Psychology, 2010, 1, 128-133
doi:10.4236/psych.2010.12017 Published Online June 2010 (http://www.SciRP.org/journal/psych)
People with Metabolic Syndrome Disorders Give
Lower Offers in Ultimatum Game
Anuja Joshi1, Sumedha Kondekar1, Prajakta Belsare2, Saroj Ghaskadbi2, Milind Watve3,4,
Maithili Jog1
1Department of Biotechnology, Abasaheb Garware College, Pune, India; 2Department of Zoology, University of Pune, Pune, India;
3Indian Institute of Science Education and Research, Pune, India; 4Anujeeva Biosciences Pvt Ltd., Pune, India.
Received April 8th, 2010; revised May 12th, 2010; accepted May 14th, 2010.
ABSTRACT
Background: The origins of the metabolic syndrome disorders are being increasingly recognized as neuro-behavioural
rather than dietary or metabolic. The neuro-behavioural origins hypothesis implies that there should be detectable be-
havioural differences between people with and without metabolic syndrome disorders. We test here whether the eco-
nomic behaviour o f individuals with any of the m etabolic syndrome disorders d iffers from that of healthy age ma tched
controls using the ultimatum bargaining game. Methods: The ultimatum game was played by 59 persons with at least
one of four metabolic syndrome disorders namely type 2 diabetes (T2D), hypertension, hypercholesterolemia and car-
diovascular disease (MS group ) and the results were compared to a healthy age matched control consisting of 71 per-
sons. Results: The MS group gave significantly lower ultimatum game offers than the control group. Testing for indi-
vidual disorders, type 2 diabetics gave significantly lower offers than the non-diabetic gro up. In binary logistic regres-
sion, ultimatum game offer was a b etter p redictor o f MS and T2D than Body Mass Index (BMI). Conclusions: There are
detectable behaviou ral d ifferen ces between individu a ls with metabolic syn drome disorders as compa red to age matched
healthy controls. The results are compatible with the neurobehavioral origins hypothesis and demonstrate further the
association between metabolic states and social and economic behaviour.
Keywords: Economic Behaviour, Fairness, Metabolic Syndrome, Serotonin, Testosterone, Ultimatum Game
1. Introduction
The cluster of diseases including insulin resistance, type
2 diabetes, hypercholesterolemia, hypertension, athero-
sclerosis and cardio-vascular disease are collectively
called insulin resistance syndrome or metabolic syn-
drome. The name itself reflects the traditional view that
the aetiology as well as pathogenesis of th ese disorders is
predominantly metabolic. The syndrome has a strong
positive association with obesity [1-3] and imbalance in
energy homeostasis is believed to be central to it. Pre-
disposition to these disorders has been said to be owing
to a “thrifty” metabolism imparted genetically or by foe-
tal programming [4,5].
From time to time the thriftiness paradigm has been
challenged on several grounds [6-8]. Some of the critics
of thriftiness family of hypotheses have completely re-
jected the concept [7,8], whereas others have pointed out
the inadequacies of the hypotheses and suggested alter-
natives which are not incompatible with thriftiness hy-
potheses [6,9]. One of the alternative hypotheses which
says that the physiological changes that underlie meta-
bolic syndrome are adaptive to a “soldier” to “diplomat”
transition in lifestyle appears to explain most of the
metabolic, immunological, reproductive and cognitive
changes known to accompany insulin resistance as well
as accommodate and reinterpret foetal programming [6].
Belsare [9] pointed out that this behavioural switch hy-
pothesis can also account for thriftiness and that thrifti-
ness can be a subset of the behavioural switch hypothesis.
