A neuroeconomic theory of rational addiction and nonlinear time-perception--论文代写范文精选

神经经济学的研究表明,每日摄入尼古丁吸烟者有强烈的偏好。大多数人计划选择更大的同时更倾向于今天可用一杯鸡尾酒。在代理后喜欢更大的奖励,在不久的将来是动态不一致的(非理性),因为他们的偏好改变随着时间的流逝。下面的essay代写范文进行详述。

Abstract 
Neuroeconomic conditions for “rational addiction” (Becker and Murphy, 1988) have been unknown. This paper derived the conditions for “rational addiction” by utilizing a nonlinear time-perception theory of “hyperbolic” discounting, which is mathematically equivalent to the q-exponential intertemporal choice model based on Tsallis' statistics. It is shown that (i) Arrow-Pratt measure for temporal cognition corresponds to the degree of irrationality (i.e., Prelec’s “decreasing impatience” parameter of temporal discounting) and (ii) rationality in addicts is controlled by a nondimensionalization parameter of the logarithmic time-perception function. Furthermore, the present theory illustrates the possibility that addictive drugs increase impulsivity via dopaminergic neuroadaptation without increasing irrationality. Future directions in the application of the model to studies in neuroeconomics are discussed. 
Keywords: Neuroeconomics; Econophysics; Addiction; Dopamine; Rationality; Tsallis' statistics

Introduction
Delay discounting in intertemporal choice refers to the devaluation of a delayed reward compared to the value of an immediate reward (Bickel & Marsch, 2001; Takahashi, 2009). Impulsivity in intertemporal choice (referred to as “impatience” in behavioral economics) is defined as strong preference of smaller but more immediate rewards over larger but more delayed ones. Economists Becker and Murphy (1988) proposed a theory of rational addiction which associates impulsivity in intertemporal choice and addictive behavior. For instance, heroin addicts prefer "sooner but (objectively) smaller" rewards (i.e., pleasures from drug intake) over "later but (objectively) larger" rewards (e.g., a long lifespan, and a healthy and rich elderly life). 

Consistent with the proposed association between impatience and addiction in the economic theory of rational addiction (Becker and Murphy, 1988), our neuroeconomic study have demonstrated that daily nicotine intake by smokers are associated with strong preference for smaller sooner rewards over larger later ones (Ohmura et al., 2005). Agent A who prefers "one glass of caipirinha available one year later" over "two glasses of caipirinha available [one year plus one week] later" is more impulsive (impatient) than agent B who prefers "two glasses of caipirinha available [one year plus one week] later" over "one glass of caipirinha available one year later". In this example 1, most people may behave like the patient agent B. 

It is to be noted that both impatient agent A and patient agent B may be rational, because, in this example 1 alone, there is no inconsistency even in impatient agent A's behavior. Suppose the next intertemporal choice example 2. There are two options: "one glass of caipirinha available today" and "two glasses of caipirinha available one week later". In example 2, most people who planned to choose the larger later option in example 1 simultaneously tend to prefer "one glass of caipirinha available today" over "two glasses of caipirinha available one week later". The combination of these two intertemproal choices in example 1 (choosing the larger later) and example 2 (choosing the smaller sooner) is time-inconsistent (irrational). 

Namely, agents who prefer larger later rewards in the distant future, but prefer smaller sooner rewards in the near future are dynamically inconsistent (irrational), because their preferences reverse as time passes (Laibson, 1997). Economists Becker and Murphy (1988)’s theory of rational addiction assumes addicts are “rational” (in time-consistency and maximization of the summed temporally-discounted utility over her lifespan) and impatient, resulting in the consumption of harmful drugs at the cost of healthy life in the old age. However, it is still possible that addicts are not only more impatient but also more irrational (i.e., more time-inconsistent) than non-drug-dependent subjects, as economists Gruber and Koszegi (2001) questioned. 

Therefore, it is important to examine neuroeconomic psychophysical, and biophysical conditions under which addicts are rational (even though they are impatient), in order to develop neuroeconomic theory of addiction and extend the frameworks of econophysics into time-inconsistency related to psychophysics of temporal cognition. I derive, in this paper, conditions on parameters in neuroeconomic theory of intertemporal choice which incorporates psychophysics of time-perception (Kim and Zauberman, 2009; Takahashi, 2005; Takahashi, 2006; Takahashi et al., 2008; Zauberman et al., 2009), and is mathematically equivalent to the q-exponential discount model based on Tsallis’ statistics (Cajueiro, 2005; Takahashi et al., 2007). Notably, the q-exponential function is a well-studied function in a deformed algebra developed in Tsallis' non-extensive thermodynamics (Tsallis, 1994). This paper is organized in the following manner. In Section 2, I briefly introduce the discount models in relation to time-inconsistency (irrationality) and time-perception, and their relations to the q-exponential discounting. In Section 3, I derive the conditions on the parameters in the introduced discount models and give neuroeconomic and biophysical and psychophysical interpretations to the conditions on the parameters. In Section 4, some conclusions from this study and future study directions by utilizing the present theoretical framework in neuroeconomics of addiction are discussed.

Conclusions and implications for neuroeconomics and econophysics 
Recent human neuropsychopharmacological studies revealed that neuropsychiatric patients such as ADHD (attention-deficit hyperactivity disorder)’s temporal discounting and time-perception may be modulated by dopamine systems in the brain (Rubia et al., 2009). Also, time-perception is related to dopaminergic drug-related habit formation (Williamson et al., 2008) and impaired time-perception is related to D2 (a subtype of dopamine receptors) functioning in the striatum (Ward et al., 2009). These findings indicate the important roles of dopamine in time-discounting and time-perception. Furthermore, we have previously shown that depressed patients (known to have impairment in serotonin activity in the brain) are more time-inconsistent than healthy subjects (Takahashi et al., 2008). 

Therefore, it can be expected that serotonin activity modulates the nondimensionalization parameter b of the psychophysical time-perception function (equation 4), resulting in exaggerated irrationality in temporal discounting. These points should be studied in future neuroeconomic studies. Finally, it is known that magnitude and sign (i.e. gain/loss) of outcomes affects discount rates (Estle et al., 2006). It is possible these effects occur via the psychophysical effects on time-perception. For instance, while waiting for a larger reward, subjects do not strongly feel the passage of physical time, resulting in the “magnitude effect” on temporal discounting (i.e., larger rewards are less steeply time-discounted than smaller rewards). If this is the case, future studies should examine whether the effects of magnitude on temporal cognition affect nonlinearity of time-perception (indicated by parameter b in equation 4).（essay代写)

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