Search

An adjusting-delay procedure was used to study the choices of pigeons and rats when both delay and amount of reinforcement were varied. In different conditions, the choice alternatives included one versus two reinforcers, one versus three reinforcers, and three versus two reinforcers. The delay to one alternative (the standard alternative) was kept constant in a condition, and the delay to the other (the adjusting alternative) was increased or decreased many times a session so as to estimate an indifference point--a delay at which the two alternatives were chosen about equally often. Indifference functions were constructed by plotting the adjusting delay as a function of the standard delay for each pair of reinforcer amounts. The experiments were designed to test the prediction of a hyperbolic decay equation that the slopes of the indifference functions should increase as the ratio of the two reinforcer amounts increased. Consistent with the hyperbolic equation, the slopes of the indifference functions depended on the ratios of the two reinforcer amounts for both pigeons and rats. These results were not compatible with an exponential decay equation, which predicts slopes of 1 regardless of the reinforcer amounts. Combined with other data, these findings provide further evidence that delay discounting is well described by a hyperbolic equation for both species, but not by an exponential equation. Quantitative differences in the y-intercepts of the indifference functions from the two species suggested that the rate at which reinforcer strength decreases with increasing delay may be four or five times slower for rats than for pigeons.

This study examined whether the experience of the death of a parent in childhood increases risk for adult psychopathology. Participants consisted of 3481 men and women gathered through the Baltimore Epidemiologic Catchment Area study in 1981 and followed through 1994-1995. The Diagnostic Interview Survey was administered by trained interviewers and was used to assess DSM-III disorders including major depression, panic, and anxiety disorders. Maternal death was not a predictor of adult psychopathology. The death of the father during childhood more than doubled the risk for major depressive disorder in adulthood. This study did not find any significant interactions between gender of the deceased parent and gender of the participant nor did the current age of the participant or their age at the time of the death of a parent affect risk for adult psychopathology. The long-term effect on adult depression of the experience of the death of the father in childhood is attributed to likely financial stresses, which may have continued for years and possibly into early adulthood, complicating the family's adaptation to the initial loss.

The recent attention given to false confessions and convictions underscores the need for a valid and applicable system of credibility assessment. The current study demonstrates the effectiveness of assessment criteria indicative of deception (ACID) training in increasing rater's ability to discriminate between honest and deceptive transcripts. ACID generates credibility assessment through analysis of behaviors related to memory and impression-management as they occur during the course of an investigative interview. Raters were taught that honest responses are longer, more vivid, and more spontaneous than deceptive responses. Conversely, deceptive responses are shorter, less vivid, more rigid, more carefully phrased, and less likely to change during the course of an investigative interview. Trained raters were able to correctly identify 77% of transcripts as honest or deceptive, whereas untrained raters correctly identified 57%. Future research should focus on using the ACID technique in more realistic situations and should involve training of professional investigators.

The authors investigate whether the choice of college textbook affects students' comprehension of the material. Forty-eight students from educational psychology courses were randomly assigned to one of two conditions: (1) unfamiliar passages drawn from the textbook used in the course, or (2) comparable passages selected from a competitor textbook. Students read three passages and completed comprehension tests and an opinion survey. No significant differences were found. Implications for textbook selection practices are presented in the discussion section. © 2008, Copyright Taylor & Francis Group, LLC.

Pigeons responded in a successive-encounters procedure that consisted of a search period, a choice period, and a handling period. The search period was either a fixed-interval or a mixed-interval schedule presented on the center key of a three-key chamber. Upon completion of the search period, the center key was turned off and the two side keys were lit. A pigeon could either accept a delay followed by food (by pecking the right key) or reject this option and return to the search period (by pecking the left key). During the choice period, a red right key represented the long alternative (a long handling delay followed by food), and a green right key represented the short alternative (a short handling delay followed by food). The experiment consisted of a series of comparisons for which optimal diet theory predicted no changes in preference for the long alternative (because the overall rates of reinforcement were unchanged), whereas the hyperbolic-decay model predicted changes in preference (because the delays to the next possible reinforcer were varied). In all comparisons, the results supported the predictions of the hyperbolic-decay model, which states that the value of a reinforcer is inversely related to the delay between a choice response and reinforcer delivery.

Rats chose between alternatives that differed in the number of reinforcers and in the delay to each reinforcer. A left leverpress led to two reinforcers, each delivered after a fixed delay. A right leverpress led to one reinforcer after an adjusting delay. The adjusting delay was increased or decreased many times in a session, depending on the rat's choices, in order to estimate an indifference point-a delay at which the two alternatives were chosen about equally often. Both the number of reinforcers and their individual delays affected the indifference points. The overall pattern of results was well described by the hyperbolic-decay model, which states that each additional reinforcer delivered by an alternative increases preference for that alternative but that a reinforcer's effect is inversely related to its delay. Two other possible delay-discounting equations, an exponential equation and a reciprocal equation, did not produce satisfactory predictions for these data. Adding an additional free parameter to the hyperbolic equation as an exponent for delay did not appreciably improve the predictions, suggesting that raising delay to some power other than 1.0 was unnecessary. The results were qualitatively similar to those from a previous experiment with pigeons (Mazur, 1986), but quantitative differences suggested that the rates of delay discounting were several times slower for rats than for pigeons.