The behavioural switch hypothesis was further refined by
Rashidi et al. [10] and Belsare et al. [11] to elaborate on
the mechanisms and pathways by which behavioural
transitions can bring about endocrine, metabolic and
immunological changes. The behavioural origins para-
digm predicts that in add ition to obesity, high population
density, suppression of physical aggression, suppression
of sexual desire and sexual activity, a perception of being
physically weak and high social manipulation skills
should be associated with many of the metabolic syn-

People with Metabolic Syndrome Disorders Give Lower Offers in Ultimatum Game 129
drome disorders [6,11]. This is potentially a major para-
digm shift by which the metabolic syndrome disorders
will be more a subject of behavioural sciences than
medicine. Although a number of predictions of the be-
havioural switch hypothesis are supported by meta-
analysis [11], more direct tests of the predictions are
needed. We state and test here one of the predictions of
the behavioural origins hypothesis. If the origins of
metabolic syndrome are behavioural, there should be
detectable behavioural ch aracteristics associated with the
metabolic syndrome disorders. Further a set of quantifi-
able behavioural changes should be able to predict
metabolic syndrome disorders in cross sectional or pref-
erably longitudinal studies. Currently we do not know
which specific set of behaviours should one look for and
the best possible assays for them. Much careful thinking,
standardization and validation would be needed before
using such predictive behavioural tests. As a first step
towards this goal we test here whether detectable and
quantifiable behavioural differences exist between indi-
viduals with one or more of the metabolic syndrome dis-
orders and age matched healthy controls. We selected a
simple bargaining game that has been used extensively in
economics and behavioural science, namely ultimatum
game [12]. Ultimatum game was selected owing to its
simplicity and a consistent demonstration that levels of
certain hormones are associated with the behavioural
outcome in the game [13-17].
1.1 Ultimatum Ga me
The ultimatum game involves two-player bargaining.
The two players are unknown to each other. One player
(player 1) plays the role of allocator and the other player
(player 2) plays the role of recipient. Player 1 is promised
some money and is asked to divide it between himself
and the other player. The rules stipulate that player 1
must make an offer, and player 2 can either accept the
offer or reject it. If player 2 accepts the offer, player 1
receives the promised money and will have to give the
offered fraction to player 2. If player 2 rejects the offer,
none of them gets any money.
If we assume that each player plays to maximize his
benefits, the rational strategies are simple. For player 2
accepting and rejecting are the only two options. Since
rejection is bound to give zero returns, accepting any
non-zero offer is the only rational strategy. Assuming
player 1 knows what is rational for player 2, offering
minimum non-zero amount would be the most rational
strategy for player 1. However, it is observed that most
people do not go by this rationale. In a large number of
studies across age groups and cultures the modal offer is
typically 50% and the mean offer lies between 40% and
50% of the total amount. Although the game is simple to
perform and analyze, the interpretation of the results is
complex. The surprising agreement about roughly equal
sharing has been commonly interpreted as a result of an
innate human tendency to appreciate fair and to retaliate
unfair decisions [12]. This interpretation is certainly at-
tractive and generally widely agreed. However the dem-
onstration that serotonin [13-15] and testosterone [16,17]
levels affect ultimatum offers has raised other possibili-
ties too. Both serotonin and testosterone are associated
with social dominance hierarchy and aggression in dif-
ferent ways. Manipulating brain serotonin levels can
change the dominant status and behaviour of an individ-
ual in a wide variety of species [18,19]. It is possible
therefore that the ultimatum game offers reflect social
hierarchical behaviour in some way and not fairness
alone. Social factors related to status and hierarchy have
also been reported as risk factors for metabolic syndrome
[20,21]. Both serotonin and testosterone play important
roles in metabolic syndrome. Chronically elevated sero-
tonin signalling in the hypothalamus induces peripheral
insulin resistance [22,23]. Testosterone levels of diabet-
ics are typically low and testosterone has a protective
role against many pathological consequences of meta-
bolic syndrome [24-26]. Since serotonin is negatively
associated with ultimatum offers and testosterone is posi-
tively associated [13-17], one may expect that diabetics
may give lower offers in ultimatum game. However, to
the best of our knowledge there are no previous studies
testing whether behaviour in ultimatum game is associ-
ated with any disorder.
2. Methods
2.1 Sample Groups
Sampling was restricted to a narrow socioeconomic sec-
tor comprising urban middle class in Pune city selected
based on the locality and type of housing. Maintaining
the socioeconomic class, 43 households and 14 work-
places were visited and all individuals between the age
groups of 40 and 75 were requested to voluntarily par-
ticipate in the study but the objective and the hypothesis
being tested was not disclosed until completing the re-
sponse sheet. The respondents were given to know the
conditions of the game, were promised an amount of INR
500 (approximate equivalent of $ 10) and asked to write
their offers to an anonymous player 2. The occupation,
height, weight and self repor ted history of any of the fol-
lowing metabolic syndrome components diagnosed were
noted. The noted disorders were type 2 diabetes (T2D),
hypertension, hypercholesterolemia and cardiovascular
disease. Since the proportion of individuals with any of
these disorders was expected to be low, in order to have
comparable numbers, the names of 30 patients with T2D
or hypertension were selected from a health camp taking
care that they belonged to the same locality and socio-
economic group. They were visited and their participa-
tion requested as above. In total the sample group con-

People with Metabolic Syndrome Disorders Give Lower Offers in Ultimatum Game 130
sisted of 71 healthy individuals (without any of the above
four disorders) and 58 with at least one of these disorders
(47 T2D, 19 hypertension, 5 hypercholesterolemia and 5
CVD).
