Transitional and steady-state choice behavior under an adjusting-delay schedule

Twelve rats made repeated choices on an adjusting-delay schedule between a smaller reinforcer (A) that was delivered immediately after a response and a larger reinforcer (B) that was delivered after a delay which increased or decreased by 20% depending on the subject's choices in successive blocks of trials. In two phases of the experiment (100 sessions and 40 sessions), reinforcer sizes were selected which enabled theoretical parameters expressing the rate of delay discounting and sensitivity to reinforcer size to be estimated from the ratio of the indifference delays obtained in the two phases. Indifference delays, calculated from adjusting delays in the last 10 sessions of each phase, were shorter when the sizes of A and B were 14 and 25 μl of a 0.6 M sucrose solution than when they were 25 and 100 μl of the same solution. The ratio of the indifference delays was significantly smaller than that predicted on the basis of an assumed linear relation between reinforcer size and instantaneous reinforcer value, consistent with a previous proposal that this relation may be hyperbolic in form. Estimates of the rate of delay discounting based on the ratio of the two indifference delays (mean, 0.08 s(-1)) were similar to values obtained previously using different intertemporal choice protocols. Estimates of the size-sensitivity parameter (mean 113 μl) were similar to estimates recently derived from performance on progressive-ratio schedules. In both phases of the experiment, adjusting delays in successive blocks of trials were analyzed using the Fourier transform. The power spectrum obtained from individual rats had a dominant frequency that corresponded to a period of oscillation of the adjusting delay between 30 and 100 trial blocks (mean, 78). Power in the dominant frequency band was highest in the early sessions of the first phase and declined with extended training. It is suggested that this experimental protocol may have utility in neurobehavioral studies of intertemporal choice.     

Matching- and nonmatching-to-sample concept learning in rats using olfactory stimuli

Previous research has shown that rats can learn matching-to-sample relations with olfactory stimuli; however, the specific characteristics of this relational control are unclear. In Experiment 1, 6 rats were trained to either match or nonmatch to sample in a modified operant chamber using common household spices as olfactory stimuli. After matching or nonmatching training with 10 exemplars, the contingencies were reversed with five new stimuli such that subjects trained on matching were shifted to nonmatching and vice versa. Following these reversed contingencies, the effects of the original training persisted for many trials with new exemplars. In Experiment 2, 9 rats were trained with matching procedures in an arena that provided for 18 different spatial locations for comparison stimuli. Five subjects were trained with differential reinforcement outcomes and 4 with only one type of reinforcer. Differential outcomes and multiple exemplars facilitated learning, and there was strong evidence for generalization to new stimuli for most rats that acquired several conditional discriminations. Performances with novel samples were generally above chance, but rarely reached the high levels obtained during baseline with well-trained stimulus relations. However, taken together, the data from the two experiments extend previous work, show that rats can learn both match and nonmatch relations with different experimental protocols, and demonstrate generalization to novel sample stimuli.     

Some determinants of remote behavioral history effects in humans

Undergraduates were exposed to a series of reinforcement schedules: first, to a fixed-ratio (FR) schedule in the presence of one stimulus and to a differential-reinforcement-of-low-rate (DRL) schedule in the presence of another (multiple FR DRL training), then to a fixed-interval (FI) schedule in the presence of a third stimulus (FI baseline), next to the FI schedule under the stimuli previously correlated with the FR and DRL schedules (multiple FI FI testing), and, finally, to a single session of the multiple FR DRL schedule again (multiple FR DRL testing). Response rates during the multiple FI FI schedule were higher under the former FR stimulus than under the former DRL stimulus. This effect of remote histories was prolonged when either the number of FI-baseline sessions was small or zero, or the time interval between the multiple FR DRL training and the multiple FI FI testing was short. Response rates under these two stimuli converged with continued exposure to the multiple FI FI schedule in most cases, but quickly differentiated when the schedule returned to the multiple FR DRL.     

On the development and mechanics of delayed matching-to-sample performance

Despite its frequent use to assess effects of environmental and pharmacological variables on short-term memory, little is known about the development of delayed matching-to-sample (DMTS) performance. This study was designed to examine the dimensions and dynamics of DMTS performance development over a long period of exposure to provide a more secure foundation for assessing stability in future research. Six pigeons were exposed to a DMTS task with variable delays for 300 sessions (i.e., 18,000 total trials; 3,600 trials per retention interval). Percent-correct and log-d measures used to quantify the development of conditional stimulus control under the procedure generally and at each of five retention intervals (0, 2, 4, 8 and 16-s) individually revealed that high levels of accuracy developed relatively quickly under the shorter retention intervals, but increases in accuracy under the longer retention intervals sometimes were not observed until 100-150 sessions had passed, with some still increasing at Session 300. Analyses of errors suggested that retention intervals induced biases by shifting control from the sample stimulus to control by position, something that was predicted by observed response biases during initial training. These results suggest that although it may require a great deal of exposure to DMTS prior to obtaining asymptotic steady state, quantification of model parameters may help predict trends when extended exposure is not feasible.     

Criminal thinking patterns, aggression styles, and the psychopathic traits of late high school bullies and bully-victims

This study explored the current psychological characteristics and criminal behavior history of individuals who retrospectively reported being bullies, bully-victims, victims, or controls (i.e. neither victims nor bullies) during their last 2 years of high school. College students (n = 960) completed measures of criminal thinking, aggression, psychopathy, and criminal behavior online. We predicted bullies and bully-victims would demonstrate the highest scores for criminal thinking, proactive aggression, psychopathy, and have the most criminal infractions. Bullies and bully-victims had significantly higher scores on criminal thinking, aggression, psychopathy, and criminal behaviors than victims or controls. Additionally, men were significantly higher in criminal thinking, aggression, psychopathy, and had more criminal acts than women. There were no gender by bully group interactions. Logistic regression analyses differentiated bully-victims from bullies. Bully-victims tended to be male, higher in criminal thinking, and higher in reactive aggression. In addition, bully-victims were distinct from victims, showing higher criminal thinking and higher proactive aggression.     

