In dieser Studie führten 37 adulte Patienten mit einer Aufmerksamkeitsdefizit-/Hyperaktivitätsstörung (ADHS) ein Delay Discounting (DD) - Paradigma aus, während gleichzeitig mittels Funktioneller-Nahinfrarotspektroskopie (fNIRS) die Gehirnaktivität der „Regions of Interest“ (ROIs) des Orbitofrontalen-Kortex (OFC) und des Dorsolateralen-Präfrontalen-Kortex (dlPFC) gemessen wurde. Mittels Fragebögen und eines Delay Discounting Tasks (DDT) wurden zusätzlich Verhaltensparameter erhoben und flossen in den Auswertungsprozess mit ein. Vorausgegangene Untersuchungen weisen auf ein hypofunktionel-les dopaminerges System bei ADHS-Patienten hin, welches mit der ADHS-Pathogenese in Zusammenhang gebracht wird. Vor allem im Präfrontalen-Kortex (PFC), bestehend unter anderem aus OFC und dlPFC, erfolgt die Metabolisierung von Dopamin durch die Catechol-O-Methyltransferase (COMT). Hierbei hängt die Metabolisierungsgeschwindigkeit vom genetischen COMT-Val158Met- Polymorphismus ab. Die Einflussnahme dieses COMT-Val158Met-Polymorphismus auf die kortikale Aktivität der ROIs und Impulsivität ist ebenfalls Gegenstand dieser Dissertation („Imaging Genetics“). Adulte ADHS Patienten zeigten eine verstärkte Aktivität des OFC der Entscheidungskategorie „verzögert“ im Verhältnis zu der Entscheidungskategorie „sofort“. Die gemessene Impulsivität korrelierte mit der kortikalen Gehirnaktivität „DD-Kontrast“. Es konnte kein Zusammenhang zwischen Verhaltensparameter und Gehirnaktivität mit dem COMT-Polymorphismus gezeigt werden. Die erhöhte Aktivität des OFC bei der Entscheidungskategorie verzögert unterstützt die These der „Delay Aversion“ des „Dual Pathway Model“. Eine enge Konnektivität der stark dopaminerg innervierten kortiko-striataler Strukturen in Form des OFC und der Amygdala, welche Einfluss auf die ADHS-Pathogenese nehmen, erscheint somit plausibel. / In this study 37 adult subjects with ADHD (Attention Deficit Hyperactivity Disorder) performed a validated Delay Discounting (DD) paradigm. By using near-infrared-spectroskopy (NIRS) functional brain activation in the regions of interest (ROIs) was measured. The ROIs are represented by the Orbito-Frontal-Cortex (OFC) and the Dorsolateral Prefrontal Cortex (dlPFC). Additionally questionnaires with relation to behaviour and a Delay Discounting Task (DDT) were interpreted. Former studies indicate a hypo-functional dopaminergic system in ADHD pathology. Mainly the Prefrontal Cortex (PFC), including the OFC and the dlPFC, metabolizes dopamine with the Catechol-O-Methyltransferase (COMT). Velocity of this metabolism depends on the COMT-Val158Met-polymorphism. This effect is generally known by the term “imaging genetics”. Adult ADHD subjects showed a stronger activation in the OFC in the DD category “delayed” than in the category “now”. Measured impulsivity correlated with the cortical brain activity “DD-Kontrast”. No significant relation between the COMT polymorphism an the cortical brain activity or behaviour could be shown. The stronger activation of the OFC in the category “delayed” underlines the thesis of “Delay Aversion” from the “Dual Pathway Model”. A close connectivity between the dopaminergic corticostriatal brain regions of the amygdala and the OFC, which have an influence to the ADHD pathology, seem to be a plausible approach.

A self-control procedure that involved a later onset of a stimulus signalling a small reinforcer within the waiting time for a larger reinforcer was investigated to determine a point of shifting preference and a discounting function as the delay varied. The results from Experiment 1 to Experiment 3 showed exclusive impulsive choices regardless of the delay. In order to examine if the results were due to the procedure and the parameters, or the species used, Experiment 4 attempted to obtain shifts in preference using simultaneous onset of stimuli with the same species. The results demonstrated no changes in preference but an increase in proportion of self-control choices was shown. Due to the limited information from the replicated studies, the accounts for the results could not be concluded. The explanations derived from choice models seemed most plausible, but limitations of the choice models were discussed.

