bluuebunny/crossref_metadata_2025 huggingface dataset:
CHOICE IN A VARIABLE ENVIRONMENT: EFFECTS OF BLACKOUT DURATION AND EXTINCTION BETWEEN COMPONENTS
Authors: Davison Michael , Baum William M.
Published: March 2006

Pigeons were trained in a procedure in which sessions included seven four‐ or 10‐reinforcer components, each providing a different reinforcer ratio that ranged from 27:1 to 1:27. The components were arranged in random order, and no signals differentiated the component reinforcer ratios. Each condition lasted 50 sessions, and the data from the last 35 sessions were analyzed. Previous results using 10‐s blackouts between components showed some carryover of preference from one component to the next, and this effect was investigated in Experiment 1 by varying blackout duration from 1 s to 120 s. The amount of carryover decreased monotonically as the blackout duration was lengthened. Preference also decreased between reinforcers within components, suggesting that preference change during blackout might follow the same function as preference change between reinforcers. Experiment 2 was designed to measure preference change between components more directly and to relate this to preference change during blackout. In two conditions a 60‐s blackout occurred between components, and in two other conditions a 60‐s period of unsignaled extinction occurred between components. Preference during the extinction period progressively fell toward indifference, and the level of preference following extinction was much the same as that following blackout. Although these results are consistent with Davison and Baum's (2000) theory of the effects of reinforcers on local preference, other findings suggest that theory is incomplete: After a sequence of reinforcers from one alternative, some residual preference remained after 60 s of extinction or blackout, indicating the possibility of an additional longer term accumulation of reinforcer effects than originally suggested.
A NEW APPROACH TO THE FORMATION OF EQUIVALENCE CLASSES IN PIGEONS
Authors: Jitsumori Masako , Siemann Martina , Lehr Manuela , Delius Juan D.
Published: March 2006

Four pigeons were given simultaneous discrimination training with visual patterns arbitrarily divided into two sets, with the stimuli in one set designated A1, B1, C1, and D1 and those in the other set designated A2, B2, C2, and D2. In sequentially introduced training phases, the pigeons were exposed to a series of reversals to establish AB and then CD equivalences. In subsequent testing sessions, a subset of stimuli from one set served as positive stimuli and those from the other set as negative stimuli on training trials, and transfer of the reinforced relation to other members of the sets was tested with nonreinforced probe trials. The pigeons were trained further on AC and BD equivalences and then were tested for the emergence of untrained AD and BC equivalences. Two of the 4 pigeons exhibited the emergence of one of these untrained equivalences, evidence for the emergence of transitive relations. This finding suggests that the pigeons established three‐member functional equivalence classes by incorporating separately trained multiple equivalence relations. Repeated reversal training and probe testing enabled us to explore the formation and expansion of functional equivalence classes in pigeons.
STIMULUS CONTROL TOPOGRAPHIES AND TESTS OF SYMMETRY IN PIGEONS
Authors: Lionello‐DeNolf Karen M. , Urcuioli Peter J.
Published: March 2006

Pigeons were tested for symmetry after A‐B training under conditions designed to avoid problems that may prevent its emergence, namely the change of stimulus location in testing relative to training and the lack of requisite discrimination training. In Experiment 1, samples appeared in two locations during baseline training to minimize the impact of stimulus location. Experiments 2 and 3 included multiple‐location training along with additional identity and symbolic matching training, respectively, to explicitly train all of the simultaneous and successive stimulus discriminations required for testing. Experiment 4 provided reinforcement for symmetrical matching relations with some stimulus sets (with multiple‐location training) prior to symmetry testing with different sets. In all experiments, pigeons showed no evidence of symmetry despite the fact that baseline (A‐B) matching transferred to novel locations. Additional tests for reflexivity (Experiment 2) yielded similar outcomes. These results indicate that the change in stimulus location is not the sole reason that pigeons do not show symmetry and increase the plausibility of arguments that symmetry and other indexes of stimulus equivalence may be beyond the capabilities of the pigeon.
RATS' PERFORMANCE ON VARIABLE‐INTERVAL SCHEDULES WITH A LINEAR FEEDBACK LOOP BETWEEN RESPONSE RATE AND REINFORCEMENT RATE
Authors: Reed Phil , Hildebrandt Tom , DeJongh Julie , Soh Mariane
Published: March 2006

Three experiments investigated whether rats are sensitive to the molar properties of a variable‐interval (VI) schedule with a positive relation between response rate and reinforcement rate (i.e., a VI1 schedule). In Experiment 1, rats responded faster on a variable ratio (VR) schedule than on a VI1 schedule with an equivalent feedback function. Reinforced interresponse times (IRTs) were shorter on the VR as compared to the VI1 schedule. In Experiments 2 and 3, there was no systematic difference in response rates maintained by a VI1 schedule and a VI schedule yoked in terms of reinforcement rate. This was found both when the yoking procedure was between‐subject (Experiment 2) and within‐subject (Experiment 3). Mean reinforced IRTs were similar on both the VI1 and yoked VI schedules, but these values were more variable on the VI1 schedule. These results provided no evidence that rats are sensitive to the feedback function relating response rate to reinforcement rate on a VI1 schedule.
DETERMINANTS OF PIGEONS' CHOICES IN TOKEN‐BASED SELF‐CONTROL PROCEDURES
Authors: Hackenberg Timothy D. , Vaidya Manish
Published: March 2006

