Stimulus and reinforcer relativity in multiple schedules: Local and dimensional effects on sensitivity to reinforcement

Pigeons' responses in two successive components of multiple schedules were reinforced according to variable-interval schedules of reinforcement that varied over five different conditions. Within each session of all conditions, line orientations of 0°, 30°, or 45° in Component 1 alternated with orientations of 45°, 60°, or 90° in Component 2. Response rates were recorded in three successive subintervals of each component. Ratios were taken between the response rate in each Component 1 line orientation and the response rate in each Component 2 orientation. These ratios were found to be power functions of the corresponding ratios of obtained reinforcement rates. Sensitivity of response ratios to changes in reinforcer ratios, given by the value of the exponent of the power function, increased systematically with increasing disparity between the dimensional values of orientation stimuli. In addition, sensitivity decreased systematically over successive subintervals of components, that is, with increasing time since component alternation. Dimensional and local (subinterval) effects interacted in that sensitivity increased with stimulus disparity to a far greater extent in the first subinterval than later in components. The data could be described by a combination of rectangular hyperbolae which attributed the interaction between local and dimensional effects to limits set by local effects on the extent that stimulus differences could affect sensitivity.     

Bi-directional relations between behavioral problems and executive function: Assessing the longitudinal development of self-regulation

During childhood, the ability to limit problem behaviors (i.e., externalizing) and the capacity for cognitive regulation (i.e., executive function) are often understood to develop in tandem, and together constitute two major components of self-regulation research. The current study examines bi-directional relations between behavioral problems and executive function over the course of childhood and adolescence. Relying on a diverse sample of children growing up in low-income neighborhoods, we applied a random intercept cross-lagged panel model to longitudinally test associations between behavioral problems and executive function from age 4 through age 16. With this approach, which disaggregated between- and within-child variation, we did not observe significant cross-lagged paths, suggesting that within-child development in one domain did not strongly relate to development in the other. We also observed a moderate correlation between the stable between-child components of behavioral problems and executive function over time in our preferred model, suggesting that these two domains may be relatively distinct when modeled from early childhood through adolescence.     

The mediation component of the hopelessness depression in relation to negative life events

A necessary test of the mediational processes component of the hopelessness theory of depression is to test whether the individuals who have negative attributional style and experience negative life events are likely to make negative attributions for the negative events they confront. The present study, using undergraduate students, find that the negative attributional style do not predict negative attributions subjects made for the negative life events they experience within a period of 3 months. However, subjects' negative attributions for the negative life events coupled with the experience of a high number of negative life events predicted their depressive symptomatology. The depressive symptomatology is found not to be mediated through hopelessness. The findings are discussed in relation to the hopelessness theory of depression.     

Life's little (and big) lessons: identity statuses and meaning-making in the turning point narratives of emerging adults

A longitudinal study examined relations between 2 approaches to identity development: the identity status model and the narrative life story model. Turning point narratives were collected from emerging adults at age 23 years. Identity statuses were collected at several points across adolescence and emerging adulthood, as were measures of generativity and optimism. Narratives were coded for the sophistication of meaning-making reported, the event type in the narrative, and the emotional tone of the narrative. Meaning-making was defined as connecting the turning point to some aspect of or understanding of oneself. Results showed that less sophisticated meaning was associated particularly with the less advanced diffusion and foreclosure statuses, and that more sophisticated meaning was associated with an overall identity maturity index. Meaning was also positively associated with generativity and optimism at age 23, with stories focused on mortality experiences, and with a redemptive story sequence. Meaning was negatively associated with achievement stories. Results are discussed in terms of the similarities and differences in the 2 approaches to identity development and the elaboration of meaning-making as an important component of narrative identity.     

