1. Introduction
Individuals constantly face numerous issues that require adjustment. Some people easily adjust to these challenges; however, others suffer from adjustment disorders. Adjustment is believed to be an innate inclination to conformity to problems and the ability to cope with potential changes (Nwoke, 2004, cited by Basil, 2011). Adjustment, in terms of the surrounding environment, is considered crucial for the individuals; all the individual’s efforts lay in this direction (Abbasian et al., 2013). Moreover, some life changes are of higher importance. Passing high-school and entry to university is considered as an essential change for individuals; their attendance in university would associate with contexts for development and learning (Tao et al., 2000, cited by Friedlander et al., 2007). Student life is associated with different challenges inside and outside the university (Clark, 2005, cited by Nazione et al., 2011). 
Such issues include missing friends and being away from home, confliction, depression, and maladjustment to other people, inability to making new friends, demotivation, mental disorders, loneliness (Isik et al., 2017), accepting responsibilities, shaping new interactions, and social obligations (Nazione et al., 2011). Students will succeed in coping with these issues and adjust to the changes in this period (Clark, 2005, cited by Nazione et al., 2011). The adjustment has multiple dimensions, including academic, emotional, and social adjustment. Academic adjustment encompasses learner’s ability to conform to the obligations and rules of the academic environment (Baker & Siryk, 1989, cited by Montgomery et al., 2019). Emotional adjustment involves biopsychological dimensions. Feelings, such as fear, tension, exhaustion, and the capability to cope with university affairs, lay in the emotional adjustment domain (Alt et al., 2016). The social adjustment can result from individuals’ communication with others and the social environment; it attempts to create a balance between one’s satisfaction regarding his/her role in the community and how he/she plays this role (Dehghannezhad, Hajhosseini, & Ejei, 2017). In this study, the academic adjustment has been explored. 
Several research studies discovered many factors affecting academic adjustment, one of which is personality traits (Richardson et al., 2012, cited by Montgomery et al., 2019). Personality traits are individual characteristics that remain constant over time and in various situations (McCrae & Costa, 1995, cited by Magee et al., 2018). The Five-Factor Model (FFM) of personality has been recognized as the most popular model during the last several decades, referring to the major 5 personality traits (neuroticism, extraversion, openness to experience, agreeableness, and conscientiousness) (Klimstra Luyckx, K., Hale III, W. W., & Goossens, 2014). 
Some researchers believe that the FFM of personality could not be a complete and comprehensive pattern in terms of personality traits. This is because other personality traits exist in addition to the five factors mentioned (Veselka et al., 2011). Ashton and Lee (2007) introduced the six-factor model of personality (HEXACO), which describes the disregarded characteristics in the FFM. Thus, the six-factor model of personality could serve as a more comprehensive and desirable model. Additionally, the six-factor model analyzes some of the constructs better than the FFM does. These 6 factors include the following: 1. honesty-humility (fairness, honesty, sincerity and greed avoidance), 2. emotionality (dependence, fearfulness, anxiety, sentimentality versus confidence, courage and resistance), 3. extraversion (social self-esteem, social boldness, sociability, liveliness vs. passiveness), 4. agreeableness (forgiveness, gentleness, flexibility, patience), 5. conscientiousness (prudence, perfectionism, delicacy, and diligence), and 6. openness to experience (creativity, accepting responsibility, unconventionality, & inquisitiveness) (Ashton & Lee, 2009).
In a study, You, Wang, C., Rodriguez, L., Wang, X., & Lu,. (2017) concluded that “neuroticism” and “extraversion and conscientiousness” predict negative and positive performance in students, respectively. Bernard, Hutchison, S., Lavin, A., & Pennington,. (1996) found that adjustment has a direct relationship with conscientiousness and agreeableness and a negative one with neuroticism. Warbah Sathiyaseelan, M., VijayaKumar, C., Vasantharaj, B., Russell, S., & Jacob. (2007) indicated that neuroticism and introversion cause stress and adjustment disorders in students. Kurtz, Puher, M. A., & Cross (2012) argued that agreeableness and openness to experience have a significant relationship with academic adjustment.
