A. W. Logue

Research on self-control: An integrating framework

The tendency to choose a larger, more delayed reinforcer over a smaller, less delayed one has frequently been termed “selfcontrol.” Three very different research traditions – two models emphasizing the control of local contingencies of reinforcement (Mischels social learning theory and Herrnsteins matching law) and molar maximization models (specifically optimal foraging theory) – have all investigated behavior within the self-control paradigm. A framework is proposed to integrate research from all three research areas. This framework consists of three parts: a procedural analysis, a causal analysis, and a theoretical analysis. The procedural analysis provides a common procedural terminology for all three areas. The causal analysis establishes that, in all three research traditions, self-control varies directly with the current physical values of the reinforcers; that is, choices increase with reinforcer amount and decrease with reinforcer delay. But self-control also varies according to past events to which a subject has been exposed, and according to current factors other than the reinforcers. Each of the three models has therefore incorporated these indirect effects on self-control by postulating unobservable mechanisms. In all three cases, these mechanisms represent a subjects behavior as a function of a perceived environment. The theoretical analysis demonstrates that evolutionary theory can encompass the research from all three areas by considering differences in the adaptiveness of self-control in different situations. This integration provides a better and more predictive description of self-control.

Adjusting delay to reinforcement: comparing choice in pigeons and humans

Indifference functions of amount and delay of reinforcement were compared for pigeon and human subjects by using Mazurs (1987) adjusting delay procedure. A model similar to the matching law (the simple reciprocal model), a hyperbolic model, three modified versions of the hyperbolic model, and a negative exponential model were evaluated. In Experiment 1 the subjects were pigeons, and in Experiments 2 and 3 the subjects were humans. In order to make the nonhuman and human situations more comparable, in Experiments 2 and 3 the reinforcer (points exchangeable for money) was discounted at a constant rate during the delay periods. The rate of this discounting varied between Experiments 2 and 3. The results of all three experiments demonstrated that a power function transformation of the hyperbolic model (in which 1 is added to the delays in the denominator of the simple reciprocal model) provided the best description of both nonhuman and human data.

Self-control across species (Columba livia, Homo sapiens, and Rattus norvegicus).

Data from six previous studies of self-control behavior were compared against predictions made by the matching law and by molar maximization. The studies involved pigeons (Columba livia), rats (Rattus norvegicus), and 3-year-old, 5-year-old, and adult humans (Homo sapiens) who had received food as the reinforcer, and adult humans who had received points exchangeable for money as the reinforcer. Neither theory proved to be an accurate or better predictor for all groups. In contrast to the predictions of these theories, self-control was shown to vary according to species, human age group, and reinforcer quality. When the reinforcer was food, the self-control of different species was found to be negatively correlated with metabolic rate; that is, larger species showed greater self-control. These results suggest that allometric scaling may prove useful in describing and predicting species differences in self-control.

Effects of deprivation level on humans' self-control for food reinforcers

Deprivation level was manipulated in fourteen food- and water-deprived adult human females to examine its effects on self-control for food (choice of larger, more delayed access to apple juice over smaller, less delayed access to apple juice). Each subject was exposed to two treatments: (1) Consumption of a 500 g tomato soup preload just prior to self-control testing and (2) no soup preload. When subjects had consumed soup, they reported significantly less hunger and showed significantly more self-control as compared to when not having consumed soup. Additionally, when subjects had consumed soup, self-control decreased as a function of session time. Subjects who reported that they were currently dieting drank significantly less juice when they had previously consumed soup than when they do not previously consumed soup. Together, the results indicate that when subjects are more deprived they may be less able to wait for food reinforcers (i.e., show less self-control). Such behaviour may be adaptive in situations in which energy is needed to survive periods of food scarcity.

Self-Control and Impulsiveness in Preschool Children

Eleven girls and nine boys, aged 41–59 months, chose repeatedly, under controlled laboratory conditions, between one sticker available immediately and three stickers available after 30 s. On the average, the children chose the immediate one sticker more often than the three delayed stickers (i.e., they more often demonstrated impulsiveness than self-control). The boys showed significantly more impulsiveness than did the girls. These data are consistent with other data collected using related procedures and preschool children, but they are in contrast to those collected using procedures very similar to those used here but with adult humans, who tend to show self-control. This research establishes a methodology and points to future directions for quantitative examination of the determinants of self-control in preschool-aged subjects.

