Variation, repetition, and choice

Experiment 1 investigated the controlling properties of variability contingencies on choice between repeated and variable responding. Pigeons were exposed to concurrent-chains schedules with two alternatives. In the REPEAT alternative, reinforcers in the terminal link depended on a single sequence of four responses. In the VARY alternative, a response sequence in the terminal link was reinforced only if it differed from the n previous sequences (lag criterion). The REPEAT contingency generated low, constant levels of sequence variation whereas the VARY contingency produced levels of sequence variation that increased with the lag criterion. Preference for the REPEAT alternative tended to increase directly with the degree of variation required for reinforcement. Experiment 2 examined the potential confounding effects in Experiment 1 of immediacy of reinforcement by yoking the interreinforcer intervals in the REPEAT alternative to those in the VARY alternative. Again, preference for REPEAT was a function of the lag criterion. Choice between varying and repeating behavior is discussed with respect to obtained behavioral variability, probability of reinforcement, delay of reinforcement, and switching within a sequence.     

Both sides get the point: Hemispheric sensitivities to sentential constraint

Behavioral studies have consistently reported striking differences in the impact of sentence-level information on the processing of words presented in the right (RVF) versus the left (LVF) visual field, with context effects apparent only for RVF items. The consistent lack of such effects in the LVF has been taken to mean that right hemisphere language comprehension is largely insensitive to message-level meaning. We used the functional specificity afforded by event-related potential measures to assess this claim. Target words completing strongly and weakly constraining sentence contexts, in which constraint arose at the sentence level rather than from lexical associations, were presented laterally in the LVF or RVF. Increased constraint significantly reduced N400 amplitudes with presentation in both VFs, with no differences in the timing or amplitude of these effects. These results are inconsistent with the view that the VF asymmetries found in behavioral measures reflect differential hemispheric capacities at the level of semantic analysis and integration, although VF-based differences on earlier components (P2) suggest asymmetries in the impact of sentential context on perceptual aspects of word processing in the two hemispheres.     

Changes in the neuropsychological correlates of clinical dimensions between the acute and stable phase of schizophrenia

This study was designed to investigate whether the neuropsychological correlates of the symptom dimensions of schizophrenia vary with the clinical state in patients followed from the acute to stable the phase of the illness. Fifteen patients were assessed for symptoms (SAPS-SANS) and undergone a complete neuropsychological assessment at two sessions. The first session (S1) was carried out within six days after admission, i.e., acute phase and the second (S2) at least two month after hospitalization, i.e., stable phase. The data were analyzed using stepwise regression models in which neuropsychological scores were in entered to predict each dimensional score. This analysis was applied on the S1 and S2 data as well as on the S2-S1 difference to assess the neuropsychological predictors of clinical changes. Generally, the results replicate the previous associations between neuropsychological and dimensional measures found in stable patients. In addition, this study shows if each dimension appears to rely on a key structure, symptom variations seems to involve changes in the spread of the dysfunction and/or changes in the connectivity between the key and other regions. The results also suggest that functional changes related to some symptoms dimensions occur to compensate for the dysfunction associated with other symptoms.     

A study of 60- to 89-mo.-old children's skill at writing numerals

The skill of writing numerals necessitates a certain developmental maturity. Studying the age at which children start to develop this skill and assessing problems they encounter while writing numerals should give direction to their training. From 8 schools a total of 267 children, ages 60 to 89 mo., were asked to write the numerals 1 to 9. Analysis showed that 80% of the children wrote most of the numerals correctly, 15% wrote inverted numerals, 2.0% wrote some numerals as letters, and 4% did not write certain numerals at all. In addition, 64% of children ages 60 to 65 mo. gave correct responses, and the perception of correct responses increased across age groups until 95% were correct in the group who were 84 to 89 mo. There was no significant difference between girls and boys in these writing skills.     

