Soo Hong Chew

The contributions of oxytocin and vasopressin pathway genes to human behavior

Arginine vasopressin (AVP) and oxytocin (OXT) are social hormones and mediate affiliative behaviors in mammals and as recently demonstrated, also in humans. There is intense interest in how these simple nonapeptides mediate normal and abnormal behavior, especially regarding disorders of the social brain such as autism that are characterized by deficits in social communication and social skills. The current review examines in detail the behavioral genetics of the first level of human AVP-OXT pathway genes including arginine vasopressin 1a receptor (AVPR1a), oxytocin receptor (OXTR), AVP (AVP-neurophysin II [NPII]) and OXT (OXT neurophysin I [NPI]), oxytocinase/vasopressinase (LNPEP), ADP-ribosyl cyclase (CD38) and arginine vasopressin 1b receptor (AVPR1b). Wherever possible we discuss evidence from a variety of research tracks including molecular genetics, imaging genomics, pharmacology and endocrinology that support the conclusions drawn from association studies of social phenotypes and detail how common polymorphisms in AVP-OXT pathway genes contribute to the behavioral hard wiring that enables individual Homo sapiens to interact successfully with conspecifics. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

Axiomatic utility theories with the betweenness property

This paper focuses on the betweenness property of expected utility theory. We provide an axiomatization of the class of betweenness-conforming utility theories. Subclasses of betweenness-conforming preferences are axiomatized with ‘substitution’ axioms of intermediate generality. The latter axioms incorporate specifically the effects of replacing a certain outcome with a lottery that is indifferent to it. Our representation is applied to the second-price auction mechanism where we show that its demand-revelation property under expected utility is not robust with respect to the class of betweenness-conforming preferences.

MIXTURE SYMMETRY AND QUADRATIC UTILITY

The independence axiom of expected utility theory has recently been weakened to the betweenness axiom. In this paper, an even weaker axiom, called mixture symmetry, is presented. The corresponding functional structure is such that utility is a betweenness functional on part of this domain and quadratic in probabilities elsewhere. The experimental evidence against betweenness provides one motivation for the more general theory presented here. Another advantage of the mixture symmetric class of utility functions is that it is sufficiently flexible to permit the disentangling of attitudes toward risk and toward randomization. Copyright 1991 by The Econometric Society.

A unifying approach to axiomatic non-expected utility theories

This paper unifies the two principal thrusts in the literature on axiomatic theories of transitive preferences which generalize expected utility theory; namely, the betweenness conforming theories and the rank-dependent theories. The unification is achieved in two respects. First, new axiomatizations are provided for the existing theories based on separability restrictions in outcome space. These axiomatizations bring into clear focus both the similarities and the differences between the existing theories. Second, an axiomatization is provided for a new class of preferences which includes existing classes as special cases.

The heritability of attitude toward economic risk

The propensity to take risk underpins a wide variety of decision-making behavior, ranging from common ones such as asking for directions and trying out a new restaurant to more substantial economic decisions involving, for instance, ones investment or career. Despite the fundamental role of risk attitude in the economy, its genetic basis remains unknown. Using an experimental economics protocol combined with a classical twin strategy, we provide the first direct evidence of the heritability of economic risk attitude, at 57%. We do not find a significant role for shared environmental effects, a common observation in behavioral genetics that is contrary to commonly held views in economics. Our findings complement recent neuroeconomic studies in enhancing the understanding of the neurobiological basis of risk taking.

A neurochemical approach to valuation sensitivity over gains and losses

Prospect theory proposes the hypothesis that people have diminishing sensitivity in valuing increases in the size of monetary outcomes, for both gains and losses. For decision-making under risk, this implies a tendency to be risk-tolerant over losses while being generally risk averse over gains. We offer a neurochemistry-based model of the diminishing valuation sensitivity hypothesis. Specifically, we propose that dopamine tone modulates the sensitivity towards valuation of gains while serotonin tone modulates the sensitivity towards valuation of losses. Consequently, higher dopamine tone would yield a more concave valuation function over gains while higher serotonin tone would yield a more convex valuation function over losses. Using a neurogenetics strategy to test our neurochemical model, we find that subjects with the 9-repeat allele of DAT1 (lower DA tone) are more risk-tolerant over gains than subjects with the 10-repeat allele, and that subjects with the 10-repeat allele of STin2 (higher 5HT tone) are more risk-tolerant over losses than subjects with the 12-repeat allele. Overall, our results support the implications of our model and provide the first neurogenetics evidence that risk attitudes are partially hard-wired in differentiating between gain- and loss-oriented risks.

Hope: An empirical study of attitude toward the timing of uncertainty resolution

Hope is experienced when there is enjoyment in delaying the resolution of uncertainty. The main objective of this article is to identify the phenomenon of hope. In addition, we empirically test several axiomatic theories of temporal preferences which have implications for attitudes toward the timing of uncertainty resolution. Overall, the data support the extension of recursive expected utility specification to incorporate a weighted utility model of attitude toward future uncertainty. We find that the instances where hopefulness are more prevalent tend to be associated with a small probability of occurrence of a large gain. Interestingly, the degree of hopefulness is not correlated with risk attitude.

The Structure of Preferences and Attitudes towards the Timing of the Resolution of Uncertainty

This paper is concerned with the phenomenon of preference for timing in the temporal resolution of uncertainty and its implications for the structure of utility functionals defined on multiperiod consumption programs. Several postulates concerning attitudes towards timing are stated using a new definition of timing premium for early resolution of uncertainty. The analysis provides an axiomatic basis for the specifications of expected utility and the more general weighted utility and implicit weighted utility functionals in temporal models. Copyright 1989 by Economics Department of the University of Pennsylvania and the Osaka University Institute of Social and Economic Research Association.

Nonexpected utility preferences in a temporal framework with an application to consumption-savings behaviour

Abstract This paper investigates the role of non-expected utility preferences in a multiperiod consumption/savings framework. Three objectives are achieved: First, it is shown that behaviour can be intertemporally consistent even if the preference ordering is not. Second, non-expected utility preference orderings are shown to be useful for disentangling the elasticity of intertemporal substitution from the degree of risk aversion. Finally, some discrimination between the non-expected utility theories that have appeared in the atemporal literature is achieved by means of axioms which arise naturally from the multiperiod framework.

Dopamine D4 Receptor Gene Associated with Fairness Preference in Ultimatum Game

In experimental economics, the preference for reciprocal fairness has been observed in the controlled and incentivized laboratory setting of the ultimatum game, in which two individuals decide on how to divide a sum of money, with one proposing the share while the second deciding whether to accept. Should the proposal be accepted, the amount is divided accordingly. Otherwise, both would receive no money. A recent twin study has shown that fairness preference inferred from responder behavior is heritable, yet its neurogenetic basis remains unknown. The D4 receptor (DRD4) exon3 is a well-characterized functional polymorphism, which is known to be associated with attention deficit hyperactivity disorder and personality traits including novelty seeking and self-report altruism. Applying a neurogenetic approach, we find that DRD4 is significantly associated with fairness preference. Additionally, the interaction among this gene, season of birth, and gender is highly significant. This is the first result to link preference for reciprocal fairness to a specific gene and suggests that gene × environment interactions contribute to economic decision making.