An adjusting-delay procedure was used to study rats' choices with probabilistic and delayed reinforcers, and to compare them with previous results from pigeons. A left lever press led to a 5-s delay signaled by a light and a tone, followed by a food pellet on 50% of the trials. A right lever press led to an adjusting delay signaled by a light followed by a food pellet on 100% of the trials. In some conditions, the light and tone for the probabilistic reinforcer were present only on trials that delivered food. In other conditions, the light and tone were present on all trials that the left lever was chosen. Similar studies with pigeons [Mazur, J.E., 1989. Theories of probabilistic reinforcement. J. Exp. Anal. Behav. 51, 87-99; Mazur, J.E., 1991. Conditioned reinforcement and choice with delayed and uncertain primary reinforcers. J. Exp. Anal. Behav. 63, 139-150] found that choice of the probabilistic reinforcer increased dramatically when the delay-interval stimuli were omitted on no-food trials, but this study found no such effect with the rats. In other conditions, the probability of food was varied, and comparisons to previous studies with pigeons indicated that rats showed greater sensitivity to decreasing reinforcer probabilities. The results support the hypothesis that rats' choices in these situations depend on the total time between a choice response and a reinforcer, whereas pigeons' choices are strongly influenced by the presence of delay-interval stimuli. (c) 2007 Elsevier B.V. All rights reserved.

Pigeons responded in a successive-encounters procedure that consisted of a search state, a choice state, and a handling state. The search state was either a fixed-interval or mixed-interval schedule presented on the center key of a three-key chamber. Upon completion of the search state, the choice state was presented, in which the center key was off and the two side keys were lit. A pigeon could either accept a delay followed by food (by pecking the right key) or reject this option and return to the search state (by pecking the left key). During the choice state, a red right key represented the long alternative (a long handling delay followed by food), and a green right key represented the short alternative (a short handling delay followed by food). In some conditions, both the short and long alternatives were fixed-time schedules, and in other conditions both were mixed-time schedules. Contrary to the predictions of both optimal foraging theory and delay-reduction theory, the percentage of trials on which pigeons accepted the long alternative depended on whether the search and handling schedules were fixed or mixed. They were more likely to accept the long alternative when the search states were fixed-interval rather than mixed-interval schedules, and more likely to reject the long alternative when the handling states were fixed-time rather than mixed-time schedules. This pattern of results was in qualitative agreement with the predictions of the hyperbolic-decay model, which states that the value of a reinforcer is inversely related to the delay between a choice response and reinforcer delivery.

The rise of mathematical models in the experimental analysis of behavior has increased over the years, and they offer several advantages. Mathematical models require theorists to be precise and unambiguous, often allowing comparisons of competing theories that sound similar when stated in words. Sometimes different mathematical models may make equally accurate predictions for a large body of data. In Such cases, it is important to find and investigate situations for which the competing models make different predictions because, unless two models are actually mathematically equivalent, they are based on different assumptions about the psychological processes that underlie ail observed behavior. Mathematical models developed in basic behavioral research have been used to predict and control behavior in applied settings, and they have guided research in other areas of psychology. A good mathematical model call provide a common framework for understanding what might otherwise appear to be diverse and unrelated behavioral phenomena. Because psychologists vary in their quantitative skills and in their tolerance for mathematical equations, it is important for those who develop mathematical models of behavior to find ways (such as verbal analogies, pictorial representations, or concrete examples) to communicate the key premises of their models to nonspecialists.

In two experiments, we investigated directed forgetting of a single item. We presented participants with two phone numbers to remember and instructed half of the participants to forget the first phone number. The first number was either learned on a single trial (Experiment 1) or on three trials (Experiment 2). In Experiment 1, there was evidence of directed forgetting as a result of differential encoding; the forget instruction affected recall and recognition for both phone numbers. In Experiment 2, the evidence favored differential rehearsal because the forget instruction affected recall but not recognition. These results indicate that instructions to forget can affect memory of single items.

It has been suggested in the identity literature that a readiness to change may play a role in identity development beyond adolescence, but an empirical investigation of this relationship had yet to be conducted until now. Therefore, the purpose of the current study was to establish a longitudinal relationship between readiness to change and adult identity development. Participants completed measures of readiness to change and identity at both the beginning and the end of the study. The results revealed a relationship between readiness to change and changes in identity exploration over the study interval, and between readiness to change and changes in identity commitment. The findings are discussed in terms of the currently available literature on identity development in adulthood. (c) 2006 Elsevier Inc. All rights reserved.