2.2 Statistical Analysis
The sample group was divided as individuals with at
least one of the metabolic syndro me disorders (MS group,
n1 = 58, 25 male, 33 female) and healthy controls (n2 =
71, 30 male 41 female). The age group distribution of the
two groups was compared with 10 year interval groups.
Since the distribution of ultimatum game offers was
highly leptokurtic with the mode at 50% represented by a
very sharp peak, the data were divided into 3 categories
namely the modal offer group (50% ± 5%), one with
lower offers than the modal group and one with higher
offers than the modal group. Frequencies in these three
groups in MS versus healthy controls were compared
using chi square test. Similar test was performed to
compare T2D versus non-diabetic groups. For other dis-
orders the number of affected individuals was too small
for a meaningful statistical test. Using MS and diabetes
separately as binary variables, logistic regression was
used to test which out of the noted variables namely sex,
occupation, body mass index (BMI) and ultimatu m game
offer predicted the disorders.
3. Results
The MS and healthy control groups did not differ sig-
nificantly in the sex and age class distribution. In the
pooled data the modal ultimatum game offers were at
50%. However, as compared to the healthy con trol group
the MS group deviated significantly from the mode,
much of the deviation being towards the left. The mean
offers by the MS group (Rs 202.55) were substantially
lower than the control group (Rs. 241.05) and frequency
below the mode was highly significantly greater than the
control group (chi square = 32.01, df = 2, p < 0.001)
(Figure 1). In both MS as well as healthy groups, the
frequencies of the three offer classes did not differ sig-
nificantly between the two sexes.
The comparison of diabetic and non-diabetic groups
showed similar pattern and the difference was highly
significant (chi square = 28.42, df = 2, p < 0.001) (Fig-
ure 2). For other disorders the sample sizes were too small
to allow a meaningful statistical test. There was a weak
negative correlation between BMI and ultimatum game
offers in the pooled dat a whi ch was non-signif icant.
Logistic regression with presence of at least one of the
metabolic syndrome disorders as a dependent binary
variable and including sex, occupation, BMI and ultima-
tum offers revealed that the effects of sex and occupation
were non-significant whereas BMI (Wald = 3.09, p =
0.078) and ultimatum offer (Wald = 3.56, p = 0.059)
Figure 1. Frequencies of ultimatum offers by people with
metabolic syndrome (MS) disorders in comparison with
healthy controls: Data are divided in three categories
namely modal (50% ± 5%), below modal and above modal
class. MS give significantly lower offers. (chi square = 32.01,
df = 2, p < 0.001)
Figure 2. Frequencies of ultimatum offers by people with
T2D in comparison with healthy controls: Data are divided
in three categories namely modal (50% ± 5%), below modal
and above modal class. Diabetics give significantly lower
offers. (chi square = 28.42, df = 2, p < 0.001)
were marginally significant with overall predictability of
the model being 62.4%. Exclusion of BMI from the re
gression rendered the effect of ultimatum offer signifi-
cant (Wald = 5.12, p = 0.02) with predictability improv-
ing to 68.6%. On exclusion of ultimatum offer the effect
of BMI was non-significant an d pred ictability declin ed to
56.78%. Considering T2D alone the patterns were very
similar. Only ultimatum offer significantly predicted T2D
in logistic regression (Wald = 4.42, p = 0.035) whereas
BMI, sex and occupation did not show significant effects,
the predictability of the mode l being 65.52%.
