Revised NEO Personality Inventory
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The Revised NEO Personality Inventory, or NEO PI-R, is a psychological personality inventory; a 240-item measure of the Big Five personality traits: Extraversion, Agreeableness, Conscientiousness, Neuroticism, and Openness to Experience. Additionally, the test measures six subordinate dimensions (known as facets) of each of the "FFM" personality factors. The test was developed by Paul T. Costa, Jr. and Robert R. McCrae for use with adult (17+) men and women without overt psychopathology. The short version, the NEO-Five Factor Inventory (NEO-FFI), has 60 items (12 items per domain). The NEO PI-R and NEO-FFI were updated in 2010 in a manual called the NEO Inventories for the NEO Personality Inventory-3, NEO Five-Factor Model 3, and NEO Personality Inventory-Revised. While the NEO PI-R is still being published, the NEO-PI-3 and NEO-FFI-3 feature updated normative data and new forms.
A list of the personality dimensions measured by the NEO PI-R, including facets, is as follows:
- Excitement Seeking
- Positive Emotion
- Openness to experience
The original version of the measurement, published in 1978, was the Neuroticism-Extroversion-Openness Inventory (NEO-I). This version only measured three of the Big Five personality traits. It was later revised in 1985 to include all five traits and renamed the NEO Personality Inventory (NEO PI). In this version, "NEO" was now considered part of the name of the test and was no longer an acronym. This naming convention continued with the third version, the NEO PI-R, published in 1990. The NEO-PI-3, an update to the NEO Inventory, was published in 2005.
A mnemonic device for the five primary factors is the acronym "OCEAN," or alternatively "CANOE".
In the 1970s, Costa and McCrae were researching how personality changed with age. Personality inventories were included in the batteries of assessments participants took in the Normative Aging Study. Costa and McCrae report that in looking at the competing factorally analyzed trait personality theories of the day, they noticed much more agreement at the level of the higher-order factors than at the lower order factors. Costa and McCrae report that they began by looking for the broad and agreed-upon traits of Neuroticism (N) and Extraversion (E), but factor analysis also led them to a third broad trait, Openness to Experience (O). The first version of the NEO only included those three factors, and was included in the Augmented Baltimore Longitudinal Study of Aging.
From this data, Costa and McCrae recognized two more factors: Agreeableness (A) and Conscientiousness (C). They then published the first manual for the NEO, which included all five factors in 1985. The assessment also included six facet sub-scales for the three original factors (N, E, & O). As research began to accumulate that the five factors were adequately broad to be useful, there were also calls for a more detailed view of personality. In 1992 Costa and McCrae published a Revised NEO manual which included six facets for each factor (30 in total).
Throughout the mid- to late-1990s, Costa and McCrae began to realize that some items on the NEO-PI-R were out-dated or too difficult to understand for participants. Research also began to show that the NEO-PI-R had the potential to be used with adolescents and children as young as 10. This possibility led Costa and McCrae to administer the NEO-PI-R to over 1,900 high school students in 2002. The sample yielded 48 "problem" items based on difficult comprehension of items and/or low corrected item total correlations (CITCs; i.e., the correlation between individual items and the rest of the test which essentially tells a researcher if the item belongs with the rest of the scale). Alternative items for the "problem" items were developed and administered to a new sample. Of the original 48 "problem" items, 37 were improved in terms of clarity and/or CITC. Therefore, Costa and McCrae published the latest version of the NEO Inventories, NEO-PI-3, in 2005 which included the revised 37 items.
Forms and administration
In the most recent publication, there are two forms for the NEO, one for self report (form S) and one for observer rating (form R). Both forms consist of 240 items (descriptions of behavior) answered on a five point scale, ranging from "strongly disagree" to "strongly agree". Finally, there is a 60-item assessment of domains only called the "NEO FFI." There are paper and computer versions of all forms available.
