Psychology
2012. Vol.3, No.1, 7-11
Published Online January 2012 in SciRes (http://www.SciRP.org/journal/psych) http://dx.doi.org/10.4236/psych.2012.31002
Friendship Motivation, Aggression, and Self-Esteem in Japanese
Undergraduate Students
Ryo Okada
Faculty of Education, Kagawa University, Kagawa, Japan
Received October 13th, 2011; revised November 14th, 2011; accepted December 17th, 2011
The purpose of this study was to examine the relationship among self-determined friendship motivation
(motivation for friendship formation), aggression, and self-esteem in a sample of 262 Japanese university
students. The hypothetical model posited that self-determined friendship motivation predicted lower le-
vels of aggression, which, in turn, predicted lower levels of self-esteem. The results showed that self-de-
termined friendship motivation predicted lower levels of anger, hostility, and physical aggression and that
hostility and anger predicted lower levels of self-esteem. Verbal aggression was found to be positively
associated with self-determined friendship motivation and self-esteem. The different relationships be-
tween self-determined friendship motivation and each facet of aggression are discussed.
Keywords: Friendship Motivation; Aggression; Self-Esteem; Self-Determination Theory
Introduction
During adolescence, friendship plays an important role in
one’s life. Hartup and Stevens (1997) stated that friends are
cognitive and affective resources that foster self-esteem and a
sense of well-being. A number of empirical studies have re-
vealed that friendship influences individuals’ well-being and
psychological adjustment (Lucas & Dyrenforth, 2006).
Researchers have recently examined the relationship between
friendship formation and motivation. Motivation for friendship
formation (i.e., friendship motivation) has been conceptualized
in various motivational theories, for example, achievement goal
theory (Elliot, Gable, & Mapes, 2006; Ryan & Shim, 2006),
self-efficacy theory (Matsushima & Shiomi, 2003; Patrick,
Ryan, & Kaplan, 2007), and social goal theory (Jarvinen &
Nicholls, 1996). Another theory, the self-determination theory
(Deci & Ryan, 2000) has proposed a comprehensive framework
for friendship motivation. It conceptualizes several types of
motivation in terms of the level of self-determination—external
regulation, introjected regulation, identified regulation, and
intrinsic motivation. External regulation refers to motivation by
contingencies such as external rewards or punishment and mo-
tivation by others’ initiative. Sometimes, individuals continue
to talk to a certain friend merely because the friend talks to
them. This is an example of external regulation. Introjected
regulation refers to motivation stemming from feelings of anxi-
ety or shame. The purpose of behaviors motivated by intro-
jected regulation is to maintain one’s self-esteem. Individuals
guided by introjected regulation believe that they “should” form
and maintain friendships with others. Identified regulation re-
fers to motivation based on perceptions of the value and impor-
tance of the activity. For individuals motivated by identified
regulation, friendships are very important interpersonal rela-
tionships. However, they also see their friendships as means to
achieve other ends such as personal happiness and growth.
Intrinsic motivation refers to spontaneous motivation charac-
terized by fun and inherent enjoyment. In this motivational state,
the friendship is a purpose. Enjoying talking to and being in the
company of friends is an example of intrinsic motivation. Em-
pirical studies have examined the role of motivation in adoles-
cents’ friendship (Boiché & Sarrazin, 2007; Hawley, Little, &
Pasupathi, 2002; Senécal, Julien, & Guay, 2003).
The different types of motivation can be placed along a
self-determination continuum, with external regulation at the
lower end of the continuum and intrinsic motivation at the
higher end. The self-determination level of an individual’s mo-
tivation is characterized by the magnitude of these four types of
motivation (Deci & Ryan, 2000). In empirical studies, Relative
Autonomy Index (RAI) was used to assess the level of self-
determination of the individuals’ motivation (Grolnick & Ryan,
1987; Levesque, Zuehlke, Stanek, & Ryan, 2004). The RAI is
formed by weighting each subscale in accord with its underly-
ing scores on the self-determination continuum in the following
formula: RAI = (–2 × external regulation) + (–1 × introjected
regulation) + (1 × identified regulation) + (2 × intrinsic motiva-
tion). Higher scores of RAI represent higher levels of self-de-
termined motivation.
