From synaptic transmission to cognition: an intermediary role for dendritic spines

Dendritic spines are cytoplasmic protrusions that develop directly or indirectly from the filopodia of neurons. Dendritic spines mediate excitatory neurotransmission and they can isolate the electrical activity generated by synaptic impulses, enabling them to translate excitatory afferent information via several types of plastic changes, including neoformation, disappearance, redistribution and changes in geometric shape. The fine line between normal and abnormal excitatory neurotransmission is mediated by the concerted action of glutamate-mediated stimulation and calcium ion entry into spines. Moreover, within the range of normal excitatory activity, dendritic spines undergo specific plastic changes to regulate different forms of afferent information that are often related to distinct modes of cognition-related electrophysiological stimulation, such as long-term potentiation or long-term depression.     

Conditioned reinforcement: Experimental and theoretical issues

The concept of conditioned reinforcement has received decreased attention in learning textbooks over the past decade, in part because of criticisms of its validity by major behavior theorists and in part because its explanatory function in a variety of different conditioning procedures has become uncertain. Critical data from the major procedures that have been used to investigate the concept (second-order schedules, chain schedules, concurrent chains, observing responses, delay-of-reinforcement procedures) are reviewed, along with the major issues of interpretation. Although the role played by conditioned reinforcement in some procedures remains unresolved, the results taken together leave little doubt that the underlying idea of conditioned value is a critical component of behavior theory that is necessary to explain many different types of data. Other processes (marking, bridging) may also operate to produce effects similar to those of conditioned reinforcement, but these clearly cannot explain the full domain of experimental effects ascribed to conditioned reinforcement and should be regarded as complements to the concept rather than theoretical competitors. Examples of practical and theoretical applications of the concept of conditioned reinforcement are also considered.     

The own-age bias in face recognition: a meta-analytic and theoretical review

A large number of studies have examined the finding that recognition memory for faces of one's own age group is often superior to memory for faces of another age group. We examined this own-age bias (OAB) in the meta-analyses reported. These data showed that hits were reliably greater for same-age relative to other-age faces (g = 0.23) and that false alarms were reliably less likely for same-age compared with other-age faces (g = -0.23). Further meta-analyses of measures of signal detection demonstrated that, although no difference in response criterion was evident (g = -0.01), discriminability was reliably better for same-age compared with other-age faces (g = 0.37). As well, children, younger adults, and older adults exhibited superior discriminability for same-age compared with other-age age faces. Thus, the OAB appears to be a robust effect that influences the accuracy of face recognition. Theoretical accounts of the OAB have generally suggested that it reflects more extensive, recent experiences with one's own age group relative to other-age groups. Additional analyses were supportive of this account as the OAB was present even for groups (e.g., older adults) that had prior experiences as members of another age group. However, the most comprehensive account of the OAB will also likely invoke mechanisms suggested by social-cognitive theories.     

Forgiveness: a review of the theoretical and empirical literature

This paper reviews the published literature addressing forgiveness as a therapeutic issue. The review revealed four major themes. These included: diverse attempts in the literature to define forgiveness; the presentation of models of intervention; resistance among theoreticians and therapists to examine forgiveness as a therapeutic construct, and empirical evidence of forgiveness intervention applied to clinical settings. These theoretical and empirical publications are described and critiqued. An evaluation is made as to the current state of the research, and suggestions for future directions.     

The nature of procrastination: a meta-analytic and theoretical review of quintessential self-regulatory failure

Procrastination is a prevalent and pernicious form of self-regulatory failure that is not entirely understood. Hence, the relevant conceptual, theoretical, and empirical work is reviewed, drawing upon correlational, experimental, and qualitative findings. A meta-analysis of procrastination's possible causes and effects, based on 691 correlations, reveals that neuroticism, rebelliousness, and sensation seeking show only a weak connection. Strong and consistent predictors of procrastination were task aversiveness, task delay, self-efficacy, and impulsiveness, as well as conscientiousness and its facets of self-control, distractibility, organization, and achievement motivation. These effects prove consistent with temporal motivation theory, an integrative hybrid of expectancy theory and hyperbolic discounting. Continued research into procrastination should not be delayed, especially because its prevalence appears to be growing.     

