Food reinforcement, delay discounting and obesity

Choice is a central construct in behavioral economics, with choice research divided into choice of concurrent alternative reinforcers, which is conceptualized as relative reinforcing value, or choice of small immediate versus larger delayed rewards, usually of the same commodity, which is conceptualized as delay of gratification and delay discounting. Relative reinforcing value, delay of gratification and delay discounting paradigms can be used to study obesity, which involves strong motivation to obtain and consume food reinforcers. Strong food reinforcement and difficulties in delay of gratification are risk factors for child weight gain, and both are related to individual differences in overweight/obesity. Delay discounting interacts with food reinforcement to predict energy intake. We provide a selective review of research on each of these areas, and argue that the division of choice into reinforcing value versus delay discounting is based on an arbitrary definition based on the temporality of choices. We present a model that integrates reinforcing value and delay discounting approaches. Implications of this theoretical approach to better understand excess energy intake and obesity are discussed.The paper represents an invited review by a symposium, award winner or keynote speaker at the Society for the Study of Ingestive Behavior [SSIB] Annual Meeting in Portland, July 2009.     

Microsaccades and preparatory set: a comparison between delayed and immediate, exogenous and endogenous pro- and anti-saccades

When we fixate an object, our eyes are not entirely still, but undergo small displacements such as microsaccades. Here, we investigate whether these microsaccades are sensitive to the preparatory processes involved in programming a saccade. We show that the frequency of microsaccades depends in a specific manner on the intention where to move the eyes (towards a target location or away from it), when to move (immediately after the onset of the target or after a delay), and what type of cue is followed (a peripheral onset or a centrally presented symbolic cue). In particular, in the preparatory interval before and early after target onset, more microsaccades were found when a delayed saccade towards a peripheral target was prepared than when a saccade away was programmed. However, no such difference in the frequency of microsaccades was observed when saccades were initiated immediately after the onset of the target or when the saccades were programmed on the basis of a centrally presented arrow cue. The results are discussed in the context of the neural correlates of response preparation, known as preparatory set.     

Interrelationships between immediate, intermediate, and delayed cutaneous reactions and their in vitro correlates

The mutual correlations between immediate, intermediate, and delayed cutaneous reactions, IgE, IgG, or combined IgG, A, and M antibody levels, and antigen- or mitogen-induced lymphocyte transformation were evaluated in a mixed group of allergic or non-allergic individuals. As might be expected, immediate and delayed reactions correlated significantly with IgE antibody levels and lymphocyte transformation, respectively. Intermediate time-course reactions did not correlate with IgG or IgG, A, and M antibody levels, but did so with immediate reactions, thus suggesting their "late phase" nature. Of particular interest was the finding of correlations that do not conform to the classical concept of the mechanisms involved in the generation of the different cutaneous reactions. Significant correlations were found between immediate or intermediate reactions and antigen-induced lymphocyte transformation, and between immediate and delayed reactions. These results are discussed in relation to recent suggestions that factors released from sensitized T cells can mediate early time-course reactions, and that such reactions may contribute to the manifestation of delayed-type hypersensitivity.     

Motivation and reinforcement in the systemic mechanisms of behavior: Dynamic reinforcement engrams

Materials are presented which suggest the interaction of motivation and reinforcement in the systemic organization of behavioral acts in individual brain neurons, it was demonstrated that immune mechanisms participate in the interaction of motivation and reinforcement. It is postulated that reinforcement during learning, by means of backward afferentation, forms molecular reinforcement engrams in the neuronal structures of the action outcome acceptor. The molecular reinforcement engrams are build by processes of the synthesis of DNA and protein molecules in ribosomes. These engrams, during the succeeding appearances of the corresponding needs, are activated by the dominant motivation and in anticipation direct animals toward the satisfaction of their unitial needs. P. K. Anokhin Research Institute of Normal Physiology, Russian Academy of Medical Sciences, Moscow. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 45, No. 4, pp. 627–637, July–August, 1995.     

Episodic future thinking reduces delay discounting and cigarette demand: an investigation of the good-subject effect

Episodic future thinking (EFT), an intervention involving mental simulation of future events, has been shown to reduce both delay discounting and cigarette self-administration. In the present study, we extended these findings by showing that EFT in a web-based sample of smokers reduces delay discounting and intensity of demand for cigarettes (ad libitum consumption) in a hypothetical purchase task. No effect was observed on elasticity of demand (sensitivity to price) or cigarette craving. We also explored whether demand characteristics (specifically, the “good-subject” effect) might be responsible for observed effects. EFT participants were significantly better able than control participants to discern the experimental hypothesis. However, EFT participants were not better than controls at identifying whether they had been assigned to the experimental group and, likewise, showed no differences in attitudes about the experiment and experimenter. Importantly, effects of EFT on delay discounting and demand remained significant even when controlling for measures of demand characteristics, indicating that EFT’s effects are independent of participants’ perceptions about the experiment.     

Functional role for Ig free light chains in immediate and delayed hypersensitivity responses

Inflammation Research -     

Self-regulation and obesity: the role of executive function and delay discounting in the prediction of weight loss

Obesity rates are rising worldwide. Executive function and delay discounting have been hypothesized to play important roles in the self-regulation of behavior, and may explain variance in weight loss treatment success. First, we compared individuals with obesity (n?=?82) to healthy weight controls (n?=?71) on behavioral and self-report measures of executive function (working memory, inhibition and shifting) and delay discounting. Secondly, the individuals with obesity took part in a multidisciplinary weight loss program and we examined whether executive function and delay discounting predicted weight change. Individuals with obesity displayed weaker general and food-specific inhibition, and weaker self-reported executive function. Better behavioral working memory and better self-reported inhibition skills in daily life were predictive of greater weight loss. As findings are correlational, future studies should investigate the causal relationship between executive function and weight loss, and test whether intervening on executive function will lead to better prevention and treatment of obesity.     