Previous studies have verified the importance of self-deter-
mined friendship motivation. Okada (2005) developed a scale
to measure friendship motivation and found that self-deter-
mined friendship motivation predicted prosocial behavior.
Richard and Schneider (2005) revealed that children with
higher levels of self-determined friendship motivation had more
relationship-maintaining goals and were liked by their peers.
Self-determined friendship motivation was also related to self-
disclosure (Okada, 2006), academic help-seeking (Okada, 2007),
social competence (Soenens & Vansteenkiste, 2005), and ex-
perience of positive life events (Shahar, Henrich, Blatt, & Ryan,
2003). These findings suggest that self-determined friendship
motivation promotes adaptive behaviors and positive interac-
tions with friends.
Although the relationship between self-determined friendship
motivation and adaptive behaviors has been verified in some

R. OKADA
studies, few studies have examined the relationship between
self-determined friendship motivation and maladaptive behav-
iors during adolescence. On the basis of some relevant studies,
it was predicted that self-determined friendship motivation was
negatively associated with maladaptive behaviors. Knee, Lons-
bary, Canevello, and Patrick (2005), for example, observed
couples discussing their relationship conflicts and examined the
relationship between their motivations and behaviors. The re-
sults showed that individuals with higher levels of self-deter-
mined motivation for their relationships (i.e., couple motivation)
displayed less defensive behaviors such as blame and down-
playing problems. In addition, Richard and Schneider (2005)
found that external regulation for friendship, which represents
lower levels of self-determined friendship motivation, was
positively related to control and revenge goals in preadolescents
and early adolescents. On the basis of these findings, it was
hypothesized that self-determined friendship motivation pre-
dicted less maladaptive behaviors.
In examining the relationship between self-determined fri-
endship motivation and maladaptive behaviors, this study fo-
cused on aggression. Aggressive or hostile individuals tend to
receive less social support (Barefoot, Dahlstrom, & Williams,
1983), and aggression and hostility can lead to poor physical
health (Miller, Smith, Turner, Guijarro, & Hallet, 1996). There-
fore, determining the factors that predict aggression will be
useful viewpoint for researchers and practitioners in this field.
Buss and Perry (1992) developed the Buss-Perry Aggression
Questionnaire and found four facets of aggression—physical
aggression, verbal aggression, anger, and hostility. Later studies
revealed that these four facets of aggression were related to
depression (Gerevich, Bácskai, & Czobor, 2007), negative in-
terpersonal relationships (Harris, 1997), anger to mistreatment
(Felsten & Hill, 1999), aggressive responses to provocation
(O’Connor, Archer, & Wu, 2001), and daily negative affect
(Harmon-Jones, 2003). People with higher levels of self-de-
termined friendship motivation find fun and personal value in
their friendships and therefore, rarely act aggressively. On the
other hand, people with lower levels of self-determined friend-
ship motivation feel obligated and anxious about relationships
with their friends, so they are inclined to feel hostile and act
aggressively. Therefore, it was hypothesized that self-deter-
mined friendship motivation predicted lower levels of the four
facets of aggression.
In previous studies (Deci, Ryan, Gagné, Leone, Usunov, &
Kornazheva, 2001; Levesque, et al., 2004), self-esteem has
been examined as an outcome variable predicted by self-de-
termined motivation. Given that self-determined friendship
motivation would be positively related to self-esteem, it was
predicted that aggression would mediate the relationship. Ac-
cording to sociometer theory (Leary, Tambor, Terdal, & Downs,
1995), self-esteem is part of a psychological system that moni-
tors acceptance and rejection by others. People can gauge
whether they are accepted or rejected by others from changes in
their self-esteem. In support of this theory, the experimental
manipulations that convey rejection reduce participants’ self-es-
teem, whereas those that convey acceptance enhance their self-
esteem (Leary & Baumeister, 2000). Because aggression is
likely to lead to rejection by friends, aggressive individuals
would report lower levels of self-esteem.
In summary, the purpose of this study was to examine a
model in which self-determined friendship motivation would
predict lower levels of aggression, which, in turn, would predict
lower levels of self-esteem. The examination of the model
would reveal the role of motivation in adolescents’ friendship
from the side of maladaptive behaviors.
