Changes In Discounting Research Articles

NICE's Discounting Review: Clear Thinking on Rational Revision Meets Obstacle of Industrial Interests.

The National Institute of Health and Care Excellence (NICE) recently published a review of discounting practice and theory as part of a consultation on its current methods guidelines. The review examines the case for revision or retention of current methods. The changes considered include eliminating favourable rates in certain special cases and the reduction of the base-case rate for costs and health effects from 3.5 to 1.5%. The review also notes the potential need to reduce the cost-effectiveness threshold to accommodate a discount rate reduction, explaining that an agreement between the UK government and the pharmaceutical industry proscribes changing NICE's threshold range until the end of 2023. We believe NICE should be commended for a useful overview of the existing literature and relevant issues. We firmly endorse NICE's view that favourable discount rates are not a good way to apply a preference for certain interventions. Similarly, we support the option of reducing the discount rate to 1.5%, which better accords with real government borrowing costs. We suggest further work to clarify the appropriate theoretical basis for the NICE's social discount rate and the sensitivity of the threshold to changes in discounting. The prospects of a necessary discount rate reduction appear to depend on whether a threshold reduction can be achieved within NICE's current range or if the range itself must be revised downwards. NICE has usefully informed the debate around discount rates. Ultimately, the path to a methodologically consistent and evidence-based revision of discounting depends on whether NICE needs to adjust the threshold too and if it is free to do so.

Maintained Physical Activity Induced Changes in Delay Discounting.

Those who discount the subjective value of delayed rewards less steeply are more likely to engage in physical activity. There is limited research, however, showing whether physical activity can change rates of delay discounting. In a two-experiment series, treatment and maintenance effects of a novel, effort-paced physical activity intervention on delay discounting were evaluated with multiple baseline designs. Using a lap-based method, participants were instructed to exercise at individualized high and low effort levels and to track their own perceived effort. The results suggest that treatment-induced changes in discounting were maintained at follow-up for 13 of 16 participants. In Experiment 2, there were statistically significant group-level improvements in physical activity and delay discounting when comparing baseline with both treatment and maintenance phases. Percentage change in delay discounting was significantly correlated with session attendance and relative pace (min/mile) improvement over the course of the 7-week treatment. Implications for future research are discussed.

Maturation of limbic corticostriatal activation and connectivity associated with developmental changes in temporal discounting

Temporal discounting (TD) matures with age, alongside other markers of increased impulse control, and coherent, self-regulated behaviour. Discounting paradigms quantify the ability to refrain from preference of immediate rewards, in favour of delayed, larger rewards. As such, they measure temporal foresight and the ability to delay gratification, functions that develop slowly into adulthood. We investigated the neural maturation that accompanies the previously observed age-related behavioural changes in discounting, from early adolescence into mid-adulthood. We used functional magnetic resonance imaging of a hypothetical discounting task with monetary rewards delayed in the week to year range. We show that age-related reductions in choice impulsivity were associated with changes in activation in ventromedial prefrontal cortex (vmPFC), anterior cingulate cortex (ACC), ventral striatum (VS), insula, inferior temporal gyrus, and posterior parietal cortex. Limbic frontostriatal activation changes were specifically associated with age-dependent reductions in impulsive choice, as part of a more extensive network of brain areas showing age-related changes in activation, including dorsolateral PFC, inferior parietal cortex, and subcortical areas. The maturational pattern of functional connectivity included strengthening in activation coupling between ventromedial and dorsolateral PFC, parietal and insular cortices during selection of delayed alternatives, and between vmPFC and VS during selection of immediate alternatives. We conclude that maturational mechanisms within limbic frontostriatal circuitry underlie the observed post-pubertal reductions in impulsive choice with increasing age, and that this effect is dependent on increased activation coherence within a network of areas associated with discounting behaviour and inter-temporal decision-making.

Maturation of limbic frontostriatal activation and connectivity associated with developmental changes in temporal discounting