<p>This paper analyses the pricing on spare parts. Empirical studies have showed that manufacturers of durable goods make an unproportional large profit on its spare parts in relation to the revenue it generates. It is first showed that according to the standard economic model the price on spare part ought to be zero since the producer include an insurance in the price of the main good. Further it is showed that moral hazard alone do not explain the pricing found in the studies. Finally an analysis of whether consumers with present-biased preferences could be a possible explanation is made. The analysis finds that it is a possibility however somewhat unlikely.</p>

This paper analyses the pricing on spare parts. Empirical studies have showed that manufacturers of durable goods make an unproportional large profit on its spare parts in relation to the revenue it generates. It is first showed that according to the standard economic model the price on spare part ought to be zero since the producer include an insurance in the price of the main good. Further it is showed that moral hazard alone do not explain the pricing found in the studies. Finally an analysis of whether consumers with present-biased preferences could be a possible explanation is made. The analysis finds that it is a possibility however somewhat unlikely.

A la hora de comprar a crédito, la evidencia empírica así como la meramente anecdótica sugieren que los consumidores se centras más en la cuantía de los pagos mensuales que en el tipo de interés del préstamo o la cantidad total que han de pagar. Los dos primeros capítulos de esta tesis exploran el papel del los problemas de auto control a la hora de explicar este comportamiento. Nuestro análisis se basa en el supuesto de descuento hiperbólico (Laibson (1997)) como forma de modelar el auto control. En el primer capitulo de la tesis consideramos un modelo de equilibrio parcial en el que la duración del préstamo y el tipo de interés están fijos y los consumidores pueden elegir cuánto tomar prestado y como repartir la devolución del préstamo entre los diferentes periodos. Mostramos que tener problemas de auto control implica mayores niveles de endeudamiento y que ser consciente de estos problemas o poseer la capacidad de comprometerse a un curso de acción reduce la presión sobre esos niveles. También demostramos que tener problemas de auto control y ser naif sobre ellos puede inducir una preferencia por los préstamos que requieren mayores cuotas hacia el final de su duración. El segundo capitulo analiza la interacción entre un prestamista monopolístico y un consumidor con descuento cuasi hiperbólico en un modelo en el que asumimos cuotas mensuales idénticas y permitimos al consumidor elegir entre distintas duraciones del préstamo. Obtenemos que mientras el tipo de interés del préstamo permanezca por encima del tipo de interés de mercado, en un contrato de equilibrio los consumidores con preferencias dinámicamente inconsistentes eligen préstamos con mayor duración (y por lo tanto con cuotas mensuales más bajas)El tercer capitulo de esta tesis, un trabajo conjunto con Alena Bicakova, proporciona evidencia empírica sobre el impacto de los problemas de auto control en el comportamiento de los consumidores a la hora de pagar sus deudas. El análisis viene motivado por resultados de encuestas que indican que un porcentaje significativo de los prestatarios atribuyen a una mala gestión de la deuda sus dificultades financieras. Esto contrasta con el argumento económico estándar según el cual la falta de pago de una deuda se debe a shocks negativos inesperados ya sea en los ingresos o en los gastos. Nuestra conjetura es que la mala gestión de la deuda y la falta de autocontrol están relacionadas y que tienen efectos adversos sobre el comportamiento de los prestatarios a la hora de devolver su deuda. Con el fin de verificar esta conjetura utilizamos una base de datos única en su naturaleza y procedente de una organización benéfica dedicada a la orientación a consumidores con créditos del Reino Unido. La orientación de crédito asiste a prestatarios seriamente endeudados mediante la elaboración y administración de unos planes de repago llamados Planes de Gestión de Deuda (DMP en ingles). Mostramos que la probabilidad de abandonar un DMP aumenta en un 12% y en un 31% respectivamente cuando las razones que se aducen para explicar el exceso de deuda (relacionadas con su mala gestión) y fumar se utilizan como indicadores. Como hasta cierto punto estos indicadores pueden usarse como una medida aproximada de los problemas de auto control, nuestros resultados sugieren una potencial relación entre las tasas de morosidad y la falta de auto control. / When buying on credit, anecdotal and empirical evidence suggest that the consumers focus more on the size of the monthly payments than on the interest charged on the loan or the total amount they pay. The first two chapters of this thesis aim to explore the role of self-control problems in explaining this puzzling behaviour. Our analysis relies on the assumption of the "quasi-hyperbolic discounting" (Laibson (1997)) to model self-control. In the first chapter of the thesis, we consider a partial equilibrium setting in which the loan maturity and the interest rates are fixed and the consumers can choose how much to borrow and how to allocate the repayments between different periods. We show that having self-control problems implies higher levels of borrowing whilst awareness of self-control problems or a lack of commitment puts downward pressure on that level. We also demonstrate that having self-control problems and being naive about them can induce a preference for back-loaded repayment plans which require higher repayments towards the end of the loan term. The second chapter looks at the interaction between a monopolistic lender and a consumer with quasi-hyperbolic discounting in a setting where we assume equal monthly payments and allow the consumer to choose between different loan maturities. We show that when market risk free rate exceeds the long run discount rate, in an equilibrium contract, the consumers with dynamically inconsistent preferences choose the loan with longer maturity (hence lower monthly payments). Third chapter of this thesis, which is a joint work with Alena Bicakova, provides empirical evidence on the impact of self-control problems on consumers' debt repayment behaviour. The analysis is motivated by the survey evidence which shows that a significant percentage of borrowers blame the debt mismanagement as the reason for running into financial troubles. This contrasts with the standard economic argument that default on debt is caused by the unexpected negative shocks to income or to expenditure. Our conjecture is that the debt mismanagement and lack of self-control are linked, and they have adverse effects on the debt repayment performance of the borrowers. In order to test this conjecture, we use a unique administrative data set of a major consumer credit counselling charity in the UK. Credit counselling assists heavily indebted borrowers by setting up and administering repayment plans, so called debt management plans or DMPs. We show that probability of dropping out from a DMP increases by 12 per cent and 31 cent when the self-reported reasons for becoming overindebted (related to debt mismanagement) and smoking are used as indicators, respectively. To the extent that these indicators can be used as a valid proxy for self-control problems, our results point to a potential link between default rates and lack of self-control.