4. Discussion
We found highly significant behavioural differences in
people with T2D, hypertension or other components of
metabolic syndrome in comparison with healthy age
matched controls. This might be unexpected by the con-
ventional view of the syndrome which assumes diet and
metabolism to be the root cause of the disorders. How-

People with Metabolic Syndrome Disorders Give Lower Offers in Ultimatum Game 131
ever, with the emerging picture of behavioural origins,
detectable behavioural differences are expected to be
present. However, currently there are no specific tools
standardized to quantitatively assess behavioural differ-
ences between healthy versus diabetic or hypertensive
people. Designing and validating such tests specifically
for this purpose would need much intensive thinking and
research inputs. Ultimatum game is a simple and popular
standard tool in studying economic and social behaviour
in humans and therefore a good test to begin investiga-
tions. The demonstration of highly significant differences
in ultimatum game should stimulate further empirical
research in the behavioural aspects of metabolic syn-
drome.
Ultimatum game is generally considered as a “fair-
ness” game. However it would be unfair to jump to the
conclusion that people with metabolic syndrome are “un-
fair” to others. This is because the fairness interpretation
of ultimatum game itself can be questioned. People may
deviate from the economically rational low offers owing
to a number of possible alternative reasons. The offers
may represent a valuation of relative social ranking with
an anonymous person being given a default equal rank-
ing. A high offer may be viewed as a costly signal in-
tended to advertise one’s own status and generosity or it
may be driven by a hidden prediction of repeated and
reciprocal interactions. All these explanations can be
grouped as social status related explanations. It can be
perhaps generalized that economic rationality prompts
low offers and social status and social justice related
factors prompt offers substantially higher than the eco-
nomically rational ones. On this scale diabetics appear to
be more inclined towards economic rationality co mpared
to social rank or social justice related factors. A change
in social rank or stress related to social subord ination has
been shown to be associated with insulin resistance syn-
drome and related physiological changes in animals as
well as humans [20,21]. The hormones which have pre-
viously been shown to affect economic game behaviour
are serotonin and testosterone both of which are known
to play a role in social dominance hierarchy [18,19].
Therefore the more plausible explanation of lower hits by
diabetics is likely to be related to a greater importance of
economic rationality as compared to an aggressive and
competitive social hierarchy. On the other hand there is
neither any a priori reason nor evidence showing that
metabolic syndrome disorders affect “fairness”.
The social rank explanation is compatible with the
upcoming paradigm of behavioural origins of metabolic
syndrome. In animal societies the physically strong and
dominant “hawk” strategists are insu lin sensitive wh ereas
weaker, subordinate but socially smart and opportunistic
“dove” strategists are relatively insulin resistant [11].
The former are typically characterized by high testoster-
one, low serotonin, low cholesterol and cortisol whereas
the later by low testosterone, high serotonin, high cho-
lesterol and cortisol levels. The dove strategists obtain
their fitness by being socially smart and opportunistic.
For them aggressive fights for higher social rank are
likely to be rather counterproductive. They may retract
from aggression but be smarter towards tapping opportu-
nities. The human coun terparts of th e “hawk ” and “dove”
strategies have been called “soldier” versus “diplomat”
strategies [6] and metabolic syndrome is claimed to be a
physiological state related to a “diplomat” personality. It
therefore makes sense for a diplomat to be economically
rational and care less about aggressive social hierarchical
struggle. The results of the survey are therefore compati-
ble with the behavioural origins paradigm of metabolic
syndrome.
Of much potential interest is the result that ultimatum
game offers are good predictors of T2D and other disor-
ders. At least in our sample ultimatum offer was a better
predictor of diabetes than BMI, although BMI has been
commonly used as a strong predictor of metabolic syn-
drome disorders. This may not be surprising because of a
duel reason . On the o n e hand in In dian p opulatio n in su lin
resistance is not very strongly associated with high BMI
[27] and on the other hand the inadequacy of obesity
alone in explaining insulin resistance syndrome is in-
creasingly being recognized. Out of the recently identi-
fied genetic markers that are significant risk factors for
type 2 diabetes very few are significantly associated with
obesity parameters [28]. Also the relationship of obesity
with life threatening disorders is not constant over time.