Four pigeons were exposed to a token‐based self‐control procedure with stimulus lights serving as token reinforcers. Smaller‐reinforcer choices produced one token immediately; larger‐reinforcer choices produced three tokens following a delay. Each token could be exchanged for 2‐s access to food during a signaled exchange period each trial. The main variables of interest were the exchange delays (delays from the choice to the exchange stimulus) and the food delays (also timed from the choice), which were varied separately and together across blocks of sessions. When exchange delays and food delays were shorter following smaller‐reinforcer choices, strong preference for the smaller reinforcer was observed. When exchange delays and food delays were equal for both options, strong preference for the larger reinforcer was observed. When food delays were equal for both options but exchange delays were shorter for smaller‐reinforcer choices, preference for the larger reinforcer generally was less extreme than under conditions in which both exchange and food delays were equal. When exchange delays were equal for both options but food delays were shorter for smaller‐reinforcer choices, preference for the smaller reinforcer generally was less extreme than under conditions in which both exchange and food delays favored smaller‐reinforcer choices. On the whole, the results were consistent with prior research on token‐based self‐control procedures in showing that choices are governed by reinforcer immediacy when exchange and food delays are unequal and by reinforcer amount when exchange and food delays are equal. Further, by decoupling the exchange delays from food delays, the results tentatively support a role for the exchange stimulus as a conditioned reinforcer.
A PROCEDURE FOR GENERATING DIFFERENTIAL “SAMPLE” RESPONDING WITHOUT DIFFERENT EXTEROCEPTIVE STIMULI
Authors: Lionello‐DeNolf Karen M. , Urcuioli Peter J.
Published: March 2006

Sidman (1994, 2000) suggested that responses as well as stimuli can join equivalence classes, a hypothesis difficult to test because differential responding typically requires different stimuli. The present experiments describe a procedure with pigeons that avoids this potential confounding effect. In Experiment 1, spacing two responses 3 s apart (a differential‐reinforcement‐of‐low‐rate [DRL] schedule) to a white stimulus on some trials produced food or the comparison stimuli in a matching task, whereas pecking 10 or more times with no temporal restrictions (a fixed‐ratio [FR] schedule) produced the same effect on other trials. Completing the alternative (unscheduled) requirement terminated the white stimulus and repeated the trial. Following such errors, pigeons learned to switch to the alternative response pattern on the repeat trials. In addition, the correct response pattern functioned as a conditional cue for comparison choice. In Experiment 2, mixed DRL‐FR training was preceded by two‐sample/two‐alternative matching‐to‐sample with DRL and FR sample‐response requirements. In a subsequent transfer test in which the correct response pattern to white served as the sample, pigeons preferentially chose the comparison previously reinforced following that pattern in the baseline task. This “unsignaled response” procedure may be useful for assessing whether differential responses can be members of acquired equivalence classes.
ACCURACY OF DISCRIMINATION, RATE OF RESPONDING, AND RESISTANCE TO CHANGE
Authors: Nevin John A. , Milo Jessica , Odum Amy L. , Shahan Timothy A.
Published: March 2006

Pigeons were trained on multiple schedules in which responding on a center key produced matching‐to‐sample trials according to the same variable‐interval 30‐s schedules in both components. Matching trials consisted of a vertical or tilted line sample on the center key followed by vertical and tilted comparisons on the side keys. Correct responses to comparison stimuli were reinforced with probability .80 in the rich component and .20 in the lean component. Baseline response rates and matching accuracies generally were higher in the rich component, consistent with previous research. When performance was disrupted by prefeeding, response‐independent food during intercomponent intervals, intrusion of a delay between sample and comparison stimuli, or extinction, both response rates and matching accuracies generally decreased. Proportions of baseline response rate were greater in the rich component for all disrupters except delay, which had relatively small and inconsistent effects on response rate. By contrast, delay had large and consistent effects on matching accuracy, and proportions of baseline matching accuracy were greater in the rich component for all four disrupters. The dissociation of response rate and accuracy with delay reflects the localized impact of delay on matching performance. The similarity of the data for response rate and accuracy with prefeeding, response‐independent food, and extinction shows that matching performance, like response rate, is more resistant to change in a rich than in a lean component. This result extends resistance to change analyses from the frequency of response emission to the degree of stimulus control, and suggests that the strength of discriminating, like the strength of responding, is positively related to rate of reinforcement.
TRANSFER OF SPECIFIC CONTEXTUAL FUNCTIONS TO NOVEL CONDITIONAL DISCRIMINATIONS
Authors: Pérez‐González Luis Antonio , Serna Richard W.
Published: March 2006