Neuropathology of Rett syndrome

Rett Syndrome is unlike any other pediatric neurologic disease, and its clinical-pathologic correlation can not be defined with standard histology techniques. Based on hypotheses suggested by careful clinical observations, the nervous system of the Rett child has been explored utilizing morphometry, golgi preparations, computerized tomography, magnetic resonance imaging, chemistry, immunocytochemistry, autoradiography, and molecular biologic techniques. From these many perspectives we conclude that Rett syndrome is not a typical degenerative disorder, storage disorder, nor the result of gross malformation, infectious or neoplastic processes. There remain regions of the brain that have not been studied in detail but the available data suggest that the neuropathology of Rett syndrome can be summarized as follows: the Rett brain is small for the age and the height of the patient; it does not become progressively smaller over three to four decades; it has small dendritic trees in pyramidal neurons of layers III and V in selected lobes (frontal, motor, and temporal); it has small neurons with an increased neuronal packing density; it has an immature expression of microtubular protein-2 and cyclooxygenase; it exhibits a changing pattern of neurotransmitter receptors with an apparent reduction in many neurotransmitters, possibly contributing to some symptomatology. A mutation in Mecp2 causes this unique disorder of brain development. Neuronal mosaicism for normal and mutated Mecp2 produces a consistent phenotype in the classic female patient and a small brain with some preserved islands of function, but with an inability to support hand use and speech. This paper summarizes our current observations about neuropathology of Rett syndrome. MRDD Research Reviews 2002;8:72-76.     

Reduction Invariance and Prelec's Weighting Functions

Within the framework of separable utility theory, a condition, called reduction invariance, is shown to be equivalent to the 2-parameter family of weighting functions that Prelec (1998) derived from the condition called compound invariance. Reduction invariance, which is a variant on the reduction of compound gambles, is appreciably simpler and more easily testable than compound invariance, and a simpler proof is provided. Both conditions are generalized leading to more general weighting functions that include, as special cases, the families of functions that Prelec called exponential-power and hyperbolic logarithm and that he derived from two other invariance principles. However, of these various families, only Prelec's compound-invariance family includes, as a special case, the power function, which arises from the simplest probabilistic assumption of reduction of compound gambles. Copyright 2001 Academic Press.     

Variable-ratio versus variable-interval schedules: response rate, resistance to change, and preference

Two experiments asked whether resistance to change depended on variable-ratio as opposed to variable-interval contingencies of reinforcement and the different response rates they establish. In Experiment 1, pigeons were trained on multiple random-ratio random-interval schedules with equated reinforcer rates. Baseline response rates were disrupted by intercomponent food, extinction, and prefeeding. Resistance to change relative to baseline was greater in the interval component, and the difference was correlated with the extent to which baseline response rates were higher in the ratio component. In Experiment 2, pigeons were trained on multiple variable-ratio variable-interval schedules in one half of each session and on concurrent chains in the other half in which the terminal links corresponded to the multiple-schedule components. The schedules were varied over six conditions, including two with equated reinforcer rates. In concurrent chains, preference strongly overmatched the ratio of obtained reinforcer rates. In multiple schedules, relative resistance to response-independent food during intercomponent intervals, extinction, and intercomponent food plus extinction depended on the ratio of obtained reinforcer rates but was less sensitive than was preference. When reinforcer rates were similar, both preference and relative resistance were greater for the variable-interval schedule, and the differences were correlated with the extent to which baseline response rates were higher on the variable-ratio schedule, confirming the results of Experiment 1. These results demonstrate that resistance to change and preference depend in part on response rate as well as obtained reinforcer rate, and challenge the independence of resistance to change and preference with respect to response rate proposed by behavioral momentum theory.     

Parents who report using illicit drugs: findings and implications from the DRUGNET study

In recent years, a national discussion has emerged concerning what parents should tell their children about their own past drug use. DRUGNET is an ongoing, on-line survey of successful, healthy, adults who occasionally use illicit drugs. This paper reviews data from a subset of this survey, namely, those respondents who were parents with self-reported use of at least one illicit drug. The sample (n = 325) was predominantly white men who reported having above average education and household incomes. Their mental health as measured by the General Well-being Schedule was similar to the national norm. Respondents reported using drugs to manage parental stress and expressed concerns over how to communicate with their children and legal risks related to their own drug use. The limitations and the implications of these data are discussed.     

From the interpersonal to the international: understanding commitment to the "war on terror"

Applying constructs from the investment model used traditionally to understand interpersonal commitment, the present investigation seeks to elucidate social cognitive antecedents of commitment to the war on terror waged by the United States. In Study 1, satisfaction with, investments in, and alternatives to the war on terror predict levels of commitment to the war beyond several important control variables. In Study 2, levels of satisfaction with, investments in, and alternatives to the war are experimentally manipulated. The highest levels of commitment to the war are observed among participants exposed to a high satisfaction, high investment, and low alternatives scenario, and the lowest levels are among those exposed to a low satisfaction, low investment, and high alternatives scenario. These results support broadening the targets of commitment normally considered within the context of the investment model and suggest applying relational models to understanding broader societal concerns.