Self-control and impulsiveness in children and adults: Effects of food preferences

Impulsivity and self-control in elementary school children and adult females: Using identical task and procedural parameters

Results of studies examining the relationship between impulsivity and age are limited because different tasks, procedural parameters, and different reinforcers have been used with different aged participants. Thus, the current study sought to rectify these differences in two experiments with children (42, ages 5-12) and adults (69 college-aged females) using the same task with identical procedural parameters. In the Self-Control Video Software Task (SCVST; Forzano and Schunk, 2008; Forzano et al., 2014) participants repeatedly choose between larger, more delayed and smaller, less delayed access to viewing video cartoons. No differences in impulsivity were found between adults and children. No age or gender differences were found among children. Differences in task and procedural parameters are identified as important in their implications for research on impulsivity.

Effects of sucrose concentration on choice in an adjusting-magnitude schedule

Rats were trained under a discrete-trials adjusting-magnitude schedule in which a response on lever A delivered either a larger or a smaller sucrose reinforcer (q_A1 = 8 μl, q_A2 = 64 μl) with equal probability, while a response on B delivered a reinforcer whose size q_B was adjusted according to the rats' choices. When A was preferred in a given block of trials, q_B was increased in the following block; when B was preferred, q_B was reduced in the following block. The oscillating changes in q_B, analysed by the Fourier transform, could be described by a power spectrum whose dominant frequency corresponded to a period of 40-50 trial blocks. The equilibrium value of q_B (q_B(50)) was inversely related to sucrose concentration; it significantly exceeded the arithmetic mean of q_A1 and q_A2 when the concentration was 0.2 or 0.4 M, but not when it was 0.8 or 1.6 M. Analysis by mixed-effects modelling revealed a trend for the power of oscillation of q_B to increase monotonically with sucrose concentration; the period of oscillation was not systematically related to sucrose concentration. These results are consistent with predictions derived from a revised version of the multiplicative hyperbolic model of intertemporal choice.

Some properties of an adjusting-magnitude schedule of reinforcement: Implications for models of choice

Rats were trained under a discrete-trials adjusting-magnitude schedule in which a response on lever A delivered either a larger or a smaller reinforcer (q_A1 and q_A2) with equal probability, while a response on B delivered a reinforcer whose size q_B was adjusted according to the rats' choices. When A was preferred in a given block of trials, q_B was increased in the following block; when B was preferred, q_B was reduced in the following block. The oscillating changes in q_B, analysed by the Fourier transform, could be described by a power spectrum with a dominant period of about 50 trial blocks. With q_A1 held constant, the equilibrium value of q_B (q_B(50)) was monotonically related to q_A2, and exceeded the arithmetic mean of q_A1 and q_A2 when q_A1 was substantially greater than q_A2. A model derived from the multiplicative model of intertemporal choice provided a post hoc description of the data. Simulation of block-by-block changes in q_B derived from the model were generally consistent with the experimental data. Implications of the results for models of risky choice and for future use of the schedule in neurobehavioural experiments are discussed.

Learning to wait for more likely or just more: greater tolerance to delays of reward with increasingly longer delays

Little research has focused on training greater tolerance to delays of rewards in the context of delayed gratification. In delayed gratification, waiting for a delayed outcome necessitates the ability to resist defection for a continuously available smaller, immediate outcome. The present research explored the use of a fading procedure for producing greater waiting in a video-game based, delayed gratification task. Participants were assigned to conditions in which either the reward magnitude, or the probability of receiving a reward, was a function of time waited and the delay to the maximum reward was gradually increased throughout this training. Waiting increased for all participants but less for those waiting for a greater reward magnitude than a greater reward probability. All participants showed a tendency to wait in a final testing phase, but training with probabilistic outcomes produced a significantly greater likelihood of waiting during testing. The behavioral requirements of delay discounting versus delay gratification are discussed, as well as the benefits of training greater self-control in a variety of contexts.