Three adolescents and 4 children participated in studies designed to examine contextually controlled conditional discrimination performance. In Study 1, participants selected Comparison B1 in the presence one stimulus (A1) and Comparison B2 in the presence of another stimulus (A2) using a matching‐to‐sample procedure. Next, contextual stimuli X1 or X2 were presented, such that in the presence of X1, selection of B1 given A1 and selection of B2 given A2 were reinforced; and in the presence of X2, selection of B2 given A1 and selection of B1 given A2 were reinforced. Then, new conditional discriminations were taught with Stimuli E and F. When the contextual Stimuli X1 and X2 were presented, participants selected the same comparisons as previously established in the EF relations in the presence of X1, but the opposite comparison as in the EF relations in the presence of X2. The results then were replicated with new Stimuli G and H. In Study 2, a new conditional discrimination, CD, was taught. Then, four combinations of two‐element samples—C1 and D1, C2 and D2, C1 and D2, or C2 and D1—were presented with X1 and X2 as comparisons. Five of 6 participants selected X1 in the presence of C1 and D1 or C2 and D2, and selected X2 in the presence of C1 and D2 or C2 and D1. Finally, in Study 3, two new discriminations IJ and JK were taught. Then, the transitive IK relations were tested with X1 and X2 as contextual stimuli. The 4 participants selected K1 in the presence of I1 and K2 in the presence of I2 when the contextual stimulus was X1—demonstrating class formation—and selected the other comparisons when the contextual stimulus was X2. These results suggest that the contextual control functions of X1 and X2 transferred even to relations that had not been directly taught. These results extend those demonstrating generalized contextual control by showing transfer of functions of the contextual stimuli in transitivity tests and when the former contextual stimuli were presented as comparisons.
RATIONAL THOUGHT AND RATIONAL BEHAVIOR: A REVIEW OF BOUNDED RATIONALITY: THE ADAPTIVE TOOLBOX
Authors: Rachlin Howard
Published: March 2006

Standard economic theory says that the rational approach to a decision is to weigh all alternatives on all relevant dimensions and then to select the one with the highest weight. Such a procedure would maximize subjective expected utility. But, because of constraints on time and available information, people and other animals often bypass this process by using “fast and frugal” heuristics to make decisions. Rationality is thus said to be “bounded” by time and information constraints. The articles in this book describe and organize common heuristics. They show that use of such heuristics is generally the best approach to many real world problems and therefore not irrational. Heuristics evolved, they say, not as deviations from rationality but as aids to rationality in cases where the standard model would have proved to be too slow or inefficient. Although the approach of almost all of the authors of these papers is that of cognitive psychology—a focus on internal cognitive mechanisms—their findings and even their theories may be interpreted in terms of reinforcement and punishment acting on behavioral patterns.
CHOICE IN A VARIABLE ENVIRONMENT: EFFECTS OF UNEQUAL REINFORCER DISTRIBUTIONS
Authors: Landon Jason , Davison Michael , Elliffe Douglas
Published: March 2006

Six pigeons were trained in a procedure in which sessions included seven unsignaled components, each offering two pecking keys, and each providing a potentially different reinforcer ratio between the two keys. Across conditions, various combinations of reinforcer ratios and reinforcer‐magnitude ratios were used to create unequal reinforcer distributions between the two alternatives when averaged across a session. The results extended previous research using the same basic procedure that had included only reinforcer distributions symmetrical around 1:1. Data analyses suggested that the variables controlling choice operated at a number of levels: First, individual reinforcers had local effects on choice; second, sequences of successive reinforcers obtained at the same alternative (continuations) had cumulative effects; and, third, when these sequences themselves occurred with greater frequency, their effects further cumulated. A reinforcer obtained at the other alternative following a sequence of continuations (a discontinuation) had a large effect and apparently reset choice to levels approximating the sessional reinforcer ratio.
SPEECH PERCEPTION IN RATS: USE OF DURATION AND RISE TIME CUES IN LABELING OF AFFRICATE/FRICATIVE SOUNDS
Authors: Reed Phil , Howell Peter , Sackin Stevie , Pizzimenti Lisa , Rosen Stuart
Published: March 2006

The voiceless affricate/fricative contrast has played an important role in developing auditory theories of speech perception. This type of theory draws some of its support from experimental data on animals. However, nothing is known about differential responding of affricate/fricative continua by animals. In the current study, the ability of hooded rats to “label” an affricate/fricative continuum was tested. Transfer (without retraining) to analogous nonspeech continua was also tested. The nonspeech continua were chosen so that if transfer occurred, it would indicate whether the animals had learned to use rise time or duration cues to differentiate affricates from fricatives. The data from 9 of 10 rats indicated that rats can discriminate between these cues and do so in a similar manner to human subjects. The data from 9 of 10 rats also demonstrated that the rise time of the stimulus was the basis of the discrimination; the remaining rat appeared to use duration.
AROUSAL, CHANGEOVER RESPONSES, AND PREFERENCE IN CONCURRENT SCHEDULES
Authors: McDevitt Margaret A. , Williams Ben A.
Published: March 2006

