2013. Vol.4, No.2, 124-132
Published Online February 2013 in SciRes
Copyright © 2013 SciRes.
Socio-Emotional Status, Education, and Time-Discounting in
Japanese Non-Smoking Population: A Multi-Generational Study
Shoko Yamane1, Taiki Takahashi2, Akiko Kamesaka3, Yoshiro Tsutsui4, Fumio Ohtake5
1Faculty of Economics, Kinki University, Osaka, Japan
2Department of Behavioral Science, Center for Experimental Research in Social Sciences,
Hokkaido University, Hokkaido, Japan
3School of Business Administration, Aoyama Gakuin University, Tokyo, Japan
4Graduate School of Economics, Osaka University, Osaka, Japan
5Institute of Social and Economic Research, Osaka University, Osaka, Japan
Received November 18th, 2012; revised December 19th, 2012; accepted January 11th, 2013
Recent studies in behavioral economics and neuroeconomics have revealed that emotion affects impulsiv-
ity in intertemporal choice. We examined the roles of socio-emotional status (i.e., perceived stress, de-
pression, quality of sleep, loneliness) in temporal discounting behavior by Japanese non-smokers in a
generation-specific manner (20 - 70 s) with a relatively large sample size (N = 3450). We observed that 1)
both men and women are the most impulsive in their 60 s; 2) education has a negative impact on impul-
sivity in men aged 40 - 49 and women aged 50 - 59; 3) perceived stress has a negative impact on impul-
sivity in men aged 60 - 69; and 4) sleeplessness has negative and positive impacts on impulsivity in men
aged 40 - 49 and women aged 30 - 39, respectively. Biological and social factors underlying observed
findings are discussed.
Keywords: Time Discounting; Impulsivity; Stress; Depression; Emotion; Behavioral Economics
Because temporal discounting behavior (intertemporal choice;
preference for smaller sooner rewards over larger later ones)
influences one’s decisions, economists and neuroeconomists
have shown tremendous interest in investigations into temporal
discounting (Frederick, Loewenstein, & O’Donoghue, 2002;
Takahashi, 2009). Recently, roles of affect in temporal dis-
counting behavior have been drawing much attention in behav-
ioral economics and neuroeconomics (Ifcher & Zarghamee,
2011; Löckenhoff, O’Donoghue, & Dunning, 2011; McClure,
Laibson, Loewenstein, & Cohen, 2004). Specifically, Ifcher and
Zarghamee (2011) demonstrated that mild positive affect sig-
nificantly reduced impulsivity in intertemporal choice. Löck-
enhoff et al. (2011) reported that non-emotional intertemporal
choice is reduced by age; while emotional intertemporal choice
is insensitive to age. However, these studies examined only
positive and/or disruptive (i.e., “visceral”; Loewenstein, 1996)
emotions’ effect on intertemporal choice.
Emotion and Intertemporal Choi c e
In the rapidly evolving field of neuroeconomics (Ernst, 2012;
Loewenstein, Rick, & Cohen, 2008; Phillips, Kim, & Lee, 2012;
Takahashi, 2009), effects of stress and depression on interterm-
poral choice have been examined (Takahashi, 2004; Takahashi
et al., 2008a; Takahashi, Shinada, Inukai, Tanida, Takahashi,
Mifune, Takagish, Horita, Hashimoto, Yokota, Kameda, &
Yamagishi, 2010), in relation to altered functioning of the stress
system (i.e., Hypothalamic-pituitary-adrenal (HPA) axis and
sympatho-adrenal medullar (SAM) system) and catechola-
mine/monoamine (dopaminergic and serotonergic) systems.
