Children's choice: Sensitivity to changes in reinforcer density

Two experiments were carried out in which children's sensitivity to changes in reinforcer density (number of reinforcers per session) was measured in a choice paradigm. In Experiment 1, 24 girls (ages 6, 9, and 12 years) performed on concurrent-chain schedules of reinforcement. The initial links were variable-interval 10-s schedules. One terminal link always gave three tokens after 30 s, but the parameters associated with the other were varied. Independent manipulations of reinforcer size (two tokens or four tokens) and prereinforcement delay (25 s or 65 s) led to equal changes in the relative density of tokens that could be earned on the schedules. Subjects at all ages were sensitive to changes in reinforcer density brought about by changes in reinforcer size, whereas only 3 12-year-olds showed sensitivity to the changes brought about by manipulation of prereinforcer delay. In Experiment 2, titration procedures were used to test the extent of this insensitivity to delay in 32 6- and 12-year-old children. In these procedures, a repeated choice of the large reinforcer increased the delay to its delivery, and a repeated choice of the small reinforcer reduced the delay to the delivery of the large reinforcer. Whereas 6-year-old boys and girls tended to maintain a strong preference for the large reinforcer, so increasing the delay to its delivery, 12-year-olds tended to distribute their responses to both alternatives, thus producing a stable level of delay to the large reinforcer. The results from the two experiments support the idea of two stages in the development of adaptive intertemporal choice.     

An account of human “impulsivity” on self-control tasks

Three experiments examined the effects of economic constraint (time restriction—trials restriction) on adult humans' performance on concurrent chained schedules of reinforcement in which terminal links differed both in reward size and pre-reward delay levels. In the first, terminal links offered a long delay (20, 30, 40, 50 sec) followed by 2 points, or a short delay (10 sec) followed by 1 point. Initial links consisted of the same variable interval schedules for each alternative. Subjects showed a conditional sensitivity to increases in delay. Under a time constraint, there was an increasing preference for the smaller reward as the delay to the larger reward was increased, whereas under a trials constraint subjects were totally insensitive to such changes. In the second experiment, this finding was replicated using long and short periods of video game playing as large and small rewards. In the third experiment terminal link parameters remained constant (2 points after 15 sec, or 1 point immediately), but initial link parameters were manipulated (either VI 1-sec, 8-sec, or 20-sec) so that the higher relative rate of reward shifted from being associated with the small reward to being associated with the large reward. Again subjects chose differently under the two constraints. Subjects under the time constraint exhibited a preference for the small reward at all levels of initial link, but under the trials constraint subjects preferred the large reward. Subjects in the time constraint condition thus exhibited a maladaptive insensitivity to changes in the initial link duration. These findings are interpreted as supporting a miscalculation rather than a discounting interpretation of human performance on “self-control” tasks.     

Choice behavior of rats in a concurrent-chains schedule: Amount and delay of reinforcement

Rats were exposed to concurrent-chains schedules in which the terminal links were equal fixed-interval schedules terminating in one or three food pellets. Choice proportions for large reward increased with increases in delay intervals programmed on fixed-interval schedules and supported the predictions derived from a general choice model originally formulated by Fantino and later developed by Navarick and Fantino. In addition, a functional equivalence of two alternatives was established by increasing delay intervals with large reward, whereas delay intervals for small reward were held constant. Functionally equivalent delay intervals with large reward, for each delay interval with small reward, can be described by a power function with exponent smaller than 1.0. A better prediction of choice proportions resulted when this function was used to derive predicted choice proportions.     