Pigeons were trained on multiple schedules that provided concurrent reinforcement in each of two components. In Experiment 1, one component consisted of a variable‐interval (VI) 40‐s schedule presented with a VI 20‐s schedule, and the other a VI 40‐s schedule presented with a VI 80‐s schedule. After extended training, probe tests measured preference between the stimuli associated with the two 40‐s schedules. Probe tests replicated the results of Belke (1992) that showed preference for the 40‐s schedule that had been paired with the 80‐s schedule. In a second condition, the overall reinforcer rate provided by the two components was equated by adding a signaled VI schedule to the component with the lower reinforcer rate. Probe results were unchanged. In Experiment 2, pigeons were trained on alternating concurrent VI 30‐s VI 60‐s schedules. One schedule provided 2‐s access to food and the other provided 6‐s access. The larger reinforcer magnitude produced higher response rates and was preferred on probe trials. Rate of changeover responding, however, did not differ as a function of reinforcer magnitude. The present results demonstrate that preference on probe trials is not a simple reflection of the pattern of changeover behavior established during training.
B. F. SKINNER'S SCIENCE AND HUMAN BEHAVIOR: ITS ANTECEDENTS AND ITS CONSEQUENCES
Authors: Catania A. Charles
Published: March 2006

Skinner's Science and Human Behavior marked a transition from a treatment of behavior that took physics as its reference science to one that emphasized behavior as a fundamental part of the subject matter of biology. The book includes what may be Skinner's earliest statement about the similarity of operant selection to Darwinian natural selection in phylogeny. Other major topics discussed in the book included multiple causation, private events, the self, and social contingencies. Among the important antecedents were Skinner's own Behavior of Organisms and Keller & Schoenfeld's Principles of Psychology. Current developments in education, behavioral economics, and some behavior therapies can be attributed at least in part to Skinner's seminal work. The effective behavioral analysis of governmental and religious systems will probably depend on elaborations of our understanding of verbal behavior.
SCIENCE AND HUMAN BEHAVIOR AT FIFTY
Authors: Pilgrim Carol
Published: March 2006

The golden anniversary of Science and Human Behavior is cause for celebration. Toward that end, the present paper is largely an historical consideration of the book, its inception and reception, both at the time of its publication and in subsequent years. The range and intensity of reactions to S&HB mark its impact and show it to be among Skinner's most important works, if not the most important. S&HB was written as an introductory psychology text—a vigorous use of the book in our teaching could do much to benefit the dissemination of behavior analysis.
THE EFFECT OF REINFORCER DELAYS ON THE FORM OF THE FORGETTING FUNCTION
Authors: Sargisson Rebecca J. , White K. Geoffrey
Published: March 2006

Pigeons were trained in a matching‐to‐sample procedure with retention intervals of 0, 2, 4, 6, and 8 s mixed within each session. In different conditions, reinforcement was delayed by 0, 1, 2, 4, 6, or 8 s from correct choice responses. Discriminability decreased with increasing retention‐interval duration and with increasing reinforcer delay. Exponential forgetting functions were fitted to discriminability measures plotted as a function of retention interval. Initial discriminability (intercept of the fitted functions) decreased with increasing reinforcer delay. Rate of forgetting (slope of the fitted functions) increased with reinforcer delay, suggesting an interaction between the effects of reinforcer delay and retention interval. The data were well described by multiplying an exponential function describing the effects of retention interval by a hyperbolic function describing the effect of reinforcer delay. This description included an interaction term that allowed for a greater effect of reinforcer delay at longer retention intervals.
BOUTS OF RESPONDING ON VARIABLE‐INTERVAL SCHEDULES: EFFECTS OF DEPRIVATION LEVEL
Authors: Shull Richard L.
Published: March 2006

Rats obtained food pellets on a variable‐interval schedule of reinforcement by nose poking a lighted key. After training to establish baseline performance (with the mean variable interval set at either 60, 120, or 240 s), the rats were given free access to food during the hour just before their daily session. This satiation operation reduced the rate of key poking. Analysis of the interresponse time distributions (log survivor plots) indicated that key poking occurred in bouts. Prefeeding lengthened the pauses between bouts, shortened the length of bouts (less reliably), and had a relatively small decremental effect on the response rate within bouts. That deprivation level affects mainly between‐bout pauses has been reported previously with fixed‐ratio schedules. Thus, when the focus is on bouts, the performances maintained by variable‐interval schedules and fixed‐ratio schedules are similarly affected by deprivation.
DATA IN SEARCH OF A PRINCIPLE: A REVIEW OF RELATIONAL FRAME THEORY: A POST‐SKINNERIAN ACCOUNT OF HUMAN LANGUAGE AND COGNITION
Authors: Palmer David C.
Published: March 2006

Responding to derived relations among stimuli and events is the subject of an accelerating research program that represents one of the major behavior analytic approaches to complex behavior. Relational Frame Theory: A Post‐Skinnerian Account of Human Language and Cognition (Hayes, Barnes‐Holmes, & Roche, 2001) offers a conceptual framework for this work and explores its implications for verbal behavior and a variety of other domains of complex human behavior. The authors dismiss Skinner's interpretation of verbal behavior as unproductive and conceptually flawed and suggest a new definition and a new paradigm for the investigation of verbal phenomena. I found the empirical phenomena important but the conceptual discussion incomplete. A new principle of behavior is promised, but critical features of this principle are not offered. In the absence of an explicit principle, the theory itself is difficult to evaluate. Counterexamples suggest a role for mediating behavior, perhaps covert, thus raising the question whether a new principle is needed at all. The performance of subjects in relational frame experiments may be a mosaic of elementary behavioral units, some of which are verbal. If so, verbal behavior underlies relational behavior; it is not defined by it. I defend Skinner's definition of verbal behavior and argue that an account of relational behavior must be integrated with Skinner's analysis; it will not replace it.
WIENER FILTER ESTIMATION OF TRANSFER FUNCTIONS
Authors: Kessel Robert
Published: March 2006

