Loss of self-control in intertemporal choice may be attributable to logarithmic time-perception
Section snippets
Background
Discounting of delayed rewards refers to the observation that the value of a delayed reward is discounted (reduced in value or considered to be worth less) compared to the value of an immediate reward [1], [2]. Studies in psychopharmacology, psychiatry, behavioral neuroscience, and economics have been focused on how subjects discount delayed rewards. Notably, it has repeatedly been demonstrated that substance abusers more steeply discount delayed rewards than non-drug dependent subjects [1].
Hypothesis
The psychophysicists Weber and Fechner proposed that the external stimulus (e.g., loudness) is scaled into a logarithmic internal representation of sensation (Weber’s law), rather than a linear internal representation [7]. Some recent studies further suggest that the mental timer also seems to be logarithmic, rather than linear, following Weber’s law [8], [9], although it is still controversial whether time estimation is processed in distributed neural networks or in central time-keeping neural
Several neuropsychopharmacological findings supporting our hypothesis
Neuropsychopharmacological studies have revealed that both acute and chronic administration of dopaminergic drugs (e.g., alcohol, heroin, and nicotine) dramatically affect individual’s degree of discounting delayed rewards [1]. For instance, parameters of hyperbolic discounting (e.g., β in Eq. (4) have been shown to be increased in drug addicts, which is supposed to associate with their impulsive decision-making in intertemporal choice and loss of self-control [1], [10], [11], [12], [13].
Conclusions
Relations between non-linearity of time-perception and subject’s parameters in discounting equations should be empirically investigated in future studies, in order to test our hypothesis. Studies employing substance abusers and administrations of dopaminergic drugs would be especially important.
Acknowledgments
The research reported in this paper was supported by a grant from the Grant-in-Aid for Scientific Research (“21st century center of excellence” grant and grant #17650074) from the Ministry of Education, Culture, Sports, Science and Technology of Japan and Yamaguchi endocrinological disorder grant.
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