The manual reports that administration of the full version should take between 30 and 40 minutes. Costa and McCrae report that the assessment should not be evaluated if there are more than 40 items missing. They also state that despite the fact that the assessment is "balanced" to control for the effects of acquiescence and nay-saying, that if more than 150 responses, or less than 50 responses, are "agree" or "strongly agree," the results should be interpreted with caution.
Scores can be reported to most test takers on "Your NEO Summary," which provides a brief explanation of the assessment, and gives the participants’ domain levels and a strengths-based description of three levels (high, medium, and low) in each domain. For example, low N reads "Secure, hardy, and generally relaxed even under stressful conditions," whereas high N reads "Sensitive, emotional, and prone to experience feelings that are upsetting." For profile interpretation, facet and domain scores are reported in T Scores and are recorded visually as compared to the appropriate norm group, much like other measures of personality.
Reliability of the NEO
The internal consistency information of the NEO presented in the manual was derived from the full job performance sample (n = 1,539). The internal consistency of the NEO-PI-R was high, at: N = .92, E = .89, O = .87, A = .86, C = .90. The internal consistency of the facet scales ranged from .56–.81. The internal consistency of the NEO-PI-3 was consistent with that of the NEO-PI-R, ranging from α = .89–.93 for domains and α = .54–.83 for facets.
For the NEO FFI (the 60 item domain only version) the internal consistencies reported in the manual were: N = .79, E = .79, O = .80, A = .75, C = .83. In the literature, the NEO FFI seems to be used as a whole more often, with investigators using the NEO PI-R usually using the items from just the domains they are interested in. A recent article using the NEO FFI to study perfectionism had the internal consistencies at: N = .85, E = .80, O = .68, A = .75, C = .83.
The literature appears to support the internal consistencies listed in the manual, but more interestingly, the NEO has been translated and evaluated in many different languages and cultures. A translation of the NEO to be used in the Philippines has the internal consistency of the domain scores from .78–.90, with facet alphas having a median of .61. Observer-ratings NEO-PI-R data from 49 different cultures was used as criterion in a recent study which tested whether individuals’ perception of the "national character" of the culture accurately reflected the personality of the members of that culture (it did not).
Test retest reliability of the NEO PI-R is also good. The test retest reliability of an early version of the NEO after 3 months was: N = .87, E = .91, O = .86. The test retest reliability reported in the manual of the NEO PI-R over 6 years was: N = .83, E = .82, O = .83, A = .63, C = .79. Costa and McCrae point out that this not only shows good reliability of the domains, but also that they are stable over a long periods of time (past the age of 30), as the scores over 6 years are only marginally more different than the scores as measured a few months apart.
Other research has shown acceptable test-retest reliability. A 2001 study by Kurtz and Parrish on the short-term test-retest reliability yielded coefficients of α = .91–.93 for domains and α =.70–.91 for facets after a one-week interval. A 2006 study by Terracciano et al. on the long-term test-retest reliability yielded coefficients of α = .78–.85 for domains and α = .57–.82 for facets after a 10-year interval.
The psychometric properties of NEO-PI-R scales have been found to generalize across ages, cultures, and methods of measurement.
The effect of age on NEO PI-R
Although individual differences (rank-order) tend to be relatevely stable in adulthood, there are maturational changes in personality that are common to most people (mean-level changes). Most cross-sectional and longitudinal studies suggest that neuroticism, extraversion, and openness tend to decline, whereas agreeableness and conscientiousness tend increase during adulthood. A meta-analysis of 92 personality studies that used several different inventories (among them NEO PI-R) found that social dominance, conscientiousness, and emotional stability increased with age, especially in the age 20 to 40.
Validity of the NEO
Costa and McCrae report in the manual extensive information on the convergent and discriminate validity of the NEO.
- For the MBTI, Introversion is correlated with the NEO facet Warmth at −0.61, and with the NEO facet Gregariousness at −0.59. Intuition is correlated with the NEO facet Fantasy at 0.43 and with the NEO facet Aesthetics at 0.56. Feeling is correlated with the NEO facet Tender-mindedness at 0.39.