Comparing hyperbolic, delay-amount sensitivity and present-bias models of delay discounting

Delay discounting is a widely studied phenomenon due to its ubiquity in psychopathological disorders. Several methods are well established to quantify the extent to which a delayed commodity is devalued as a function of the delay to its receipt. The most frequently used method is to fit a hyperbolic function and use an index of the gradient of the function, k, or to calculate the area under the discounting curve. The manuscript examines the behavior of these quantification indices for three different datasets, as well as provides information about potential limitations in their use. The primary limitation examined is the lack of mechanistic specificity provided by either method. Alternative formulations that are thought to provide some mechanistic information are examined for the three separate datasets: two variants of a hyperboloid model (Rachlin, 1989, Judgment, decision and choice. New York: W.H. Freeman) and the quasi-hyperbolic model (Laibson, 1997, Q. J. Econ., 112, 443-477). Examination of the parameters of each formulation suggests that the parameters derived from the quasi-hyperbolic model allows groups and conditions within the three datasets to be reliably distinguished more readily than the hyperboloid models. However, use of the quasi-hyperbolic model is complex and its limitations might offset its ability to discriminate within the datasets. "This article is part of a Special Issue entitled: SQAB 2014".

Distributed and accumulated reinforcement arrangements: evaluations of efficacy and preference

We assessed the efficacy of, and preference for, accumulated access to reinforcers, which allows uninterrupted engagement with the reinforcers but imposes an inherent delay required to first complete the task. Experiment 1 compared rates of task completion in 4 individuals who had been diagnosed with intellectual disabilities when reinforcement was distributed (i.e., 30-s access to the reinforcer delivered immediately after each response) and accumulated (i.e., 5-min access to the reinforcer after completion of multiple consecutive responses). Accumulated reinforcement produced response rates that equaled or exceeded rates during distributed reinforcement for 3 participants. Experiment 2 used a concurrent-chains schedule to examine preferences for each arrangement. All participants preferred delayed, accumulated access when the reinforcer was an activity. Three participants also preferred accumulated access to edible reinforcers. The collective results suggest that, despite the inherent delay, accumulated reinforcement is just as effective and is often preferred by learners over distributed reinforcement.

Rats show preference for delayed rewards on the radial maze

Rats on an eight-arm radial maze chose between four arms on which a small reward could be obtained after a short delay and four arms on which a larger reward could be obtained after a longer delay. Experiments 1 and 2 showed that rats preferred the long-delay, large-reward arms over the short-delay, small-reward arms. This preference was particularly marked when the arms were made into enclosed alleys. Experiment 3 showed that this effect was not produced by a preference for staying in enclosed alleys. We argue that the rats endured longer delays to obtain larger rewards when fear of predation was minimized.

Measuring impulsivity and modeling its association with cigarette smoking

Two types of behavioral measure are primarily used to examine impulsivity in humans and animals: Go/No-go tasks to assess inhibition and relative preference tasks to assess delay aversion. Several examples of each type of task are described so that common cognitive processes and variables affecting performance can be identified. Data suggest that smokers are more impulsive on each of these impulsivity measures than nonsmokers. Several models can be proposed to account for this group difference: (a) the differences predate and, possibly, are causally related to the initiation of cigarette smoking; (b) higher levels of impulsivity are associated with continued smoking, either through an association with heightened positive subjective effects of nicotine or heightened negative effects of nicotine abstinence (withdrawal); (c) nicotine causes neuroadaptations that result in elevated impulsivity in smokers. Studies relating to each of these models are reviewed, and it is concluded that all three models may contribute to the observed higher levels of impulsivity in smokers. However, pertinent studies are limited and additional systematic research is needed.

