"Know Thyself": A Review of True Self

Throughout the years "Know Thyself", as an old aphorism, has been discussed by laypeople and researchers alike. It continues to hold a vital position in contemporary psychology. According to the traditional psychoanalytic and humanistic theories, being aware of and behaving in accordance with one's true self, improves an individual's psychological health. However, what the "true self" is, and how it affects people's daily lives, continues to be explored. In the present study, we reviewed the history and definition of the true self. Based on the characteristics found in previous research, we tentatively defined the true self as "a set of mental representations of the inherent, private, and stable attributions of oneself; reflective of whom an individual thinks he/she really is." Following that, we reviewed several ways of measuring or assessing the true self, and compared advantages and disadvantages of them. We also reviewed the effects the true self has on people's meaning in life, decision satisfaction, and moral judgment, as well as psychological health. Finally, we suggested that it is crucial to define the true self more clearly, to develop methods to measure or assess it more accurately, and to investigate the fundamental mechanisms by which it benefits to people.


Introduction
The notion of "Know Thyself" can be traced back to Socrates and the ancient Greeks. They inscribed this motto on the temple of Apollo to caution people in looking at and being aware of themselves. Hereafter, this notion has been spread far and wide, becoming one of the classic themes of literature and film from ancient to modern times. In these stories, heroes experience a variety of hardships to seek their real identity and memories, understand who they are and ultimately gain happiness.
Besides the fondness for this theme from laypeople, researchers from many different subjects such as philosophy, anthropology, sociology, and so on have never stopped devoting their effort to this task. With the development and progress of psychology today, investigation through scientific methods is possible. After years of accumulation and development, theories and studies about this theme have become a systematic and essential branch of personality and social psychology [1]. Modern psychology has covered almost all phenomena about the self, including self-concept, self-efficacy, self-regulation, and so on. Nevertheless, few of them have actually investigated the core aspect of the theme "Know Thyself"-a "true self".
In the following section, we will tease out the research on true self and review the definition, characteristics, measurement methodology, and psychological functioning of it.

Definition and Characteristics of True Self
Early in the history of psychology, theorists from classic schools have deliberated between the definitions and characteristics of the true self. For example, in the psychoanalytic tradition, Horney argued that true self (in her words, "real self") is the most alive, unique, personal center of oneself, and the only part that can and wants to grow [2]. According to Winnicott, only the true self can be creative and feel real. It is essentially not reactive to external stimuli, but primary [3]. In humanistic tradition, Rogers suggested that the true self is constituted of essential and inner aspects of one's real identity. Although this identity may not be perfect and is not often validated as real by those that are significant in the individual's life, it allows a sense of fulfillment and reality [4,5]. According to Maslow, every one of us has an essential inner nature which is instinctoid, intrinsic, given, natural, and unchangeable to some extent. True self (in his words, "authentic selfhood") "can be defined in part as being able to hear these impulse-voices within oneself, i.e., to know what one really wants or does not want, what one is fit for and what one is not fit for, etc." [6].
Although psychoanalytic and humanistic psychologists have defined and described the true self to some extent, these definitions are ambiguous and open to interpretation. In recent years, cognitive psychologists have attempted at defining the true self more distinctly from various different aspects. For example, Bargh, Mckenna, & Fitzsimons defined the true self as "those identity-important and phenomenally real aspects of self not often or easily expressed to others" [7]. Schlegel and her associates defined the true self as "who a person really is, regardless of his or her outward behavior" [8]. And they defined the true self-concept as "a cognitive schema representing those aspects of the self that are considered, by the person, to be most emblematic of his or her true nature" [9]. Furthermore, Sheldon, Gunz, & Schachtman defined the true self through a somewhat distinctive method. They asserted that for a vast majority of their lives, people wear masks in society and distort who they really are. Only when in a safe and unguarded state, are they likely to take off the masks. Therefore, they also refer to the true self as "unguarded self," and defined it operationally as "the way people behave among their closest friends and confidants" [10].
Besides the definitions addressed, researchers also clarify the characteristics of the true self by investigating people's beliefs and attitudes upon the true self. The results can be concluded as follows.
(1) Privacy. People's overt behavior in daily life is usually inconsistent with their true self [10]. They believe that chronic private thoughts and feelings are more informative and diagnostic of the true self within themselves and others than chronic objectively observable behavior [11,12]. Teenagers believe that only their closest friends can know their true self [13,14]. It seems that people are hesitant to reveal their true selves to others with the rejection of this kind of self-disclosure being especially harmful to one's self-esteem [15]. Therefore, Landau et al. likened the true self to "a core-like entity embedded inside of an external casing or shell" [16].
(2) Inherency. People believe that the true self is something that is inherent and not created but could be discovered [17]. And the best indicator of the true self is the reactions over which the individual may exert relatively little voluntary control (e.g., mental states and emotion), but not the products of personal choice, which need much conscious effort (e.g., behavior) [12]. Similarly, the decisions made by intuitive, gut feelings are seen by the laypeople as reflecting the true self more, rather than the decisions made by deliberative, rational analysis [18].
(3) Stability. It is generally believed that the self-aspects and attributes that are most likely to be present across occasions, constitute the true self [12]. On the other hand, it is also believed that the events that reflect the true self most, would occur more frequently and that these attributes are rated as more stable than general ones [19,20]. Based on the above review, although the true self is an aged topic, there is no accepted definition of it by far [10]. The privacy of the true self causes great difficulty in defining it. However, an accurate and clear definition of psychological phenomena is a prerequisite for researchers to discuss, verify, and develop each other's results. Therefore, defining the true self is one of the tasks in great demand of prompt solutions.
Swann & Bosson asserted that in its most common usage, the self refers to a set of representations about oneself, parallel to the representations people have of others [21]. Referring to the definitions and characteristics of the true self obtained in previous studies, we can define it tentatively as: a set of mental representations of the inherent, private, and stable attributions of oneself; reflective of whom an individual thinks he/she really is. While this definition may not entirely grasp the concept of the phenomenon perfectly, but it is intended to be a fulcrum for the true self researchers to investigate more deeply at the present stage.