Takahashi and colleagues have previously observed that de-
pressed patients are impulsive in the near future (Takahashi et
al., 2008), and low cortisol (a human stress steroid hormone)
levels were associated with impulsive intertemporal choice by
men (Takahashi, 2004), salivary alpha-amylase (a non-invasive
biomarker of SAM activation) is negatively related to impulsiv-
ity in both men and women (Takahashi et al., 2010). Also, a
reduction in serotonergic activities increases impulsivity in
intertemporal choice (Schweighofer, Bertin, Shishida, Okamoto,
Tanaka, Yamawaki, & Doya, 2008). These findings indicate
that negative affect, as well as positive affect, influences tem-
poral discounting behavior. However, to date, no study exam-
ined the roles of negative affect (especially, social emotions) in
intertemporal choice in a large sample. Concerning social emo-
tions, a recent neuroendocrinological study observed that lone-
liness increased impulsivity via biological pathways distinct
from the signaling pathways in which testosterone affects im-
pulsivity (Fujisawa, Nishitani, Ishii, & Shinohara, 2011). Also,
recent studies in health economics asked effect of loneliness on
health and cognitive functioning in relation to retirement from
labor markets (Coe & Zamarro, 2011; Bonsang, Adam, &
Perelman, 2012). Therefore, it may have implications for both
labor and health economics to investigate the role of loneliness
in impulsivity in intertemporal choice.
Age and Intertemporal Choice
In addition to the roles of affect in intertemporal choice, the
effect of age on intertemporal choice has been studied (Green,
Fry, & Myerson, 1994; Read & Read, 2004; Loeckenhoff, 2011;
Steinberg, Graham, O’Brien, Woolard, Cauffman, & Banish,
2009). Green et al., (1994) reported that temporal discounting
was highest for children and lowest for older adults; in contrast,
Read and Read (2004) observed that older people discount
more than younger people and that middle aged people discount
less than either group. Apparently, more studies with a large
sample size regarding the relationship between age and tempo-
ral discounting are needed.
Education and Intertemporal Choice
Education may lower endogenous time-discount rate, be-
cause economists Becker and Mulligan (1997) argue that edu-
cation can be understood as an investment in patience. Educa-
tion can be understood as a tool that helps people to perceive
future pleasures as less remote. In neuroeconomics, Berns,
Laibson, and Loewenstein (2007) have emphasized the role of
anticipation of future events in making choices whose conse-
quences play out over time. Also, Peters and Büchel (2010)
demonstrated that episodic future thinking reduces impulsivity
in intertemporal choice, via cognitive function-related brain
regions. Kirby, Winston, and Santiesteban (2005) reported that
high grades in the college student are associated with patience
in intertemporal choice (lowered time-discount rate). Because
education systems differ across countries and generations, it is
important to examine the relationship between education and
temporal discounting in Japan with multiple-generations.
Some studies in labor economics have examined the roles of
sex in economic decision (Fehr-Duda, De Gennaro, & Schubert,
2006; Kimmo & Brent, 2010) because there are large differ-
ences not only in the relative compensation, but also in the
presence of women in the highest paid jobs (e.g., Azmat, Güell,
& Manning, 2004; Arulampalam, Booth, & Bryan, 2007). Be-
cause the movement of women into the Japanese society has
changed in several decades, it may be interesting to see the
relationship between intertemporal choice and sex over genera-
Sleep and Intertemporal Choice
In both behavioral economics and neuroeconomics, effect of
sleep deprivation on economic decision-making has been at-
tracting attention, because effect of sleep deprivation on impul-
sivity is important in considering workplace safety (Acheson,
Richards, & de Wit, 2007; Reynolds & Schiffbauer, 2004a;
Venkatraman, Huettel, Chuah, Payne, & Chee, 2011). Reynolds
and Schiffbauer (2004b) reported that sleep deprivation in-
creased impulsivity in intertemporal choice. Menz, Büchel, and
Peter (2012) demonstrated that sleep deprivation altered neural
processing underlying decision under risk. It is therefore im-
portant to examine the effect of sleeplessness on intertemporal
choice in large samples.
