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Pigeons pecked on two response keys that delivered reinforcers on a variable-interval schedule. The proportion of reinforcers delivered by one key was constant for a few sessions and then changed, and subjects' choice responses were recorded during these periods of transition. In Experiment 1, response proportions approached a new asymptote slightly more slowly when the switch in reinforcement proportions was more extreme. In Experiment 2, slightly faster transitions were found with higher overall rates of reinforcement. The results from the first session, after a switch in the reinforcement proportions, were generally consistent with a mathematical model that assumes that the strength of each response is increased by reinforcement and decreased by nonreinforcement. However, neither this model nor other similar models; predicted the `'spontaneous recovery” observed in later sessions: At the start of these sessions, response proportions reverted toward their preswitch levels. Computer simulations could mimic the spontaneous recovery by assuming that subjects store separate representations of response strength for each session, which are averaged at the start of each new session.

In three experiments, pigeons chose between a small amount of food delivered after a short delay and a larger amount delivered after a longer delay. A discrete-trial adjusting-delay procedure was used to estimate indifference points-pairs of delay-amount combinations that were chosen about equally often. In Experiment 1, when additional reinforcers were available during intertrial intervals on a variable-interval schedule, preference for the smaller, more immediate reinforcer increased. Experiment 2 found that this shift in preference occurred partly because the variable-interval schedule started sooner after the smaller, more immediate reinforcer, but there was still a small shift in preference when the durations and temporal locations of the variable-interval schedules were identical for both alternatives. Experiment 3 found greater increases in preference for the smaller, more immediate reinforcer with a variable-interval 15-s schedule than with a variable-interval 90-s schedule. The results were generally consistent with a model that states that the impact of any event that follows a choice response declines according to a hyperbolic function with increasing time since the moment of choice.

Earlier studies have demonstrated a significant relation between scores on the Physical Anhedonia Scale-but not on the Perceptual Aberration Scale-and premorbid social adjustment in schizophrenics (Chapman, Chapman, & Raulin, 1976, 1978; Schuck, Leventhal, Rothstein, & Irizarry, 1984). A similar relation between scores on these 2 scales and interpersonal competence in college students has also been noted (Beckfield, 1985; Haberman, Chapman, Numbers, & McFall, 1979; Numbers & Chapman, 1982). The present study extends this work by examining the relation of premorbid adjustment to scores on these 2 scales among young, nonpsychotic psychiatric inpatients. Consistent with the earlier findings, anhedonic Ss had poorer premorbid social competence when compared with nonanhedonic Ss, whereas no relation was found between scores on perceptual aberration and premorbid social competence.

In a discrete-trials procedure with pigeons, a response on a green key led to a 4-s delay (during which green houselights were lit) and then a reinforcer might or might not be delivered. A response on a red key led to a delay of adjustable duration (during which red houselights were lit) and then a certain reinforcer. The delay was adjusted so as to estimate an indifference point-a duration for which the two alternatives were equally preferred. Once the green key was chosen, a subject had to continue to respond on the green key until a reinforcer was delivered. Each response on the green key, plus the 4-s delay that followed every response, was called one “link” of the green-key schedule. Subjects showed much greater preference for the green key when the number of links before reinforcement was variable (averaging four) than when it was fixed (always exactly four). These findings are consistent with the view that probabilistic reinforcers are analogous to reinforcers delivered after variable delays. When successive links were separated by 4-s or 8-s “interlink intervals” with white houselights, preference for the probabilistic alternative decreased somewhat for 2 subjects but was unaffected for the other 2 subjects. When the interlink intervals had the same green houselights that were present during the 4-s delays, preference for the green key decreased substantially for all subjects. These results provided mixed support for the view that preference for a probabilistic reinforcer is inversely related to the duration of conditioned reinforcers that precede the delivery of food.

Twenty acquisition curves were obtained from each of 8 pigeons in a free-operant choice procedure. Every condition began with a phase in which two response keys had equal probabilities of reinforcement, and, as a result, subjects' responses were divided fairly evenly between the two keys. This was followed by a phase in which one key had a higher probability of reinforcement than the other, and the development of preference was observed. In all but a few cases, response proportions increased for the key with the higher probability of reinforcement. In most conditions, the two probabilities differed by .06, but the actual probabilities varied (from .16 and .10 in one condition to .07 and .01 in another). Development of preference for the key with the higher probability of reinforcement was slower when the ratio of the two reinforcement probabilities was small (.16/.10) than when it was large (.07/.01). This finding is inconsistent with the predictions of several different quantitative models of acquisition, including the kinetic model (Myerson & Miezin, 1980) and the ratio-invariance model (Horner & Staddon, 1987). However, the finding is consistent with a hypothesis based on Weber's law, which states that the two alternatives are more discriminable when the ratio of their reinforcement probabilities is larger, and, as a result, the acquisition of preference is faster.