- For the Self-Directed Search (a personality inventory developed by John L. Holland for careers work), Artistic is correlated with the NEO facet Aesthetic at 0.56, Investigative is correlated with the NEO facet Ideas at 0.43, and Social is correlated with the NEO facet Tender-mindedness at 0.36.
In terms of criterion validity there have been the following recent studies. Conard, 2005, found that Conscientiousness significantly predicted the GPA of college students, over and above using SAT scores alone. Cano-Garcia and his two colleagues in 2005 correlated a Spanish version of the NEO to predictors of teacher burnout in Sevilla, Spain. Neuroticism was related to the "emotional exhaustion" factor of burnout at 0.44, and Agreeableness related to the "personal accomplishment" factor of burnout (which is negatively scored when predicting burnout) at 0.36. Wang, Jome, Haase, & Bruch, in 2006, found that in and minority students Extraversion was correlated to Career Decision Making Self-Efficacy (CDMSE) at 0.30, and that Neuroticism was strongly related to Career Commitment while controlling for CDMSE (r = .42). Finally, Korukonda reported in 2007 that Neuroticism was positively related to computer anxiety, while Openness and Agreeableness was negatively related.
Critiques of the NEO Inventories
Widiger provided a critical review of the NEO-PI-R for the 12th edition of the Mental Measurements Yearbook, a source that includes critiques for a vast number of psychological measures that are commonly used in the field. Widiger praised the NEO-PI-R for its development using a thorough factor analytic method but found issue with the lack of validity to control for social desirability. Widiger argued that test developers cannot assume participants will be honest, especially in settings where it benefits people to present themselves in a better light (e.g., forensic or personnel settings). Ben-Porath and Waller agreed with this argument and pointed out that the NEO Inventories would be improved with the addition of a control for dishonesty or social desirability.
Juni also provided a critical review of the NEO-PI-R for the 12th edition of the Mental Measurements Yearbook. Juni praised the NEO-PI-R for including both a self- and other-report, making it easier for clinicians to corroborate information that is collected from a self-report filled out by a client or participant. However, Juni heavily criticized the NEO-PI-R for its conceptualization using the Five Factor Model (FFM) of personality. Juni argued that the existence of the FFM was purely a phenomenological and atheoretical concept that only gained popularity due to the clout that the authors (McCrae and Costa) held in the psychological community.
NEO-FFI and TIPI: shortened versions of the NEO PI-R
A shortened version of NEO PI-R exists called the NEO Five-Factor Inventory (NEO-FFI) with 60 items and designed to take 10–15 rather than 45–60 minutes to administer. This test was revised in 2004.
Additionally, a brief measure of personality called the Ten Item Personality Inventory (TIPI) has been developed as a way to measure the Big Five personality traits in situations when time is limited. The scale is psychometrically inferior to larger, multiple-item scales; however, it does reach acceptable levels of convergence with more widely used Big Five measures, test-retest reliability, and patterns of predicted correlates, and thus may be useful in situations where very brief measures of personality are necessary.