Intertemporal Choice and Field Behavior
With respect to the relationships between impulsivity in in-
tertemporal choice and field behavior, a recent behavioral eco-
nomic study (Chabris, Laibson, Morris, Schuldt, & Taubinsky,
2008) demonstrated that time-discount rate measured in the
laboratory could predict various types of field behaviors (e.g.,
exercise, BMI, smoking). Hence, it can be said that assessment
of time-discount rates in multi-generational Japanese popula-
tion may be important for a better understanding of Japanese
economic situations (e.g., gender gap in the labor market, in-
come inequality over generations, pension problems). In the
investigations into the relationships between Socio-emotional
status, education, and time-discounting, it is important to ex-
clude the habitual smokers, because chronic nicotine intake is
associated with an increase in impulsivity in intertemporal choice
for gain in Japanese people (Ohmura, Takahashi, & Kitamura,
Overall, the present study examined the relationships of
various types of socio-demographic variables to impulsivity in
intertemporal choice in non-smokers. This study is the first to
examine this in a large sample. It is expected that relationships
between the variables and impulsivity in intertemporal choice
may vary across generations.
Our data were obtained from “Survey of Living Preferences
and Satisfaction” conducted by the 21st Century COE program
of Osaka University in February 2011. This survey consists of
100 questions about detailed data on individual attributes. 5386
Japanese men and women between the ages of 20 and 65 were
chosen by two-stage sampling and surveyed by the visit-re-
placement method.
Assessment of Time-Discount Rate
The key variable, time discounting, is obtained by following
procedure. The respondents were told to choose between two
options, “A” and “B”. The respondent receives JPY 10,000
(around USD 120) today when he chooses option “A”, while he
receives a different amount in seven days when he chooses
option “B”1. This question consists of nine choices. For exam-
ple in sixth choice, the respondents compare JPY 10,000 today
to JPY 10,383 (around USD 125) in seven days. In this case,
choosing option “B” instead of option “A” is the same as re-
ceiving 200% of the annual interest rate.
The questionnaire is presented in Table 1, where the amount
received under option “A” is specified as JPY 10,000 and the
imputed interest rate for option “B” changes from 10% to
Table 1.
Questionnaire to elicit time-discount rate. Suppose you have two mutu-
ally-exclusive options to receive some money. You may choose Option
“A”, to receive 10,000 JPY in two days; or Option “B”, to receive a
different amount in nine days. Compare the amounts and delay until its
receipt in Option “A” with Option “B” and indicate which option you
would prefer for each pair of all nine choice pairs.
Option A
(Receipt in Today)
Option B
(Receipt in 7 days)
Interest rate
(Annual) Circle A or B
JPY 10,000 JPY 9980 10% A B
JPY 10,000 JPY 10,000 0% A B
JPY 10,000 JPY 10,029 10% A B
JPY 10,000 JPY 10,076 40% A B
JPY 10,000 JPY 10,191 100% A B
JPY 10,000 JPY 10,383 200% A B
JPY 10,000 JPY 10,575 300% A B
JPY 10,000 JPY 11,917 1000% A B
JPY 10,000 JPY 195,689 5000% A B
1The exchange rate was about $1 = ¥83 at February 2011.
Copyright © 2013 SciRes. 125
The authors expected that the respondents would choose op-
tion “A” at low interest rates, but as the imputed interest rate
rises, the authors expected they would ultimately switch to
option “B” at a certain critical high rate. The individual re-
spondents’ discount rates can be inferred by estimating the
interest rate at which respondents are indifferent between the
delayed receipt of option “B” and the more immediate receipt
of option “A”.
The present study employed the procedures of measurement
and analysis of time-discount rate similar to the authors’ previ-
ous study (Ikeda, Kang, & Ohtake, 2010; Kimball, Sahm, &
Shapiro, 2008). The authors estimated the gross discount rate
for each respondent according to a lognormal distribution func-
tion. This estimation enables us to obtain the interest rates be-
tween which he switched his choice from option “A” to “B”.
for each respondent, including those who stuck to option “A” or
“B”. It is to be noted that the authors utilized logged gross
time-discount rate as a dependent variable, following our pre-
vious study.
Assessment of Education
The authors assessed the respondents’ education level by
four categories. The variable of education takes 1) if the re-
spondent graduated primary or middle school (N = 539); 2) if
graduated high school or two-year college (including those who
left college without a diploma; N = 3417); 3) if graduated four-
year college (including those who left graduate school without
master degree; N = 1225); and 4) if graduated higher than mas-
ter’s course (N = 102).