Reasons for the lack of association between changes in health behavior and improved health status: an exploratory study

Persons with arthritis who attended a 12-hour self-management course generally showed improved health behaviors and improved health status. However, no association was found between the two. We therefore interviewed 54 course participants to determine factors that were associated with positive and negative health-status outcomes. Persons having positive outcomes indicated that they had more control over their disease and had a positive emotional status. Persons with negative outcomes indicated a lack of control and generally had a negative emotional status. These differences were statistically significant.     

Treatment for primary HIV infection: projecting outcomes of immediate,interrupted, or delayed therapy

With limited data available on the optimal treatment of primary HIV infection, disease modeling can be used to project clinical outcomes and inform decision makers. The authors developed a simulation model to evaluate the clinical outcomes and life expectancy projections for three primary HIV infection treatment strategies: 1) continuous antiretroviral therapy (ART) initiated at CD4 count <350 cells/mm(3); 2) continuous ART initiated immediately on diagnosis of primary HIV infection; and 3) ART initiated on diagnosis followed by structured treatment interruption. Projected life expectancies for the three strategies were 23.92, 24.46, and 26.07 years, respectively. The impact of key variables was assessed in sensitivity analysis, with the structured treatment interruption strategy remaining the most effective over a broad range of inputs. The immunologic benefit associated with immediate therapy and the potential for antiretroviral resistance due to structured treatment interruption have the most important impact on the optimal strategy. Based on current data, immediate treatment on diagnosis of primary HIV infection followed by structured treatment interruption will likely yield the best outcome. These results can assist decision makers and those planning clinical trials in defining evidence-based performance measures for primary HIV infection treatment and future trials.     

A study of relation between phrasing and intertrial interval in reinforcement pattern learning in rats

Effects of the temporal interval on reinforcement pattern learning were investigated in four experiments using a runway. The reinforced trial was always the first trial for R5N sequence (Experiments 1a and 1b), and the fourth trial for 3NR2N sequence (Experiments 2a and 2b). Group S-ITI received the given sequence at 30-s ITI, Group L-INT received the same procedure as Group S-ITI except for a 30-min ITI inserted between Trials 3 and 4 (Experiments 1a and 2a). Group L-ITI received at 30-min ITI, Group S-INT did as Group L-ITI except for the ITI between Trials 3 and 4 was 30 seconds (Experiments 1b and 2b). It was found that the running speed on each of Trials 1 and 4 was faster than any other trials under R5N and 3NR2N sequences for Group L-INT. That is, the running pattern for Trials 1-3 was similar to that for Trials 4-6. On the other hand, the running speed on Trial 4 under R5N sequence and that on Trial 1 under 3NR2N sequence did not increase for Group S-INT. These results suggest that a longer or shorter ITI plays the roles of both phrasing cue and discriminative stimulus. For Group S-ITI and Group L-ITI, there was little evidence that sequences were phrased. Therefore, when trials are separated by equal ITIs, neither 30-s ITI nor 30-min ITI becomes a phrasing cue.     

Understanding and modeling health behavior: the multi-stage model of health behavior change

The purpose of this study was to evaluate the Multi-Stage Model (MSM). The MSM proposes eight different stages that are distinguished by cognitions and behavior and concepts of habituation as well. The MSM stages were assessed in 835 rehabilitation patients with a questionnaire. People in the different stages were compared and trends across the means of individuals in the different stages were evaluated to test for discontinuity patterns. Discontinuity patterns across the stages were found in social-cognitive variables such as intention, self-efficacy, outcome expectancies and social support. Most predictions according to stage differences were empirically found. This supported the validity of the MSM. Implications for further investigations and stage-specific interventions are discussed.     

Responses to an intense sweetener in humans: immediate preference and delayed effects on intake

Preferences for five aspartame concentrations (0.008, 0.028, 0.094, 0.235 and 0.627%) in a dairy product were assessed in men and women by 1) brief-exposure sensory evaluation tests and 2) intake tests. Sensory evaluation gave different preferred concentrations as compared to actual intake. In sensory evaluation tests, the lowest three intensities were preferred by most subjects; in intake tests, 0.028% was clearly preferred. The 24-h spontaneous food intake after intake test sessions was recorded. A peak of 24-h energy intake was observed after intake of 0.028% aspartame yogurt. This peak was 400 kcal higher than the 24-h caloric intake observed after tests of the sweetest yogurt (p less than 0.01), much more than accounted for by differences in yogurt intake. So the intake of yogurt plus aspartame exerted strong delayed effects. These effects are likely dependent on sensory factors (concentration) rather than postingestive mechanisms (dose).     

Change in feelings of regret over time: relation to decision-making style, behavior, and coping methods

This study investigated the change in feelings of regret over time in relation to decision-making style, critical thinking, behavior, and coping methods with the regret. Seventy undergraduate students completed a questionnaire on critical thinking, decision-making styles, feelings of regret and the coping methods in five different situations: entrance examinations, declarations of love, skiing, career changes, and investments. Results showed the following. First, in situations which normally occur only once (i.e., entrance examinations), subjects who indicated inaction felt increased regret over time, but those who indicated action felt decreased regret. Conversely, in situations which occur regularly (i.e., declarations of love and skiing), both of those who indicated action and inaction felt decreased regret. Second, people who indicated action coped with their regret using the method of rationalization more often than those who indicated inaction. In situations which normally occur only once, analytic decision-makers tended to cope with their regret by improving their behavior more than intuitive decision-makers. Finally, critical thinkers tended to adopt an analytic style more often than an intuitive style.