Measurement of the True Self
As mentioned above, it is difficult to define the true self operationally due to its tendency to not always be expressed in overt behavior. Therefore, the criterion to judge the measurement of it is difficult to determine. Despite this, researchers have made various attempts in measuring the true self. In an earlier study, Turner & Schutte used open-ended measures to approach it. Specifically, participants were asked to describe the occasions and behaviors in which their true selves could or couldn't be expressed and the reason why they felt so [22]. However, because the results obtained by this method were only able to be used in qualitative analysis and not quantitative, this method was not generalized.
Another method is to let participants describe their true self by asking participants who they believe they really are. The results obtained through this kind of method have been referred to as "true self-concept [23]." This measurement allows a closer look at the content and construct of the true self-concept, and provides a comparison with the other types of self-concept (e.g., actual self, ideal self, social self, et al.). For example, Sheldon et al. measured the true self-concept by dint of the characteristics of the "unguarded self" mentioned above. Specifically, they asked participants to "rate your true self-those characteristics that you possess but are not always able to express socially for whatever reason. Think about those traits you are only able to express around those people closest to you" [10].
However, given the privacy of the true self and the fact that most of the research in this area is aimed to explore the relationship between the true self and psychological/social adjustment, to some extent the content of the true self is not our concern. Rather, it is more important to measure whether, or to what extent an individual can be aware of their true self and the psychological importance of it.
Schlegel and her associates have combined the measurements of the true self-concept and social cognition methodologies to measure the accessibility of the true self-concept [7,9]. The theoretical base of it is that shorter response time to a concept is indicative of higher accessibility of it in the cognitive structure [24]. Specifically, participants can select from a list supplied by researchers or enumerate themselves, ten trait words representative of their true self. Then, they complete a "me/not me" task [25]. Dozens of trait words containing the true self words that participants enumerated earlier are presented on a computer screen one by one in random order. Participants are required to judge whether these words are self-descriptive by pressing a key labeled either "Me" or "Not me" as quickly as possible. Finally, researchers partial out the response times of other self-descriptive words from those of true self-descriptive words. Although since the latter is usually faster than the former, we can reverse this difference value. In doing so, we can obtain the pure true self-concept accessibility, which controls an individual's response tendencies. The faster the response time is, the more the participant is considered to be aware of his/her true self.
Schlegel and her associates also developed another method to rate how people know their true selves. This method involves measuring the metacognitive experience of ease. Participants are asked to list eight words that describe their true self. Specifically, they are asked to list words they would use to describe who they really are, even if those characteristics differ from how they sometimes act in daily life. And then, they rate how difficult they feel it is for them to perform this task. The easier they feel, the more the participant is considered to be aware of his/her true self [9,17].
Based on the above review, we can see that the development in measuring the true self is subject to two problems in large measure. First, the conceptual definition. In most of the explicit measures, it is necessary to tell the participants clearly what they need to describe. Moreover, even in the implicit measures, researchers also must find appropriate criteria according to the conceptual definition to confirm whether they have measured what they intend. At the current stage, this standard has not yet been met. For example, in the "unguarded self" measure in Sheldon et al. [10], researchers do not know whether the "unguarded self" is the same as the true self, or if it is only a part of the true self. Second, criteria. Schlegel and her associates developed a series of measurements of the true self, and their effort makes substantial contribution to approach it factually from different aspects. However, researchers still are unable to confirm whether they have measured participants' true self because there is no valid criterion. For the measures of general or actual self-concept, we can judge the accuracy and validity not only according to the observable behavior expressed by people themselves, but also according to the informant-ratings. Nevertheless, the true self usually is not expressed in overt behavior and therefore cannot be observed by others. As a result, the usual criteria are not appropriate for this unique psychological variable. Overall, it is important to develop methods that could examine the validity of the true self measures in the future.

