interference was inversely related to response similarity, but this relationship may not appear in the absence of sufficient stimulus similarity. The findings are interpreted in the light of a hypothesis which views motor interference as a tendency for responses to deflect from their own courses and be pulled towards those of other responses with which they are at conflict.