Personality And Change Across The Life Span: A Psychological Perspective

Is Personality Change Possible?

Overwhelming evidence suggests that the subject psychology and personality have are associated and are useful tools in various applied settings including health, economics, and education just to mention a few. According to Allemand & Martin (2017), personality entails the automatic and enduring patterns of thoughts and behaviors that make it possible to distinguish an individual from the next. Apart from this, Alwin (2019), also indicates that personality traits are often thought, feelings and behavioral patterns so ingrained in an individual that they get deployed even in different environments. Notably, the manifestation of personality is non-conscious and occurs seamlessly. According to Gordon Allport one of the earliest describers of personality, there are three different kinds of personality traits including common, central and cardinal. While common traits are shared by several people, central ones make up and individual’s personality. In other words they are unique. On the other hand, cardinal traits are ones’ which are dominant in such a way that an individual gets associated and primarily regarded for those traits.  Another psychologist Hans Eysenck suggest that there are three personalities including extroversion, neuroticism and psychoticism. In general different psychologists and scholars have described and categorized personality into numerous groups. However, the popular and widely accepted psychological theories on personalities indicate that there are five main broad personality dimensions including Agreeableness, Conscientiousness, Extroversion, Neuroticism and Openness. It is essential to note that these five personality traits exists as a broad continuum. This is to say that individual’s personality’s fall within the spectrum for each identified trait. For instance, an individual may be naturally extroverted but still exhibit openness and neuroticism.

Furthermore, Bleidorn et al (2018), indicates that personality traits are characterized with both stability as well as the ability to change across the lifespan. In most cases, the age-related changes in individual’s personality is attributed to responses to both social roles and responsibilities over time. For instance, evidence indicates that individuals tend to be more conscientious and agreeable during their working period unlike when they retire. What is more, people tend to be more introverted when married and less introverted when single due to meeting new people from time to time. Apart from this, solders and military personnel often demonstrated a decrease in agreeableness following training. In other words, it can be generalized that personality changes usually result from individual’s interaction and the degree to which they invest in social roles. Notably, since social roles and expectations tend to vary across different cultures, it is correct to say that the personality changes across the lifespan varies across social settings and culture.

The Extent to Which Personality Change Is Likely to Occur across the Lifespan

Additionally, it is essential to note that personality is not fully dictated by biological and other intrinsic factors, instead, individuals’ immediate environments could significantly impact on their personality. Numerous cross-cultural studies reveal that there is age-related personality changes across cultures. For instance, a study by Bleidorn et al (2021), examining changes in personality across Western cultures established that cultural variation in physical and mental health significantly impacts on individual’s life-course trajectory of personality.

Apart from this trajectory of personality change across the lifespan varies across culture. For instance, a cross-sectional study by Borghuis et al (2017), established that Western cultures tend to be more consensual and uniform in regard to patterns of personality change unlike African and Asian cultures who tend to be random. It was deduced that the difference in personality change across these three cultures is attributed to the fact that Western cultures tend to be more conforming to social norms whereas most Asian and African cultures are associated with less conforming to social standards.

Personality traits are ever shifting and individuals undergo significant transformation cross the lifespan.  A study by Ekstrom & Federico (2019) affirms that as individuals age, they become more conscientious and agreeable while being less neurotic. On the other hand, notable traits such as narcissisms and psychopathy tend to go down as one ages. Furthermore, research indicates that individuals develop into altruistic and trusting traits with age. This is so because with age individual’s will power generally increases and they tend to have more control of their emotions. Notably, aside from being somewhat fixed in childhood, especially between the ages of 3-12, personalities tend to be fluid and malleable around the age of 30.  Usually, the fluidity and malleability of individual’s personality in adulthood results to the ability to balance expectations and societal demands.

Hopwood & Bleidorn (2018), denotes that personalities are intrinsically lined to individual’s wellbeing as they age. For instance, individuals with a higher self-esteem and control are usually likely to be healthier and with relatively higher levels of neuroticism unlike those with lower self-esteem. In summary, while some scholars argue that personality is sometimes stable, overwhelming evidence suggests that personality is malleable and significantly changes across the lifespan.