Delay discounting, the belief that rewards decline in value over time, is a phenomenon observed in several clinical disorders, including Attention Deficit / Hyperactivity Disorder (ADHD), substance abuse disorders, and other impulse control disorders. Delay discounting behavior is characterized by a tendency to choose smaller, more immediate rewards over larger, more delayed rewards. This tendency has been associated with behavioral impulsivity and inability to delay gratification observed in the aforementioned clinical disorders. It has been suggested that time perception may be a salient feature of delay discounting. If the larger, longer-term reward is perceived as being more temporally remote, its relative value decreases and is associated with greater cost, and one becomes more likely to choose the more immediate reward over the longer-term (though optimal) choice. Time perception has been studied in clinical populations, with increased variability of responses as well as both under-production and overestimation of time intervals observed in those with ADHD and other disorders associated with impulsivity. The present study used informational feedback via a metronome to change belief regarding duration of a second--either increasing or decreasing it by approximately 20%. Participants were 132 college-aged students with and without a diagnosis of ADHD. Measures of impulsivity and ADHD symptomatology were collected as well, and participants completed several cognitive tasks measuring working memory and processing speed to explore the impacts of these measures on delay discounting and time perception. While participants were able to reliably incorporate the altered second belief into short estimations of time (i.e., less than a minute), the manipulation failed to generalize to longer-duration temporal estimations, and it did not affect delay discounting. Neither ADHD symptomatology, impulsivity, nor performance on the cognitive tasks were related to delay discounting behaviors, though a working memory measure was correlated with baseline (pre-manipulation) time and one longer duration estimation. This lends support to a relationship between working memory and temporal perception, though the relationship between temporal perception and delay discounting remains elusive. Directions for future studies to clarify the role of temporal processing and ADHD in delay discounting are discussed. / text