Pharmacological interventions in autism: theoretical and practical issues

Focused on issues of drug treatment in relation to autism. Pharmacological treatment studies in autism are complicated by various factors including a tremendous range of syndrome expression, a lack of robust animal models of the disorder, and various methodological problems. Theories have tended to follow treatments, and various neurochemical systems have been the focus of study. Neurochemical systems potentially implicated include those involving dopamine, norepinephrine, serotonin, and neuropeptides. The dopaminergic system has been the most extensively studied. Treatments developed are effective relative to certain disabling symptoms but "core" problems (e.g., in social relatedness and communication) appear less responsive to medications. The development of new approaches to assessment, including integration of behavioral and pharmacological approaches, is an important research priority.     

Morphological changes in dendritic spines of Purkinje cells associated with motor learning

Experience-dependent changes of spine structure and number may contribute to long-term memory storage. Although several studies demonstrated structural spine plasticity following associative learning, there is limited evidence associating motor learning with alteration of spine morphology. Here, we investigated this issue in the cerebellar Purkinje cells using high voltage electron microscopy (HVEM). Adult rats were trained in an obstacle course, demanding significant motor coordination to complete. Control animals either traversed an obstacle-free runway or remained sedentary. Quantitative analysis of spine morphology showed that the density and length of dendritic spines along the distal dendrites of Purkinje cells were significantly increased in the rats that learned complex motor skills compared to active or inactive controls. Classification of spines into shape categories indicated that the increased spine density and length after motor learning was mainly attributable to an increase in thin spines. These findings suggest that motor learning induces structural spine plasticity in the cerebellar Purkinje neurons, which may play a crucial role in acquiring complex motor skills.     

The cognitive and neurological basis of developmental dyslexia: a theoretical framework and review.

It is argued that developmental dyslexics have difficulty in accessing the meaning of written words via phonological recoding, although they can successfully access meaning by a direct visual route. This difficulty with phonological recording is explained in terms of a short-term memory deficit. It is suggested that developmental dyslexia is a genetically-based dysfunction of the inferior parietal lobule and evidence is reviewed that this region is important in both reading and short-term memory. Implications for remedial instruction are discussed.     

Nonshared environment: a theoretical, methodological, and quantitative review

When genetic similarity is controlled, siblings often appear no more alike than individuals selected at random from the population. Since R. Plomin and D. Daniels' seminal 1987 review, it has become widely accepted that the source of this dissimilarity is a variance component called nonshared environment. The authors review the conceptual foundations of nonshared environment, with emphasis on distinctions between components of environmental variance and causal properties of environmental events and between the effective and objective aspects of the environment. A statistical model of shared and nonshared environmental variables is developed. A quantitative review shows that measured nonshared environmental variables do not account for a substantial portion of the nonshared variability posited by biometric studies of behavior. Other explanations of the preponderance of nonshared environmental variability are suggested.     

Lexical ambiguity resolution across languages: a theoretical and empirical review

Words that involve completely different meanings across languages but possess significant overlap in form are referred to as homographic noncognates or interlexical homographs (e.g., red is a color word in English but means "net" in Spanish). An important question in the investigation of the processing of these words is whether or not both meaning and form are integral to their representation leading to language-specific processing of these items. In contrast, some theories have been put forth indicating that the processing of these words is nonselective with regards to language. Simply stated, when one of these words is encountered, all of the relevant meanings are accessed regardless of the specific demands of the task and the base language that is being used. In the present, critical review, evidence purported to favor each view is presented along with a discussion of the methodological and analytic constraints that moderate the reported findings. The data lead to the conclusion that there is a time course involved in the activation of multiple meanings such that a primary or dominant meaning (sometimes biased by frequency) is typically accessed more readily, followed by the opposite language meaning. These results indicated that studies should focus on manipulating the timing intervals between the presentation of these words and subsequent responses that are required by a particular task.     