Hopwood et al (2021), denotes that the extent to which a personality change is likely to occur across the lifespan is demonstrated in three broad perspectives including the radical contextual perspective, the biological essentialist perspective and the compromise perspective. According to the radical contextual perspective, different personality traits tend to be vulnerable to change over time and their stability indexes tend to be considerably low.  The biological essential perspective theorizes that personalities tend to be stable over time and are usually the products of genetic factors unlike environmental factors. This particular theory dictates that personality stability should be equally high for both men and women, especially during adulthood and only minimal changes happening across the lifespan. On the other hand, the compromise perspective borrows from both the radical contextual and biological essentialist perspectives.  The compromise perspective golds that personality tends to be moderately stable, regardless of the fact that noticeable changes may present themselves along the lifespan.

Individuals Consciously Initiate Personalities Trait Changes As They Encounter and Transition across Varying Social Contexts

According to Javaras (2019), individuals usually tend to consciously initiate personalities trait changes as they encounter and transition across varying social contexts. This is the reason why individual naturally adjust their personality traits to suite particular social contexts including friends and family as well as work scenarios. For instance O’Meara & South (2019), asserts that while openness and emotional traits are enhanced among parents and relatives, agreeable and conscientious traits are often more likely to be portrayed amongst friends and colleagues.  In this connection, it is conclusive that personality trait stability is positively correlated to individuals’ bio-psycho-social interaction with their immediate environment.  Furthermore, based on the numerous studies conducted on change in personality traits across the life span, it can be deduced that personality continuity is often modest between childhood and adulthood. However, personalities tend to be more consistent during old age. This is usually so due to individuals’ increased ability to adapt to various environment conditions during old age.

To sum up, compelling evidence suggests that personalities are often fairly flexible and individuals can change their personality. All personality traits including extroversion, emotional stability, openness, agreeableness and conscientiousness can be changed. However, it is essential to note that changing a personality trait requires that individuals behave in a manner that embodies the trait they are seeking to develop. A recent report revealed that individuals can develop extroversion over a span of as low as four months. Inn this connection, it can be deduced that personality traits are malleable and can be changed when enough effort is put in place.

Even though numerous studies suggest that stability exists in all the big five personality traits including Agreeableness, Conscientiousness, Extraversion, Neuroticism and Openness, there is strong evidence which suggests that personality traits do change due to crucial life events. These cluster of traits determine individuals’ levels of personality and how it changes through life. The whole issue is that there is pattern of consistency that starts around age of three and at sometimes very earlier as discussed by Roy et al (2018). Also, when psychologists study young people, they do not apply same approach as done to adults. Instead, they work on the issue of temperament and the person’s reaction intensity. As per Stieger et al (2021), the earlier temperament will serve as the foundation for personality traits later in life. Similarly, other sources have confirmed same results by describing that personality will tend to be better over time. This is referred as the “maturity principle” whereby people they tend to become emotionally stable, more extraverted and conscientious as they continue to get older. Over a long haul all these personality traits will be pronounced. Some individuals will have less changes compared to other but generally the maturity approach will apply to all people.  As per various sources for instance Roberts et al (2017), argues that psychotherapy, a key aspect in individual’s life has demonstrated the ability to impact on personality. Moreover, a recent meta-analysis of 307 studies revealed that psychological interventions significantly changed participants’ personality to up to between one-fifth to one-third of the standard deviation with large effects noted in Neuroticism and Extroversion traits.

Conclusion

Various psychological theories explain how personality develops and changes through life. The Freud’s theory of psychosexual development is widely applied in explaining how personality develops and changes across the lifespan. According to this particular theory, individual under go through a series of personality development stages including the oral, anal. Phallic, latency and genital stages. Freud theorized that life was basically built around tension resulting from sexual energy and pleasure arising from the discharge of the sexual energy. Furthermore, Freud stresses that the first five years of an individual’s life are vital towards the development of their adult personality. In this connection, it is essential that individuals are guided in the first five years of their life in order to ensure that they adopt a personality that is consistent and not in conflict with social norms.