Effects of multiple delayed rewards on delay discounting in an adjusting amount procedure

It has been suggested that when the delivery of several rewards is separated in time, e.g. one reward immediately and a second reward a few moments later, the value of an alternative that includes these "bundled" rewards will be the sum of the hyperbolic discount functions of the individual rewards. The current study examined this hypothesis using an adjusting amount procedure. In this procedure, rats chose between a delayed food alternative and an immediate food alternative, where the amount of immediate food altered according to each rat's choices. The size of the immediate reward when rats were indifferent between the delayed and immediate alternatives indexed the value of the delayed alternative. Discount functions describing the relationship between the indifference points and the delay to food were created for conditions in which the delay alternative consisted of a single reward (150mul of sucrose solution) delayed by 0, 2, 4, 8, or 16s following the reinforced response. These functions were used to predict the indifference points in other conditions for which an additional 150mul of sucrose solution was delivered at 0, 4, 8, or 16s following the reinforced response. The model fit the data well. However, there were systematic deviations that suggested animals were sensitive to the context within which delays were presented, in addition to the delays themselves. That is, preference for the delayed alternative was lower than predicted when the delay to the additional reward was long (8 or 16s) and higher than the predicted values when it was short (0 or 4s).

Children's food preferences: a longitudinal analysis

OBJECTIVE

To compare children's food preferences longitudinally and identify factors related to food preferences.

DESIGN

Mothers completed the Food Preference Questionnaire for children at 2 to 3 years of age (T1), 4 years (T2), and 8 years (T3) and for themselves at T1 and T3. Both groups completed a Food Neophobia Scale at T3.

SUBJECTS

70 child/mother pairs who had participated continuously in the longitudinal study.

STATISTICAL ANALYSES PERFORMED

Changes in food preferences over time were tested with paired t tests and correlations. Consistency percentages were calculated by summing the consistent matches (like/like) for each food between two time periods. Similarly, concordance percentages were calculated for child/mother pairs by summing the concordant matches for each food. General linear models were developed to identify influences on children's food preferences.

RESULTS

Although children liked most foods, the number of liked foods did not change significantly during the 5 to 5.7 years of the study. The strongest predictors of the number of foods liked at age 8 years (R2=0.74) were the number liked at 4 years (P<.0001) and the food neophobia score (P=.0003). Newly tasted foods were more likely to be accepted between T1 and T2 than T2 and T3. Mothers' and children's food preferences were significantly but moderately related. Foods disliked by mothers tended not to be offered to children.

APPLICATIONS/CONCLUSIONS

The important role of children's early food preferences is confirmed by this study. Mothers influence children via their own preferences, which may limit foods offered to children.

Maintenance of self-imposed delay of gratification by four chimpanzees (Pan troglodytes) and an orangutan (Pongo pygmaeus)

Delay maintenance, which is the continuance over time of the choice to forgo an immediate, less preferred reward for a future, more preferred reward, was examined in 4 chimpanzees (Pan troglodytes) and 1 orangutan (Pongo pygmaeus). In the 1st experiment, the apes were presented with 20 chocolate pieces that were placed, one at a time, into a bowl that was within their reach. The apes could consume the available chocolate pieces at any time during a trial, but no additional pieces would be given. The total length of time taken to place the 20 items into the bowl ranged from 60 s to 180 s. All 5 apes delayed gratification on a majority of trials until all 20 chocolate pieces were presented. Unlike in most experiments with human children using this test situation, attention by the apes to the reward was not detrimental to delay maintenance. In a 2nd experiment with the chimpanzees only, 4 foods of differing incentive value were presented in different trials in the same manner as in Experiment 1. The chimpanzees were highly successful in obtaining all food pieces, and there was no difference in performance as a function of food type.

Temporal discounting: basic research and the analysis of socially important behavior

Recent basic research on human temporal discounting is reviewed to illustrate procedures, summarize key findings, and draw parallels with both nonhuman animal research and conceptual writings on self-control. Lessons derived from this research are then applied to the challenge of analyzing socially important behaviors such as drug abuse, eating and exercise, and impulsiveness associated with attention deficit hyperactivity disorder. Attending to the broader temporal context in which behavior occurs may aid in the analysis of socially important behavior. Applying this perspective to the study of behavior in natural environments also highlights the importance of combining methodological flexibility with conceptual rigor to promote the extension of applied behavior analysis to a broader array of socially important behaviors.