In addition, Suso-Ribera , Gallardo-Pujol, (2016) suggested no significant relationship between agreeableness and openness to experience and adjustment. Akbari and Aghayousefi (2010) reported no relationship between neuroticism and academic development. Furthermore, Mirheidari, Mirhashemi, M., & Abolmaali,. (2017) indicated no relationship between extraversion and openness to experience and academic performance. 
Psychological capital is considered as another factor that might affect academic adjustment. Psychological capital is defined as a positive psychological state and a realistic and flexible approach to life; it comprises 4 components, i.e. self-efficacy, hopefulness, optimism, and resiliency (Luthans, Avolio, Avey, & Norman, 2007). Self-efficacy is defined as a firm belief in one’s capabilities and aptitudes to utilize cognitive-emotional resources to reach goals (Wang et al., 2018). Bandura (1995) stated that individuals with reduced self-efficacy encounter troubles and avoid them, which prevents form a reasonable adjustment. Besides, people with strong self-efficacy easily cope with problems; therefore, they easily adjust themselves to unfamiliar situations. 
Hopefulness is described as a motivation for reaching one’s goals (Luthans, 2007, cited by Wang, Wang, X., & Xia, 2018). Azizi Nejad (2016) indicated that increasing the level of hopefulness results in a better adjustment to the academic environment. Besides, Du, King. (2013) reported that hopefulness could affect academic adjustment and performance. Optimism is a compilation of optimistic attitudes toward oneself, people, things, events, and the world, based on which results are expected to be desirable and promising (Chapin & Colman, 2009). Bayrami, Hashemi, T., Daneshfar, S., & Bahador. (2013) argued that optimism is among the most essential predictors of psychological adjustment. Bretherton McLean. (2014 and 2015) and Pritchard, Wilson, G. S., & Yamnitz et al. (2007) observed a relationship between optimism and adjustment. Resiliency is interpreted as a personal capability or aptitude (Van der Meulen van der Velden, P. G., Setti, I., & van Veldhoven,, 2018). Resiliency is a dynamic process, causing conformity to unfavorable conditions and enabling oneself to maintain his/her mental health while encountering threats (Bonanno, 2004, cited by Gouzman et al., 2015). Temprado, Agut, S., & Collado, (2017) and Gouzman et al. (2015) suggested that resiliency plays a crucial role in adjustment to a complex situation.
Most previous studies investigated the relationship between personality traits and psychological capital, and adjustment; however, the academic adjustment domain has been less of their concern. Furthermore, studies concerning the relationship between adjustment and personality traits have been mostly based on the FFM. Moreover, the majority of the previous studies separately investigated the components of psychological capital. In other words, the impact of psychological capital has been neglected as a synergetic whole in terms of academic adjustment. Thus, the present study aimed at predicting academic adjustment concerning personality traits and psychological capital.
2. Methods
This was a cross-sectional research. The study population included the University of Kashan’s graduate students. It was conducted in the February-March 2018. According to Krejcie and Morgan (1970), a total of 380 (190 females and 180 males) students were selected by cluster sampling method. Initially, 4 faculties (Humanities, Chemistry, Engineering, Architecture, & Arts) at the University of Kashan were randomly selected. Then, classes were randomly selected as the final cluster, and questionnaires were distributed among the selected students. The inclusion criteria were an age group of 18-22 years (BSc. students) and consent for participation in the study. The exclusion criterion was incomplete or distorted answers to the questionnaires. A total of 380 questionnaires were eventually obtained.
Moreover, 20 incomplete and distorted questionnaires were rejected. Finally, the data obtained from 360 questionnaires (180 females and 170 males) were used for data analysis. The required data were collected using the Adjustment Inventory for College Students (AICS) (AICS; Sinha & Singh, 1995), HEXACO Personality Inventory (Ashton & Lee, 2008) and Luthans’ Psychological Capital Questionnaire (PCQ) (Luthans, et al., 2007). To analyze the achieved data, step by step regression analysis was used. Furthermore, the study objectives were entirely explained to the study participants. Moreover, written informed consent forms were obtained from those who agreed to participate in the study. To maintain anonymity, the study participants’ personal information was excluded. 