Evaluating research institutions: Lessons from the CGIAR

Investing in research is a long-term, risky proposition. In agriculture, it could take fifteen years or more for a research finding to show an improvement in a farmer’s field. Yet, research institutions, like other organizations it needs to be evaluated. For more than twenty years, independent panels of outside experts have evaluated each of the international research centers that the Consultative Group of International Agricultural Research (CGIAR) supports. This paper examines the evolution of this review system, outlines the key methodological challenges faced, and draws lessons for others engaged in evaluating research institutions. It notes that the scope of the CGIAR reviews have been broadened over time in response to users’ concerns. Reviews now cover four dimensions of performance: research results, quality and relevance of research, vision and strategic directions, and management efficiency. The methodological challenges faced in measurement, valuation, and attribution are reviewed, along with practices found to be helpful in addressing these concerns. The paper concludes that the panel approach to institutional evaluation has served CGIAR’s needs well, and recommends it as an evaluation technique for integrating quantitative and qualitative dimensions of institutional performance. His recent work has concentrated on the governance and management of the CGIAR and the individual research centers it supports, including questions of evaluating management effectiveness. Prior to joining the World Bank in 1979, he was Assistant Professor of Political Science at Bogazici University (Istanbul) and Senior Research Director of Systems Research Incorporated (Lansing, Michigan).     

Effects of the Novel Acetylcholinesterase InhibitorN-Octyl-1,2,3,4-tetrahydro-9-aminoacridine on Locomotor Activity and Avoidance Learning in Mice

The acetylcholinesterase reversible inhibitorN-octyl-1,2,3,4-tetrahydro-9-aminoacridine (THA-C8) is a new synthesized derivative of tacrine (THA) characterized by an alkyl chain in the molecular structure which ameliorates the penetrability of the compound into the central nervous system. THA-C8 (0.1–5 mg/kg) significantly reduced spontaneous locomotor activity in CD1 mice at a dose of 3 mg/kg. Moreover, THA-C8 (0.2–2 mg/kg) significantly improved shuttle-box avoidance acquisition at doses (0.25, 0.3, 1 mg/kg) not affecting locomotion and that are much lower than the doses reported to be effective for THA in animal models. From the data reported it seems that the new compound could be interesting for therapeutic purposes.     

Exocentric pointing in three-dimensional space

A study is reported of an exocentric pointing task in all three dimensions, in near space, with only two visible luminous objects--a pointer and a target. The task of the subject was to aim a pointer at a target. The results clearly show that visual space is not isotropic, since every set direction appeared to consist of two independent components--one in the projection onto a frontoparallel plane (tilt), the other in depth (slant). The tilt component shows a general trend across subjects, an oblique effect, and can be judged monocularly. The slant component is symmetrical in the mid-sagittal plane, requires the use of binocular information, and shows considerable differences between subjects. These differences seem to depend on the amount of binocular information used by each subject. There was a remarkably high level of consistency in the exocentric pointing, despite the absence of environmental cues. The within-subject consistency in the settings of the pointer corresponds to a consistency of about 1 min of arc in disparity of its tip, even though the pointer and target are separated by more than 5 deg.     

Piaget and Vygotsky: Many resemblances,and a crucial difference

Piaget and Vygotsky are two influential developmental psychologists. One can even say that their contributions to developmental psychology, albeit different, are similarly remarkable and unique. This article is in four parts. In the first part, I refer briefly to a commonly noticed difference between Vygotsky’s and Piaget’s theories. In the second part, I show that there are many resemblances between Vygotsky and Piaget. In the third part, I argue that in spite of such resemblances, there exists a crucial, and generally unnoticed, difference between Piaget’s and Vygotsky’s theories, and that this difference underlies the way each author addresses the following issues: 1) the origins of development and the motor of development; 2) the relationships among equal peers vs. those based on authorities, as they are sources of development and learning; 3) the more appropriate methods for studying developmental changes; 4) the importance of the distinction between true vs. necessary knowledge; and 5) the role of transformation and personal reconstruction vs. that of transmission and social influence in the phenomena of development and learning. Finally, I summarize the main ideas and arguments which I elaborate throughout this article, and mention what can be gained when the generally ignored aforementioned difference is noticed.     

Counseling and Mental Health Care in Palestine

The authors provide a brief overview of counseling and mental health care in Palestine, including their history and a summary of their current status. Finally, a discussion is presented of future trends in the development of the profession with regard to recent changes in the region.