Abstract. This study investigated whether a reflective journal writing assignment would improve students' course performance. A total of 166 students from undergraduate sections of a course taught by the same instructor over three semesters completed the assignment as part of their requirements. Students (N = 317) from five previous semesters of the same course taught by the same instructor, who were not required to complete the assignment, served as a comparison group. Intervention and comparison groups were comparable on a variety of variables including all assignments, excepting the journal assignment. The findings are interpreted within the context of factors such as students' study habits and motivation. © 2006, Copyright Taylor & Francis Group, LLC.

Pigeons responded on concurrent-chains schedules with equal variable-interval schedules as initial links. One terminal link delivered a single reinforcer after a fixed delay, and the other terminal link delivered either three or five reinforcers, each preceded by a fixed delay. Some conditions included a postreinforcer delay after the single reinforcer to equate the total durations of the two terminal links, but other conditions did not include such a postreinforcer delay. With short initial links, preference for the single-reinforcer alternative decreased when a postreinforcer delay was present, but with long initial links, the postreinforcer delays had no significant effect on preference. In conditions with a postreinforcer delay, preference for the single-reinforcer alternative frequently switched from above 50% to below 50% as the initial links were lengthened. This pattern of results was consistent with delay-reduction theory (Squires & Fantino, 1971), but not with the contextual-choice model (Grace, 1994) or the hyperbolic value-added model (Mazur, 2001) as they have usually been applied. However, the hyperbolic value-added model could account for the results if its calculations were expanded to include reinforcers delivered in later terminal links. The implications of these findings for models of concurrent-chains performance are discussed.

Presidential nominations in recent years have been settled with increasing speed, most of the time in the early stages of the primaries and caucuses, and certainly before the national convention, which has become more of a rally. Even when the battle for the Democratic Presidential nomination continued to the end of the primary season in 2008, it was settled before the convention. Analysts have emphasized the importance of the “invisible primary” and the front-loaded delegate selection schedule in explaining the early resolution of Presidential nomination contests. However, not enough attention has been paid to a much more fundamental change in our political parties and party system: The old umbrella parties have been replaced by ideological polarization between the parties and ideological homogenization within the parties. Our new party system dates back about forty years, and features increased ideological unity and decreased factionalism, making it easier to settle nominations. Even today's front-loaded nominating calendar would not have prevented some of the hotly contested conventions of the old umbrella parties. Polity (2009) 41, 312-330. doi:10.1057/pol.2009.4; published online 11 May 2009

In this article, the intellectual thought of a group of key late 19th century national administrative reformers is isolated and analyzed. These reformers were interested in reforming the civil, military and business administrative functions of the executive branch to provide for greater elite administrative supervision over and intervention in the national society and economy. The reformers often articulated their reform purposes, motives and goals in the Hamiltonian language of administrative authority and popular deference to executive administrative counsels. An important key to understanding this article is recognizing that while environmental social and economic conditions had changed significantly for the Gilded Age reformers since the American constitutional founding, many elements of the Hamiltonian tradition still resonated with the reformers a full century later. In this way, the historically transmitted ideology and rhetoric of Hamiltonian thought can be seen as having an independent, causative impact on the administrative reformers' purposes, motives and goals related to executive administrative reform.

This paper explores the Post Cold War origins of the organized criminal violence that once gripped Colombia and now grips Mexico and particularly the highly controversial counterinsurgency strategy used in Colombia that forms the basis for the current strategy in Mexico. It argues that ideology is a reason why the military aspect of these problems was neglected for so long and the reason its detractors see it as a strategy that reduces national sovereignty and endangers democracy when statistics on control of territory, reduction of violence and democratic progress demonstrate the opposite to be true. The paper uses the term “colombianization” to emphasize Colombia’s dramatic shift from almost ungovernable to one of the most stable countries in the region. Colombianization is defined not as a counterdrug strategy as are both the Colombian and Mexican U.S. assistance strategies but as an integrated, law-based, counterinsurgency strategy implemented from the bottom up that facilitates the establishment of elite consensus and puts the country on a path toward rule of law. Ironically, it was democratic and free market reforms that strengthened the forces of instability in both Colombia and Mexico and the militarization of security that appears to facilitate democratic stability. This study uses local level assessments of Plan Colombia and local interviews conducted in Chihuahua and Michoacán to evaluate the prospects of colombianization in urban and rural Mexico. Colombia's experience suggests that colombianization can stabilize the country and help reactivate the economy but democratic progress is painfully slow and the strategy has little impact on the drug industry and the corruption associated with it.

This article examines the debate over the compatibility of trade and the environment. First, it discusses the range of arguments in the debate from trade being inherently beneficial to inherently harmful to the environment. Second, the entry examines the place of the environment within the GATT/WTO and various controversies surrounding the GATT/WTO and environmental protection. Finally, the article examines the role of multilateral environmental agreements in protecting the environment and their possible consequences for the international trading system.