Choice in a successive-encounters procedure and hyperbolic decay of reinforcement

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.     

PREFERENCE FOR A STIMULUS THAT FOLLOWS A RELATIVELY AVERSIVE EVENT: CONTRAST OR DELAY REDUCTION?

Several types of contrast effects have been identified including incentive contrast, anticipatory contrast, and behavioral contrast. Clement, Feltus, Kaiser, and Zentall (2000) proposed a type of contrast that appears to be different from these others and called it within-trial contrast. In this form of contrast the relative value of a reinforcer depends on the events that occur immediately prior to the reinforcer. Reinforcers that follow relatively aversive events are preferred over those that follow less aversive events. In many cases the delay reduction hypothesis proposed by Fantino (1969) also can account for such effects. The current experiments provide a direct test of the delay reduction and contrast hypotheses by manipulating the schedule of reinforcement while holding trial duration constant. In Experiment 1, preference for fixed-interval (FI) versus differential-reinforcement-of-other-behavior (DRO) schedules of reinforcement was assessed. Some pigeons preferred one schedule over the other while others demonstrated a position (side) preference. Thus, no systematic preference was found. In Experiment 2, a simultaneous color discrimination followed the FI or DRO schedule, and following training, preference was assessed by presenting the two positive stimuli simultaneously. Consistent with the contrast hypothesis, pigeons showed a significant preference for the positive stimulus that in training had followed their less preferred schedule.     

Asymmetry of the group context effect on delay discounting

Binary choice delay discounting tasks require participants to indicate preference between smaller, immediate, and larger, delayed rewards. Previous research indicates that when the delayed reward is shared with others, the delayed outcome is preferred compared with when the outcomes are for the self only, resulting in lower rates of delay discounting. The present series of studies sought to replicate and extend this finding. Study 1 compared delay discounting on a standard task in which both immediate and delayed outcomes are for the self and a group context task where the delayed outcome was shared with one other person. Replicating previous results, group context resulted in lower rates of delay discounting, and this effect was independent of how the shared outcome was presented. Study 2 compared delay discounting on a standard task and a group context task where the immediate outcome was shared. In contrast to Study 1, group context resulted in higher rates of delay discounting, suggesting that preference in intertemporal choice tracks the shared outcome. Moreover, this effect was not independent of how the shared outcome was presented. This is the first study to reveal that group context, when applied to the immediate outcome, can result in higher rates of delay discounting.     

Cheating among children: Temptation,loss framing,and previous cheating

Although early economic approaches to misbehavior merely compare the monetary utility of accessible options, self-concept maintenance models introduce moral considerations to the equation. These assume that people trade off possible gains to be made from moral transgressions with associated decreases in self-esteem. On the basis of the assumption that the development of moral values among children is weaker than in adults, we expected children's behavior to be close to that of the hypothetical homo economicus, with their decisions as to whether to cheat therefore being influenced by decision theory elements: normative elements such as temptation magnitude, and behavioral elements such as framing. As children should pay no heed to moral considerations in dynamic multiple task settings, behavior opposite to “moral cleansing” was expected, with a first lie predicting later lies. In addition to testing the above ideas, the present study adopted a novel methodology. Our hypotheses were tested in a lab-in-the-field study using a modified “roll a die” method in a naturalistic setting for children of ages 7 to 10. We modified the method to identify both true and declared values of die rolls (a novel DICE+ electronic die was used). As expected, children were sensitive to temptation and cheated more willingly for more attractive prizes. Girls (but not boys) lied more (in terms of both frequency and magnitude) to avoid losses (with loss framing) than to make gains (with gain framing). Previous lying correlated positively with lying on subsequent tasks.     