Adjustment Inventory for College Students (AICS)
This developed by A.K.P Sinha and R.P. Singh (1995). It has 60 Items. AICS measures adjustment in three dimensions, including academic, emotional, and social adjustment (the academic adjustment subscale has been of concern in the present study). This questionnaire is of high validity and reliability. In addition, the validity and reliability of all three emotional, academic, and social domains are acceptable. Coefficients of this instrument’s 3 domains have been estimated to be 0.95, 0.94, 0.93 and 0.96, respectively through a split-half method, and 0.93, 0.96, 0.90 and 0.93, respectively test-retest approach, by its developers. Cronbach’s alpha coefficients calculated by Navidi (2005) were 0.72 to 0.80 for subscales and general adjustment (Naveedi, 2005, cited by Naveedy, 2009). In another study using this test on 164 individuals, Naveedy, (2009) reported the Cronbach’s alpha coefficients for general, academic, emotional, and social adjustment as 0.82, 0.70, 0.68, and 0.65, respectively. In the current study, Cronbach’s alpha coefficients for the total score, academic, emotional, and social adjustment were calculated as 0.87, 0.74, 0.65, and 0.68 respectively.
HEXACO Personality Inventory
The HEXACO Personality Inventory developed by Ashton & Lee (2008) and has 60 items and measures 6 personality traits. Respondents use a 5-point Likert-type scale (1=totally disagree; 5=totally agree) to answer each item. The internal consistency coefficients for honesty-humility (sincerity, fairness, greed avoidance, and modesty), emotionality (sentimentality, fearfulness, dependence, and anxiety), extraversion (social self-esteem, social boldness, sociability, and liveliness), agreeableness (forgiveness, gentleness, flexibility, and patience), conscientiousness (organization, diligence, perfectionism, and prudence) and openness to experience (aesthetic appreciation, inquisitiveness, creativity, and unconventionality) in a sample of students has been reported from 0.77 to 0.80 using Cronbach’s alpha coefficients (Ashton and Lee, 2009, cited by Aghababaei,Błachnio 2014). 
In Iran, Palahang et al. (2009) have supported the factor structure of the long form of this inventory. The internal consistency of the components of this inventory has been calculated to range from 0.65 to 0.75 (cited by Aghababaei, Błachnio 2014). Besides, the convergent validity of the 60-item Persian version of this scale has been reported as 0.49 (Aghababaei, Błachnio 2014). 
According to Khezri et al. (2016), Cronbach’s alpha coefficients for honesty-humility, emotionality, extroversion, agreeableness, conscientiousness, and openness to experiences have been reported as 0.669, 0.480, 0.708, 0.631, 0.548, and 0.419, respectively. In the present study, the Cronbach’s alpha coefficients for honesty-humility, emotionality, extroversion, agreeableness, conscientiousness, and openness to experiences were 0.70, 0.65, 0.78, 0.69, 0.68, and 0.60, respectively.
Psychological Capital Questionnaire (PCQ)
The PCQ developed by Luthans (2002) consists of 24 questions and 4 subscales (self-efficacy, hopefulness, resilience, and optimism). There are 6 questions for each subscale, and the items are answered on a 6-point Likert-type scale (1=totally disagree; 6=totally agree). The total score range of this test varies from 24-144. Questions 1-6 are related to self-efficacy, questions 7-12 are related to hopefulness, questions 13-18 are related to resiliency, and questions 19-24 are related to optimism (Luthans, 2002). The total score of psychological capital is calculated by adding up the scores of the 4 subscales. 