The use of a Wiener filter estimate for the linear transfer function can significantly improve the description of behavioral dynamics. This report presents a two‐pass, Monte‐Carlo‐based algorithm that is well suited to repeated‐trials local average measurements. The Wiener filter transfer functions strongly suppress noise artifacts as well as allow reliable transfer function determination under a much wider class of reinforcement schedules. Implications of expanding the possible form of experimental design are considered along with improvements in the fidelity of resulting predictions.
DISCOUNTING OF DELAYED FOOD REWARDS IN PIGEONS AND RATS: IS THERE A MAGNITUDE EFFECT?
Authors: Green Leonard , Myerson Joel , Holt Daniel D. , Slevin John R. , Estle Sara J.
Published: March 2006

Temporal discounting refers to the decrease in the present, subjective value of a reward as the time to its receipt increases. Results from humans have shown that a hyperbola‐like function describes the form of the discounting function when choices involve hypothetical monetary rewards. In addition, magnitude effects have been reported in which smaller reward amounts are discounted more steeply than larger amounts. The present research examines the cross‐species generality of these findings using real rewards, namely food pellets, with both pigeons and rats. As with humans, an adjusting amount procedure was used to estimate the amount of immediate reward judged equal in value to a delayed reward. Different amounts of delayed food rewards (ranging from 5 to 32 pellets in pigeons and from 5 to 20 pellets in rats) were studied at delays varying from 1 s to 32 s. A simple hyperbola, similar to the hyperbola‐like mathematical function that describes the discounting of hypothetical monetary rewards in humans, described the discounting of food rewards in both pigeons and rats. These results extend the generality of the mathematical model of discounting. Rates of discounting delayed food rewards were higher for pigeons than for rats. Unlike humans, however, neither pigeons nor rats showed a reliable magnitude effect: Rate of discounting did not vary systematically as a function of the amount of the delayed reward.
THE EFFECTS OF BEHAVIORAL HISTORY ON RESPONSE ACQUISITION WITH IMMEDIATE AND DELAYED REINFORCEMENT
Authors: Snycerski Susan , Laraway Sean , Huitema Bradley E. , Poling Alan
Published: March 2006

Effects of prior exposure to the experimental chamber with levers present or absent and variable‐time (VT) 60‐s water deliveries arranged during one, five, or no 1‐hr sessions were examined in rats during a 6‐hr response‐acquisition session in which presses on one lever produced water delivery immediately or after a 15‐s resetting delay, and presses on the other lever canceled scheduled water deliveries. Response acquisition was (a) slower to occur when water deliveries were delayed, (b) most consistent in groups that had received five VT sessions, and (c) impaired by the presence of levers only when there had been five VT sessions and water deliveries were delayed during the acquisition session.
THE EFFECTS OF MORPHINE ON THE PRODUCTION AND DISCRIMINATION OF INTERRESPONSE TIMES
Authors: Odum Amy L. , Ward Ryan D.
Published: March 2006

Recent experiments suggest that the effects of drugs of abuse on the discrimination of the passage of time may differ for experimenter‐imposed and subject‐produced events. The current experiment examined this suggestion by determining the effects of morphine on the discrimination of interresponse times (IRTs). Pigeons pecked a center key on a random‐interval 20‐s schedule of matching‐to‐sample trials. Once the interval had timed out, a choice trial randomly followed either a short (2‐ to 3‐s) or long (6‐ to 9‐s) IRT on the center key. Pecking the side key lit one color produced food after a short IRT, and pecking the side key lit the other color produced food after a long IRT. Two experimental phases differed in the functional role of the different key colors. Under control conditions, the IRT distributions had two modes, one at the lower bound of the short category and a smaller one at the lower bound of the long category. Pigeons accurately categorized the duration of the IRTs: One key color was pecked following short IRTs and the other key color was pecked following long IRTs. Morphine flattened the IRT distribution and reduced the accuracy of categorizing IRTs. Categorization of long IRTs was particularly disrupted. Morphine did not produce overestimation of time as assessed by the production or categorization of IRTs. These results are similar to those obtained previously for the effects of morphine on the discrimination of the duration of experimenter‐imposed events.
A DAY OF GREAT ILLUMINATION: B. F. SKINNER'S DISCOVERY OF SHAPING
Authors: Peterson Gail B.
Published: March 2006

