supporters_v12Most people have heard of Big-Five personality Model, (Acronyms to remember OCEAN) which is often used in social psychology studies. Humans, including most animals, expressed many unique characteristics, but grouped into these big 5 categories. The traits are expressed on the continuum scale. But below are some examples and what high scores on each trait would mean (if I remember right I study the model briefly in Intro Psych and Animal Cognition, but I want to add in here because it is related to the article I read.)

Openness – Being curious, and open-minded, etc.

Conscientiousness- Oriented, dedicated, and organized, etc.

Extraversion- Sociable, outgoing, etc.

Agreeableness- trusting, kind, tolerant, etc.

Neuroticism- anxious, irritable and watchful, etc.

One thing to note is that scoring high or low on these traits do not meant “good” or “bad.” People are different; some showed higher score on one trait than the other, both within themselves and in comparison to others.

Buss (2009) proposed evolutionary toolkits that could essentially be used as a framework for social psychology studies that investigate personalities in humans, 2). Individual differences are driving factors in human psychology, behaviors and cognition.

With regards to point 1, psychology major students and researchers have proposed various theoretical framework and explaining many observed phenomenon and results. However, students, including me, are very aware that most psychology theories are arbitrary and distinct from one another, which makes it difficult to fully connect all different theories in a coherent and systematic way.

Anyway here is what Buss (2009) proposed and explained how using evolutionary psychology framework could help and explain different phenomenon, including personality and individual differences.

The article began with why individual differences in personalities are important for empirical and theoretical reasons in researches.

  1. Well documented for the existence in many studies.
  2. Have heritable component.
  3. Results in evolutionarily important consequences (for e.g., survival, mating, parenting, social skills, etc.)
  4. Within same sex, differences in personalities exist. The differences affect behaviors profoundly.

Tool kits discussed in the study:

  1. Life history theory– the key idea is that individuals allocate the energy differently based on their environmental, social and physiological context. The energy is distributed towards growth/development or mating or parenting, etc. However, energy is limited and finite; organisms invested differentially in one or the other. The bottom line is that personalities are based on the trade-off strategies individuals employ in life.
  1. Costly Signaling Theory– the social signals are costly but honest. They cannot be fake signals. For example, if you have Lamborghini, your wealth cannot be a fake one (even though you could borrow it from a friend or a company). Your signals imply that you are truly rich.Another classic example is peacock’s beauty feathers. Those are true signals to peahen in a sense that these peacocks are healthy (physically attractive) and can avoid predations despite having such troublesome tails. Individual differences in personalities can be partly explained by signaling theories. For example, if you have resources, you are more likely to be have generous personalities, and are both extraverted and social, throwing parties, giving gifts and paying for the groups, etc.
  1. Biological framework is also mentioned.

Balancing Selection

  • “Environmental Heterogeneity in Fitness Optima “ – natural selection produces different heritable individual differences. One of the example mentioned was 7R allele of DRD4 gene, associated with extraversion and openness trait. Those who migrate to different locations have longer- allele DRD4 genes. Some studies also showed that those who live in small islands for 20 generations or more showed lower scores on extraversion and openness to experience. In this example, some environments favor individuals with risk-taking traits and others favor individuals with more of a cautious approach to experiences. Artificial selections of dogs whose common ancestors are more wolf-like and wild, also showed traits that are human-likable after many generations.
  • Frequency dependent selection– the expression of a particular trait and whether it is being selected or not dependent relatively on how others in the society or the niche behave. A classic example is a dove and hawk. Imagine doves and hawk compete for limited food resources, apples. When the dove compete with hawk, hawk wins because it fights off the dove. More hawks would spread and more doves would die off as doves could not get food. As the frequency of hawk number proliferates, more hawks would compete with other hawks than doves (more hawks in the population, hawk would see another hawk more often). They would fight each other off and those, fewer numbers of doves in the population, get apples without injuries. Then doves would proliferate again and more hawks go extinct in the population.

For personality trait example, think about the psychopathy trait (as a cheating strategy) in the population. How many people would express? The trend is that Up and down, up and down, up and down. The originally adaptive trait becomes less adaptive as the individual with other trait becomes more adaptive.

  1. Mutation Load: Every human carries mutations, but some are more fatal than the others. Buss (2009) proposed that mutations, which have effects on phenotypes and personalities such as emotional unstability, disagreeableness, could in turn result in social selection. People would be differentially attracted to individuals with those traits, caused by mutation. Buss mentioned and cited this statement in the paper: Mutation load thus can create relationship load.

Again the central idea is that the environmental context and genetic components shape individual differences. By using these theoretical tool kits proposed in the article, future psychological studies would have a coherent framework in explaining observed patterns and individual differences and advance scientific understanding in a systematic, rather than random, approach.


My summary is not complete at all. Many of the important implications and clarifications were not mentioned in my writing that were described and elaborated the original article. My writings are just personal inspirations, perspectives and public communication. You should click the article below and read it fully, if you desire.

Tonight I was planning to do the reading and writing 3 (This is the third article I am exploring) on the suggested reading list. I couldn’t find this special issue article online. But I think I found a similar topics by Buss in 2009, and it’s awesome, informative, and updated.

Buss, D. M. (2009). How can evolutionary psychology successfully explain personality and individual differences? Perspectives on Psychological Science, 4, 359-366.

But this is the one on the suggested reading list and I just add in here so I can keep track of it.

Buss, D.M. (Ed.)(1990). Biological foundations of personality: Evolution, behavioral genetics, and psychophysiology. Journal of Personality. [special issue].



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