Cross-cultural research on NEO PI-R
Cross-cultural stability of an instrument can be considered evidence of its validity. A huge amount of cross-cultural research has been carried out on the Five-Factor Model of Personality by utilizing the NEO-PI-R and the shorter version, the NEO-FFI. McCrae and Allik (2002) have presented a collection of selected invited papers from various researchers across the globe covering various issues in cross-cultural research on the FFM. This volume has also presented data about the FFM from several cultures. The robustness of the FFM has been proven across different cultures; for example, Chinese (McCrae, Costa, & Yik, 1996; Yik & Bond, 1993), Estonian & Finnish (Pulver, Allik, Pulkkinen, & Hämäläinen, 1995), Filipino and French (McCrae, Costa, del Pilar, Rolland, & Parker, 1998), India (Lodhi, Deo, & Belhekar, 2002), Portuguese (Lima, 2002), Russian (Martin, Oryol, Rukavishnikov, & Senin, 2000), South Korean (Piedmont & Chae, 1997), Turkish (Gülgöz, 2002), Vietnamese (Leininger, 2002), sub-Saharan cultures like Zimbabwe (Piedmont, Bain, McCrae, & Costa, 2002), etc. Angleitner and Ostendorf (2000) presented the evidence for robustness of the FFM in German speaking countries like Austria, former East and West Germany, and Switzerland. Rolland (2000), on the basis of the data from sixteen cultures, asserted that the neuroticism, openness, and conscientiousness dimensions are cross-culturally valid. Rolland further states that extraversion and agreeableness dimensions that are components of interpersonal circumplex are more sensitive to cultural context. McCrae, Costa, Lima, Simões, Ostendorf, Angleitner, Marušic, Bratko, Caprara, Barbaranelli, Chae, and Piedmont (1999) showed that the age differences in the five-factors of personality across the adult life span are parallel in samples from Germany, Italy, Portugal, Croatia and South Korea. McCrae (2001) examined the data from 26 cultures and showed that the age and gender differences resembled those found in the American sample. The intercultural factor analysis yielded a close approximation to the five-factor model and the factor scores were meaningfully related to other cultural level variables. McCrae (2002) extended earlier data to 36 cultures and the analysis of age and gender differences, the generalizability of culture profiles across gender and age groups, and culture level factor structure and correlates were replicated. McCrae, Terracciano et al. (2005) further reported data from 51 cultures and presented findings that supported the rough scalar equivalence of NEO-PI-R five factors and facets across cultures, suggesting that aggregate personality profiles provide insight into cultural differences.
Brain and genetics
The NEO PI-R has been used in numerous research studies that investigate a link between genotype and personality or brain and personality — as in the competing personality inventory of C. Robert Cloninger. Such studies are not always conclusive; for example, one study found some evidence for an association between NEO PI-R facets and polymorphism in the tyrosine hydroxylase gene, while another study reported that they could not confirm the finding.
In a classic study published in Science in 1996, a relationship between the serotonin transporter gene regulatory region (5-HTTLPR) and the neuroticism subscale was found. Individuals with a shorter allele version had higher neuroticism scores. The effect was significant for heterozygotes and even stronger for people homozygous for the allele. Although this is an important finding, this specific gene only contributes 4% of the overt variation in the neuroticism trait, and only 8% of the genetic variation. The authors conclude that "if other genes were hypothesized to contribute similar gene dosage effects to anxiety, approximately 10 to 15 genes might be predicted to be involved."
- B. Bell, C. L. Rose, & A. Damon (1972). "The normative aging study: An interdisciplinary and longitudinal study of health and aging". Aging & Human Development 3 (1): 5–17. doi:10.2190/GGVP-XLB5-PC3N-EF0G.
- McCrae, R. M., & John, O. P. (1992). "An introduction to the five-factor model and its applications" (PDF). Journal of Personality 60 (2): 175–215. doi:10.1111/j.1467-6494.1992.tb00970.x. PMID 1635039.
- Costa, P. T.; McCrae, R. R. (1976). "Age differences in personality structure: A cluster analytic approach". Journal of gerontology 31 (5): 564–570. doi:10.1093/geronj/31.5.564. PMID 950450.
- Shock, N. W., Greulich, R. C., Andres, R., Arenberg, D., Costa, P. T., Jr., Lakatta, E. G., et al. (1984). Normal human aging: The Baltimore longitudinal study of aging. Bethesda, MD: National Institutes of Health.
- Costa, P. T., Jr., & McCrae, R. R. (1985). The NEO personality inventory manual. Odessa, FL: Psychological Assessment Resources.
- Briggs, S. R. (1989). The optimal level of measurement for personality constructs. In D. M. Buss, & N. Cantor (Eds.), Personality psychology: Recent trends and emerging directions (pp. 246–260). New York: Springer-Verlag.