The question-behaviour effect: A theoretical and methodological review and meta-analysis

Research has demonstrated that asking people questions about a behaviour can lead to behaviour change. Despite many, varied studies in different domains, it is only recently that this phenomenon has been studied under the umbrella term of the question-behaviour effect (QBE) and moderators of the effect have been investigated. With a particular focus on our own contributions, this article: (1) provides an overview of QBE research; (2) reviews and offers new evidence concerning three theoretical accounts of the QBE (behavioural simulation and processing fluency; attitude accessibility; cognitive dissonance); (3) reports a new meta-analysis of QBE studies (k = 66, reporting 94 tests) focusing on methodological moderators. The findings of this meta-analysis support a small significant effect of the QBE (g = 0.14, 95% CI = 0.11, 0.18, p < .001) with smaller effect sizes observed in more carefully controlled studies that exhibit less risk of bias and (4) also considers directions for future research on the QBE, especially studies that use designs with low risk of bias and consider desirable and undesirable behaviour separately.     

Intelligence and leadership: a quantitative review and test of theoretical propositions

Meta-analysis was used to aggregate results from studies examining the relationship between intelligence and leadership. One hundred fifty-one independent samples in 96 sources met the criteria for inclusion in the meta-analysis. Results indicated that the corrected correlation between intelligence and leadership is.21 (uncorrected for range restriction) and.27 (corrected for range restriction). Perceptual measures of intelligence showed stronger correlations with leadership than did paper-and-pencil measures of intelligence. Intelligence correlated equally well with objective and perceptual measures of leadership. Additionally, the leader's stress level and the leader's directiveness moderated the intelligence-leadership relationship. Overall, results suggest that the relationship between intelligence and leadership is considerably lower than previously thought. The results also provide meta-analytic support for both implicit leadership theory and cognitive resource theory.     

Empathic understanding: a review of the concept and some theoretical considerations

A review of the psychoanalytic literature shows that empathy has always played an important part in the practice of psychoanalysis, but that as a concept it has not been well understood. This confusion and a certain mistrust of empathy that it engenders were traced to an incomplete understanding of the meaning of the term, and to the lack of an affect theory that could explain the communication involved in the empathic process. These problems were examined and suggestions for their resolution were made. A line of affective development that culminated in empathic understanding was proposed. An operational approach to empathy was described and the role of empathy as the basis for and the prelude to psychoanalytic interpretation was discussed.     

The Tower of Babel: Searching for core clinical,theoretical and ethical issues in psychotherapy

This paper is about how different groups of therapists view the others now that UKSPC has voted to initiate a register and 1992 is here. Therapy has a set of common aims and these link all therapies together. This paper tries to draw fundamental conclusions for practitioners and trainees. It is a first step in the author's investigations of the frame or field of psychotherapy, which holds both clients and psychotherapists. Mental health practitioners are joined together by a common bond of having the same type of vocation: to help those who are in emotional pain. It is posited that what happens in one part of the field of mental health care affects all other parts of the field.     

The significance of occupations in work careers: An empirical and theoretical review

The central position of occupations in work careers has been a widely accepted position in the study of careers. Furthermore, it has also been commonly believed that most work careers follow the temporal sequence of occupational choice, occupational preparation and training, and occupational entry and retention. An analysis of research findings, however, shows that most individuals do not make stable occupational choices as the first step in their work careers, nor do they show a strong commitment to a particular occupation during their work careers. On the contrary, occupational mobility is far more characteristic of most work careers than occupational stability. One possible explanation of the high rates of occupational mobility is that individuals are responding to opportunities that develop during the course of their careers. As opportunities unfold during work careers, individuals use those opportunities to make future career and occupational choices. Thus, careers may be more accurately considered as a series of responses to a succession of opportunity situations than the effort to realize a predetermined occupational goal.     