abstract: Research in the area of childhood trauma has shown a substantial amount of psychological maladjustment following the experience of traumatic events in childhood. Trauma survivors are at risk for developing a multitude of adverse psychological outcomes as well as unsafe behaviors following the event of trauma. One unifying theme within these psychological sequelae is the nature of impulsive behaviors. Delay-discounting refers to the subjective decrease in value of a reward when its presentation is delayed. Delay-discounting is often used as an index of impulsive behavior. This study poses two primary questions: 1) Can childhood trauma predict rates of delay-discounting? 2) Could delay-discounting predict psychological maladjustment for individuals who have experienced childhood trauma? This study will seek to answer these questions using an online version of the Kirby et al., 1999 hypothetical delay-discounting method, as well as the Barratt Impulsiveness Scale (BIS-11), to measure trait impulsivity. Measures of depression (BDI-II), life events (LEC), post-traumatic stress (PCL-C), and drug and alcohol abuse (DAST-20) will also be included. Participants included a sample of university students ages 18-52 (n=521, females = 386, males = 135) with a mean age of 25.19 years. Results indicated that childhood trauma was not a significant predictor of delay-discounting rate, nor was delay-discounting rate a significant predictor of psychological maladjustment. Limitations and future directions are discussed. / Dissertation/Thesis / M.S. Psychology 2012

The present study used a discounting task with differing contextual variables to examine how variables effect discounting between studies and future health related behaviors. Thirty nine participants completed two discounting questionnaires, each included hypothetical food choices paired with a weight loss or stable weight. Participants were instructed to complete each survey based on either their current weight or a gain of 75 pounds, and each survey included two identical hypothetical menu options. One menu incorporated low calorie foods, while the other incorporated moderately healthy foods, and participants were instructed to select the menu they preferred based on weight loss/no weight loss and hypothetical weight presented in instruction. Visual analysis of the results showed a difference in discounting across the conditions; participants appeared to be more impulsive at their current weight. At normal weight, visual analysis of the switch values show that the proportional value of the switch ranged from 1.0 at the lowest proportional delay level to .75 at proportional delay 1. In the hypothetical weight gain condition, this occurred at a level of .95 at the lowest proportional delay and .75 at delay 1. In a visual analysis of AUC comparisons, participants’ scores are higher in the 75 pound weight condition than the normal weight condition, and farther from 0 in the 75 pound weight condition.

The present study used healthy questionnaires to evaluate the compounding effects of weight loss and weight gain in choosing to exercise. The questionnaire was distributed to 31 participants via social media outlets. Demographic information was also recorded such as height, weight, ethnicity, and income. The height and weight recorded was used to correlate the BMI with the AUC values. This data did not show a strong correlation between body mass index with high or low AUC values, these values were evenly distributed between underweight, normal/average weight, and overweight participants. . The questionnaires designed to assess how people view exercise and to determine if there is a pattern with sequencing delays with the calculated switch point and AUC. Statistical and visual analyses were conducted at the group and participant level. The switch points, were documented from each delay and was calculated to determine the compounding sequence that was preferred from each participant. The results from the study indicated that participants chose to exercise immediately within the first day, when the consequence was to lose weight. The results for the gain condition indicated that participants would gain weight instead of exercise, to a certain limit (100 days), when they chose to then engage in exercise behavior regularly. The conclusion of this study shows that the longer the delay the less valued the outcome is. This is important when understanding the obesity epidemic within the United States.

In this dissertation, we experimentally examine individual preferences of effort, including time and risk preferences. In Chapter 3, we find that at least in certain settings and mindsets, individuals are very patient in their time preferences for effort, choosing to distribute effort evenly over time periods. However, they do not always live up to the stated plans, suggesting dynamic inconsistency or possibly two separate decision-making systems in the mind. This relates to our model in Chapter 2: a dual-self model of allocating effort between time periods in working toward a larger goal including incomplete information between different mindsets in the same person. Chapter 4 examines the risk preferences for effort, as a measurement of the utility function of effort, and finds that in this setting, subjects are very risk-averse over effort, compared to their preferences over money: they greatly avoid the possibility of having to complete a large number of tasks. These experiments and model help provide an understanding of how individuals allocate the scarce resource of time and energy to tasks they must complete.