Despite the seminal studies of response differentiation by the method of successive approximation detailed in chapter 8 of The Behavior of Organisms (1938), B. F. Skinner never actually shaped an operant response by hand until a memorable incident of startling serendipity on the top floor of a flour mill in Minneapolis in 1943. That occasion appears to have been a genuine eureka experience for Skinner, causing him to appreciate as never before the significance of reinforcement mediated by biological connections with the animate social environment, as opposed to purely mechanical connections with the inanimate physical environment. This insight stimulated him to coin a new term (shaping), and also led directly to a shift in his perspective on verbal behavior from an emphasis on antecedents and molecular topographical details to an emphasis on consequences and more molar, functional properties in which the social dyad inherent to the shaping process became the definitive property of verbal behavior. Moreover, the insight seems to have emboldened Skinner to explore the greater implications of his behaviorism for human behavior writ large, an enterprise that characterized the bulk of his post‐World War II scholarship.
Effects of Plaque Control on the Patency of Dentinal Tubules: An In Vivo Study in Beagle Dogs
Authors: Suge Toshiyuki , Kawasaki Akiko , Ishikawa Kunio , Matsuo Takashi , Ebisu Shigeyuki
Published: March 2006

Background: The aim of this in vivo study was to evaluate the effects of plaque control on the patency of dentinal tubules using vital teeth of beagle dogs.

Methods: Class V cavities were prepared on the cervical areas of the mandibular and maxillary molars in each dog with a diamond point. To simulate the state of dentinal hypersensitivity, the teeth were etched with 50% citric acid for 2 minutes to obtain patent dentinal tubules. Plaque control was achieved by brushing the left‐side teeth every day, whereas no plaque control was performed for the right‐side teeth. A dentin biopsy was performed after 1, 2, and 3 weeks using the cylindrical diamond point to obtain dentin specimens.

Results: In the plaque control group, some of the dentinal tubules were occluded with precipitate (Ca/P = 1.49), and the diameter of the dentinal tubules decreased from 2.42 ± 0.33 μm (mean ± SD) to 1.11 ± 0.51 μm after 7 days, although most of the dentinal tubules remained open. In contrast, no precipitate was observed in the dentinal tubules of the non‐plaque control group. Also, the diameter of the dentinal tubules increased from 2.42 ± 0.33 to 2.9 ± 0.49 μm, due to the demineralization of the peritubular and intertubular dentin.

Conclusion: Plaque control plays a key role in reducing the patency of dentinal tubules and, therefore, might promote the natural repair of dentinal hypersensitivity.
Description of the Subgingival Microbiota of Periodontally Untreated Mexican Subjects: Chronic Periodontitis and Periodontal Health
Authors: Ximenez‐Fyvie Laurie Ann , Almaguer‐Flores Argelia , Jacobo‐Soto Velia , Lara‐Cordoba Monica , Sanchez‐Vargas Luis O. , Alcantara‐Maruri Eulalio
Published: March 2006

Background: Recent studies have suggested that changes in the prevalence and/or proportion of distinct microorganisms characterize the subgingival microbial profiles of populations around the world. At present, no information is available on the subgingival microbiota of Mexican subjects. The purpose of the present study was to determine the microbial composition of subgingival plaque in Mexican subjects with untreated chronic periodontitis.

Methods: A total of 44 chronic periodontitis and 20 periodontally healthy subjects (who were currently non‐smokers) were selected. Clinical measurements including plaque accumulation, gingival erythema, bleeding on probing, suppuration, probing depth, and attachment level were recorded at six sites of every tooth. Up to 28 subgingival plaque samples were obtained from each subject and individually analyzed to determine the levels, proportion, and prevalence of 40 microbial species using the checkerboard DNA‐DNA hybridization technique.

Results: Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythensis were the only species that presented higher mean levels in periodontitis subjects. The proportions of P. gingivalis (P <0.001), T. forsythensis (P <0.01), and red complex species (P. gingivalis, T. forsythensis, and T. denticola; P <0.001) as a group were also significantly higher in periodontitis subjects. Periodontally healthy subjects harbored a significantly larger proportion of Actinomyces species (P <0.05). No significant differences were detected in the percentage of carriers of any of the species tested.

Conclusions: Our results revealed that the subgingival microbiota of untreated chronic periodontitis Mexican subjects was characterized by increases in the level, prevalence, and proportion of classic periodontal pathogens. However, the prevalence and proportion of specific microbial species varied significantly from the results of other reports on subjects from different geographical locations.
Periodontitis Deteriorates Metabolic Control in Type 2 Diabetic Goto‐Kakizaki Rats
Authors: Pontes Andersen Carla C. , Buschard Karsten , Flyvbjerg Allan , Stoltze Kaj , Holmstrup Palle
Published: March 2006

Background: Epidemiologic and clinical studies have indicated that periodontal disease (PD) may cause disturbances in general health and even affect diabetes. The aim of this study was to gain knowledge on the effect of PD on diabetes metabolic control in a new model for type 2 diabetes–associated PD (i.e., the Goto‐Kakizaki [GK] rat).

Methods: GK rats represented the type 2 diabetes group and were allocated into two groups: diabetes or diabetes + PD group; Wistar rats represented the non‐diabetes group and were divided into non‐diabetes + PD and non‐diabetes groups. PD was induced by placing ligatures around second maxillary molars, and the animals were followed for 6 weeks. Serum insulin, glucose, and free fatty acid levels were evaluated; interleukin (IL)‐1β, IL‐6, and tumor necrosis factor‐α were measured in adipose tissue supernatant; glucose tolerance and insulin resistance were calculated. Further, alveolar bone destruction was estimated morphometrically and radiographically.