Along with increasing mean BMI in the population, the
optimum BMI ensuring minimum mortality rate appears
to have increased substantially over the last hundred
years [29]. This is more compatible with the speculation
of behavioural origins hypothesis that the relative rather
than absolute obesity is the true risk factor [6] and that
obesity functions as a behavioural signal [30]. It would
be interesting to test whether ultimatum game is a better
predictor of metabolic syndrome across cultures and eth-
nicities. One may also speculate whether it would be
possible to design a set of behavioural tests that may be
predictive of T2D and related chronic conditions in lon-
gitudinal studies. This small study should therefore
stimulate further studies along three paths. One would be
to test the robustness of the association of ultimatum
game offers with metabolic syndrome cross culturally,
the other to design and standardize a set of tests to cover
a wider variety of behaviours that could be markers of
metabolic syndrome and the third to test whether the set
of behavioural differences can predict the development
of metabolic syndrome disorders in longitudinal studies.
5. Acknowledgements
Prajakta Belsare was supported by CSIR, India and

People with Metabolic Syndrome Disorders Give Lower Offers in Ultimatum Game 132
Maithili Jog by BCUD, University of Pune during the
study.
REFERENCES
[1] O. Bosello and M. Zamboni, “Visceral Obesity and
Metabolic Syndrome,” Obesity Reviews, Vol. 1, No. 1,
2000, pp. 47-56.
[2] S. M. Grundy, “Obesity, Metabolic Syndrome, and Car-
diovascular Disease,” The Journal of Clinical Endocri-
nology & Metabolism, Vol. 89, No. 6, 2004, pp. 2595-
2600.
[3] D. E. Moller and K. D. Kaufman, “Metabolic Syndrome:
A Clinical and Molecular Perspective,” Annual Review of
Medicine, Vol. 56, February 2005, pp. 45-62.
[4] J. V. Neel, “Diabetes Mellitus: A Thrifty Genotype Ren-
dered Detrimental by Progress?” American Journal of
Human Genetics, Vol. 14, No. 4, 1962, pp. 353-362.
[5] C. N. Hales and D. J. P. Barker, “Type 2 (Non-Insu-
lin-Dependent) Diabetes Mellitus: The Thrifty Phenotype
Hypothesis,” Diabetologia, Vol. 35, No. 7, 1992, pp. 595-
601.
[6] M. G. Watve and C. S. Yajnik, “The Evolutionary Ori-
gins of Insulin Resistance: A Behavioral Switch Hy-
pothesis,” BMC Evolutionary Biology, Vol. 7, April 2007,
p. 61.
[7] J. R. Speakman, “Thrifty Genes for Obesity and the
Metabolic Syndrome-Time to Call off the Search?” Dia-
betes and Vascular Disease Research, Vol. 3, No. 1, May
2006, pp. 7-11.
[8] J. R. Speakman, “A Non-Adaptive Scenario Explaining
the Genetic Predisposition to Obesity: The ‘Predation
Release’ Hypothesis,” Cell Metabolism, Vol. 6, No. 1,
July 2007, pp. 5-12.
[9] P. V. Belsare, “Reconciliation of Thriftiness and Behav-
ioural Switch,” Comments on BMC Evolutionary Biology,
Vol. 7, 2007, p. 61.
[10] A. Rashidi, T. B. L. Kirkwood and D. P. Shanley,
“Metabolic Evolution Suggests an Explanation for the
Weakness of Antioxidant Defenses in Beta-Cells,” Mecha-
nisms of Ageing and Development, Vol. 130, No. 4, Janu-
ary 2009, pp. 216-221.
[11] P. V. Belsare, M. G. Watve, S. S. Ghaskadbi, D. S. Bhat,
C. S. Yajnik and M. M. Jog, “Metabolic Syndrome: Ag-
gression Control Mechanisms Gone out of Control,”
Medical Hypotheses, Vol. 74, No. 3, March 2010, pp.
578-589.
[12] R. H. Thaler, “Anomalies: The Ultimatum Game,” The
Journal of Economic Perspectives, Vol. 2, No. 4, Fall
1988, pp. 195-206.
[13] E. Emanuele, N. Brondino, M. Bertona, S. Re and D.
Geroldi, “Relationship between Platelet Serotonin Con-
tent and Rejections of Unfair Offers in the Ultimatum
Game,” Neuroscience Letters, Vol. 437, No. 2, 2008, pp.
158-161.
[14] M. J. Crockett, L. Clark, G. Tabibnia, M. D. Lieberman
and T. W. Robbins, “Serotonin Modulates Behavioral
Reactions to Unfairness,” Science, Vol. 320, No. 5884,
June 2008, p. 1739.