Method
Participants and Procedure
The participants comprised 262 Japanese university students
(101 men and 161 women) with a mean age of 20.10 years (SD
= 1.05). All participants were volunteers and were informed at
the start that the outcome and participation would not affect
their course grades. After the orientation, the participants filled
a questionnaire.
Measures
Self-determined friendship motivation was measured by the
Friendship Motivation Scale developed by Okada (2005). This
scale assesses the reasons for forming friendships and interact-
ing with friends. There are four subscales of four items each:
external regulation (e.g., “Because my friends would get mad at
me if I’m not with them”), introjected regulation (e.g., “Be-
cause I would feel anxious if I didn’t have any friends”), identi-
fied regulation (e.g., “Because I value getting to know my
friends better”), and intrinsic motivation (e.g., “Because I’m
glad to be intimate with my friends”). The instruction was
“Why do you have close relationships with your friends or
spend time together with your friends?” Participants were also
instructed that “friends” does not refer to specific friends but
friends in general. Participants were asked to rate each item on
a 5-point Likert scale ranging from 1 (not true) to 5 (true). The
reliabilities for each subscale were verified in a sample of
Japanese university students (Cronbach alphas ranged from .61
to .86, and test-retest coefficients during the three weeks ranged
from .68 to .80; Okada, 2005). In the present study, the alphas
for the subscales were .45 for external regulation, .74 for intro-
jected regulation, .80 for identified regulation, and .88 for in-
trinsic motivation. Although the value of external regulation
was relatively small, omission of an item slightly improved the
value (α = .55). The descriptive score of external regulation was
the average of the three items, and the descriptive scores of the
other three subscales were calculated by averaging each of the
four item scores. For the purpose of this study, the RAI was
calculated same as previous studies (Grolnick & Ryan, 1987;
Levesque, et al., 2004; Losier & Vallerand, 1994). The RAI is
formed by weighting each subscale in accord with its underly-
ing scores on the self-determination continuum in the following
formula: RAI = (–2 × external regulation) + (–1 × introjected
regulation) + (1 × identified regulation) + (2 × intrinsic motive-
tion). In the subsequent analyses, the RAI score was used as an
index of self-determined friendship motivation.
The Japanese version of the Buss and Perry Aggression
Questionnaire (Buss & Perry, 1992) developed by Ando, Soga,
Yamasaki, Shimai, Shimada, Utsuki, Oashi, and Sakai (1999)
was used to assess aggression. This scale consists of four sub-
scales of physical aggression (5 items; e.g., “If somebody hits
me, I hit back”), verbal aggression (6 items; e.g., “I tell my
friends openly when I disagree with them”), anger (5 items; e.g.,
“I have trouble controlling my temper”), and hostility (6 items;
e.g., “I sometimes feel that people are laughing at me behind
my back”). Participants were asked to rate each item on a 5-
point Likert scale ranging from 1 (not true) to 5 (true). The
8

R. OKADA
reliabilities for each subscale were verified in a sample of
Japanese university students (Cronbach alphas ranged from .70
to .78, and test-retest coefficients during the three weeks ranged
from .70 to .80; Ando, et al., 1999). In the present study, the
alphas for the subscales were .78 for physical aggression, .75
for verbal aggression, .76 for anger, and .74 for hostility. The
descriptive scores of the four subscales were calculated by av-
eraging the item scores.
Self-esteem was measured with the Japanese version of Ro-
senberg’s Self-Esteem Scale (10 items) developed by Yama-
moto, Matsui, and Yamanari (1982). Participants were asked to
rate each item on a 5-point Likert scale ranging from 1 (not true)
to 5 (true). The Cronbach alpha was .84 in the present study. The
descriptive score was calculated by averaging ten item scores.