Correlational studies have indicated that the scores of this instrument, are highly associated with the scores of Snyder Hope Scale (1996), Wagnild and Young Resilience Scale (1993), Schier and Carver Optimism Scale (1985), and Parker Self-efficacy Scale (1998) (Cited by Golestaneh et al., 2017). The validity of this test was reported to be 0.90 by Luthans. Additionally, he reported the validity of self-efficacy, hopefulness, resilience, and optimism as 0.82, 0.81, 0.78, and 0.65, respectively (Luthans, 2007). 
Using Cronbach’s alpha coefficient, Jafari and Hesampour (2017) reported the reliability of this scale as 0.85. Furthermore, Farhadi Saki, K., Ghadampour, E., Khalili geshnigani, Z., & Chehri (2016) reported the general validity and the validity of hopefulness, optimism, self-efficacy, and resilience subscales as 0.88, 0.88, 0.65, 0.80, and 0.65, respectively. Cronbach’s alpha coefficients in the present study for the total score and the scale’s components have been equal to 0.89, 0.87, 0.70, 0.82, and 0.69, respectively.
3. Results 
To investigate the relationship between personality traits and psychological capital, and academic adjustment, Pearson’s correlation coefficients were computed. To determine the contribution of the personality traits and psychological capital to predict the academic adjustment, a stepwise multiple regression analysis was conducted. Personality traits and psychological capital served as the predictors, and the academic adjustment was predicted. The results of the descriptive statistics for all variables are presented in Table 1. The correlation coefficients between personality traits and psychological capital are presented in Table 2. The obtained results suggested a significant correlation between academic adjustment and honesty-humility (r=-0.19, P<0.01), emotionality (r=0.14, P<0.01), extraversion (r=-0.14, P<0.01), conscientiousness (r=-0.32, P<0.01), and openness to experience (r=-0.10, P<0.05). Table 3 lists the regression analysis results in predicting academic adjustment based on psychological capital. The achieved results demonstrated that conscientiousness, emotionality, and honesty-humility predicted 13% of the academic adjustment variance. The correlation coefficients between academic adjustment and psychological capital are represented in Table 4. Significant correlations between academic adjustment and psychological capital (r=-0.17, P<0.01), self-efficacy (r=-0.15, P<0.01), hopefulness (r=-0.19, P<0.01), optimism (r=-0.11, P<0.05), and resilience (r=-0.12, P<0.01) were observed. The regression analysis results predicting academic adjustment based on psychological capital are reported in Table 5. The collected results revealed that hopefulness predicts 3% of the academic adjustment variance.

According to Table 5, the merely hopefulness component, among the psychological capital components, was found to be a significant predictor of academic adjustment of the studied students. Hopefulness has explained 3% of the adjustment variance in the students. 
According to Table 6, there was a correlation between psychological capital and personality traits, including honesty-humility (r=-0.08), emotionality (r=-0.13), extraversion (r=0.49), adjustment (r=0.19), conscientiousness (r=0.34), and openness to experience (r=0.25).

According to Table 7, extraversion, conscientiousness, and emotionality, among the 6 personality traits, were the most significant predictors of psychological capital of the university students. First, extraversion has explained 24% of the variance of psychological capital in the students. The conscientiousness being added to the equation at the second stage, the variance of the psychological capital of the students has increased to 29%. Moreover, at the third stage, adding the emotionality trait to the equation has raised the variance of academic adjustment of the students to 30%. Accordingly, extraversion, conscientiousness, and emotionality, among the personality traits, had the most contribution to explain the variance of the student’s psychological capital.

4. Discussion
The desirable adjustment to the environment could indicate that the individual has the opportunity to develop socio-cultural networks; it may be a key to prospects, like graduation or employment (Sheehan, 2015). Regarding the importance of adjustment in academic situations, the primary purpose of this study was to predict academic adjustment based on personality traits and psychological capital.
The obtained results revealed a significant relationship between academic adjustment and personality traits (honesty-humility, emotionality, extraversion, conscientiousness, and openness to experience). The results of the Ehyakonnande, M., Yousefi, F., & Khormaie (2017), Shu, McAbee, S. T., & Ayman,. (2017), Perera et al. (2015), Nyazi (2013), Kurtz et al. (2012), and De Vries et al. (2011) were consistent with the present study findings. 