Delay discounting of different outcomes: Review and theory

Steep delay discounting is characterized by a preference for small immediate outcomes relative to larger delayed outcomes and is predictive of drug abuse, risky sexual behaviors, and other maladaptive behaviors. Nancy M. Petry was a pioneer in delay discounting research who demonstrated that people discount delayed monetary gains less steeply than they discount substances with abuse liability. Subsequent research found steep discounting for not only drugs, but other nonmonetary outcomes such as food, sex, and health. In this systematic review, we evaluate the hypotheses proposed to explain differences in discounting as a function of the type of outcome and explore the trait- and state-like nature of delay discounting. We found overwhelming evidence for the state-like quality of delay discounting: Consistent with Petry and others' work, nonmonetary outcomes are discounted more steeply than monetary outcomes. We propose two hypotheses that together may account for this effect: Decreasing Future Preference and Decreasing Future Worth. We also found clear evidence that delay discounting has trait-like qualities: People who steeply discount monetary outcomes steeply discount nonmonetary outcomes as well. The implication is that changing delay discounting for one outcome could change discounting for other outcomes.     

Juvenilized play fighting in subordinate male rats

As pairs of male juvenile sibling rats that are housed together become sexually mature, they develop a dominance-subordinance relationship. These dominance relationships appear to be reflected in the play fighting of the pairmates both as juveniles and as young adults, in that the seemingly subordinate partner initiates more playful attacks at both ages. However, as adults, even though it is the subordinate that initiates more playful attacks, it is the subordinate that is pinned on his back by the partner most often. Dominant pairmates were found to switch to defensive patterns typically found in adult males. In contrast, the subordinates, when contacted on the nape, were more likely to retain the juvenile pattern of turning over to supine. Therefore, the subordinate pairmate of an adult pair of male siblings both initiates more playful attacks and defends itself in a more juvenile manner than its dominant partner, and this leads to it being pinned more frequently. This pattern of behavior by subordinate rats is suggested to function as a friendship maintenance mechanism permitting co-existence in multimale colonies.     

大学生未来取向与学习自主性的关系研究:学业延迟满足和时间管理倾向的多重中介作用

本研究旨在探讨未来取向和学习自主性的关系,分析学业延迟满足、时间管理倾向的作用.采用问卷法对731名大学生进行调查,研究表明:(1)大学生未来取向、学业延迟满足、时间管理倾向和学习自主性之间均存在显著相关;(2)大学生学业延迟满足、时间管理倾向在未来取向和学习自主性间存在中介效用,即未来取向直接影响大学生的学习自主性,...     

DELAY‐AMOUNT TRADEOFFS IN CHOICES BY PIGEONS AND RATS: HYPERBOLIC VERSUS EXPONENTIAL DISCOUNTING

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.     

EVALUATION OF AN ENHANCED STIMULUS‐STIMULUS PAIRING PROCEDURE TO INCREASE EARLY VOCALIZATIONS OF CHILDREN WITH AUTISM

Evidence to support stimulus‐stimulus pairing (SSP) in speech acquisition is less than robust, calling into question the ability of SSP to reliably establish automatically reinforcing properties of speech and limiting the procedure's clinical utility for increasing vocalizations. We evaluated the effects of a modified SSP procedure on low‐frequency within‐session vocalizations that were further strengthened through programmed reinforcement. Procedural modifications (e.g., interspersed paired and unpaired trials) were designed to increase stimulus salience during SSP. All 3 participants, preschoolers with autism, showed differential increases of target over nontarget vocal responses during SSP. Results suggested an automatic reinforcement effect of SSP, although alternative interpretations are discussed, and suggestions are made for future research to determine the utility of SSP as a clinical intervention for speech‐delayed children.     

个体与群体情境下3～5岁幼儿延迟满足的实验研究

采用实验法以90名3~5岁的儿童为被试,探讨其在个体和群体情境中延迟满足的特点。研究结果表明:3~5岁幼儿的延迟满足能力存在着显著的年龄差异,随着年龄的增长而不断提高;3岁幼儿延迟满足能力较弱,而4、5岁的幼儿在这种能力上有了较明显的发展,但从整体上来看,幼儿阶段的延迟满足能力仍然很低;3~5岁幼儿的延迟满足能力在不同的情境、不同性别中不存在显著的差异。