Two experiments measured pigeons' choices between probabilistic reinforcers and certain but delayed reinforcers. In Experiment 1, a peck on a red key led to a 5-s delay and then a possible reinforcer (with a probability of .2). A peck on a green key led to a certain reinforcer after an adjusting delay. This delay was adjusted over trials so as to estimate an indifference point, or a duration at which the two alternatives were chosen about equally often. In all conditions, red houselights were present during the 5-s delay on reinforced trials with the probabilistic alternative, but the houselight colors on nonreinforced trials differed across conditions. Subjects showed a stronger preference for the probabilistic alternative when the houselights were a different color (white or blue) during the delay on nonreinforced trials than when they were red on both reinforced and nonreinforced trials. These results supported the hypothesis that the value or effectiveness of a probabilistic reinforcer is inversely related to the cumulative time per reinforcer spent in the presence of stimuli associated with the probabilistic alternative. Experiment 2 tested some quantitative versions of this hypothesis by varying the delay for the probabilistic alternative (either 0 s or 2 s) and the probability of reinforcement (from .1 to 1.0). The results were best described by an equation that took into account both the cumulative durations of stimuli associated with the probabilistic reinforcer and the variability in these durations from one reinforcer to the next.

Ten acquisition curves were obtained from each of 4 pigeons in a two‐choice discrete‐trial procedure. In each of these 10 conditions, the two response keys initially had equal probabilities of reinforcement, and subjects' choice responses were about equally divided between the two keys. Then the reinforcement probabilities were changed so that one key had a higher probability of reinforcement (the left key in half of the conditions and the right key in the other half), and in nearly every case the subjects developed a preference for this key. The rate of acquisition of preference for this key was faster when the ratio of the two reinforcement probabilities was higher. For instance, acquisition of preference was faster in conditions with reinforcement probabilities of .12 and .02 than in conditions with reinforcement probabilities of .40 and .30, even though the pairs of probabilities differed by .10 in both cases. These results were used to evaluate the predictions of some theories of transitional behavior in choice situations. A trial‐by‐trial analysis of individual responses and reinforcers suggested that reinforcement had both short‐term and long‐term effects on choice. The short‐term effect was an increased probability of returning to the same key on the one or two trials following a reinforcer. The long‐term effect was a gradual increase in the proportion of responses on the key with the higher probability of reinforcement, an increase that usually continued for several hundred trials. 1990 Society for the Experimental Analysis of Behavior

Students from the 5th, 8th, and 11th grades (55 male and 53 female) were asked to describe their ideal self-image. Analyses revealed a number of gender and developmental differences not found with other self-image measures. A greater proportion of females than males mentioned two of the categories related to family life: marriage and improving relations with their family of origin. Mentions of categories surrounding athletics were more prevalent among males. Grade level differences in the content of the ideal self-image reflected cognitive-developmental shifts away from concrete descriptors, changes in physical maturity and the heightened importance of peer relationships around adolescence, and the approach of developmental milestones. Fewer students mentioned physical appearance at higher grade levels. Mentions of athletic abilities and social acceptance peaked at the 8th grade, while mentions of college, marriage, and having children rose at higher grade levels. Differences in the content areas mentioned by average versus advanced track students appeared to reflect differences in both cognitive-developmental level and socialization experiences. © 1990 Plenum Publishing Corporation.

This experiment measured pigeons' choices between delayed reinforcers and fixed‐ratio schedules in which a force of approximately 0.48 N was needed to operate the response key. In ratio‐delay conditions, subjects chose between a fixed‐ratio schedule and an adjusting delay. The delay was increased or decreased several times a session in order to estimate an indifference point—a delay duration at which the two alternatives were chosen about equally often. Each ratio‐delay condition was followed by a delay‐delay condition in which subjects chose between the adjusting delay and a variable‐time schedule, with the components of this schedule selected to match the ratio completion times of the preceding ratio‐delay condition. The adjusting delays at the indifference point were longer when the alternative was a fixed‐ratio schedule than when it was a matched variable‐time schedule, which indicated a preference for the matched variable‐time schedules over the fixed‐ratio schedules. This preference increased in a nonlinear manner with increasing ratio size. This nonlinearity was inconsistent with a theory that states that indifference points for both time and ratio schedules can be predicted by multiplying the choice response‐reinforcer intervals of the two types of schedules by different multiplicative constants. Two other theories, which predict nonlinear increases in preference for the matched variable‐time schedules, are discussed. 1990 Society for the Experimental Analysis of Behavior

In this paper, we analyze the political and socioeconomic factors that may be associated with black and female employment in American public higher education. We develop representation ratios for black females, black males, white females, and white males who serve as full-time faculty members in public higher education institutions in the American states. Our analysis shows that region, in this case the South, provides the best indicator for black female and black male faculty employment in public higher education. The percentage of black state legislators is also associated with black faculty employment. For white women, we found that although they are well represented on faculties, their numbers do not reach their share of the population. None of the variables examined explained their employment as faculty members. Women as a group had a particularly weak presence in state legislatures and continue to have less political power than blacks and white males. We suggest a number of possible avenues for future research to clarify these findings.