The Psychological Functioning of the True Self
As mentioned above, traditional psychoanalytic and humanistic theorists have preliminarily enunciated not only the definition and characteristics of the true self, but also the significant effects it can have on psychological health. In psychoanalytic tradition, Horney argued that alienation from the true self is one of the major causes of neuroses [2]. Laing contended that schizophrenia is derived from the fact that one's personality is not true self-expression but rather largely a series of impersonations, or an entirely false self. In other words, people wear masks to cater to the acclaim of others. On the one hand, these false selves represented by the masks, conflict with each other within-person. This ultimately results in fragmentation of personality. On the other hand, once the veil of the false self is suddenly removed, the "self will pour out accusations of persecution at the hands of that person with whom the false self has been complying for years" [26]. Miller agreed with Laing and suggested that the response to parents' expectations and compromise to their demands from childhood could not lead to the development of true self, but a false self. This false self gives rise to mental problems such as vacuum, anxiety, and depression [27]. In humanistic tradition, Rogers considered that the reason many clients feel embarrassed is due to not knowing of their true selves, and being unable to express it. The treatment aim is to help the clients become aware of their true selves and express themselves more authentically in social intercourse [4,5].
Both psychoanalytic and humanistic theorists agreed upon the fact that being aware of and behaving in accordance with one's true self can have a positive effect on psychological and social adjustment. And the primary aim of treatment is to help people become acquainted with and express their true selves. Modern psychology has validated and expanded these classic assertions derived from clinical-and case-studies more thoroughly using scientific and empirical methods.

The true Self and Meaning in Life and Decision Satisfaction
A series of studies conducted by Schlegel and her associates demonstrated that the true self provides every individual with a unique life philosophy. This philosophy helps people to decide what goals, behaviors, and relationships are valuable, and endows them with more meaning and value. As a result, this increased awareness of one's true self allows people to gain a sense of meaning in life [9] and acquire more satisfaction through their decisions [28].
In the initial study, Schlegel et al. demonstrated that the higher the accessibility of one's true self-concept, the greater meaning in life they were likely to feel, using the "me/not me" task [9]. Furthermore, results held even after controlling for the accessibility of actual self-concept, other resources of meaning in life (e.g., positive emotion, basic needs satisfaction, et al.), and the likeability of the true self trait words. Moreover, when people were primed by the true rather than actual self trait words listed by themselves earlier, they felt a greater sense of meaning in life. This outcome confirms the causal direction of these two variables. Given the "me/not me" task could only measure the unconscious aspect (accessibility) of the true self-concept, Schlegel et al. then further investigated the relationship between the conscious subjective experience of true self-concept and meaning in life, by measuring and manipulating metacognitive experience of ease. The results showed that the individuals described their true self more easily and readily were also more likely to report that they felt more meaning in life [8].
To further ascertain the mechanism in which the true self-concept promotes the experience of meaning in life, Schlegel et al. tested functions of the metaphors of self-discovery and self-creation in this process [17]. The former prescribes that there is an innate set of characteristics or a real self within each person. It implies that there is something about the self that is inherently true. The latter on the other hand, prescribes that there is nothing about the self that is true or essential waiting for people to find. It implies that the self is based on the experiences and choices. The results demonstrate that the more agreement there is with the discovery metaphor, the stronger the belief of the true self is. Furthermore, the discovery rather than creation metaphor contributes to the capacity for true self-concept to facilitate meaning in life. It seems that when people believe the self to be something discoverable, it is likely to be seen as something essential, unchangeable, core, and unique, which can then be used to guide their choices. On the contrary, when people believe that the self is created, it is more so seen as a choice among endless possibilities [17,29].
In the following study, Schlegel et al. examined the capacity for the true self to guide significant life decisions as an internal compass. In turn, decision satisfaction serves as a signal that one knows his true self sufficiently. In a series of correlational, experimental, and daily diary studies, participants that were able to easily describe their true self-concept, reported more decision satisfaction. On the other hand, manipulated decision satisfaction also affects participants' perception of true self-concept [28].