De Vries et al. (2011) reported that the honesty-humility trait is among the best predictors of academic performance and criteria, leading to a desirable adjustment. Students and learners who gain high scores on honesty-humility are reluctant to benefit from others and try to avoid harmful academic behaviors. The avoidance of greed and moderation, among the elements of honesty-humility, are considered as the most important predictors of academic performance (De Vries et al., 2011).
Dabas & Pandey (2017) and Ahadi and Puente-Diaz (2011) argued that only neuroticism (emotionality) and adjustment were related to each other. Fear, sadness, and seclusion, guilt, anger, and confusedness are the main characteristics of neurotic people. Similarly, people with neuroticism have unrealistic and irrational thoughts and orientations. Thus, such individuals have lacked the ability to adapt to unfamiliar and stressful conditions, as well as to communicate with others (McCray and Costa, 2008).
Extroverts can communicate profoundly and in a friendly manner with others and can easily interact with others. The extroverts are interactive, collectivist, independent, and tenacious. They express their ideas in the group and tend to take the responsibility of group leadership. They are always active and energetic and enjoy the pleasant emotions of love and joy. Such characteristics could play an essential role in reaching a desirable adjustment (cited by Seyyedi, 2014).
Conscientious individuals tend to be more inclined to plan, schedule, and organize activities, and not to eliminate pleasures and follow the system, frameworks, and rules (Fayard et al., 2012). Students and learners with characteristics, study with hard effort, assiduity, motivation, and accountability; subsequently, they reach a better development and performance in education (Petska, 2006). As a result, a desirable academic adjustment will be obtained.
According to Bardi,Guerra, V. M., & Ramdeny,. (2009), open-minded individuals are always ready to receive and consider new socio-cultural ideas and values and have a better performance in adapting to unfamiliar environments, including university. This makes open-minded individuals look healthier and more nutritious and more successful in their interactions and establish a proper adjustment to the university.
The achieved results indicated a significant relationship between psychological capital and academic adjustment. The study findings were consistent with those of Liu, Zhao, Y., Tian, X., Zou, G., & Li, et al. (2015) regarding the relationship between psychological capital and academic adjustment. Besides, psychological capital always has a significant influence on the individuals’ performance in academic settings (Avi, 2010). A high level of psychological capital can help to improve adaptability and achieve success and self-awareness. Each component of psychological capital can play a constructive role in individuals’ performance. Individuals with high self-efficacy in academic affairs have made significant efforts pursuing their goals; despite various difficulties encountered, they seriously endeavor.
In summary, individuals with high psychological capital have strong willpower to use alternatives to reach their goals and always remain optimistic about achieving positive results. Individuals with high self-efficacy can rely on this feature to create a pleasant atmosphere in their surroundings. All of these features manifested by psychological capital, help the individual to form a proper adjustment to the new environment and create innovative techniques (Luthans, Avey, J. B., & Patera, 2008).
The analysis indicated a significant relationship between personality traits and psychological capital. In this regard, there was no relationship between honesty-humility and psychological capital. Moreover, there was a significant negative relationship between emotionality (neuroticism) and psychological capital. Furthermore, the relationship between psychological capital and the other 4 factors, i.e. extraversion, agreeableness, conscientiousness, and openness to experience, was positively significant. This finding is consistent with those of Bozgeyilkly (2017), Luthans, Youssef, C. M., Sweetman, D. S., & Harms (2013), Lorenz et al. (2016); however, it was is inconsistent with the Yildizs’ study (2018).
