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Andrew Clapper

The University of North Carolina at Chapel Hill

February 19, 2007

Psych 270 - 001



The study of personality and its relationship with health has regained popularity lately, and the relatively new field of evolutionary psychology may offer an explanation for the association between socially desirable personality traits and good health.  Because primates tend to have a natural limit on the size of groups they can comprehend, personality may act as a form of selection in the evolution of humans.  I therefore propose that socially desirable personality traits will lead to better health. 




The human neocortex may impose a limit on the number of people it allows us to consider part of our group (Dunbar, 1992).  If this is true, when the number of friends we have exceeds this limit, we will be forced to choose who we keep as members of our group, and who is rejected.  Therefore, inclusion and ostracism are important selection factors on human evolution, because being rejected by your group will increase the likelihood that you will not pass on your genes (Dawkins, 1989).  It then follows that being included and even favored by your group will increase the likelihood that you will have offspring (Starr, 2006).  It has been shown that people that score high in extraversion, agreeableness, conscientiousness, emotional stability, and openness tend to be more socially successful, for various reasons (Larsen & Buss, 2008).  Because high scores on the aforementioned personality traits will lead to social success, I propose that they will be strongly associated with overall health, and thus will demonstrate a negative association with the least healthy people.  I also submit that high scores on the Five Factor personality model will accurately predict academic performance as demonstrated by grade point average.  Smith (2006) found evidence to support these claims, although the measurement of reaction time appeared to explain the relationship between low IQ and death (Dreary & Der, 2005). 




The participants included 220 subjects and approximately 13 administrators.  Students enrolled in the Laboratory Research in Psychology class for the spring 2007 semester at the University of North Carolina at Chapel Hill were subjects.  The administrators were teaching assistants for each section of the class, plus the lecturer and coordinating instructor.  The subjects reported to room 110 of Davie Hall at the University of North Carolina at Chapel Hill to participate in the study during their regularly scheduled class time.  Each subject sat in front of one of the standard computers for the room and turned on the monitor.  Then each subject logged in to his or her computer according to the particular class section and password for his or her section.  Next, he or she double clicked the BCR icon on the desktop display to activate the BCR program.  Each subject then went into the available studies listed in the software and selected the file for the personality and health study.  The subjects followed prompts that appeared on the computer screens that gave directions and asked specific questions.

The first 50 items of the study were questions taken from the International Personality Item Pool.  They were used to measure the five personality factors.  The names of the factors are Intellect, Emotional Stability, Conscientiousness, Extraversion, and Agreeableness.  Each factor was evaluated according to the average response to ten questions about that factor. 

The next 28 items of the study were reaction time tasks, which were recorded as geometric mean reaction times.  They were followed by 28 items of the choice reaction time task.  The data consist of geometric mean reaction times and the geometric mean reaction times for correct responses. 

The third data set evaluated health behaviors according to the inventory proposed by Vickers, Conway, & Hervig (1990).  The data consist of the average response for the factors of Wellness Maintenance and Enhancement, Accident Control, Traffic Risk, and Substance Risk.  The last data set consisted of five questions about current health status and one question about the subject's current GPA.  The health status questions evaluated Days Missed Due to Illness, Other Days of Illness, Susceptibility to Minor Illness, Susceptibility to Major Illness, and Time to Recover.  The final question requested the subject's current grade point average. 

The study results were saved on the psych 270 networked hard drive, and later they were compiled by the coordinating instructor into one file for the SPSS statistics program.  I combined the measurements of Days Missed Due to Illness and Other Days of Illness in order to determine the total days unwell.  I also combined Susceptibility to Minor Illness and Susceptibility to Major Illness to find the susceptibility to any illness. 


The average overall score on the Five Factor Personality Model was positively correlated with Grade Point Average (r = .08, p = .26).  Average overall score on the Five Factor Personality Model and the total days unwell were negatively correlated (r = -.19, p < .05).  Average overall score on the Five Factor Personality Model and the susceptibility to any illness were also negatively correlated (r = -.23, p < .05).




            I hypothesized that the average overall score on the Five Factor Personality Model will be strongly associated with overall health.    I also proposed that the overall score on the Five Factor Personality Model would be associated with Grade Point Average.  The data gathered from the study appears to support my hypothesis, although the association between overall score on the Five Factor Personality Model and Grade Point Average is not very significant.  It is possible that social inclusiveness may play a part in the relationship between personality and health.  In order to evaluate the relationship between inclusiveness, personality, and health, an objective and measurable definition of inclusiveness should be found in order to be included in the study.  Also, the study can be improved by using different sampling methods.  For example, a more random sample could be obtained by using an automatic dialing computer with data from a local phone book to ask individuals to take part in the study.  It may be the case that the study needs larger samples in order to get normal sized distribution of data.  Average number of hours of sleep per night may help explain both higher average scores on reaction tests and long term health, and it therefore also deserves investigation. 




Dawkins, R.  (1989) The Selfish Gene.  30th anniversary edition, Oxford University Press, New York, NY, 1-45.


Deary, I. J. & Der, G. (2005). Reaction time explains IQ's association with death. Psychological Science, 16, 64-69.


Dunbar, R.I.M. (1992) Neocortex size as a constraint on group size in primates, Journal of Human Evolution 22: 469-493.  


International Personality Item Pool: A Scientific Collaboratory for the Development of Advanced Measures of Personality Traits and Other Individual Differences ( Internet Web Site.


Larsen, R & Buss, D.  (2008) Personality Psychology.  Third edition, McGraw Hill, New York, NY, 86-91, 275-276.


Smith, T. W. (2006). Personality as risk and resilience in physical health. Current Directions in Psychological Science, 15, 227-231.


Starr, Cecie.  (2006) Biology: Concepts and Applications.  Sixth Edition, Thomson Brooks/Cole, Belmont, CA, 238-257, 780-794. 


Vickers, R. R., Jr., Conway, T. L., & Hervig, L. K. (1990). Demonstration of replicable dimensions of health behaviors. Preventive Medicine, 19, 377-401.

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