Assessment of Socio-Emotional Status and
The socio-emotional status are obtained, with Likert scales,
by the degree of agreement for the following sentences; “I’ve
been feeling stressed lately”, “I’ve been feeling depressed
lately”, “I’ve been feeling lonely lately”, and “I haven’t been
sleeping well lately”. Each response was on five point scale
from 1 (I totally disagree to it) to 5 (I totally agree to it). That is,
the high score means that he perceives stress more.
Assessment of Drinking
The authors obtain the drinking habit of the respondents us-
ing answers to the question “Do you drink alcoholic bever-
ages?”. It was measured by six point ordinal scale, such as 1) if
“Don’t drink at all” (N = 1287), 2) if “Hardly drink” (N =
1240), 3) if “Drink sometimes” (N = 1385), 4) if “A can of beer
or its equivalent a day, everyday” (N = 828), 5) if “Three cans
of beer or its equivalent a day, everyday” (N = 550), and 6) if “Five
cans of beer or its equivalent a day, everyday” (N = 79).
Time-Discount Rate across Generations
The samples sizes for different age groups (“generations”)
are presented in Table 2. Time-discount rate (logged gross
time-discount rate) over generations of men and women are
presented in Figures 1(a) and (b), respectively. Correlations
between time-discount rate and other variables are presented in
Tables 3(a)-(l), by generations. Though not tested statistically,
Table 2.
Number of subjects by generation.
Generations Male Female Total
20 - 29 64 113 177
30 - 39 152 287 439
40 - 49 269 495 764
50 - 59 325 499 824
60 - 69 363 525 888
70 - 79 162 196 358
Total 1335 2115 3450
0.1 .2.3 .4 .5 .6.7 .8 .91
log gross time discount rate
20 30 40 50 60 70
0.1 .2.3 .4.5 .6.7 .8.91
log gross time discount rate
20 3040 506070
Figure 1.
(a) Time-discount rate of men; (b) Time-discount rate of
the readers can see that men and women had highest time-dis-
count rate in their sixties (Figures 1(a) and (b)). Furthermore,
men generally had higher time-discount rate than women within
all generations.
Education and Time-Discount Rate
First, the authors examine the relationship between time-
discount rate and education. It was observed significant nega-
tive correlations between education level and time-discounting
of men aged 40 - 49 (Table 3(c)) and women aged 50 - 59 (Ta-
ble 3(j)). Although the correlations between education level
and time-discount rate were not always significant, the direc-
tion of the effect of education level on time-discounting were
mostly negative, consistent with previous studies indicating that
more educated people are more patient in intertemporal choice
(Kirby et al., 2005). It is to be noted that this effect of education
level on time-discount rate is not because more educated people
smoke less. The present subjects were all non-smokers.
Copyright © 2013 SciRes.
Copyright © 2013 SciRes. 127
Table 3.
(a) Men aged 20 - 29 (N = 64); (b) Men aged 30 - 39 (N = 152); (c) Men aged 40 - 49 (N = 269); (d) Men aged 50 - 59 (N = 325); (e) Men aged 60 -
69 (N = 363); (f) Men aged 70 - 79 (N = 162); (g) Women aged 20 - 29 (N = 113); (h) Women aged 30 - 39 (N = 287); (i) Women aged 40 - 49 (N =
495); (j) Women aged 50 - 59 (N = 499); (k) Women aged 60 - 69 (N = 525); (l) Women aged 70 - 79 (N = 196).