Getting precise and pragmatic about the assessment of bullying: the development of the California Bullying Victimization Scale

Accurate assessment of bullying is essential to intervention planning and evaluation. Limitations to many currently available self-report measures of bullying victimization include a lack of psychometric information, use of the emotionally laden term "bullying" in definition-first approaches to self-report surveys, and not assessing all components of the definition of bullying (chronicity, intentionality, and imbalance of power) in behavioral-based self-report methods. To address these limitations, we developed the California Bullying Victimization Scale (CBVS), which is a self-report scale that measures the three-part definition of bullying without the use of the term bully. We examined test-retest reliability and the concurrent and predictive validity of the CBVS across students in Grades 5-12 in four central California schools. Concurrent validity was assessed by comparing the CBVS with a common, definition-based bullying victimization measure. Predictive validity was examined through the co-administration of measures of psychological well-being. Analysis by grade and gender are included. Results support the test-retest reliability of the CBVS over a 2-week period. The CBVS was significantly, positively correlated with another bullying assessment and was related in expected directions to measures of well-being. Implications for differentiating peer victimization and bullying victimization via self-report measures are discussed.     

No postnatal maternal effect on male aggressiveness in wild-derived strains of house mice

Male aggressiveness is a complex behavior influenced by a number of genetic and non-genetic factors. Traditionally, the contribution of each of these factors has been established from experiments using artificially selected strains for high/low aggressive phenotypes. However, little is known about the factors underlying aggressive behavior in natural populations. In this study, we assess the influence of genetic background vs. postnatal maternal environment using a set of cross-fostering experiments between two wild-derived inbred strains, displaying high (STRA, derived from Mus musculus domesticus) and low (BUSNA, derived from Mus musculus musculus) levels of aggressiveness. The role of maternal environment was tested in males with the same genetic background (i.e. strain origin) reared under three different conditions: unfostered (weaned by mother), infostered (weaned by an unfamiliar dam from the same strain), and cross-fostered (weaned by a dam from a different strain). All males were tested against non-aggressive opponents from the A/J inbred strain. Resource-holding potential was assessed through body weight gains and territory ownership. The STRA males were shown to be aggressive in both neutral cage and resident-intruder tests. On the contrary, the BUSNA males were less aggressive in all tests. We did not find a significant effect of postnatal maternal environment; however, we detected significant maternal effect on body weight with differences between the strains, fostering type and interactions between these factors. We conclude that the aggressiveness preserved in the two strains has significant genetic component whose genetic basis can be dissected by quantitative trait loci analysis.     

Multidimensional treatment foster care (MTFC): results from an independent replication

This study examines 24‐months post‐baseline outcomes for thirty‐five Swedish antisocial youths who received either treatment in multidimensional treatment foster care (MTFC) or treatment as usual (TAU). MTFC is a community‐based treatment programme that has been successful in treating chronic juvenile offenders in the USA. This study is the first randomized control study outside the USA. The youth treated in the MTFC programme consistently showed some statistically significant positive treatment effects compared to the youth exposed to TAU. The results suggest that MTFC might be an effective method in treating youth with severe behaviour problems in a Swedish context. The authors conclude that the programme ought to be of great interest for Swedish social services as an alternative to traditional care.     

Gender Role Traits Among Individuals with Social Anxiety Disorder

The present study investigated differences between individuals with and without social anxiety disorder (SAD) in instrumentality and expressiveness, personality traits traditionally linked to the male and female gender roles, respectively. Based on evolutionary and self-discrepancy theories, it was hypothesized that individuals with SAD would score lower on instrumentality and report a discrepancy between their perceived and ideal level of instrumentality compared to control participants. Sixty-four patients with SAD and 31 non-anxious control participants completed a battery of questionnaires, including ratings of their perceived and ideal gender role attributes and current psychosocial distress. Results supported the hypotheses, and provided initial evidence that a discrepancy between perceived and ideal instrumentality may be linked to social anxiety severity, depression and lower quality of life. No differences were detected between groups in expressiveness. The present findings suggest that individuals with SAD perceive themselves to be deficient in instrumentality. They also suggest that increasing instrumentality among individuals with SAD may be beneficial for treatment.     

Building a Committed Hospice Volunteer Workforce—Do Variables at the Experience Stage Matter?

Volunteers are crucial to the survival of non‐profit organisations, who therefore have a fundamental interest in sustaining voluntary engagement over time. A central variable regarding sustained voluntary engagement is volunteers' organisational commitment, which has so far been a neglected research issue. The study at hand therefore explicitly focuses on hospice volunteers' commitment. Starting from the assumption that variables at the experience stage of volunteerism may be relevant in predicting volunteer commitment, questionnaire data on volunteers' motives, motive fulfilment and role identity were collected in a sample of hospice volunteers (N = 276). Results of multiple regression analyses show positive relationships between altruistic motive fulfilment and a volunteer role identity on the one hand and volunteer commitment on the other. Observed interaction effects imply that altruistic motive fulfilment is of importance both at the initial phase of volunteering and for long‐term volunteers. Moreover, interaction effects provide evidence that the fulfilment of egoistic motives is of particular importance amongst volunteers to whom egoistic motives are central. Thus, the fulfilment of altruistic motives and facilitating the development of a volunteer role identity should be permanent concerns in building a committed workforce. Egoistic motive fulfilment in contrast is of special relevance, when egoistic motives for volunteering are strong. Copyright © 2014 John Wiley & Sons, Ltd.