Another personality change theory is the expectancy-value theory. While the Freud’s personality theory is general and encompasses all personality traits, the expectancy value theory is usually linked to Conscientiousness. This is so because the theory focuses on aspects such as individual’s values, motives and goals. Apart from this, the theory is versatile in the sense that it draws from individuals personal motives and their personality disposition to show how identity shapes individuals values, behavior and decisions they make in life. According to the expectancy value theory, varying individuals stories and their attachment to different domains is as a result of their beliefs.

Olaru & Allemand et al (2021), established that personality traits often continue to change in early adulthood into old age. In this particular cross sectional study it was revealed that individuals in the middle age often score higher as compared to young adults in regard to variables such as agreeableness, emotional stability and lower in openness and extroversion.

Additionally, an emerging body of research suggests that most people’s personalities often evolve across the lifespan. In a study conducted at the University of California, researcher explored the overall life span trends in the big five personality traits including conscientiousness, agreeableness, neuroticism, openness and extraversion of over a hundred thousand adults aged between 21 to 60 years old. Results obtained from this particular study proved to be contradictory with other studies conducted on the subject. This is so because of personality traits such as conscientious-ness, often characterized by aspects such as discipline and organization as well as success at workplace was found to increase across the life span with most changes happening at the age of 20 to 25. On the other hand, associated with aspects of generosity, and being helpful was found to increase especially above the age of 30 years old and further improved throughout the late 50’s and 60’s.  The study deduces that noticeable changes in these two personality traits can be associated with the changing adult roles across the lifespan. This is so because ideally, both agreeableness and conscientiousness tend to grow as people mature and learn how to better manage their finances, jobs and relationships.  Apart from this, most of the personality changes observed in the study demonstrated to be consistent across gender lines except for extraversion and neuroticism where females scored considerably higher than their male counterparts.  In summary, just like other numerous studies conducted on the subject, this particular study demonstrated personality traits often change over the lifespan.

Besides, another study by Roy et al (2018), on the effects of psychological intervention on personality change and psychological distress amongst Japanese cancer patients contributes to the existing large pool of evidence on the subject. Here, the study comprised three sessions including medication and provision of essential psychological information as well as one on one counseling utilizing the structured association technique. The final analysis revealed that the intervention had enhanced the overall short-term personality change, adaptive coping as well as the overall psychological wellbeing of the cancer patients.

A wide range of psychological interventions have the ability to potentially influence the personality of individuals at different ages across the lifespan. Among the broad interventions modalities that may be utilized to influence personality include cognitive remediation therapies as well as behavioral and cognitive-behavioral therapies, According to Stieger et al (2021), behavioral and cognitive behavioral therapies are designed to address behaviors, thoughts and emotional patterns of individuals that dictate their personality. An existing body of knowledge suggests that the development of cognitive and behavioral cognitive therapies has taken shape in three waves. The first wave is through behavioral therapy which mainly focuses on the aspect of behaviorism and examines observable behavioral factors paramount in shaping personality (Roy et al, 2018). The use of behavioral therapy is widely used around the glove today with most scholars considering it instrumental as it focuses on altering environmental to either promote or reduce undesirable behavior. Among the behavioral techniques widely used today include stimulus control, exposure and contingency management. While stimulus control entails the increasing of cues to bring out desired behaviors and subsequently decreasing cues bringing out undesired behavior, exposure encompasses the repeated presentation of cues mainly associated with undesirable events. On the other hand, contingency management narrows down to utilizing various forms of punishment to either promote of reduce certain behaviors.

The second wave is that of cognitive therapies. Among the widely used cognitive therapies over the last two decades include Beck’s cognitive therapy and Elli’s rational emotive behavior therapy (Roy et al, 2018). Unlike behavioral therapies, cognitive interventions usually adopt a cognitive conceptualization in which individuals thoughts are considered to significantly impact on both behavior and emotion. Here, the primary assumption is that inaccurate and maladaptive thought patterns underlie emotional and behavioral complications. In other words, cognitive theories use a processes referred to as cognitive restructuring where adopted techniques challenge maladaptive thoughts and promote the development of adaptive alternatives. Numerous cognitive restructuring techniques exists including identification of cognitive errors such as dichotomous thinking and overgeneralization as well as examining the presence and/or absence of maladaptive thoughts. Here, it is essential to note that over the decades, cognitive theories have been used alongside behavioral techniques in a group of techniques referred to as Cognitive-Behavioral-Therapies (CBT).