Choice in a self-control paradigm: effects of reinforcer quality

Pigeons were exposed to a self-control paradigm in which they chose between larger, more delayed and smaller, less delayed reinforcers. Reinforcer quality (i.e., the type of grain associated with each alternative) was varied across conditions. Choice behavior was influenced by grain quality; proportions of responses for the larger, more delayed alternative changed as a function of the grains associated with the response alternatives. Furthermore, the percentage deviation from mean baseline response proportions generally decreased as a function of the relative grain types associated with each response alternative. Manipulation of reinforcer quality can significantly influence the degree of self-control typically exhibited by pigeons.

Should Students Assessed as Needing Remedial Mathematics Take College-Level Quantitative Courses Instead? A Randomized Controlled Trial

Many college students never take, or do not pass, required remedial mathematics courses theorized to increase college-level performance. Some colleges and states are therefore instituting policies allowing students to take college-level courses without first taking remedial courses. However, no experiments have compared the effectiveness of these approaches, and other data are mixed. We randomly assigned 907 students to (a) remedial elementary algebra, (b) that course with workshops, or (c) college-level statistics with workshops (corequisite remediation). Students assigned to statistics passed at a rate 16 percentage points higher than those assigned to algebra (p < .001), and subsequently accumulated more credits. A majority of enrolled statistics students passed. Policies allowing students to take college-level instead of remedial quantitative courses can increase student success.

Effects of reinforcer type on rats' sensitivity to variation in reinforcer amount and reinforcer delay.

Twenty rats, divided into two groups, served as subjects in an experiment that examined choices between reinforcers that varied in amount or delay. One group received food reinforcers, and the other water reinforcers. No difference was found between the two groups in their values of sA (tendency of choice behavior to vary in accordance with variation in reinforcer amount). However, Group Food had significantly lower values of sD (tendency of choice behavior to vary in accordance with variation in reinforcer delay) than did Group Water, and Group Foods values of s As D (a measure related to self-control-choices of larger, more delayed over smaller, less delayed reinforcers) tended to be greater than for Group Water. Finally, over the session, sA and s As D showed no significant change, overall response rates decreased, and sD increased. Taken together, these results suggest that, independent of deprivation level, self-control for water is less than self-control for food.

Probability and delay of reinforcement: an examination of Mazur's equivalence rule

It has recently been proposed that the probability of an event (e.g. delivery of a reinforcer) can be interpreted as functionally equivalent to the delay of an event. The present experiment examined the equivalence rule that states that reinforcer probability is functionally equivalent to a set of variable delays. A titration procedure was used in which pigeons chose between a standard, probabilistic alternative, and an adjusting, delayed alternative. Reinforcer probability was manipulated by varying the number of keypecks required to obtain a reinforcer. The duration of the adjusting alternative varied as a function of a pigeons previous choices. There were six standard probabilities. The results indicated that the pigeons were sensitive to changes in the standard probabilities and that there were significant relations between: (1) reinforcer probability and the mean adjusted delay of reinforcement, and (2) the obtained and predicted adjusted delays. The present results support Mazurs conception of the relation between reinforcer probability and delay, and extend his conception to a different method of manipulating reinforcer probability.

Hunger, Satiety, and Food Preferences: Effects of the Brain and the Body on the Self-control of Eating

Publisher Summary Many individuals in developed countries must constantly choose between an energy intake that is not so pleasurable in the short term but is healthy in the long term (self-control) and energy intake that is pleasurable in the short term but is unhealthy in the long term (impulsiveness). They must choose between eating full-fat ice cream and sitting on the couch now versus having clear arteries and normal insulin levels 30 years from now. In what ways do our bodies influence these choices? This chapter describes some of the ways in which our physiology affects the self-control of eating. The influence of our physiology on impulsive eating has much more than a theoretical effect. In comprehending the effects of different factors on self-control, it is helpful first to understand self-controls constituent components, reinforcer amount and reinforcer delay. Choices of certain combinations of relatively smaller and larger reinforcer amounts, and of relatively smaller and larger reinforcer delays, constitute self-control and impulsiveness. Much research indicates that reinforcer amounts are valued less—are discounted—if they are delayed. Further, that discounting occurs according to a hyperbolic function. It then follows that, under certain conditions, if someone is choosing between two reinforcers of different amounts and different delays, the value functions for the two reinforcers will cross.