The true Self and Morality
People believe that the true self is morally good [30]. On the one hand, the perception of one's morality affects the perception of this person's true self. Newman, Bloom, & Knobe showed that people believe the morally good (rather than morally bad and nonmoral) behavior of themselves and others reflect one's true self [31]. And this effect has been proven to be universal. The results held even when the judges themselves were from the misanthropes who view humans negatively or from different cultures [32]. And the results also held even when targets were from either ingroup or outgroup [33].
On the other hand, the perception of one's true self could affect the judgment of morality, and may even affect decision-making regarding moral behavior. When people feel that they are aware of an individual's true self, they are likely to believe that individual to be more moral [34]. Results from research on authenticity also demonstrated that experiencing inauthenticity made people feel immoral and impure, whereas being authentic to oneself was experienced as a form of virtue [35]. Furthermore, thinking and making decisions following their true self (rather than just what seems rationale), lead to more willingness in behaving morally [36].
Above all, many researchers have agreed upon the relationship between the true self and morality as not being the result of a unique understanding about the true self, but rather an example of psychological essentialism, which is one of the general human cognitive tendencies [32,37].

The True Self and Psychological Health
Sheldon et al. evaluated the discrepancy between true self concept and the character expressed in social life (social character), and examined the relationship between this discrepancy and subjective well-being [10]. The results showed that after controlling for many other factors, the closer social character was to the true self-concept, the more people were likely to feel authentic and happy. Additionally, the more characteristics expressed in a specific social role represent one's true and central self, the more people were satisfied with that social role, and the more happy they felt in that role [38,39].
A series of studies of intrinsic self also demonstrated that affirmation or activation of the authentic and intrinsic aspects of the self rather than extrinsic aspects, would reduce defensive responses, self-handicapping attributions, and conformity. And it would lead to increased performance on the following tasks which have the potential to threaten one's self-worth [15,19,40]. These results demonstrate the positive effects and role of the true self in maintaining one's sense of self-worth.
Conversely, feeling unaware of or behaving inconsistently with one's true self is called true self-alienation or otherwise referred to as false self. It leads to absent-minded performance in the task [41], low academic motivation [42], low self-esteem, high depression, and hopelessness about the future [43].
The literature reviewed above shows the psychological functioning of the true self. Future research may continue to investigate the positive effects of the true self on physical and mental health. However, in consideration from an alternate perspective, if the true self is so beneficial to an individual's mental health and daily life, why is it that most want to conceal it? Some factors have been proven to inhibit the expression of the true self. For example, the absence of concern and support from parents and peers can reduce teenagers' knowledge and behavior of the true self [43,44]. Moreover, a reduction of free will can also reduce one's perceived true self-knowledge and further make one feel alienated from his/her true self [45].
Besides these specific factors, there are some essential reasons that lead people to hide their true self for a vast majority of their life. If the true self is really an unchanging entity deep inside oneself, being consistent with it at all times would entail that the behavior pattern is unitary and invariant. However, diverse situations and social roles require different behaviors [46][47][48]. As Gergen said, "For one, a demand for thoroughgoing consistency would fly in the face of a major mode of social adaptation. It would essentially freeze the individual personality in such a way that the person would fail to meet the requisites of a changing social environment" [49]. In contrast, maybe "the healthy, happy, human being wears many masks" [50]. Empirical studies on self-monitoring [51][52][53] and functional flexibility [54] also suggest that adjusting behaviors reasonably according to situations entails psychological as well as social adaptability. Perhaps the relationship between the true self and psychological health is dependent on the extent to which the true self is expressed. It is also possible that there are some key variables (e.g., patterns of expression) that moderate the relationship between the expression of the true self and psychological health. These unattended problems represent necessary future directions in research.

Conclusions and Future Directions
It is important to note that all of the studies reviewed above were conducted in western cultural backgrounds, and culture may be an important variable in research on true self. This is important because in western countries, which tend to be more individualistic, the self is viewed as something internal, and expressing one's thought and individuality are highly valued. On the contrary, in eastern countries which tend to be more collectivistic, the self is based on the harmony of interpersonal relationships and following social or group regulation as these are highly valued aspects in such societies [55]. As a result, changing one's behavior based on different situations and social roles in order to maintain harmonious relationships is central to the people in these east countries. Some cross-cultural studies have shown that the negative effects of cross-situational self-concept inconsistency (a manifestation of being unable to express one's true self) on the sense of authenticity, quality of relationships, and well-being were weaker for easterners than westerners [56][57][58]. Hence, the positive effects of the true self also may be weaker in eastern cultures. In fact, expressing the true self obdurately despite surroundings may even result in some negative effects. However, in regard to western cultures, future research is necessary to confirm the cross-cultural universality of the results obtained to explore the function of culture in this process.
In conclusion, over the past several decades, researchers from many schools have overcome a multitude of obstacles to explore the mysteries of the true self and have been able to make decent progress. However, to a considerable extent, this area is undiscovered. Future research is necessary to find more essential characteristics of the true self and develop an accurate definition widely accepted firstly. And then develop a measurement with acceptable reliability and validity based on the concept. Finally, it is needed to confirm the cross-culture universality of the result obtained from the western countries by now and investigate the negative effects of expressing the true self inappropriately and thoroughly despite changes of surroundings.