Loss of self-control in intertemporal choice may be attributable to logarithmic time-perception

https://doi.org/10.1016/j.mehy.2005.04.040Get rights and content

Summary

Impulsivity and loss of self-control in drug-dependent patients have been associated with the manner in which they discount delayed rewards. Although drugs of abuse have been shown to modify perceived time-duration, little is known regarding the relationship between impulsive decision-making in intertemporal choice and estimation of time-duration.

In classical economic theory, it has been hypothesized that people discount future reward value exponentially. In exponential discounting, a temporal discounting rate is constant over time, which has been referred to as dynamic consistency. However, accumulating empirical evidence in biology, psychopharmacology, behavioral neuroscience, and neuroeconomics does not support the hypothesis. Rather, dynamically inconsistent manners of discounting delayed rewards, e.g., hyperbolic discounting, have been repeatedly observed in humans and non-human animals. In spite of recent advances in neuroimaging and neuropsychopharmacological study, the reason why humans and animals discount delayed rewards hyperbolically is unknown. In this study, we hypothesized that empirically-observed dynamical inconsistency in intertemporal choice may result from errors in the perception of time-duration. It is proposed that perception of temporal duration following Weber’s law might explain the dynamical inconsistency. Possible future study directions for elucidating neural mechanisms underlying inconsistent intertemporal choice are discussed.

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.

References (16)

There are more references available in the full text version of this article.

Cited by (0)

View full text