Stimulant effects in attention deficit hyperactivity disorder: theoretical and empirical issues

The explanatory utility of a theory or model of ADHD or any disorder depends fundamentally on its capacity to address issues of causality. What causes a particular child to develop ADHD? What mechanisms are responsible for temporal and setting-related variations in symptom severity, and how are these mechanisms affected by pharmacological intervention? And, what processes determine whether gains in one domain will propagate across one or more others? It should be evident from the foregoing discussion that comprehensive answers to such questions are most likely to emerge through implementation of research strategies that (a) integrate biological and psychological levels of explanation, (b) permit analysis of causal hypotheses, and (c) address mechanisms involved in both etiology and mediation of treatment response. Although extant neurobiological studies of ADHD are as compelling as they are exciting, they are limited by a troubling reductionistic emphasis. The predominant animal models focus on a narrow range of behaviors that are presumed to be central to ADHD because of the topographic similarity they bear to those represented by the diagnostic criteria incorporated into the diagnostic nomenclature. These models would become increasingly valuable to the extent that future research examined the extent to which ecologically relevant behaviors (e.g., social behavior) are compromised in the animal strains and whether the observed compromises are parallel to the correlates of ADHD observed in humans. Similarly, human molecular genetic studies have provided a glimpse into the possible role that genes related to dopaminergic neurotransmission may play in the etiology of ADHD. Yet, the features of ADHD have been conceptualized in these investigations as a unitary collection of characteristics, and this has precluded analysis of what specific syndromal feature (if any single one) is affected by the implicated genes. It is intriguing to speculate whether varying combinations of genes governing properties of DA receptors and reuptake molecules are associated with different patterns of symptom severity or responses to stimulant medications. As testing procedures for determining genotypes with respect to these features become more affordable and available, it should become increasingly feasible to examine such issues empirically. Research on the utility of stimulant drugs as a treatment for ADHD also has yielded useful information. Although the effects of MPH are of short duration, the breadth of their impact is impressive. The clinical effectiveness of these medications is no longer in doubt, and patterns of relations among outcome measures represent a potentially fruitful target of scientific inquiry. Finally, data supporting a neurobiological substrate for ADHD, evidence indicating that task and setting variables moderate the expression of the syndrome's diagnostic features (see Barkley, 1998, for a review), and the causal emphasis of the conceptual model with which the discussion began collectively argue for a diathesis-stress conception of the syndrome. And, as foregoing comments make clear, task and setting variables and the mechanisms through which they influence symptom expression are as important to the phenomenon as are neurobiological predisposing causes. This has significant implications for assessment strategies employed in diagnosis and evaluation of treatment-outcome. Specifically, it suggests that theory-based experimental manipulations of task and setting variables designed to impose challenge on hypothesized core features of the disorder are more likely to yield insights into the causal mechanisms governing behavioral organization in affected children than strategies emphasizing static identification of diagnostic correlates. It is hoped that such an approach will accelerate the discovery of increasingly effective assessment and intervention strategies.     

Personality,epistemology and psychotherapists' choice of theoretical model: a review and analysis

This article reviews a body of research, empirical and speculative, describing variables thought to determine a psychotherapist's choice of theoretical orientation. The review finds two types of variables (1) the influences of training, colleagues, supervisors, initial clinical experience and (2) the effects of personality traits and epistemological values, beliefs and philosophy. The weight of evidence from the reviewed studies of cognitive behavioural/behavioural and psychodynamic psychotherapists, and an analysis of the data, suggests that personality and epistemic traits are significantly involved in orientation choice. This has implications for training, practitioner and client outcome satisfaction, and understanding the poor communication that exists between these two major orientations.