In explaining the relationship between emotionality (neuroticism) and self-efficacy, it can be stated that dominant experiences are considered to be the most effective factors affecting self-efficacy. Therefore, due to anxiety and reduced control over stimuli, stressors and excitements, emotionality influences cognitive and behavioral activities, failing and defected performance (Shokri, Kadivar, P., & Daneshvar Pour, 2008). Failure to achieve the desired and expected outcomes, the lack of success, decreased self-esteem, and insufficient motivation will lead a neurotic person to fail to gain successful and dominant experiences (Kooshki, Hooman, H., & Yarmohammadi, 2010). Given the vital role of dominant and successful experiences in self-efficacy, the continuity of failure in achieving goals decreased self-efficacy (Mirkhani, ., Bagherian, F., & Shokri2013). Individuals with a high level of emotionality (neuroticism) have a great tendency to negative attitudes, seriously emphasize undesirable events (Tuersky & Griffin, 1991), tend to use dysfunctional strategies, advocate unpleasant emotional states, and concentrate on weaknesses (Snyder, 1995). All of these factors might reduce the hope for the future in a neurotic person (Dehghan, Atashpuor, H., & Shefti, 2014). Emotional individuals are characterized by a tendency to negative emotions, depressed mood, and frustration. Favorable emotions, hopefulness, and positive attitudes are associated with optimism in individuals. Thus, those people with neurotic characteristics conflict with optimism and are unable to be optimistic about the future (Hamidi, 2016).
Extrovert people have a strong assertion, which helps them achieve their goals more efficiently and results in a more positive performance in them. Extrovert individuals, therefore, have two sources of self-efficacy, i.e. dominant experiences and social satiation. Thus, self-efficacy and extraversion are directly associated with each other (Kooshki et al., 2010). In addition, relying on features, such as being active, interactive, and fervent and being decisive about reaching success, hope for making progress in the future, and look forward to the future positively assists them in this regard. These factors help them to more readily get prepared to succeed in the future and bear the expectations of desirable results in themselves, as well as make them optimistic about the future (Khormaie et al., 2014).
By shaping desirable expectations in themselves, agreeable people improve the sense of self-sacrifice, forgiveness, humility, trust, intimacy, sympathy with others, the assurance of achieving goals, and development from the perspective of the future. These factors result in improving success and enhancing self-efficacy and hope for the future, accordingly (Khormaie, Farmani, A., & Soltani, 2014).
Conscientious people will be able to achieve continuous successes through hard efforts, commitment, punctuality, and discipline at work. Therefore, they are expected to have strengthened self-efficacy and less tendency to inefficient strategies (Baranian , Hajiyakhchali, A., Atashafrouz 2017). Conscientious people are hard-working and select goals that require a lot of effort (Snyder, 1995). Similarly, with high hopes and optimism, they make hard efforts in complicated and stressful situations.
If having a strong desire and motivation to look for new and innovative experiences and behaviors in community affairs, people with an openness to experience find a higher level of self-efficacy. Additionally, when these individuals turn into passive, withdrawn, and receptive learners in academic environments, their self-efficacy could continuously decrease; ultimately, their willingness and motivation to work activities will be declined (Baranian et al., 2017).
The statistical population of the study was limited to the University of Kashan; thus, generalizing the results must be done with caution. The use of the questionnaire, which is considered as a self-reporting tool and may not be carefully responded by the respondents, was another limitation of this research. Studies on academic adjustment have been descriptive-correlative; therefore, it is suggested that different academic groups be compared by causal-comparative investigations. Besides, to determine the role and impact of each variable affecting the academic adjustment, studies with interventional plans should be conducted.
5. Conclusion
The study results indicated a relationship between personality traits and psychological capital and academic adjustment. Furthermore, educational-counseling interventions oriented on personality and psychological capital could be helpful in promoting student’s academic adjustment.
Ethical Considerations
Compliance with ethical guidelines
All ethical principles were considered in this article. The participants were informed about the purpose of the research and its implementation stages; they were also assured about the confidentiality of their information; Moreover, They were allowed to leave the study whenever they wish, and if desired, the results of the research would be available to them.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Authors' contributions
All authors contributed equally in preparing all parts of the research.

Conflict of interest
The authors declared no conflict of interest.


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