Results
Descriptive Statistics and Correlations among
Variables
Descriptive statistics and Pearson correlations among vari-
ables are presented in Table 1. Consistent with predictions, RAI
was negatively related to anger (r = –.24, p < .001) and hostility
(r = –.29, p < .001). The relation between RAI and physical
aggression was marginally significant (r = –.10, p < .10). Un-
expectedly, RAI was positively associated with verbal aggres-
sion (r = .18, p < .01). RAI was also positively related to
self-esteem (r = .25, p < .001). Anger and hostility were nega-
tively related to self-esteem (rs = –.18 and –.38, ps < .01, re-
spectively). Against predictions, verbal aggression was posi-
tively associated with self-esteem (r = .34, p < .001). The rela-
tion between physical aggression and self-esteem was nearly
zero (r = –.00, n.s.).
Examination of the Hypo thetical Model
It was hypothesized that self-determined friendship motiva-
tion would predict lower levels of aggression, which, in turn,
would predict higher levels of self-esteem. The hypothetical
model was constructed in the following manner. Paths from
RAI to four aggression scores and paths from four aggression
scores to self-esteem were postulated. Covariances among four
aggression scores were also included.
The model was tested using structural equation modeling
with AMOS 17.0. The model fit was assessed by the following
statistics (Byrne, 2001): the chi-square value (nonsignificant
values represent an acceptable fit), the Goodness of Fit Index
(GFI; values above .90 represent an acceptable fit), Adjusted
Goodness of Fit Index (AGFI; values above .90 represent an
acceptable fit), Comparative Fit Index (CFI; values above .90
represent an acceptable fit), and the Root Mean Square Error of
Approximation (RMSEA; values below .08 represent an ac-
ceptable fit).
The analysis showed that the hypothetical model adequately
fit the data, χ2 (1) = 1.95, n.s., GFI = 1.00, AGFI = .95, CFI =
1.00, and RMSEA = .06. The path from physical aggression to
self-esteem (β = .03) and the covariance between verbal ag-
gression and hostility (r = .03) were nonsignificant; these pa-
rameters were therefore fixed at zero in the final model. Be-
cause the path from RAI to physical aggression (β = –.10, p
< .10) and the path from anger to self-esteem (β = –.11, p < .10)
were marginally significant, these paths were freely estimated
again. The final model is depicted in Figure 1. The analysis
showed that the model adequately fit the data, χ2 (3) = 2.32, n.s.,
GFI = 1.00, AGFI = .98, CFI = 1.00, RMSEA = .00, and the
change of chi square values was also nonsignificant (Δχ2 (2) =
0.37, n.s.). The RAI predicted higher levels of verbal aggres-
sion (β = .18, p < .01) and lower levels of anger and hostility
(βs = –.24 and –.29, ps < .001, respectively). The path from
RAI to physical aggression was negative at a marginally sig-
nificant level (β = –.10, p < .10). Verbal aggression predicted
higher levels of self-esteem (β = .34, p < .001) and hostility
predicted lower levels of self-esteem (β = –.32, p < .001). An-
ger predicted lower levels of self-esteem at a marginally sig-
nificant level (β = –.11, p < .10).
Discussion
The purpose of this study was to examine a model in which
self-determined friendship motivation would predict lower
levels of aggression, which, in turn, would predict lower levels
of self-esteem. Consistent with the hypothetical model, path
analyses showed that self-determined friendship motivation
predicted lower levels of anger, hostility, and physical aggres-
sion, and hostility and anger predicted lower levels of self-
esteem. People with higher levels of self-determined friendship
motivation are likely to feel less anger and hostility and to act
less aggressively in their relationships with friends, because
they are motivated by their interest in friends or the importance
of friendship. People who display less hostility and anger to-
ward friends are likely to be more accepted, and those who
interact with others in a hostile and angry manner tend to be
avoided and rejected. Hostility and anger lead to rejection by
Table 1.
Pearson correlations among variables, means, and standard deviations.
1 2 3 4 5 Mean SD
1. RAI 5.87 2.77
2. Physical aggression –.10† 2.70 0.81
3. Verbal aggression .18** .33*** 2.90 0.77
4. Anger –.24*** .42*** .18*** 2.84 0.84
5. Hostility –.29*** .29*** –.03 .43*** 3.03 0.72
6. Self-esteem .25*** –.00 .34*** –.18** –.38*** 3.13 0.68
†p < .10, **p < .01, ***p < .001.