The last wave comprises of the acceptance and commitment therapy as well as dialect behavior therapy (Roy et al, 2018). Unlike the two waves addressed above, techniques in the third wave emphases on the context and functions of thoughts, emotion and behavior and not their content. Roy et al (2018) indicates that these techniques are designed to enable individuals flexibly respond to thoughts, emotions and events. While psychological interventions especially cognitive behavioral therapies took shape in three waves, most of the interventions addressed above are often jointly. Evidence suggests that when the interventions are used collectively tend to have more profound impacts of individuals behaviors and personalities unlike when used alone. For instance, Stieger et al (2021), found out that when used jointly behavioral and behavioral cognitive interventions had a significant impact on the personality change of cancer patients in Kazakhstan. The study sought to examine how behavioral techniques such as stimulus control and cognitive techniques such as Beck’s cognitive theory impacted on patient’s major personalities such as agreeableness, extraversion, conscientiousness and neuroticism. Based on the results obtained from this study, it can be deduced that a combination of both behavioral and cognitive behavioral techniques tend to be more precise when it comes to examining patients personalities and gradual change over time. In summary, behavioral and cognitive behavioral therapies have been jointly used across the years to enhance patient’s outcomes. Most importantly, these psychological intervention have proven to be instrumental towards shaping and guiding personality change. Additionally, it is evident that these interventions are of a time-limited intervention usually weeks to months.

Conclusion

As depicted earlier, personality refers to individual differences in their thought patterns thinking, feelings and behavior. Notably, personality is not independent, instead, our personalities are shaped by various aspects ranging from biological to immediate social environment. The Big five personality traits include extraversion, agreeableness, openness, conscientiousness and neuroticism. Here, it is essential to note that each of these personality traits represents a continuum. This is to say that individual do not often have specific personalities, instead, they fall anywhere on the continuum for each trait. Additionally, personality traits are not stable, instead they are malleable and for that reason individual’s personalities change significantly across the lifespan, especially in adulthood. Moreover, a wide range of psychological interventions have the ability to potentially influence the personality of individuals at different ages across the lifespan. Among the widely utilized psychological interventions include behavioral and behavioral cognitive techniques. While both techniques have the ability to impact of individual’s personality, utilizing one technique alongside the other yields better outcomes. 

Importance of using well-validated psychometric measures

At the present time, an increasing number of measurement instruments or questionnaires such as the Newcastle Health Consortium Conscientiousness Test (NHCCT) that assess psycho-social attributes and several results in health are obtainable to be employed in public health researches, clinical practices and to evaluate and improve population’s health Polit, D. F. (2015).  Even though many tools have been developed, most of them do not have adequate validation. Literature shows that the need for a deep evaluation of the measurement attributes of questionnaires used in the measurement tools. Appropriate research has to cautiously select the accurate and adequate tool, so as to ensure attainment of their outcomes. It is essential to comprehend the measurement instruments in particulars – measurement properties, assessment forms, domains, and items –, before employing them (Souza et al 2017). The excellence of the data provided by instruments is dependent, at the very least partly, on their psychometrics attributes.

Prior to being considered a suitable tool, the instruments ought to accord accuracy, validity and understandable data for the assessment of population health. Furthermore, the measure ought to provide systematically robust outcomes. The suitability of results of presented by the measures is a result of both the validity and reliability of instruments. In spite of divergences in some points, research is undivided in view of the validity and reliability as the main instruments’ measurement attributes (Bogg & Roberts, 2004).

A perfect example of validity and reliability and validity is illustrated below: the shots are placed in right target center. This association can also be applicable to evaluate the attributes of instrument of measurements. Founded on the presented information, one has to consider that it is relevant to discourse the approaches of examination of apparatuses’ dimension properties of clinical practice, research, and health assessment (Godin & Shephard, 1985). The major aspects of the assessment of validity and reliability of instruments of measurement, in addition to the commonly used statistical assessments are presented, exemplified and discoursed below.

A good measure of non-verbal fluid intelligence for use in an adult education context.