- Costa, P. T., Jr., & McCrae, R. R. (1992). NEO PI-R professional manual. Odessa, FL: Psychological Assessment Resources, Inc.
- McCrae R. R., Costa P. T., Martin T. A. (2005). "The NEO-PI-3: A more readable revised NEO personality inventory". Journal of Personality Assessment 84 (3): 261–270.
- McCrae, R. R., & Costa, P. T., Jr., (2010). NEO Inventories: Professional manual. Lutz, FL: Psychological Assessment Resources, Inc.
- Sherry, S. B.; Hewitt, P. L.; Flett, G. L.; Lee-Baggley, D. L.; Hall, P. A. (2007). "Trait perfectionism and perfectionistic self-presentation in personality pathology". Personality and Individual Differences 42 (3): 477–490. doi:10.1016/j.paid.2006.07.026.
- Church, A. T.; Katigbak, M. S. (2002). "Indigenization of psychology in the Philippines". International Journal of Psychology 37 (3): 129–148. doi:10.1080/00207590143000315.
- Katigbak, M. S.; Church, A. T.; Guanzon-Lapeña, M. A.; Carlota, A. J.; Pilar, G. H. (2002). "Are indigenous personality dimensions culture specific? Philippine inventories and the five-factor model". Journal of personality and social psychology 82 (1): 89–101. doi:10.1037/0022-35188.8.131.52. PMID 11811638.
- Terracciano, A.; Abdel-Khalek, A. M.; Ádám, N.; Adamovová, L.; Ahn, CK; Ahn, HN; Alansari, BM; Alcalay, L et al. (2005). "National Character Does Not Reflect Mean Personality Trait Levels in 49 Cultures". Science 310 (5745): 96–100. doi:10.1126/science.1117199. PMC 2775052. PMID 16210536.
- McCrae, R. R.; Costa, P. T. (1983). "Joint factors in self-reports and ratings: Neuroticism, extraversion and openness to experience". Personality and Individual Differences 4 (3): 245–255. doi:10.1016/0191-8869(83)90146-0.
- Kurtz J. E., Parrish C. L. (2001). "Semantic response consistency and protocol validity in structured personality assessment: The case of the NEO PI-R.". Journal of Personality Assessment 76: 315–332.
- Terracciano A., Costa P. T. Jr., McCrae R. R. (2006). "Personality plasticity after age 30". Personality and Social Psychology Bulletin 32: 999–1009.
- McCrae R. R., Kurtz J. E., Yamagata S., Terracciano A. (2011). "Internal consistency, retest reliability, and their implications for personality scale validity". Pers Soc Psychol Rev. PMID 20435807.
- Paul T. Costa, Jr. & Robert R. McCrae (2006). "Age Changes in Personality and Their Origins: Comment on Roberts, Walton, and Viechtbauer (2006)" (PDF). Psychological Bulletin 132 (1): 26–28. doi:10.1037/0033-2909.132.1.26. PMID 16435955.
- Brent W. Roberts, Kate E. Walton, Wolfgang Viechtbauer (January 2006). "Patterns of Mean-Level Change in Personality Traits Across the Life Course: A Meta-Analysis of Longitudinal Studies" (PDF). Psychological Bulletin 132 (1): 1–25. doi:10.1037/0033-2909.132.1.1. PMID 16435954.
- Conard, M. A. (2006). "Aptitude is not enough: How personality and behavior predict academic performance". Journal of Research in Personality 40 (3): 339–346. doi:10.1016/j.jrp.2004.10.003.
- Francisco Javier Cano-García, Eva Maria Padilla-Muñoz & Miguel Ángel Carrasco-Ortiz (2005). "Personality and contextual variables in teacher burnout" (PDF). Personality and Individual Differences 38 (4): 929–940. doi:10.1016/j.paid.2004.06.018.