discounting Drinking Education Stress Depression Sleeplessness Loneliness
discounting 1
Drinking .037 1
Education .054 .100 1
Stress .047 .079 .039 1
Depress .062 .038 .052*** .545 1
Sleepless .074 .105 .062*** .301*** .348 1
Loneliness .119 .073 .075*** .451*** .678 .241 1
discounting Drinking Education Stress Depression Sleeplessness Loneliness
discounting 1
Drinking .122 1
Education .153 .024 1
Stress .005 .076 .077 1
Depress .041 .035 .024*** .645 1
Sleepless .071 .028* .137*** .345*** .496 1
Loneliness .035 .015 .036*** .358*** .571*** .445 1
discounting Drinking Education Stress Depression Sleeplessness Loneliness
discounting 1
Drinking .015 1
Education .207*** .151 1
Stress .007 .052 .021 1
Depress .044 .055 .006*** .635 1
Sleepless .014*** .19 .065*** .337*** .461 1
Loneliness .009 .128 .030*** .413*** .535*** .432 1
discounting Drinking Education Stress Depression Sleeplessness Loneliness
discounting 1
Drinking .011 1
Education .069 .021 1
Stress .087 .021 .064 1
Depress .035 .013 .081*** .703 1
Sleepless .026 .020 .118*** .437*** .582 1
Loneliness .024 .004 .067*** .439*** .625*** .567 1
discounting Drinking Education Stress Depression Sleeplessness Loneliness
discounting 1
Drinking .005 1
Education .014 .006 1
Stress .096* .092 .026 1
Depress .019 .072 .027*** .684 1
Sleepless .011 .026 .005*** .334*** .450 1
Loneliness .045 .040 .017*** .385*** .564*** .477 1
discounting Drinking Education Stress Depression Sleeplessness Loneliness
discounting 1
Drinking .134 1
Education .023 .079 1
Stress .052 .099 .031 1
Depress .032 .164 .086*** .648 1
Sleepless .060 .160 .115*** .391*** .460 1
Loneliness .063 .084* .126*** .549*** .669*** .421 1
discounting Drinking Education Stress Depression Sleeplessness Loneliness
discounting 1
Drinking .118 1
Education .106 .003 1
Stress .127 .014 .085 1
Depress .114 .117 .117*** .665 1
Sleepless .015 .054 .044*** .520*** .551 1
Loneliness .017 .067* .147*** .380*** .535*** .286 1
discounting Drinking Education Stress Depression Sleeplessness Loneliness
discounting 1
Drinking .005 1
Education .058 .015 1
Stress .027 .05 .009 1
Depress .044 .07 .091*** .687 1
Sleepless .076* .099 .076*** .417*** .561 1
Loneliness .030 .013 .057*** .414*** .586*** .483 1
discounting Drinking Education Stress Depression Sleeplessness Loneliness
discounting 1
Drinking .001 1
Education .054 .034 1
Stress .037 .035*** .113 1
Depress .019 .040*** .123*** .692 1
Sleepless .034 .017 .099*** .342*** .470 1
Loneliness .008 .042* .077*** .368*** .531*** .496 1
discounting Drinking Education Stress Depression Sleeplessness Loneliness
discounting 1
Drinking .046 1
Education .064*** .128 1
Stress .072 .016 .032 1
Depress .030 .015* .080*** .740 1
Sleepless .028 .034*** .156*** .335*** .462 1
Loneliness .055 .034 .026*** .425*** .514*** .491 1
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Copyright © 2013 SciRes. 129
discounting Drinking Education Stress Depression Sleeplessness Loneliness
discounting 1
Drinking .011 1
Education .076 .056 1
Stress .029 .015 1
Depress .062 .035 .022*** .679 1
Sleepless .074 .015 .064*** .398*** .531 1
Loneliness .069 .030 .017*** .433*** .607*** .527 1
discounting Drinking Education Stress Depression Sleeplessness Loneliness
discounting 1
Drinking .194 1
Education .076 .104 1
Stress .049 .029 .041 1
Depress .004 .015 .021*** .630 1
Sleepless .025 .052 .016*** .312*** .431 1
Loneliness .084 .100 .051*** .349*** .534*** .479 1
Socio-Emotional Status and Time-Discount Rate
Next, the authors performed correlation analysis between
socio-emotional status (i.e., depression, stress, loneliness) and
time-discounting. It was observed that stress was negatively
related to time-discount rate of men aged 60 - 69 (Table 3(e)),
indicating that relatively old men with high perceived stress are
less impulsive in intertemporal choice. Other factors of socio-
emotional status (i.e., depression, loneliness) were not signifi-
cantly related to time-discount rate for all generations.