The homogeneity or internal consistency shows if all sub-parts of the instrument measure the same attributes. For instance, in case an instrument that is designed to evaluate an individual’s job satisfaction has 9 domains, then all the domain’s items of ‘salary’ ought to evaluate this concept, and not a dissimilar construct, like ‘benefits’, – for it is the only way that the tool will display internal consistency (John, 2021). This reflects a significant property measure for instruments that are designed to measure a single construct.

Stability denotes a measure of how comparable outcomes are if measured at different times, that is, it is an evaluation of the uniformity of measurement when repeated. Assessment of stability can be using the test and re-test methodology (Allison et al 2011). The methodology consists of application of same measurements during two dissimilar times. The employment of this methodology necessitates that the feature to be assessed remains consistent in both test moments and all changes in scores can be instigated by casual errors: for instance, if one completes research and retests it after some time duration, it is required that the outcomes remain similar. The intra-class correlation co-efficient denotes one of the most employed in estimating constant variable stability, for the reason that it accounts for errors in the measurement (Burke, 1972). Other correlation co-efficient, like the Spearman or Pearson, are not appropriate for such types of reliability tests, for the reason that they do not take into account measurement. The test and re-test reliability has the tendency of reducing errors when the test re-application times are extended (Mauger & Kolmodin, 1975).

The time duration between measurement acts to influence the understanding of reliability in the test and re-test; consequently, the time duration of 10 days to 14 days is considerable as appropriate for the test-retest. In relation to sample, a subject number of at least fifty subjects is considerable as adequate or appropriate (Mohammadbeigi et al 2015). For the interpretation of results, least values of 0.70 can be considerable as satisfactory.

Reliability denotes the competence to replicate consistent results in space and time, or from dissimilar observations, illustrating features of homogeneity, equivalence, stability, and coherence. It reflects a main attribute criterion for an appropriate instrument (Fernández-Villa et al 2015). Reliability denotes primarily equivalence of a measure, internal consistency and stability. It is imperative to highpoint that the consistency does not reflect a fixed attribute of a questionnaire tool. To the contrary, reliability depends on the functions of the instruments, on the population where it is used, on the context and on the circumstances in which it is used; that is, a similar instrument may not be measured as reliable in different conditions (Parsons et al 2019). Estimates of reliability are influenced by numerous features of the assessment setting (administration method, type of instrument, sample characteristics, raters) and the statistical methodology employed. Consequently, the outcomes of a research employing measurement instruments can be construed when the statistical method and the assessment environments are clearly presented (Bilbao et al 2018).

Equivalence refers to the degree of harmony between two or more observers relating to an instrument score (Bitan et al 2020). A key approach of evaluating the equivalence degree is employing the inter-observation reliability, which takes in account the self-determining partaking of 2 or more raters. In such a case, the instrument measuring is undertaken through rating. For instance, research which enjoys two competent raters who involve in filling of a comparable instrument, equivalence is realized when they have the same score. Reliability of inter-observation is dependent mainly on ensuring standardization for the test application and adequate training procedure of the raters. In case of high concordance for an instrument between the available raters, it is inferable that errors were minimalized (Sliwinski et al 2018).

Validity denotes the aspect that a tool evaluates exactly what it is designed to measure. It does not reflect an instrument attribute and ought to be established relating to a specific issue, once it designed to refers to a specific population (Worm-Smeitink et al 2017). The measurement attributes – reliability and validity – are not completely independent aspects. Research affirms that instruments that are not reliable may not be valid; though, reliable instruments, can, occasionally, be regarded as invalid. Therefore, high reliability does not guarantee instruments validity.