- Wang, N.; Jome, L. M.; Haase, R. F.; Bruch, M. A. (2006). "The role of personality and career decision-making self-efficacy in the career choice commitment of college students". Journal of Career Assessment 14 (3): 312–332. doi:10.1177/1069072706286474.
- Appa Rao Korukonda (2007). "Differences that do matter: A dialectic analysis of individual characteristics and personality dimensions contributing to computer anxiety". Computers in Human Behavior 23 (4): 1921–1942. doi:10.1016/j.chb.2006.02.003.
- Widiger, T. A. (1992). Review of the Revised NEO Personality Inventory. In J. C. Conoley & J. C. Impara (Eds.), The twelfth mental measurements. Lincoln, NE: Buros Institute of Mental Measurements. Retrieved from Mental Measurements Yearbook database.
- Ben-Porath Y. S., Waller N. G. (1992). "Five big issues in clinical personality assessment: A rejoinder to Costa and McCrae". Psychological Assessment 4 (1): 23–25.
- Juni, S. (1995). Review of the Revised NEO Personality Inventory. In J. C. Conoley & J. C. Impara (Eds.), The twelfth mental measurements. Lincoln, NE: Buros Institute of Mental Measurements. Retrieved from Mental Measurements Yearbook database.
- Mccrae, R. R., & Costa, P. T. (February 2004). "A contemplated revision of the NEO Five-Factor Inventory". Personality and Individual Differences 36 (3): 587–596. doi:10.1016/S0191-8869(03)00118-1.
- Gosling, S. D., Rentfrow, P. J., & Swann, W. B. (June 2003). "A very brief measure of the Big-Five personality domains". Journal of Research in Personality 37 (6): 504–528. doi:10.1016/S0092-6566(03)00046-1.
- McCrae, R. R. & Allik, J. (Eds.) (2002), The Five-Factor model of personality across cultures. N.Y.: Kluwer Academic Publisher.
- McCrae, R. R., Costa, P. T. Jr., & Yik, M. S. M. (1996). Universal aspects of Chinese personality structure. In M. H. Bond (Ed.), The handbook of Chinese psychology. Hong Kong: Oxford University Press.
- Yik, M. S. M.; Bond, M. H. (1993). "Exploring the dimensions of Chinese person perception with indigenous and imported constructs: Creating a culturally balanced scale". International Journal of Psychology 28: 75–95. doi:10.1080/00207599308246919.
- Pulver, A.; Allik, J.; Pulkkinen, L.; Hämäläinen, M. (1995). "The Big Five Personality Inventory in two non-Indo-European languages". European Journal of Personality 9 (2): 109–124. doi:10.1002/per.2410090205.
- McCrae, R. R.; Costa, P. T. Jr.; Pilar, G. H.; Rolland, J. P.; Parker, W. D. (1998). "Cross-cultural assessment of the five-factor model: The revised NEO Personality Inventory". Journal of Cross-Cultural Psychology 29: 171–188. doi:10.1177/0022022198291009.
- Lodhi, P. H., Deo, S., & Belhekar, V. M. (2002). The Five-Factor model of personality in Indian context: measurement and correlates. In R. R. McCrae & J. Allik (Eds.), The Five-Factor model of personality across cultures (pp. 227–248). N.Y.: Kluwer Academic Publisher.
- Lima, M. P. (2002). Personality and culture: The Portuguese case. In R. R. McCrae & J. Allik (Eds.), The Five-Factor model of personality across cultures (pp. 249–260). N.Y.: Kluwer Academic Publisher.
- Martin, T. A., Oryol, V. E., Rukavishnikov, A. A., & Senin, I. G. (2000, July). Applications of the Russian NEO-PI-R. Paper presented at the XXVIIth International Congress of Psychology, Stockholm, Sweden.
