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The role of the medial prefrontal cortex in delay discountingBeckwith, Steven Wesley January 2017 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Increased delay discounting (DD) has been associated with and is theorized to contribute to alcoholism and substance abuse. It is also been associated with numerous other mental disorders and is believed to be a trans-disease process (i.e., a process that occurs in and contributes to multiple different pathologies). Consequently insights gained from studying DD are likely to apply to many different diseases. Studies on the neurobiological underpinnings of DD have two main interpretations. The first interpretation is that two different neurobehavioral systems exist, one favoring delayed rewards (executive system) and one favoring immediate rewards (impulsive system), and the system with the greater relative activation determines choice made by an individual. Alternatively, a single valuation system may exist. This system integrates different information about outcomes and generates a value signal that then guides decision making. Preclinical investigations have steered clear of these two different interpretations and rather focused on the role of individual structures in DD. One such structure, the rat mPFC, may generate an outcome representation of delayed rewards that is critically involved in attributing value to delayed rewards. Moreover, there is evidence indicating the rat mPFC may correspond to the primate dlPFC, an executive system structure.
The current body of work set about testing the hypotheses that the mPFC is necessary for attributing value to delayed rewards and that decreasing the activity in an executive system area, and thus the executive system, shifts inter-temporal preference towards immediate rewards. To this end the rat mPFC was inactivated using an hM4Di inhibitory designer receptor exclusively activated by designer drugs (DREADD; experiment 1) or microinjections of tetrodotoxin (TTX; experiment 2) while animals completed an adjusting amount DD task. Activation of the hM4Di inhibitory DREADD receptor caused a decrease in DD, opposite of what was predicted. Electrophysiological recordings revealed a subpopulation of neurons actually increased their firing in response to hM4Di receptor activation, potentially explaining the unpredicted results. Microinjections of TTX to completely silence neural activity in the mPFC failed to produce a change in DD. Together both results indicate that mPFC activity is capable of manipulating but is not necessary for DD and the attribution of value to the delayed reward. Consequently, a secondary role for the rat mPFC in DD is proposed in line with single valuation system accounts of DD. Further investigations determining the primary structures responsible for sustaining delayed reward valuation and how manipulating the mPFC may be a means to decrease DD are warranted, and continued investigation that delineates the neurobiological processes of delayed reward valuation may provide valuable insight to both addiction and psychopathology.
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The economics of altruism, paternalism and self-controlBreman, Anna January 2006 (has links)
Paper 1: Give More Tomorrow Many charities ask donors to commit to monthly contribution schemes. Monthly contributors give a fixed sum every month, which is automatically deducted from their bank account. These donors are the most profitable ones for a charity. On average, they give more than donors who contribute sporadically. They also facilitate the long-run financial planning of the charity, and they reduce the administrative and fundraising costs. What will influence a donor's decision to commit to a monthly contribution scheme? If the costs and benefits associated with contributing to a charity occur at different points in time, the answer will depend on the donor's inter-temporal preferences. More specifically, it will be of importance whether donors are time consistent or whether they exhibit present-biased preferences. This paper designs and tests a fundraising strategy that allows for present-biased preferences among donors. The strategy, Give More Tomorrow, was implemented as a randomized field experiment in collaboration with a large charity. 1134 donors that make monthly contributions were randomly assigned to one of two treatment groups. In the first group, monthly donors were asked to increase their donation starting immediately. In the second group, monthly donors were asked to increase their donations starting two months later. Mean donations were 32 percent higher in the latter group, a highly significant difference. Donations conditional on giving were also significantly higher in the latter group. The effect of the GMT strategy is economically large and highly profitable to the charity. Paper 2: Crowding Out or Crowding In? The crowding-out hypothesis says that private givers, who are also taxpayers, will use their tax-financed donations as a substitute for their voluntary donations, thus reducing the net effectiveness of grants (Warr, 1982, 1983; Roberts, 1984; Bernheim, 1986; and Andreoni, 1988). While theory predicts a one-to-one relationship between government grants and private donations, econometric and experimental studies have found evidence of partial or no crowding out (see, e.g., Khanna et al., 1995; Payne, 1998; Khanna and Sandler, 2000; and Okten and Weisbrod, 2000). A recent contribution to this literature argues that government grants reduce the organizations' fundraising efforts, which may indirectly cause a decrease in private contributions (Andreoni and Payne, 2003). This paper employs a previously unexplored panel dataset to test whether government grants crowd out private donations to charitable organizations, controlling for changes in the organizations' fundraising behavior. The data covers all registered charitable organizations in Sweden between 1989 and 2003. We have a total of 361 organizations where the largest group is health related. The panel data allows us to control for unobserved organizational heterogeneity and time fixed effects. Furthermore, we use a 2SLS specification to control for possible endogeneity in government grants and fundraising expenditures. Complete crowding out can be strongly rejected. In the 2SLS regression, the estimated crowd-out is small and highly significant in the full sample, on average 5.0%. In the disaggregated sample, we cannot reject zero crowding out for any type of organization in the 2SLS regressions. Furthermore, we find strong evidence that organizations are net revenue maximizing, indicating that fundraising activities are efficient. Paper 3: Is Foreign Aid Paternalistic? (with Ola Granstrom and Felix Masiye) In this paper, we experimentally investigate whether donors are paternalistically altruistic when contributing to foreign aid. A paternalist may be defined as someone who advances other people's interests, such as life, health, or safety, at the expense of their liberty or autonomy. In economic theory, a donor is said to be paternalistically altruistic if he cares about a recipient's wellbeing, but does not fully respect the recipient's preferences (Pollak, 1988; Jones-Lee, 1991, 1992; Jacobsson et al., 2005). In a double-blind experiment, a subject chooses whether to make a monetary or a tied transfer (mosquito nets) to an anonymous household in Zambia. Recipients have revealed preferences for money, as their willingness to pay for mosquito nets is positive but below the market price. A monetary transfer will therefore preserve the household's preferences while a tied transfer is paternalistic. The mean donation of mosquito nets differs significantly from zero, thereby implying paternalistic preferences among donors. Paternalistic donors constitute 65 percent of the total sample, whereas purely altruistic donors constitute 15 percent. We conclude that health-focused paternalistic rather than purely altruistic preferences dominate the foreign-aid giving of individuals. Paper 4: Altruism without Borders? (with Ola Granstrom) Why do individuals contribute to foreign aid? Does the willingness to give increase the more we know about the recipients? Although there is some literature on the strategic interests of countries in providing foreign aid, (see, e.g., Alesina and Dollar, 2000) very little is yet known about which preferences guide the foreign-aid giving of individual donors. This paper experimentally tests altruism over borders. We design a cross-country dictator game where the degree of identification of the recipient is varied in four treatments: (1) anonymity, (2) photo, (3) information and (4) photo and information. In addition, questionnaire data on donor characteristics is gathered. The mean donation is 55%, which is considerably higher than in standard dictator games. In contrast to previous within-country experiments, we find no significant effect of identification on donations. Furthermore, we find that women donate significantly more than men (64 compared to 50 percent) and that those who state that aid is too large donate significantly less than those who state that aid is too small (24 compared to 67 percent). / Diss. Stockholm : Handelshögskolan, 2006 S. 5-7: Summary of Papers, S. 13-125: 4 papers
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