[15] E. Emanuele, M. Bertona, S. Re and N. Brondino, “Hu-
man Economic and Financial Behavior: The Serotonergic
Hypothesis,” Bioscience Hypotheses, Vol. 2, No. 2, 2009,
pp. 109-110.
[16] P. J. Zak, R. Kurzban, S. Ahmadi, R. S. Swerdloff, J.
Park, L. Efremidze, K. Redwine, K. Morgan and W.
Matzner, “Testosterone Administration Decreases Gener-
osity in the Ultimatum Game,” PLoS ONE, Vol. 4, No. 12,
December 2009, p. e8330.
[17] T. C. Burnham, “High-Testosterone Men Reject Low
Ultimatum Game Offers,” Proceedings of the Royal Soci-
ety B, Vol. 274, No. 1623, 2007, pp. 2327-2330.
[18] E. T. Larson and C. H. Summers, “Serotonin Reverses
Dominant Social Status,” Behavioural Brain Research,
Vol. 121, No. 1-2, June 2001, pp. 95-102.
[19] D. H. Edwards and E. A. Kravitzt, “Serotonin, Social
Status and Aggression,” Current Opinion in Neurobiol-
ogy, Vol. 7, No. 6, 1997, pp. 812-819.
[20] E. Agardh, A. Ahlbom, T. Andersson, et al., “Work
Stress and Low Sense of Coherence is Associated with
Type 2 Diabetes in Middle-Aged Swedish Women,”
Diabetes Care, Vol. 26, No. 3, March 2003, pp. 719-724.
[21] R. M. Sapolsky, “The Influence of Social Hierarchy on
Primate Health,” Science, Vol. 308, No. 5722, April 2005,
pp. 648-652.
[22] S. Luo, J. Luo and A. H. Cincotta, “Chronic Ventrome-
dial Hypothalamic Infusion of Norepinephrine and Sero-
tonin Promotes Insulin Resistance and Glucose Intoler-
ance,” Neuroendocrinology, Vol. 70, No. 6, December
1999, pp. 460-465.
[23] S. Luo, A. H. Meier and A. H. Cincotta, “Bromocriptine
Reduces Obesity, Glucose Intolerance and Extracellular
Monoamine Metabolite Levels in Ventromedial Hypo-
thalamus of Syrian Hamsters,” Neuroendocrinology, Vol.
68, No. 1, 1998, pp. 1-10.
[24] A. Holmang and P. Bjorntorp, “The Effects of Testoster-
one on Insulin Sensitivity in Male Rats,” Acta physi-
ologica Scandinavica, Vol. 146, No. 4, December 1992,
pp. 505-510.
[25] R. F. Spark, “Testosterone, Diabetes Mellitus, and the
Metabolic Syndrome,” Current Urology Reports, Vol. 8,
No. 6, 2007, pp. 467-471.
[26] M. Muller, D. E. Grobbee, I. den Tonkelaar, S. W. J.
Lamberts and Y. T. van der Schouw, “Endogenous Sex
Hormones and Metabolic Syndrome in Aging Men,” The

People with Metabolic Syndrome Disorders Give Lower Offers in Ultimatum Game 133
Journal of Clinical Endocrinology & Metabolism, Vol. 90,
No. 5, 2005, pp. 2618-2623.
[27] C. S. Yajnik, “Obesity Epidemic in India: Intrauterine
Origins?” Proceedings of the Nutrition Society, Vol. 63,
No. 3, August 2004, pp. 387-96.
[28] S. Pecioska, M. C. Zillikens, P. Henneman, et al., “Asso-
ciation between Type 2 Diabetes Loci and Measures of
Fatness,” PLoS ONE, Vol. 5, No. 1, January 2010, p.
e8541.
[29] D. Su, “Body Mass Index and Old Age Survival: A
Comparative Study between the Union Army Records
and the NHANES-I Epidemiological Follow-Up Sam-
ple,” American Journal of Human Biology, Vol. 17, No. 3,
2005, pp. 341-354.
[30] M. Mankar, R. S. Joshi, P. V. Belsa re, M. M. Jog and M.
G. Watve, “Obesity as a Perceived Social Signal,” PLoS
ONE, Vol. 3, No. 9, September 2008, p. e3187.