An experimental analysis of impulsivity and impulse control in humans

In choosing between small, immediate and large, delayed reward, an organism behaves impulsively if it chooses the small reward and shows impulse control if it chooses the large reward. Work with nonhumans suggests that impulsivity and impulse control may be derived from gradients of delayed reinforcement. A model developed by Ainslie and by Rachlin suggests that preference for the rewards should be a function of when the choice is made: small reward with no delay may be preferred to large reward with delay X, but adding delay T to both alternatives should shift preference to the large reward. Three experiments investigated this preference reversal in humans, using termination of 90 dba white noise as the reinforcing event. Experiment 1 showed that under some instructional conditions 90-sec noise off with no delay was preferred over 120-sec noise off after a 60-sec delay, but that preference shifted to the large reward when a 15-sec delay (T) was added to both alternatives. Experiment 2 replicated this preference reversal under two conditions of large, delayed reward, and with three rather than two values of T. Experiment 3 confirmed this effect of T and showed that some humans committed themselves to the large reward when commitment could be made some time before presentation of the reward alternatives. These data support the Ainslie-Rachlin model and extend it to human choice behavior.     

Commitment, choice and self-control

When offered a choice (Choice Y) between a small immediate reward (2-sec exposure to grain) and a large reward (4-sec exposure to grain) delayed by 4 sec, pigeons invariably preferred the small, immediate reward. However, when offered a choice (Choice X) between a delay of T seconds followed by Choice Y and a delay of T seconds followed by restriction to the large delayed reward only, the pigeon's choice depended on T. When T was small, the pigeons chose the alternative leading to Choice Y (and then chose the small, immediate reward). When T was large, the pigeons chose the alternative leading to the large delayed reward only. The reversal of preference as T increases is predicted by several recent models for choice between various amounts and delays of reward. The preference for the large delayed alternative with long durations of T parallels everyday instances of advance commitment to a given course of action. Such commitment may be seen as a prototype for self-control.     

Evaluative verbalization and delay maintenance behavior in children

An experiment is presented which examined the influence of verbalizations on children's tendencies to postpone immediate gratification in terms of increased delayed reward. Children's verbalizations were varied in terms of their evaluative valence and whether they focused upon the reward itself or the delay task. During a delay task children in experimental groups periodically verbalized evaluative statements that were either positive (I like …) or negative (I don't like …) and which focused upon either the reward itself (… the tokens) or the delay behavior (… to wait). Children who focused on reward, under conditions of either positive or negative evaluation, postponed immediate gratification less than control subjects who made no verbalization. Children who evaluated delay behavior positively postponed immediate gratification longer than silent subjects, though children who negatively evaluated delay behavior did not differ from subjects who did not verbalize. The results are interpreted in terms of the influence of evaluative valence and focus as parameters of plans for delay behavior.     

The Effect of Symbolic Distancing on Delay Tolerance across the Preschool Period

ABSTRACT

We aimed to longitudinally examine how symbolic distancing affects preschool children’s delay tolerance in a delay choice task. We presented children with choices between a smaller immediate reward and a larger delayed reward in conditions with either symbolic stimuli or edible rewards. Overall, symbolic distancing modulated children’s delay tolerance. In particular, whereas in the first phase (T1: 3- and 4-year-olds) children presented with edible rewards chose the larger option more often than children presented with symbolic stimuli, in the second phase (T2: 5- and 6-year-olds), there was no significant difference between children presented with symbolic stimuli and those presented with edible rewards. These results are discussed by examining how children’s delay tolerance changes during the development and comparing children to adult humans in a similar task.     

Scaling Incentives: Determining Preference and Indifference in 8- to lO-Year-Old Girls

The present study adopted procedures similar to those used by Logan (1965) to determine choice behavior in children. The objective was to provide an improved methodology in delay-of-gratification studies, thus avoiding the problems associated with scaling different kinds of rewards, and to provide approximate functions relating a delay-of-token reward to choice behavior. Thus, 7 girls aged 8 to 10 years were exposed to a choice paradigm in which a larger reward (2 tokens) was pitted against a smaller reward (1 token); access to these rewards was delayed a certain period of time. The results of this experiment showed that as the delay of the larger reward increased, preference for the smaller reward increased in an orderly fashion. The finding that delay shifted preference from the larger to the smaller reward is discussed in relation to current theory. The results of this experiment also provide evidence for the utility of tokens in scaling incentives for choice studies.     