Event Abstract Back to Event Maturation of limbic frontostriatal activation and connectivity associated with developmental changes in temporal discounting M. Brammer1, A. Christakou1, 2* and K. Rubia1 1 King’s College London, Institute of Psychiatry, United Kingdom 2 University of Reading, Centre for Integrative Neuroscience and Neurodynamics and Department of Psychology, United Kingdom Temporal discounting quantifies the ability to refrain from preference of immediate rewards, in favour of delayed, larger rewards. This ability to delay gratification develops slowly into adulthood. We investigated the neural maturation that accompanies the previously observed age-related behavioural changes in discounting, from early adolescence into mid-adulthood. We used functional magnetic resonance imaging of a hypothetical discounting task with monetary rewards delayed in the week to year range. Age-related reductions in choice impulsivity were associated with changes in activation in ventromedial prefrontal cortex (vmPFC), anterior cingulate cortex, ventral striatum (VS), insula, inferior temporal gyrus, and posterior parietal cortex. Limbic frontostriatal activation changes were specifically associated with age-dependent reductions in impulsivity. The maturational pattern of functional connectivity included strengthening in activation coupling between ventromedial and dorsolateral PFC, parietal and insular cortices during selection of delayed alternatives, and between vmPFC and VS during selection of immediate alternatives. We conclude that maturational mechanisms within limbic frontostriatal circuitry underlie the observed post-pubertal reductions in impulsivity with increasing age, and that this effect is dependant on increased activation coherence within a network of areas associated with discounting behaviour and inter-temporal decision-making. Conference: The 20th Annual Rotman Research Institute Conference, The frontal lobes, Toronto, Canada, 22 Mar - 26 Mar, 2010. Presentation Type: Poster Presentation Topic: Frontal Lobe Development Citation: Brammer M, Christakou A and Rubia K (2010). Maturation of limbic frontostriatal activation and connectivity associated with developmental changes in temporal discounting. Conference Abstract: The 20th Annual Rotman Research Institute Conference, The frontal lobes. doi: 10.3389/conf.fnins.2010.14.00050 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 28 Jun 2010; Published Online: 28 Jun 2010. * Correspondence: A. Christakou, University of Reading, Centre for Integrative Neuroscience and Neurodynamics and Department of Psychology, London, United Kingdom, Anastasia.Christakou@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers M. Brammer A. Christakou K. Rubia Google M. Brammer A. Christakou K. Rubia Google Scholar M. Brammer A. Christakou K. Rubia PubMed M. Brammer A. Christakou K. Rubia Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Analytical methods to detect within-individual changes in discounting.

Discounting, as a quantifiable measure of impulsivity, is often estimated within individuals via nonlinear regression. Here, we describe how to directly estimate within-individual change of the discounting parameter between 2 conditions and subsequently statistically test for that change using the discounting data from a single individual. To date, there has been no systematic description of how to conduct such an analysis. Employing the method allows investigators and clinicians to evaluate whether a single individual has statistically changed the way he or she discounts between 2 conditions (e.g., in the absence or presence of a pharmacologic, different time points, different rewards, etc.). We further describe a meta-analytic approach for combining estimated changes in discounting from individuals in a sample to make population inference. By providing more precise population estimates, this approach increases statistical power over traditional analytic methods.

Measuring state changes in human delay discounting: an experiential discounting task

A new experiential discounting task (EDT) is presented. Unlike existing question-based measures of delay discounting, which rely on imagined consequences during task completion, this EDT requires that participants experience choice consequences (i.e. delays and pseudo consumatory responses) during the measurement period. As a preliminary examination of this task’s sensitivity to variability in discounting, 12 participants (six females) completed a timing test (production and reproduction), a question-based measure of delay discounting, and the EDT during non-sleep-deprived (awake 7 h) and sleep-deprived (awake 21 h) conditions. Based on evidence that sleep deprivation increases impulsive behavior, it was hypothesized that participants would underrepresent time intervals in both production and reproduction procedures and discount significantly more with the discounting procedures while sleep deprived. Unfortunately, data from the question-based discounting procedure could not be reported due to invalid task completion. However, as hypothesized, certain production and reproduction intervals were underrepresented on the timing test, and discounting was significantly steeper on the EDT when participants were sleep deprived. Also, rate of discounting on the EDT was better characterized by a hyperbolic function than by exponential function, which is consistent with previous delay-discounting research. These preliminary results suggest this EDT may be a useful measure for assessing state changes in discounting processes.

A MULTIFACTOR ANALYSIS OF COUNTRY FUND RETURNS

AbstractPrevious closed‐end country fund research concludes that returns behave more like the U.S. market than like their target markets. We argue this finding may be biased by model misspecification and inappropriate estimation techniques. We propose a single‐equation model containing five hypothesized factors of fund returns. We estimate this model for nineteen pooled seasoned funds using a time‐series cross‐section regression that corrects for two types of autocorrelation. We show that returns are strongly related to target markets. Returns are also related to changes in discounts, exchange rates, and other countries' markets, but are only weakly related to the U.S. market.JEL classification: G10, G12

?Investor sentiment? and the closed-end fund puzzle: A 7 percent solution

Lee, Shleifer, and Thaler (1991) argue that the “irrational noise trader” model of DeLong, Shleifer, Summers, and Waldmann (1990) “... is consistent with the published evidence on closed-end fund prices. ...” However, Lee, Shleifer, and Thaler provide no indication of how much of the variability of a closed-end fund's discounts and premiums is due to such “investor sentiment.” Using the signal extraction technique of French and Roll (1986) to measure noise, this article estimates that on average only 7 percent of the variance of a standardized measure of weekly changes in discounts and premiums can be attributed to noise-trading activity. “Investor sentiment,” therefore, seems to account for very little of a closed-end fund's discount and premium variability over time.