Results: Rats with diabetes + PD became almost 30% more glucose intolerant (P <0.01) and presented a 25% increase in IL‐1β in adipose tissue (P <0.05) compared to rats from the diabetes group. Moreover, PD associated with diabetes resulted in more alveolar bone destruction in comparison to PD in the absence of diabetes (P <0.01).

Conclusions: Our results indicated that PD deteriorates metabolic control in diabetes, which emphasizes that PD may play a significant role for the course of diabetes. The GK rat can represent a suitable model for further studies on the association between PD and diabetes.
Phosphorus Runoff during Four Years following Composted Manure Application
Authors: Wortmann Charles S. , Walters Daniel T.
Published: March 2006

Repeated manure application can lead to excessive soil test P (STP) levels and increased P concentration in runoff, but also to improved water infiltration and reduced runoff. Research was conducted to evaluate soil P tests in prediction of P concentration in runoff and to determine the residual effects of composted manure on runoff P loss and leaching of P. The research was conducted from 2001 to 2004 under natural runoff events with plots of 11‐m length. Low‐P and high‐P compost had been applied during the previous 3 yr, resulting in total applications of 750 and 1150 kg P ha−1 Bray‐P1 in the surface 5 cm of soil was increased from 16 to 780 mg kg−1 with application of high‐P compost. Runoff and sediment losses were 69 and 120% greater with no compost than with residual compost treatments. Runoff P concentration increased as STP increased, but much P loss occurred with the no‐compost treatment as well. Agronomic soil tests were predictive of mean runoff P concentration, but increases in STP resulted in relatively small increases in runoff P concentration. Downward movement of P was not detected below 0.3 m. In conclusion, agronomic soil tests are useful in predicting long‐term runoff P concentration, and risk of P loss may be of concern even at moderate soil P levels. The residual effect of compost application in reducing sediment and runoff loss was evident more than 3 yr after application and should be considered in P indices.
Influence of Soil Properties and Aging on the Toxicity of Copper on Compost Worm and Barley
Authors: Daoust Catherine M. , Bastien Christian , Deschênes Louise
Published: March 2006

Influence of soil properties and aging on Cu partitioning and toxicity was assessed on 10 artificial soils constituted using a statistical design considering pH (5.5 and 7.5), organic matter (1–30% [w/w]), and clay content (5–35% [w/w]). Total Cu as well as water‐, CaCl2–, and diethylene triamine pentaacetic acid (DTPA)–extracted Cu fractions were determined for each soil mixture. Ecotoxic effect was assessed by determining growth inhibition of barley (Hordeum vulgare L.) and compost worm (Eisenia fetida) mortality. Analyses were repeated after a 16‐wk aging period of the soils at pH 7.5 (8 × 2‐wk wetting and drying cycle). Results indicated that pH was the main factor controlling Cu partitioning, ahead of organic matter and clay content. Calcium chloride (0.5 M)–extracted Cu fractions showed the best correlation with toxic responses (r = 0.55–0.66; p < 0.05), while total and DTPA‐extracted Cu concentrations could not explain differences in toxicity. Direct regressions between toxicity and soil properties (pH, organic matter, and clay content) provided better explanation of variance: r2 = 0.50 (p = 0.00006) for compost worm mortality, r2 = 0.77 (p < 0.00001) for barley shoot inhibition, and r2 = 0.92 (p < 0.00001) for barley root inhibition. Copper toxicity was mainly influenced by pH and, to a lesser extent, by organic matter and clay content. Aging in organic soils revealed a slight reduction in ecotoxicity while an increase was observed in soils with low organic matter content. Further investigation using longer aging periods would be necessary to assess the significance of this observation.
An Axenic Plant Culture System for Optimal Growth in Long‐Term Studies
Authors: Henry Amelia , Doucette William , Norton Jeanette , Jones Scott , Chard Julie , Bugbee Bruce
Published: March 2006

The symbiotic co‐evolution of plants and microbes leads to difficulties in understanding which of the two components is responsible for a given environmental response. Plant–microbe studies greatly benefit from the ability to grow plants in axenic (sterile) culture. Several studies have used axenic plant culture systems, but experimental procedures are often poorly documented, the plant growth environment is not optimal, and axenic conditions are not rigorously verified. We developed a unique axenic system using inert components that promotes plant health and can be kept sterile for at least 70 d. Crested wheatgrass (Agropyron cristatum cv. CDII) plants were grown in sand within flow‐through glass columns that were positively pressured with filtered air. Plant health was optimized by regulating temperature, light level, CO2 concentration, humidity, and nutrients. The design incorporates several novel aspects, such as pretreatment of the sand with Fe, graduated sand layers to optimize the air–water balance of the root zone, and modification of a laminar flow hood to serve as a plant growth chamber. Adaptations of several sterile techniques were necessary for maintenance of axenic conditions. Axenic conditions were verified by plating and staining leachates as well as a rhizoplane stain. This system was designed to study nutrient and water stress effects on root exudates, but is useful for assessing a broad range of plant–microbe–environment interactions. Based on total organic C analysis, 74% of exudates was recovered in the leachate, 6% was recovered in the bulk sand, and 17% was recovered in the rhizosphere sand. Carbon in the leachate after 70 d reached 255 μg d−1 Fumaric, malic, malonic, oxalic, and succinic acids were measured as components of the root exudates.
Impact of Data Quality and Model Complexity on Prediction of Pesticide Leaching
Authors: Dann R. L. , Close M. E. , Lee R. , Pang L.
Published: March 2006