- Piedmont, R. L.; Chae, J. H. (1997). "Cross-cultural generalizability of the five-factor model of personality: Development and validation of the NEO-PI-R for Koreans". Journal of Cross-Cultural Psychology 28 (2): 131–155. doi:10.1177/0022022197282001.
- Gülgöz, (2002). Five-Factor Model and NEO-PI-R in Turkey. In R. R. McCrae & J. Allik (Eds.), The Five-Factor model of personality across cultures (pp. 175–196). N.Y.: Kluwer Academic Publisher.
- Leininger, A. (2002). Vietnamese American personality and acculturation: An exploration between personality traits and cultural goals. In R. R. McCrae & J. Allik (Eds.), The Five-Factor model of personality across cultures (pp. 197–227). N.Y.: Kluwer Academic Publisher.
- Piedmont, R. L., Bain, E., McCrae, R. R., & Costa, P. T. Jr. (2002). The applicability of Five Factor Model in sub Saharan culture: The NEO-PI-R in Shona. In R. R. McCrae & J. Allik (Eds.), The Five-Factor model of personality across cultures (pp. 155–174). N.Y.: Kluwer Academic Publisher.
- Angleitner, A., & Ostendorf, F. (2000, July). The FFM: A comparison of German speaking countries (Austria, Former East and West Germany, and Switzerland). Handout of the paper presented at the XXVIIth International Congress of Psychology, Stockholm, Sweden.
- Rolland, J. P. (2000, July). Cross-cultural validity of the five factor model of personality. Paper presented at the XXVIIth International Congress of Psychology, Stockholm, Sweden.
- McCrae, R. R.; Costa, P. T. Jr.; Lima, M. P.; Simões, A.; Ostendorf, F.; Angleitner, A.; Marušic, I.; Bratko, D. et al. (1999). "Age differences in personality across the adult life span: Parallels in five cultures". Developmental Psychology 35 (2): 466–477. doi:10.1037/0012-16184.108.40.2066. PMID 10082017.
- McCrae, R. R. (2001). "Trait psychology and culture: exploring intercultural comparisons". Journal of Personality 69 (6): 819–846. doi:10.1111/1467-6494.696166. PMID 11767820.
- McCrae, R. R. (2002). NEO-PI-R data from 36 cultures: Further Intercultural comparisons. In R. R. McCrae & J. Alik. (Eds.), The Five-Factor model of personality across cultures (pp. 105–125). New York: Kluwer Academic Publisher.
- McCrae, R. R.; Terracciano, A. (2005). "Personality Profiles of Cultures: Aggregate Personality Traits". Journal of Personality and Social Psychology 89 (3): 407–425. doi:10.1037/0022-35220.127.116.117. PMID 16248722.
- Persson M.-L. Wasserman D.; G. Jonsson E.; Bergman H.; Terenius L.; Gyllander A.; Neiman J.; Geijer T. (July 2000). "Search for the influence of the tyrosine hydroxylase (TCAT)n repeat polymorphism on personality traits". Psychiatry Research 95 (1): 1–8. doi:10.1016/S0165-1781(00)00160-8.
- Mamoru Tochigi, Takeshi Otowa, Hiroyuki Hibino, Chieko Kato, Toshiyuki Otani, Tadashi Umekage, Takeshi Utsumi, Nobumasa Kato, Tsukasa Sasaki (March 2006). "Combined analysis of association between personality traits and three functional polymorphisms in the tyrosine hydroxylase, monoamine oxidase A and catechol-O-meethyltransferase genes". Neuroscience Research 54 (3): 180–185. doi:10.1016/j.neures.2005.11.003. PMID 16360899.
- Lesch, K. P., Bengel, D., Heils, A., Sabol, S., Greenberg, B., Petri, S., Benjamin, C., Hamer, D. & Murphy, D. (1996). "Association of Anxiety-Related Traits with a Polymorphism in the Serotonin Transporter Gene Regulatory Region". Science 274 (5292): 1527–1530. doi:10.1126/science.274.5292.1527. PMID 8929413.