Sleeplessness and Time-Discount Rate
The authors then analyzed the relationship between sleep-
lessness and time-discount rate, to examine the role of the qual-
ity of sleep in impulsivity in intertemporal choice. It was found
that sleeplessness had opposite effects on time-discount rate
between men and women; i.e., sleeplessness was negatively and
positively associated with time-discount rate of men aged 40 -
49 (Table 3(c)) and women aged 30 - 39 (Table 3(h)), respec-
Drinking and Time-Discount Rate
Because time-discount rate is related to the intake of addic-
tive drugs (Bickel & Marsch, 2001) in drug-dependent subjects,
the authors examined the relationship between alcohol intake
and time-discounting in the present non-alcoholic population.
The authors observed no significant relationship between drink-
ing and time-discount rate for gain. This indicates that alcohol
intake by non-alcoholic subjects does not significantly relate to
impulsivity in intertemporal choice for gain, consistent with our
previous study with Japanese university students, reporting that
alcohol intake was only related to procrastination (i.e., temporal
discounting of loss), but not impulsivity (i.e., temporal dis-
counting of gain) in non-alcoholic students (Takahashi, Ohmura,
Oono, & Radford, 2009).
To our knowledge, this is the first study to demonstrate that 1)
both men and women have the highest time-discount rate in
their 60 s; 2) education has a negative impact on time-discount
rate of men aged 40 - 49 and women aged 50 - 59; 3) perceived
stress has a negative impact on time-discount rate of men aged
60 - 69; and 4) sleeplessness has negative and positive impacts
on time-discount rate of men aged 40 - 49 and women aged 30 -
39, respectively, in a multi-generational Japanese population.
Also, it was observed that men were generally more impulsive
in intertemporal choice than women, consistent with a previous
study with American subjects (Kirby & Markovic, 1996). Fur-
thermore, alcohol intake did not influence intertemporal choice
for gain by the present Japanese subjects, consistent with our
previous study with non-alcoholic Japanese university students
(Takahashi et al., 2009) which demonstrated that alcohol use is
related to temporal discounting of loss, but unrelated to tempo-
ral discounting of gain.
It is also to be underscored that our present Japanese sample
did not include habitual smokers, which can exclude our previ-
ously-reported dose-dependent effect of nicotine intake on in-
tertemporal choice by Japanese subjects (Ohmura et al., 2005).
These findings have some implications for behavioral econom-
ics and neuroeconomics, as well as evolutionary biology and
economics, which are addressed below.
Some behavioral economic and/or psychological studies sug-
gests that adult human time-discount rates decline monotoni-
cally over the life course and are much lower by age seventy
than in young adulthood (e.g., Green, Myerson, & Ostaszewski,
1999). A recent developmental psychological study also re-
ported that children’s time-discount rate decreases according to
their age (Steinberg et al., 2009). Evolutionary psychologists
Daly and Wilson (2005) questioned the evolutionary biological
foundations of the age-dependence of time-discount rate. An
evolutionary economist Rogers (1994) has argued that the
age-dependence of human time and risk preference is optimally
determined by intergenerational resource transfers and the ef-
fects of personal reputation on the fitness prospects of family
members. Our present finding that humans are most impulsive
in their 60 s irrespective of sex should be taken into account in
these evolutionary economic and biological studies.
As stated earlier, it makes an economic sense that education
is related to a reduction in time-discount rate (Becker & Mulli-
gan, 1997). The presently-observed negative relationships be-
tween education and time-discount rate of men in 40 s and
women in 50 s are consistent with the economic theory. The
reason why a strong negative effect of education on time-dis-
count rate did not exist in other generations should further be
examined in future behavioral economic studies in relation to
changes in Japanese educational systems.
There was a negative correlation between perceived stress
and time-discount rate of men in their 60 s, but not of women in
the same age range. This is consistent with our previous neu-
roeconomic studies which demonstrated that a cortisol (a stress
steroid hormone) level had a negative impact on time-discount
rate of men (Takahashi, 2004) but not in women (Takahashi et
al., 2010). In our previous study (Takahashi et al., 2010), how-
ever, another biological marker of stress (i.e., salivary alpha-
amylase) was negatively related to time-discount rate, irrespec-
tive of subject’s sex. It is therefore possible that the pres-
ently-assessed “perceived stress” is more strongly related to
chronic activation of HPA system, rather than SAM system.
