The integration of continuous and discrete latent variable models: potential problems and promising opportunities

Structural equation mixture modeling (SEMM) integrates continuous and discrete latent variable models. Drawing on prior research on the relationships between continuous and discrete latent variable models, the authors identify 3 conditions that may lead to the estimation of spurious latent classes in SEMM: misspecification of the structural model, nonnormal continuous measures, and nonlinear relationships among observed and/or latent variables. When the objective of a SEMM analysis is the identification of latent classes, these conditions should be considered as alternative hypotheses and results should be interpreted cautiously. However, armed with greater knowledge about the estimation of SEMMs in practice, researchers can exploit the flexibility of the model to gain a fuller understanding of the phenomenon under study.     

Potential noradrenergic targets for cognitive enhancement in schizophrenia

Substantial evidence suggests that alterations in noradrenergic function contribute to the cognitive impairments of schizophrenia. Activation of post-junctional alpha 2a-adrenergic receptors in the prefrontal cortex by the alpha 2a-selective agonist guanfacine has demonstrated some preliminary benefit in subjects with schizophrenia treated with atypical antipsychotics. alpha 1-adrenergic receptor activity may be less important in mediating the cognitive impairments of schizophrenia. beta-adrenergic receptors may serve as another potential target for cognitive remediation in schizophrenia. However, the potential increase in memory consolidation in schizophrenia patients produced by beta-adrenergic agonists may be outweighed by the impairment in cognitive flexibility and executive functioning produced by beta-adrenergic agonists. Finally, norepinephrine reuptake inhibitors, such as atomoxetine, hold promise as potential cognitive enhancers in schizophrenia because of their ability to indirectly but selectively increase extracellular dopamine concentrations in the prefrontal cortex.     

Complementary and supplementary fit: a theoretical and empirical integration

Complementary and supplementary fit represent 2 distinct traditions within the person-environment fit paradigm. However, these traditions have progressed in parallel but separate streams. This article articulates the theoretical underpinnings of the 2 traditions, using psychological need fulfillment and value congruence as prototypes of each tradition. Using a sample of 963 adult employees ranging from laborers to executives, the authors test 3 alternative conceptual models that examine the complementary and supplementary traditions. Results show that an integrative model dominates the other two, such that both traditions simultaneously predict outcomes in different ways.     

Nothing compares 2 views: change blindness can occur despite preserved access to the changed information

Change blindness, the failure to detect visual changes that occur during a disruption, has increasingly been used to infer the nature of internal representations. If every change were detected, detailed representations of the world would have to be stored and accessible. However, because many changes are not detected, visual representations might not be complete, and access to them might be limited. Using change detection to infer the completeness of visual representations requires an understanding of the reasons for change blindness. This article provides empirical support for one such reason: change blindness resulting from the failure to compare retained representations of both the pre- and postchange information. Even when unaware of changes, observers still retained information about both the pre- and postchange objects on the same trial.     

Aerobic physical activity effects on psychological well-being in low-income Hispanic children

Psychological well-being has been generally associated with vigorous aerobic activity and structured aerobic activity in adolescents and children. Low-income children are at greater risk than the general population for experiencing high environmental stress and increased mental health problems. This study investigated the effects of a structured physical fitness program on psychological well-being in low-income Hispanic children. A total of 66, 33 girls, 33 boys, in Grade 4 were randomly assigned to either an Aerobic intensity (n = 34) or a Control intensity physical activity program (n = 32) for 6 wk. Psychological well-being was defined as scores on trait anxiety, depression, and self-esteem, measured, respectively, by the Trait Anxiety Inventory, Beck Depression Inventory, and Rosenberg Self-esteem scale. Analysis showed the children in the Aerobic intensity program significantly (p < .05) improved their cardiovascular fitness as measured by the PWC170 test. After the program was over, the children in this Aerobic group reported significantly (p < .05) less depression. The main effect for self-esteem reflected the Aerobic group's greater self-reported self-esteem. No differences were found on trait anxiety. The effects on depression and self-esteem may only be attributed to the cardiovascular improvement given the higher intensity physical activity program because causation was not assessed here.     

Age differences in rereading

Younger and older adults read a series of expository and narrative passages twice in order to answer comprehension questions. Reading time was used to index attentional allocation to word, textbase, and situation model processing and to assess shifts in the allocation policy from the first to the second reading. Older readers' comprehension was at least as good as that of younger readers. Analysis of reading times suggested that for both genres, older adults allocated more attention to situation model features than younger adults did on the first reading, whereas young and old allocated attention similarly to this level of representation on the second reading, suggesting that mature readers may give greater priority to situation model construction when first encountering text. Also, for both genres, older adults showed relatively less facilitation than the young in word-level processing in rereading, suggesting that representation at this level is not as firmly established during reading or decays more quickly for older readers. For narrative texts only, this pattern also obtained for textbase processing. Collectively, these data show that age equivalence in text comprehension at the molar level may be accomplished through different processing routes at the molecular level.     

Conditions affecting the revelation effect for autobiographical memory

In four experiments involving 184 participants, people rated their confidence that particular events had happened in their childhood (e.g., "Broke a window playing ball"). If participants had to unscramble a key word in a phrase just before rating it (e.g., "Broke a nwidwo [window] playing ball"), confidence ratings increased-the revelation effect. However, the pattern of revelation effects depended on the particular way in which participants processed key words (e.g., visualizing vs. counting vowels in the word window) approximately 10 min prior to rating life events that contained those words. Prior exposure to key words never in itself directly affected confidence ratings. These results demonstrate that one can manipulate the revelation effect by altering the processing that participants perform on words prior to unscrambling them. These results also pose difficulties for many accounts of the revelation effect. The major puzzle posed by our present findings is that unscrambling key words increases confidence that an event has happened in childhood, whereas prior exposure to these words does not.     

Learning and production of movement sequences: behavioral, neurophysiological, and modeling perspectives

A wave of recent behavioral studies has generated a new wealth of parametric observations about serial order behavior. What was a trickle of neurophysiological studies has grown to a steady stream of probes of neural sites and mechanisms underlying sequential behavior. Moreover, simulation models of serial behavior generation have begun to open a channel to link cellular dynamics with cognitive and behavioral dynamics. Here we review major results from prominent sequence learning and performance tasks, namely immediate serial recall, typing, 2 x N, discrete sequence production, and serial reaction time. These tasks populate a continuum from higher to lower degrees of internal control of sequential organization and probe important contemporary issues such as the nature of working-memory representations for sequential behavior, and the development and role of chunks in hierarchical control. The main movement classes reviewed are speech and keypressing, both involving small amplitude movements amenable to parametric study. A synopsis of serial order models, vis-a-vis major empirical findings leads to a focus on competitive queuing (CQ) models. Recently, the many behavioral predictive successes of CQ models have been complemented by successful prediction of distinctively patterned electrophysiological recordings. In lateral prefrontal cortex, parallel activation dynamics of multiple neural ensembles strikingly matches the parallel dynamics predicted by CQ theory. An extended CQ simulation model--the N-STREAMS neural network model--exemplifies ongoing attempts to accommodate a broad range of both behavioral and neurobiological data within a CQ-consistent theory.