观点采择因素对3～4岁儿童延迟满足决策的影响

通过采用延迟满足决策任务,要求儿童分别为自己和他人做出决策,本研究考察了观点采择因素对儿童情感决策发展的影响。实验一选取3岁和4岁儿童各40名,结果发现3岁儿童和4岁儿童在为自己选和为他人选两种条件下的表现均无显著差异,都倾向于做出延迟选择。实验二选取3岁和4岁儿童各60名,在为他人的选择中进一步区分了不同的观点提示条件,并增加了观点采择测验任务。结果发现,4岁儿童的观点采择能力得到了初步的发展,在不同的观点提示条件下为他人选择时分别表现出了与为自己选择不同的决策趋势;3岁儿童尚未获得观点采择能力,在各种不同观点提示条件下为自己和为他人做选择时差异均不显著。本研究结果表明,观点采择能力对儿童情感决策的影响是发展性的。随着观点采择能力的发展,儿童逐渐能够确立正确的延迟动机,为他人做出有效的决策。     

Choice between delayed reinforcers and fixed-ratio schedules requiring forceful responding.

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

Waiting by mistake: Symbolic representation of rewards modulates intertemporal choice in capuchin monkeys,preschool children and adult humans

In the Delay choice task subjects choose between a smaller immediate option and a larger delayed option. This paradigm, also known as intertemporal choice task, is frequently used to assess delay tolerance, interpreting a preference for the larger delayed option as willingness to wait. However, in the Delay choice task subjects face a dilemma between two preferred responses: “go for more” (i.e., selecting the larger, but delayed, option) vs. “go for sooner” (i.e., selecting the immediate, but smaller, option). When the options consist of visible food amounts, at least some of the choices of the larger delayed option might be due to a failure to inhibit a prepotent response towards the larger option rather than to a sustained delay tolerance. To disentangle this issue, we tested 10 capuchin monkeys, 101 preschool children, and 88 adult humans in a Delay choice task with food, low-symbolic tokens (objects that can be exchanged with food and have a one-to-one correspondence with food items), and high-symbolic tokens (objects that can be exchanged with food and have a one-to-many correspondence with food items). This allows evaluating how different methods of representing rewards modulate the relative contribution of the “go for more” and “go for sooner” responses. Consistently with the idea that choices for the delayed option are sometimes due to a failure at inhibiting the prepotent response for the larger quantity, we expected high-symbolic tokens to decrease the salience of the larger option, thus reducing “go for more” responses. In fact, previous findings have shown that inhibiting prepotent responses for quantity is easier when the problem is framed in a symbolic context. Overall, opting for the larger delayed option in the visible-food version of the Delay choice task seems to partially result from an impulsive preference for quantity, rather than from a sustained delay tolerance. In capuchins and children high-symbolic stimuli decreased the individual’s preference for the larger reward by distancing from its appetitive features. Conversely, the sophisticated symbolic skills of adult humans prevented the distancing effect of high-symbolic stimuli in this population, although this result may be due to methodological differences between adult humans and the other two populations under study. Our data extend the knowledge concerning the influence of symbols on both human and non-human primate behavior and add a new element to the interpretation of the Delay choice task. Since high-symbolic stimuli decrease the individual’s preference for the larger reward by eliminating those choices due to prepotent responses towards the larger quantity, they allow to better discriminate responses based on genuine delay aversion. Thus, these findings invite greater caution in interpreting the results obtained with the visible-food version of the Delay choice task, which may overestimate delay tolerance.     

How do African grey parrots (Psittacus erithacus) perform on a delay of gratification task?