This issue should be examined in future studies on the rela-
tionship between negative affect and economic decision-mak-
ing. On the other hand, loneliness and depression did not dra-
matically affect time-discount rate in the present non-clinical
subjects. Our previous study (Takahashi et al., 2008a) reported
that clinically depressed subjects had higher time-discount rate
in the near future. It is therefore important to ask the distinction
between non-clinical and clinical states of being depressed
among healthy and clinical subjects.
Consistent with previous laboratory experimental studies
(Acheson et al., 2007; Reynolds & Schiffbauer, 2004b), sleep-
lessness tended to enhance women’s time-discount rate in their
30 s. In contrast, sleeplessness was negatively related to men’s
time-discount rate in their 40 s. A recent neurobiological study
demonstrated that sleep deprivation has more detrimental effect
on cognitive performance in female rats, in comparison to male
rats (Hajali, Sheibani, Esmaeili-Mahani, & Shabani, 2012).
Therefore, it may be conceivable that there are neurobiological
sex differences in the relationships between sleep deprivation
and impulsivity in intertemporal choice. Another possibility is
that sleeplessness is related to differences in socioeconomic
status in men aged 40 - 49. These possibilities should more
extensively be studied in future economic research.
In line with evolutionary biological theory (Daly & Wilson,
2005) and an experimental study (Kirby & Markovic, 1996),
the present study revealed that men were generally more impul-
sive than women in intertemporal choice. This gender differ-
ence is not due to a difference in smoking status between men
and women, because our present subjects were non-smokers.
Our previous neuroeconomic study demonstrated that testos-
terone (a male steroid hormone) is nonlinearly related to
time-discount rate (Takahashi et al., 2006). A more recent study
by labor economists also reported a nonlinear relationship be-
tween testosterone and risk-aversion in women (Sapienza, Zin-
gales, & Maestripieri, 2009). Taken together, studies in neu-
roeconomics should examine the roles of sex steroid hormones,
in addition to stress steroid hormones, in determining a gender
difference in economic decision-making across generations.
Apart from the main objectives of the present study, it is
striking that education markedly reduces negative affect such as
depression and loneliness in most generations (though there are
some exceptions). Future studies in economics of education
should pursuit this effect of education on emotion, in order to
further establish the relationships between education and hap-
Concerning the relationship between age and temporal dis-
counting, the roles of anticipatory time-perception and respon-
sivity of brain reward systems (e.g., the striatum) have recently
been attracting much attention (Löckenhoff, 2011; Löckenhoff
et al., 2011). Our previous studies indicate that anticipatory
time-perception may be related to impulsivity in temporal dis-
counting behavior (Takahashi, 2005; Takahashi et al., 2008). It
is therefore important to examine the role of age-dependency of
time-perception in intertemporal choice, in future behavioral
economic studies. Moreover, it is known that there are some
“anomalies” in intertemporal choice (e.g., hyperbolic discount-
ing, sign effect, subadditive discounting, delay-speedup asym-
metry, and interval effect) (Frederick, Shane, Loewenstein, &
O’Donoghue, 2002; Kinari, Ohtake, & Tsutsui, 2009; Scholten
& Read, 2010; Takahashi, 2009). Future studies in behavioral
economics should examine whether these anomalies in in-
tertemporal choice are related to socio-emotional status, age,
and education.
It is now discussed that several limitations exist in the pre-
sent study. First, the present study only examined Japanese
population. Drinking and smoking habit differ across societies
and cultures, future studies should examine other populations.
Second, biological markers of stress and depression (e.g., cor-
tisol and serotonin) were not examined in the present study.
Future studies should examine the roles of neurobiological
markers in the relationships between emotion, demographics,
and impulsivity in intertemporal choice, to help us to develop
neuroeconomic understandings of human intertemporal choice.
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