Accurate input data for leaching models are expensive and difficult to obtain which may lead to the use of “general” non‐site‐specific input data. This study investigated the effect of using different quality data on model outputs. Three models of varying complexity, GLEAMS, LEACHM, and HYDRUS‐2D, were used to simulate pesticide leaching at a field trial near Hamilton, New Zealand, on an allophanic silt loam using input data of varying quality. Each model was run for four different pesticides (hexazinone, procymidone, picloram and triclopyr); three different sets of pesticide sorption and degradation parameters (i.e., site optimized, laboratory derived, and sourced from the USDA Pesticide Properties Database); and three different sets of soil physical data of varying quality (i.e., site specific, regional database, and particle size distribution data). We found that the selection of site‐optimized pesticide sorption (Koc) and degradation parameters (half‐life), compared to the use of more general database derived values, had significantly more impact than the quality of the soil input data used, but interestingly also more impact than the choice of the models. Models run with pesticide sorption and degradation parameters derived from observed solute concentrations data provided simulation outputs with goodness‐of‐fit values closest to optimum, followed by laboratory‐derived parameters, with the USDA parameters providing the least accurate simulations. In general, when using pesticide sorption and degradation parameters optimized from site solute concentrations, the more complex models (LEACHM and HYDRUS‐2D) were more accurate. However, when using USDA database derived parameters, all models performed about equally.
Modeling the Swelling Curve for Packed Soil Aggregates Using the Pedostructure Concept
Authors: Braudeau Erik , Mohtar Rabi H.
Published: February 2006

The swelling curve is generally studied as structural soil volume dependence on water content during swelling, and not on time. In this paper, we show how the swelling curve defined as the specific volume of the soil as a function of time, V(t), represent the dynamic properties of the pedostructure where the shrinkage curve represents and characterizes the hierarchical and functional organization of the soil medium. This paper presents the development and experimental evaluation of the swelling curve for a dry bed of packed aggregates immersed in water using the pedostructure concept. Pedostructure‐based parametric functions for the soil structure and water interaction represented by soil shrinkage and matric water potential curves were used to derive the swelling curve equation. This equation represents the kinetic of absorption of water by swelling of the primary peds within the pedostructure. Experiments on wetting‐drying cycles of reconstituted soil samples were conducted to obtain the parameters needed for the swelling curve equation. The simulated swelling curves using the derived equation agreed well with the measured data. The new swelling equation shows only one additional parameter; namely, the time to half charge, t1/2, which seems to be a characteristic of the clay type. It was found to be near 2100 s for kaolinitic soils and found to be independent of the clay content; as it decreased by a factor of two to three due to the presence of smectites in the sample. This paper gives access to the study of the kinetic of water absorption by primary peds.
Surface‐Soil Properties and Water Contents across Two Watersheds with Contrasting Tillage Histories
Authors: Tomer M. D. , Cambardella C. A. , James D. E. , Moorman T. B.
Published: February 2006

Soil properties and water contents (θ) vary spatially, but management effects on spatial patterns are poorly understood. This study's objective was to compare surface‐soil properties and θ in two small watersheds (30–43 ha) in Iowa's loess hills. Both watersheds were in continuous corn (Zea mays L.) from 1972 through 1995, one (CW1) under conventional tillage and the other (RW3) under ridge tillage. In 1996, CW1 was converted to no‐till. Surface‐soil (0–0.2 m) samples were collected along hillslope transects during 2002 and 2003, including four dates with water‐content measurements by gravimetry in both watersheds. Soil bulk density (ρb), organic carbon (OC), and texture were determined, along with terrain attributes (elevation, slope, surface curvature, contributing area, and wetness index). After accounting for landscape‐position effects, RW3 had more OC (2.1 versus 1.7%) and smaller ρb (1.16 versus 1.25 Mg m−3) than CW1 (P < 0.001). Larger θ values occurred in RW3 (P < 0.002) when θ was >33%. Landscape position and terrain attributes better explained variation in θ in RW3 than CW1. Also, OC was correlated with θ in RW3, but not in CW1. Soil textures were similar (within 2%,) but finer in CW1 (P < 0.05). Pedotransfer functions confirmed that differences in soil properties between watersheds resulted in greater θ in RW3 than CW1, particularly at low soil‐water potential, and that more distinct patterns of θ should occur in RW3. Results indicate long‐term conventional tillage in CW1 affected soil properties and water‐holding characteristics in ways that decreased water retention and muted spatial patterns of θ.