The purpose of this article is to uncover the political factors associated with greater income parity for black men, black women, and white women relative to white men in the American states. Variables are constructed for federal, state, and local government employment, state electoral competition, federal procurement, black state legislators, and women state legislators along with a number of socioeconomic factors. It is discovered that the political variables carry less weight than the socioeconomic ones. These findings raise questions about the future prospects for increased earnings parity for minorities and women as previous federal efforts to eliminate racial and gender discrimination appear to have been weakened and state political factors have little relationship with greater income equality.

It is well known that conduction in YBa2Cu3O7 (YBCO) is by means of copper "planes" and "chains," where planes and chains describe the degree of bonding between copper and oxygen. Changes of conductivity versus temperature have been used to show that conduction in YBCO in the normal state is 3-dimensional, while conduction approaching the onset of the superconducting state is first 2-dimensional and then 3-dimensional. We have found another method to monitor this 2-to-3 transition. Using square samples, and measuring the voltage at each corner caused by a current applied to the opposite corners, one can find the conductivities along the x-axis and the y-axis. The ratio of these conductivities is unity for homogeneous samples in the normal state. However, in transition to the superconducting state, the ratio of conductivities changes. We examine this change as a function of sample purity, sample history, and exposure to an external magnetic field. Our data are consistent with data reported in the literature, and they suggest the existence of another state change deep in the superconducting state, which is only observable with the application of a magnetic field., Measurements were also carried out to correlate the anisotropy with sample porosity. Measurements of normal state resistivity, critical temperature, and critical current characterize the sample's porosity, and these data affect the anisotropy in the superconducting state in a manner directly proportional to the porosity., (C)1998 Kluwer Academic Publishers

The author agrees with James Moor that computer technology, because it is 'logically malleable', is bringing about a genuine social revolution. Moor compares the computer revolution to the 'industrial revolution' of the late 18th and the 19th centuries; but it is argued here that a better comparison is with the 'printing press revolution' that occurred two centuries before that. Just as the major ethical theories of Bentham and Kant were developed in response to the printing press revolution, so a new ethical theory is likely to emerge from computer ethics in response to the computer revolution. The newly emerging field of information ethics, therefore, is much more important than even its founders and advocates believe.

Most nurse educators would agree that critical thinking is an essential competency for the professional nurse in today's ever-changing health care environment. In fact, critical thinking has been identified as an integral component of professional nursing practice and has been incorporated in accreditation guidelines (1-3). As a result of this imperative, professional programs of nursing must explicate a clear definition of critical thinking, identify specific learning outcomes reflective of critical thinking abilities, and select appropriate ways to measure the achievement of these outcomes in graduating students. Although much has been written about the need for critical thinking skills, the concept and measurement of critical thinking within the context of nursing education has not yet been clearly defined (4-6). As a result, nursing programs are developing their own conceptual definitions of critical thinking and using a variety of methods to measure outcomes (5). The authors caution that to ensure validity of findings, the instruments used must reflect the individual program's definition of the concept. In most cases, outcomes have been assessed using a cross-sectional design that compares students at different levels or types of programs or are measured as an end-of-program outcome. While such designs can provide educators with knowledge of students' critical thinking abilities at a particular point in the educational process, longitudinal data are needed to assess the effects of the educational program.

In response to public criticisms about the outcomes of higher education, colleges and universities have implemented comprehensive assessment programs. In nursing education, outcomes assessment has become a criteria for accreditation. Yet, currently no guidelines exist describing “best practices” in nursing education outcomes assessment. Experts in educational assessment provide helpful guidelines for nurse educators as they establish comprehensive assessment plans. The authors provide a review of the literature in the field of assessment and offer strategies for developing successful assessment programs in nursing education.

Nurses are challenged to advance the theoretical foundations of community practice. This paper offers ideas on what-has been done and what needs to be done to meet this challenge. Within a community health nursing perspective, the paper defines community, proposes an integrated knowledge development framework that focuses on community, analyses contemporary theoretical and philosophical foundations of community in nursing, considers three worldviews in which nursing can be framed, and examines parameters for knowledge development for the future.

The primary purposes of this study were to identify the best teaching practices for adult baccalaureate (BSN) nursing students and to examine if adult students' teaching preferences differed from those of traditional BSN students. The sample consisted of 206 adult and traditional students in four BSN programs. The adult nursing student sample was further subdivided into two groups: adults with no prior nursing education (adult non-nurses) and adults with prior nursing education (RN'S). Using a two-part, self-administered questionnaire, respondents were asked to rate the frequency with which 41 teaching strategies were used in their best and in their worst classroom learning experiences in nursing. In most cases, adult non-nurses' teaching preferences did not vary significantly from the preferences of traditional students. However, adults with no prior nursing education did show a preference for knowledgeable and organized instructors. In contrast RNs' preferred classroom situations were where time on task was emphasized, cooperative learning was encouraged, and expectations for learning were high. Results indicate that classroom teaching preferences vary as a function of prior experience with the subject matter and are not attributable to age itself. Findings suggest that prior experience with course content is a more important consideration in planning programs than generalized adult experience.