R. OKADA
.99
.91
-.32
***
-.11
†
.34
***
.97
.18
**
-.24
***
-.29
***
-.10
†
.74
.94
RAI
Verbal
aggression
Anger
H o stility
Self-esteem
P h ysical
aggression
Figure 1.
A hypothetical model of the relationship among RAI, aggression subscales, and self-
esteem. The covariances among the aggression subscales are omitted in this figure. †p
< .10, **p < .01, ***p < .001.
others and could therefore decrease self-esteem, as suggested in
sociometer theory (Leary & Baumeister, 2000; Leary, et al.,
1995).
It was surprising to find that self-determined friendship mo-
tivation predicted higher levels of verbal aggression, which, in
turn, predicted higher levels of self-esteem. This is an unex-
pected finding. A plausible explanation is that verbal aggres-
sion helps maintain relationships with friends. The content of
the items that tap verbal aggression (“I tell my friends openly
when I disagree with them,” “When people annoy me, I may
tell them what I think of them”) seems to be similar to assertion,
which is a component of interpersonal competence. Buhrmester,
Furman, Wittenberg, and Reis (1988) suggested that asserting
displeasure with others was an aspect of interpersonal compe-
tence and was positively related to social self-esteem. Soenens
and Vansteenkiste (2005) found that self-determined friendship
motivation predicted higher levels of social competence, which
was a similar construct to interpersonal competence. It can be
that people with higher levels of self-determined friendship
motivation maintain positive relationships with friends through
asserting their own opinion honestly, consequently maintaining
high self-esteem.
Physical aggression was not found to be significantly related
to self-esteem. Generally, aggression is likely to lead to rejec-
tion by others, and rejection will decrease self-esteem. On the
other hand, aggressive behavior can help in restoring self-es-
teem that has been lowered by negative evaluation and feed-
back (Baumeister, Smart, & Boden, 1996). If the attempt to
restore self-esteem succeeds, aggression can be associated with
higher levels of self-esteem. The nonsignificant relationship
between physical aggression and self-esteem in this study may
partly reflect the need for aggressive responses as a means to
restore self-esteem.
The main contribution of this study was to reveal that friend-
ship motivation could influence self-esteem through lower lev-
els of maladaptive behaviors. Previous studies have mainly
examined the relationship between self-determined friendship
motivation and adaptive behaviors (Okada, 2007; Richard &
Schneider, 2005; Soenens & Vansteenkiste, 2005). The present
study focused on aggression as a maladaptive behavior and
revealed the relationship between self-determined friendship
motivation and aggression. It was suggested that self-determined
friendship motivation not only promotes adaptive behaviors but
also suppresses aggressive and hostile behaviors.
It is important to note that some of the relationships found in
this study were relatively weak. For example, the path coeffi-
cient from RAI to physical aggression was –.10 in the path
analysis, although the value was marginally significant. This
may partly be because general aggression in daily life was ex-
amined in this study. Another line of research has examined
aggressive responses in specific situations manipulated experi-
mentally such as provocation, ego-threat, and social exclusion
(Baumeister, et al., 1996; O’Connor, et al., 2001; Twenge,
2006). Future studies should examine the relationship between
self-determined friendship motivation and aggression in situa-
tions manipulated to prompt aggressive responses.
There are some limitations to this study. First, the quality of
friendships has not been measured. From previous studies, it
was assumed that the good-quality relationships with friends
mediated the relationship between aggression and self-esteem
(Leary & Baumeister, 2000). If so, aggression (especially, hos-
tility and anger in this study) would predict poor relationships
with friends, which, in turn, would be associated with lower
levels of self-esteem. Future studies should examine the quality
of friendships as well. Second, all the variables were measured
simultaneously. The model examined in this study assumed the
causal order that self-determined friendship motivation affects
aggression, which, in turn, affects self-esteem. The simultane-
ous measurement, however, makes it difficult to interpret the
findings in terms of causality. For example, it may be that peo-
ple with lower levels of self-esteem display more hostility and
anger. To verify the causal relationships among self-determined
friendship motivation, aggression, and self-esteem, a longitudi-
nal measurement is required.
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10

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