Reliability and validity of their new conscientiousness measure, based on the information

Various psychometric properties and features form a strategic foundation for testing meaningful aspects and appropriate elements characterizing the targeted psychometric measure. For example, as it is highlighted by Ziegler and Brunner (2016) if a particular test is publicized as a crucial tool for measuring and diagnosing a specific mental illness such as bipolar disorder. The whole issue is those psychometric properties related to a particular test present what users and creators will argue about whether the tool works as required. The concept is that the whole aspect of validity and reliability of a psychometric measurement should focus on the particular feature (Ahmad et al 2018). There are some psychometric features regarding truth and reliability; they tend to speak about the quality of different parts constituting the entire test. For instance, some confirm the topic of volume and quality, with others giving weight to the constituent elements making the test. Karatzias et al (2016) argues that when confirming the issue of validity and reliability on the psychometric tests, there is a need for one to consider the totality as well as the psychometric features and properties possessed by the test. This will dictate whether the test confirms either the multiple or single construct (Li et al 2018). At some level, this psychometric element property can be termed gender equality.

Additionally, it is well evidenced that psychometric features and properties can always be expressed quantitatively. Foa et al (2016) argues that numerical quantities, for example, index and coefficient, are the numerical value that can be used to represent a specific property. For instance, this shows that the reliability coefficient can be described as a numerical value that professionals and most learners well know. Reliability can be expressed as the quantitative value that helps assess the validity of a particular phenomenon being identified when evaluating elements such as personality. Likewise, it sufficiently evidenced and supported by different sources that a large number of psychometric features and properties of a specific test can be expressed numerically to account for the issue of reliability and validity (Fernández-Villa et al 2015).

Moreover, in consideration of the central concept of this report, different arguments can be supported to analyze and describe the reliability of the Newcastle Health Consortium Conscientiousness Test (NHCCT). As per Bilbao et al (2018) NHCCT involves a 30-item measure describing the conscientiousness encompassing short sentences which individuals are required to rate give a five-scale range. As articulated by Parsons et al (2019) reliability is the whole ability to reproduce consistency within a specific time and space, thus presenting the concept of stability, homogeneity, and equivalence. Therefore, in relation to the provided NHCCT, one can argue that the element of equivalence, stability, and internal consistency supports the subject of reliability. First of all, the issue of stability determines how similar results are when it is done frequently at different times and spaces (Bitan et al 2020). In the NHCCT, it is evident that the test confirms the retest method. It has applied exact measurement at two various times, and this has been supported by the measures that have remained the same in both tests. The test has applied an intraclass correlation coefficient, thus confirming the stability of various stability. The number of samples used in the trial has demonstrated reliability as it is adequate, ensuring the satisfaction of the entire measurement. Secondly, the measurements are homogenous with the internal consistency as the variables used to measure the same characteristics and results. The tool has five scale range that articulates the key variables supporting the psychometric variable targeted. Also, the means correspond to the inter-observer reliability that included independent participation of different raters regarding equivalence (Ahmad et al 2018). This is well represented by the standardization of the test application, as the errors were minimized as much as possible. It can be argued that nothing is missing when confirming reliability in the NHCCT. This shows that the psychometric test has included the element of validity. Therefore, it is beneficial to have access to it when assessing personal traits, among other variables in psychometric evaluation.

NHCCT has included various concepts that correspond to other assessments such ass BFI-C, BFI-A, and LSI. Concerning BFI-C, there is evidence of convergent validity on the new measure. According to Li et al (2018) convergent validity includes two standards that measure the same construct, thus showing they are connected and related to each other. It is evidenced that the variable used in the BFI-C and NHCCT conforms to similar constructs. Both have identical time and values, thus conforming to the convergent validity. To the NHCCT and BFI-A, there is high divergence. Foa et al (2018) defines discriminant validity as the degree to which a measure or a test diverges from the other test that the primary construct is entirely unrelated to it. In terms of predictive validity, NHCCT and LSI seem to be related. Mohammadbeigi et al (2015) described predictive validity as the extent to which performance on a specific measure or test is related to the later version the particular standard or test was designed for. Both have used one variable to predict the results or outcomes based on the information that other variables offer. This shows that the score can expect an effect on another criterion measure.

Thus, based on the information provided above, the NHCCT has confirmed the element of validity, and it is valuable in psychometric evaluation. The essence of fact illustrates this: content validity, construct validity, and criterion validity. Similarly, the subject of internal consistency, equivalence, and stability remains part of the reliability when it comes to the valuation of the NHCCT (Parsons et al 2019). There is homogeneity and interobserver reliability when comparing NHCCT and other assessments such as BFI-A, BFI-C, and the LSI. This shows that no valuable insights have been left out in the NHCCT as it has found out and evaluated the construct of interest. The statistical analysis undergone by the NHCCT is consistent with the applied procedures, conditions, and interpretations (Worm-Smeitink et al 2017). The test produces consistent results, thus measuring reliability precisely and predicting behavior and relationship of various variables supporting different concepts connected to the field of psychology. 