Humans and other animals often find it difficult to choose a delayed reward over an immediate one, even when the delay leads to increased pay-offs. Using a visible incremental reward procedure, we tested the ability of three grey parrots to maintain delay of gratification for an increasingly valuable food pay-off. Up to five sunflower seeds were placed within the parrot’s reach, one at a time, at a rate of one seed per second. When the parrot took a seed the trial was ended and the birds consumed the accumulated seeds. Parrots were first tested in daily sessions of ten trials and then with single daily trials. For multiple trial sessions, all three parrots showed some limited improvement across 30 sessions. For single trial sessions, only one parrot showed any increase in seed acquisition across trials. This parrot was also able to consistently obtain two or more seeds per trial (across both multiple and single trial conditions) but was unable to able to wait 5 s to obtain the maximum number of seeds. This parrot was also tested on a slower rate of seed presentation, and this significantly reduced her mean seed acquisition in both multiple and single trial conditions, suggesting that both value of reward available and delay duration impact upon self-control. Further manipulation of both the visibility and proximity of seeds during delay maintenance had little impact upon tolerance of delays for both parrots tested in this condition. This task demanded not just a choice of delayed reward but the maintenance of delayed gratification and was clearly difficult for the parrots to learn; additional training or alternative paradigms are required to better understand the capacity for self-control in this and other species.     

Prevention of anxiety symptoms in children: results from a universal school-based trial

The present study evaluated the effectiveness of a universal school-based cognitive behavior prevention program (the FRIENDS program) for childhood anxiety. Participants were 638 children, ages 9 to 12 years, from 14 schools in North Rhine-Westphalia, Germany. All the children completed standardized measures of anxiety and depression, social and adaptive functioning, coping strategies, social skills, and perfectionism before and after the 10-week FRIENDS program and at two follow-up assessments (6 and 12 months) or wait period. Children who participated in the FRIENDS program exhibited significantly fewer anxiety and depressive symptoms, and lower perfectionism scores than children in the control group at 12-month follow-up. Younger children (9-10-year-olds) displayed treatment gains immediately after the intervention, whereas older children (11-12-year-olds) showed anxiety reduction only at 6- and 12-month follow-up. Perfectionism and avoidant coping acted as mediators of pre- to postintervention changes in anxiety scores. This study provides empirical evidence for the utility of the FRIENDS program in reducing anxiety and depressive symptoms among German children.     

Negative reinforcement and choice in humans

Participants chose between reinforcement schedules differing in delay and/or duration of noise offset. In Experiment 1 it was found that (1) immediate reinforcement was preferred to delayed reinforcement when amounts (durations) of reinforcement were equal; (2) a relatively large reinforcer was preferred to a smaller one when both reinforcers were obtained immediately; and (3) preference for an immediate, small reinforcer versus a delayed, large reinforcer increased as the delay preceding the large reinforcer increased, a sign of “impulsivity”. In Experiment 2, the schedules differed in amount or delay and equal intervals were added either to the constant parameter or the varied parameter. A shift from virtually exclusive preference to indifference occurred in the latter case but not the former, a result supporting a model of self-control that assumes that the value of a schedule depends on the ratio of amount and delay, and that choice between schedules depends on the ratio of these values.     

Stimulus Equivalence: Effects Of A Default-response Option On Emergence Of Untrained Stimulus Relations

Human subjects were exposed to a concurrent-chains schedule in which reinforcer amounts, delays, or both were varied in the terminal links, and consummatory responses were required to receive points that were later exchangeable for money. Two independent variable-interval 30-s schedules were in effect during the initial links, and delay periods were defined by fixed-time schedules. In Experiment 1, subjects were exposed to three different pairs of reinforcer amounts and delays, and sensitivity to reinforcer amount and delay was determined based on the generalized matching law. The relative responding (choice) of most subjects was more sensitive to reinforcer amount than to reinforcer delay. In Experiment 2, subjects chose between immediate smaller reinforcers and delayed larger reinforcers in five conditions with and without timeout periods that followed a shorter delay, in which reinforcer amounts and delays were combined to make different predictions based on local reinforcement density (i.e., points per delay) or overall reinforcement density (i.e., points per total time). In most conditions, subjects' choices were qualitatively in accord with the predictions from the overall reinforcement density calculated by the ratio of reinforcer amount and total time. Therefore, the overall reinforcement density appears to influence the preference of humans in the present self-control choice situation.     

