Synaptic plasticity in the hypoglossal nucleus of female canaries: structural correlates of season, hemisphere, and testosterone treatment

The caudal portion of the hypoglossal nucleus (nXIIts) contains the motor neurons that control the syrinx in songbirds. In canaries, song occurs seasonally, is principally produced by males, and appears to be produced predominantly by muscles on the left side of the syrinx. The present study measures the effect of seasonal change and manipulation of testosterone levels on synapse number and morphology in nXIIts in adult female canaries. We find that synapse density is lower in testosterone-treated birds than in control birds and lower in fall than in spring. The number of vesicles per presynaptic profile increases in the spring as a result of a general increase in this measure in all synapses. The number of vesicles per presynaptic profile also increases with testosterone treatment, primarily due to an increase in the proportion of synapses associated with unusually high vesicle counts. Together, these changes suggest that large reserves of neurotransmitter may be necessary to sustain singing. Several ultrastructural differences between hemispheres are found. Postsynaptic thickenings are longer, and postsynaptic processes are larger on the left side than on the right side. In the spring, there are more vesicles per synapse on the left than on the right, but this lateralization is reversed in the fall. Thus, lateralization of song production is associated with lateral asymmetries in synapse morphology. These hemispheric differences are relatively small, like those seen at the light microscope level, encouraging further consideration of peripheral as well as CNS sources of functional lateralization. The seasonal and testosterone-induced changes in synapse number and morphology may be components of the periodic reorganization of canary vocalization.     

Visual gap and offset discrimination and its relation to categorical identification in brief line-element displays

Visual processing was investigated in judgments of relative line position. Stimulus continua were generated by bisecting a straight line and displacing the segments. Experiment 1 measured discrimination of pairs of longitudinally displaced segments at equal steps along the continuum. At long (2 s) durations discrimination fell smoothly, but at short (100 ms) durations it was sharp-peaked. In Experiment 2 the short-duration stimuli were labeled with subsets of the labels no gap, just a gap, and more than just a gap. Theoretical discrimination performances were computed and the one based on no gap and just a gap closely fitted observed performance. Experiments 3 and 4 were similar to 1 and 2, with lateral replacing longitudinal displacement. Similar "categorical" performance was obtained. It was concluded that there are discrete mechanisms for early detection of relative line position and that 2 labels can be used to characterize performance in each direction.     

The effect of response bias on recall performance, with some observations on processing bias

We explored Roediger and Payne's proposal that response bias does not affect recall performance and that it is therefore not necessary to control for response productivity in recall studies. Two initial experiments, contrary to expectation, corroborated Roediger and Payne's findings: Forced recall did not produce more correct recalls than free recall, even though forced recall produced substantially more false alarms than did free recall. However, in succeeding experiments involving pictorial and verbal stimuli, reliable response-bias effects on recall were demonstrated. The stimuli yielding response-bias effects were those associated with higher probabilities of being guessed by chance. In addition, some of the data suggest that processing-bias effects (differential retrieval effort) may be unintentionally induced by instructions and may significantly affect recall memory. Consequently, it is necessary to assess or to control response-bias effects and, possibly, processing-bias effects in recall experiments in which level of recall is of interest.     

Varieties of size-specific visual selection

Compared time to evaluate stimuli of varying sizes. When Ss expect an upcoming stimulus to be a certain size, response time increases with the disparity between expected and actual size. There are, however, 2 size adjustment processes, and they reflect 2 types of visual selection. In the first, a shape-specific image representation is used to separate a visual object from a superimposed distractor. These representations require the type of slow size scaling demonstrated in imagery experiments. The second size scaling process is faster and not shape-specific. At any given time the visual system is set to process information at a particular scale, and that scale can be adjusted to match an object's size. Because both selection mechanisms depend on size, they probably occur at a relatively low, spatially organized processing level. These findings lead to a new explanation for results that had been taken as evidence for attentional selection at the level of object representations.     

Characteristics of Alcoholism Among Catholic Sisters: Results of a National Survey

In this article the author reports results from a national survey of recovering alcoholic Catholic Sisters, describing their addiction history, treatment, and the role of the community.     

KIRKPATRICK'S LEVELS OF TRAINING CRITERIA: THIRTY YEARS LATER

Kirkpatrick's model (1959a, 1959b, 1960a, 1960b) of training evaluation criteria has had widespread and enduring popularity. This model proposed four "levels" of training evaluation criteria: reactions, learning, behavior, and results. Three problematic assumptions of the model may be identified: (1) The levels are arranged in ascending order of information provided. (2) The levels are causally linked. (3) The levels are positively intercorrelated. This article examines the validity of these assumptions, the frequency of each level in published evaluation studies, correlations from the literature in regard to Assumptions 2 and 3, and implications for the researcher and training manager.     

A FIELD STUDY OF THE RELATIONSHIP BETWEEN THE ORGANIZATIONAL FEEDBACK ENVIRONMENT AND PERFORMANCE

This field study used the Job Feedback Survey (Herold & Parsons, 1985) and performance data gathered from multiple sources to examine the relationship between the perceived organizational feedback environment and performance. Regression analyses indicated that, while holding the other feedback variables constant, feedback from supervisory and organizational sources was related to reported job performance while feedback from peers and self was not. Most of the unique variance in performance explained by feedback was also accounted for by feedback from organizational and supervisory sources. Negative expressions from organizational/supervisory sources (e.g., the supervisor expressing anger, the company communicating dissatisfaction with poor performance) were related to lower performance, and positive job changes initiated by these sources (e.g., increasing responsibility, assignment to special jobs) were related to higher performance. Higher performers did not receive more feedback than lower performers but did receive more total positive feedback. Supplemental issues, possible explanations, and implications of the findings are discussed.     

RECONSIDERING THE EMPLOYMENT INTERVIEW: A REVIEW OF RECENT LITERATURE AND SUGGESTIONS FOR FUTURE RESEARCH

Literature since the last comprehensive review of research on the employment interview is summarized, and suggestions for future studies in this area are described. Major changes in findings regarding the validity of the interview, the impact of applicant sex, and the effect of interviewer characteristics/behavior on applicant reactions, as well as other issues, are reported. Contrary to the widely held belief that the interview has low validity, recent research indicates at least modest validity for this selection tool. Conversely, the effect of the campus interview on applicant reactions has been seriously questioned. Researchers are urged to examine several areas in social psychology, including the literature on attitudes-intentions-behavior, the elaboration likelihood model, and theories of discrimination to achieve greater understanding of the employment interview.     

Hemispheric preference and progressive-part or whole practice in beginning typewriting

This investigation explored the interaction of progressive-part versus whole methods of practice with hemispheric preference for processing information and the impact of each upon high school students' speed and accuracy in beginning typewriting. Zenhausern's Differential Hemispheric Activation Test was scored in such a way that it was possible to plot the scores along a continuum. Analysis of variance gave significant F ratios on 3 of the 4 testing days. The continuous scores were divided into five categories: middle, left moderates, right moderates, extreme rights, and extreme lefts. The moderate-left group speed was consistently the fastest group, and the extreme rights were consistently the slowest group. This difference was significant for all four testing days with the moderate-left mean speed varying between 4 to 6 words per minute faster each testing day. The extreme rights were consistently the most accurate, even though not statistically significantly so. There was no significant difference between method of practice and typewriting speed or between method of practice and typewriting accuracy; however, on all four testing days the mean gross speed of the whole practice learning group was 0.73 to 0.99 words per minute faster than the progressive-part group. A two-way analysis of variance indicated no interaction between method or practice and hemispheric preference.