References

Ahmad, N., Roslan, S., Othman, S., Shukor, S. F. A., & Bakar, A. Y. A. (2018). The validity and reliability of psychometric profile for Depression, Anxiety and Stress Scale (DASS21) Instrument among Malaysian undergraduate students. International Journal of Academic Research in Business and Social Sciences, 8(6), 812-827.

Allemand, M., & Martin, M. (2017). On correlated change in personality. European Psychologist.

Allison, C., Baron-Cohen, S., Wheelwright, S. J., Stone, M. H., & Muncer, S. J. (2011). Psychometric analysis of the Empathy Quotient (EQ). Personality and Individual Differences,51(7), 829-835.

Alwin, D. F. (2019). Aging, personality, and social change: The stability of individual differences over the adult life span. In Life-span development and behavior (pp. 135-186). Routledge.

Bilbao, A., García-Pérez, L., Arenaza, J. C., García, I., Ariza-Cardiel, G., Trujillo-Martín, E., … & Martín-Fernández, J. (2018). Psychometric properties of the EQ-5D-5L in patients with hip or knee osteoarthritis: reliability, validity and responsiveness. Quality of Life Research, 27(11), 2897-2908.

Bitan, D. T., Grossman-Giron, A., Bloch, Y., Mayer, Y., Shiffman, N., & Mendlovic, S. (2020). Fear of COVID-19 scale: Psychometric characteristics, reliability and validity in the Israeli population. Psychiatry research, 289, 113100.

Bleidorn, W., Hopwood, C. J., & Lucas, R. E. (2018). Life events and personality trait change. Journal of personality, 86(1), 83-96.

Bleidorn, W., Hopwood, C. J., Back, M. D., Denissen, J. J., Hennecke, M., Hill, P. L., … & Zimmermann, J. (2021). Personality trait stability and change. Personality Science, 2, 1-20.

Bogg, T., & Roberts, B. W. (2004). Conscientiousness and Health-Related Behaviors: A MetaAnalysis of the Leading Behavioral Contributors to Mortality. Psychological Bulletin, 130(6), 887– 919. https://doi.org/10.1037/0033-2909.130.6.887

Borghuis, J., Denissen, J. J., Oberski, D., Sijtsma, K., Meeus, W. H., Branje, S., … & Bleidorn, W. (2017). Big Five personality stability, change, and codevelopment across adolescence and early adulthood. Journal of Personality and Social Psychology, 113(4), 641.

Burke, H.R. (1972). Raven’s Progressive Matrices: Validity, Reliability, and Norms. The Journal of Psychology, 82, 253-257.

Ekstrom, P. D., & Federico, C. M. (2019). Personality and political preferences over time: Evidence from a multiwave longitudinal study. Journal of personality, 87(2), 398-412.

Fernández-Villa, T., Molina, A. J., García-Martín, M., Llorca, J., Delgado-Rodríguez, M., & Martín, V. (2015). Validation and psychometric analysis of the Internet Addiction Test in Spanish among college students. BMC public health, 15(1), 1-9.

Foa, E. B., McLean, C. P., Zang, Y., Zhong, J., Rauch, S., Porter, K., … & Kauffman, B. Y. (2016). Psychometric properties of the Posttraumatic Stress Disorder Symptom Scale Interview for DSM–5 (PSSI–5). Psychological Assessment, 28(10), 1159.

Godin, G., & Shephard, R.J. (1985). A simple method to assess exercise behavior in the community. Canadian Journal of Applied Sport Sciences, 10(3): 141-6

Hopwood, C. J., & Bleidorn, W. (2018). Stability and change in personality and personality disorders. Current Opinion in Psychology, 21, 6-10.

Hopwood, C. J., Schwaba, T., Milfont, T. L., Sibley, C. G., & Bleidorn, W. (2021). Personality change and sustainability attitudes and behaviors. European Journal of Personality, 08902070211016260.