Affective state and preference for immediate versus delayed reward

Fifty-two 9-year-olds were randomly assigned to success and failure treatment conditions involving acceptance or rejection of a drawing made for an art show. In a pilot study, this treatment was shown to influence significantly subjects' affective states. Just after treatment, subjects were presented with choices between pairs of small immediate and large delayed rewards. As predicted, subjects who had experienced success chose more often the large delayed reward than those who failed (p < .02). Prior expectancy for success and sex were not significantly related to choice behavior. The influence of affective state on various parameters of the choice paradigm was discussed, and other evidence was cited indicating that affective state is a major determinant of self-gratification behavior.     

Trust matters: Seeing how an adult treats another person influences preschoolers' willingness to delay gratification

Holding out for a delayed reward in the face of temptation is notoriously difficult, and the ability to do so in childhood predicts diverse indices of life success. Prominent explanations focus on the importance of cognitive control. However, delaying gratification may also require trust in people delivering future rewards as promised. Only limited experimental work has tested this idea, and such studies with children were focused on general reward expectations, so evidence was ambiguous as to whether social trust played a role. The present study provides the first targeted test of a role for social trust in children's willingness to delay gratification. Children observed an adult behave in either a trustworthy or untrustworthy manner toward another adult, then were tested in the classic delay of gratification task by that adult. Children were less likely to wait the full delay period, and waited less time overall, for a reward promised by an untrustworthy adult, relative to children tested by a trustworthy adult. These findings demonstrate that manipulations of social trust influence delaying gratification, and highlight intriguing alternative reasons to test for individual differences in delaying gratification and associated life outcomes.     

Time and rate measures in choice transitions

Three experiments with pigeons studied the relation between time and rate measures of behavior under conditions of changing preference. Experiment 1 studied a concurrent chain schedule with random-interval initial links and fixed-interval terminal links; Experiment 2 studied a multiple chained random-interval fixed-interval schedule; and Experiment 3 studied simple concurrent random-interval random-interval schedules. In Experiment 1, and to a lesser extent in the other two experiments, session-average initial-link wait-time differences were linearly related to session-average response-rate differences. In Experiment 1, and to a lesser extent in Experiment 3, ratios of session-average initial-link wait times and response rates were related by a power function. The weaker relations between wait and response measures in Experiment 2 appear to be due to the absence of competition between responses. In Experiments 1 and 2, initial-link changes lagged behind terminal-link changes. These findings may have implications for the relations between fixed- and variable-interval procedures and suggest that more attention should be paid to temporal measures in studies of free-operant choice.     

Two tests of the stuck-in-time hypothesis

The authors report 2 experiments that test the stuck-in-time hypothesis, which argues that animals cannot time-date events and thus do not remember when events occurred and do not anticipate future events. In Experiment 1, rats in the experimental condition could earn a large reward by reentering the 1st arm that they visited on a radial maze. They did not learn to reenter this arm early and did no better than did a control group that was not given a large reward for reentering the first arm. In Experiment 2, rats in the experimental group could earn a large reward by delaying entry into a distinctive arm. These rats did not learn to delay entry into the distinctive arm, and they performed no better than did the control-group rats, which did not receive a large reward for delayed entry. These experiments provide further evidence in support of the stuck-in-time hypothesis.     

Self-control and choice in humans: Effects of video game playing as a positive reinforcer

Participants chose between reinforcement schedules differing in delay of reinforcement (interval between a choice response and onset of a video game) and/or amount of reinforcement (duration of access to the game). Experiment 1 showed that immediate reinforcement was preferred to delayed reinforcement with amount of reinforcement held constant, and a large reinforcer was preferred to a small reinforcer when both were obtainable immediately. Imposing a delay before the large reinforcer produced a preference for the immediate, small reinforcer in 40% of participants. This suggested a limited degree of “impulsivity.” In Experiment 2, unequal delays were extended by equal intervals, the amounts being kept equal. Preference for the shorter delay decreased, an effect that presumably makes possible the “preference reversal” phenomenon in studies of self-control. Overall, the results demonstrate that video game playing can produce useful, systematic data when used as a positive reinforcer for choice behavior in humans.