Javaras, K. N., Williams, M., & Baskin-Sommers, A. R. (2019). Psychological interventions potentially useful for increasing conscientiousness. Personality Disorders: Theory, Research, and Treatment, 10(1), 13.

John, O. P. (2021). History, Measurement, and Conceptual Elaboration of the Big-Five Trait Taxonomy: The Paradigm Matures. In O. P. John & Robins, R. W. (Eds.), Handbook of Personality Theory and Research (4th Edition)

Karatzias, T., Shevlin, M., Fyvie, C., Hyland, P., Efthymiadou, E., Wilson, D., … & Cloitre, M. (2016). An initial psychometric assessment of an ICD-11 based measure of PTSD and complex PTSD (ICD-TQ): Evidence of construct validity. Journal of Anxiety Disorders, 44, 73-79.

Li, J., Zhao, Y., Kong, F., Du, S., Yang, S., & Wang, S. (2018). Psychometric assessment of the short grit scale among Chinese adolescents. Journal of Psychoeducational Assessment, 36(3), 291-296.

Mauger, P. A., & Kolmodin, C. A. (1975). Long-term predictive validity of the Scholastic Aptitude Test. Journal of Educational Psychology, 67(6), 847-851.

Mohammadbeigi, A., Mohammadsalehi, N., & Aligol, M. (2015). Validity and reliability of the instruments and types of measurments in health applied researches. Journal of rafsanjan university of medical sciences, 13(12), 1153-1170.

O’Meara, M. S., & South, S. C. (2019). Big Five personality domains and relationship satisfaction: Direct effects and correlated change over time. Journal of personality, 87(6), 1206-1220.

Olaru, G., & Allemand, M. (2021). Correlated personality change across time and age. European Journal of Personality, 08902070211014054.

Parsons, S., Kruijt, A. W., & Fox, E. (2019). Psychological science needs a standard practice of reporting the reliability of cognitive-behavioral measurements. Advances in Methods and Practices in Psychological Science, 2(4), 378-395.

Polit, D. F. (2015). Assessing measurement in health: Beyond reliability and validity. International journal of nursing studies, 52(11), 1746-1753.

Roberts, B. W., Luo, J., Briley, D. A., Chow, P. I., Su, R., & Hill, P. L. (2017). A systematic review of personality trait change through intervention. Psychological Bulletin, 143(2), 117.

Roy, S., Drake, A., Fuchs, T., Dwyer, M. G., Zivadinov, R., Chapman, B. P., … & Benedict, R. H. (2018). Longitudinal personality change associated with cognitive decline in multiple sclerosis. Multiple Sclerosis Journal, 24(14), 1909-1912.

Sliwinski, M. J., Mogle, J. A., Hyun, J., Munoz, E., Smyth, J. M., & Lipton, R. B. (2018). Reliability and validity of ambulatory cognitive assessments. Assessment, 25(1), 14-30.

Souza, A. C. D., Alexandre, N. M. C., & Guirardello, E. D. B. (2017). Psychometric properties in instruments evaluation of reliability and validity. Epidemiologia e servicos de saude, 26, 649-659.

Stieger, M., Allemand, M., Roberts, B. W., & Davis, J. P. (2021). Mindful of personality trait change: Are treatment effects on personality trait change ephemeral and attributable to changes in states?. Journal of personality.

Stieger, M., Flückiger, C., Rüegger, D., Kowatsch, T., Roberts, B. W., & Allemand, M. (2021). Changing personality traits with the help of a digital personality change intervention. Proceedings of the National Academy of Sciences, 118(8).

Worm-Smeitink, M., Gielissen, M., Bloot, L., Van Laarhoven, H. W. M., Van Engelen, B. G. M., Van Riel, P., … & Knoop, H. (2017). The assessment of fatigue: Psychometric qualities and norms for the Checklist individual strength. Journal of psychosomatic research, 98, 40-46.

Ziegler, M., & Brunner, M. (2016). Test standards and psychometric modeling. In Psychosocial skills and school systems in the 21st century (pp. 29-55). Springer, Cham.