Friday, December 27, 2013

Life History Strategy and the Allure of the Dark Side: Evidence against a General Factor of Personality
In a previous post, I discussed evidence for and against a general factor of personality (GFP). Existing theories of personality organise personality traits in a hierarchical structure, in which a small number of broad factors, say five or six, subsume a vast number of narrower traits. Some psychologists have proposed a higher order general factor that combines all the broad traits into one super-factor composed of all the socially desirable features of personality. According to one theory, the general factor of personality represents an evolved “slow” life history strategy associated with long-term mating as opposed to a "fast" strategy associated with short-term mating. However, a recent study suggests that both slow and fast life history strategies each combine mixtures of desirable and undesirable traits. The findings of this study might help explain not only why so many people have “dark personalities” embodying socially undesirable traits, but why these traits can actually attractive. The so-called general factor of personality might represent an imagined ideal that few people embody rather than a single underlying dimension of human personality variation.   

The Dark Side has a strange allure for many people

Currently, the most widely accepted model of personality traits model is the Big Five, which consists of neuroticism, extraversion, agreeableness, conscientiousness, and openness to experience, all of which are considered to be separate and distinct from each other. A more recent model which has become increasingly popular, the HEXACO, adds a sixth factor of honesty-humility to the Big Five.[1] Although they disagree about the exact number, both of these models agree that the top of the personality hierarchy consists of multiple and distinct factors. However, some psychologists, have argued that these broad factors are not actually independent and that there is higher order super-factor atop the personality hierarchy that combines all of them into one (Musek, 2007). For example, Rushton and Irwin (2011) argued that this general factor is a dimension of “good personality” as opposed to a “difficult personality”, with desirable traits manifested at one end, e.g. someone who is friendly, cooperative, relaxed, reliable, and clever compared to someone who does not get along with others, and is selfish, manipulative, irritable and dense. Studies on the GFP have found that it is positively correlated with subjective well-being, self-esteem, trait emotional intelligence, and even general intelligence apparently. Perhaps, this combination of traits should be called the “best” personality rather than merely “good”?  

Rushton and Irwing proposed that this general factor of personality reflects a single broad dimension that has been selected for in human evolution they call the K-factor. This K-factor supposedly applies to a whole range of human characteristics that are said to have co-evolved, including altruism, intelligence, attachment styles, growth, longevity, sexuality, and fecundity and which “form a coherent whole” (Rushton & Irwing, 2011). The idea of a K-factor is the basis for what is called life history theory which looks at individual differences in human reproductive strategies. According to this theory, people with a “slow” life history strategy (characterised by a preference for long-term mating) exhibit a high K-factor, whereas people with a “fast” life history strategy (characterised by a preference for short-term mating and promiscuity) exhibit a low K-factor.

According to a number of studies, slow life history strategy is associated with better mental and physical health and subjective well-being and with greater relationship satisfaction. On the other, fast life history strategy has been linked with socially undesirable characteristics, such as criminality and antisocial behaviour including sexual coercion (Sherman, Figueredo, & Funder, 2013). If this is true, then it would seem that from an evolutionary standpoint the slow strategy is desirable in every way, while the fast strategy is completely undesirable. This is problematic because if one strategy is “better” in every way, the alternative strategy should have died out long ago for failure to compete. However, the fact that so many people still utilise a fast strategy suggests that it may be adaptive under some circumstances.

In spite of the alleged global adaptive superiority of the slow strategy, there is evidence that this strategy involves costs as well as benefits and conversely that the fast strategy enjoys its own advantages, in spite of its drawbacks. This is because socially desirable behaviours are generally those that are good for other people but not necessarily oneself, while socially undesirable behaviours inflict costs on other people rather than on the self. Social norms then tend to favour behaviour that is closer to the slow end of the continuum. Hence, even though the slow strategy is desirable from the viewpoint of society, it is not always in the interests of the individual. For example, being honest and altruistic benefits society but may be costly to the individual. Conversely, lying and cheating are costly to society but may benefit the individual, at least in the short term. The slow strategy might be smarter in the long-term, but generally requires individuals to make sacrifices for the good of others.

This might be taking the slow strategy a bit too far

Recently Sherman et al. (2013) tested the idea that the slow and fast strategies respectively combine both adaptive and maladaptive traits. Previous studies on life history strategy that found that the slow strategy was associated with just about every benefit one could want have been based on self-report measures of behaviour and personality. Similarly, most studies that have been used to validate a GFP have relied on self-report as well. A problem with self-report measures is that people’s responses may reflect evaluative biases. Because the slow strategy is so socially normative, people’s responses may be biased towards reporting what is considered “normal”. This could explain to some extent why the slow strategy is supposed to be associated with physical and mental health, considering that the latter are also normative. Sherman et al.’s research therefore used studies based on direct observations of behaviour as well as participants’ reports of their behaviour in the last 24 hours to overcome some of the limitations of self-report measures. Trained raters were asked to assess how closely individual participants matched a template for either a slow or fast life history strategy based on assessments of their behavior. The template for the slow pattern included qualities such as responsible, warm, compassionate and capable of close relationships. The fast template included qualities of unpredictable, deceitful, manipulative, and non-conforming. The resulting pattern that emerged was that those who more closely matched the slow template were described as kind, considerate, and hard working, yet also socially awkward, insecure, shy, lacking expressiveness and emotionally over-controlled. Those who more closely matched the fast template were described as unpredictable, hostile, moody, manipulative and impulsive, yet also talkative, socially skilled, dominant, assertive charming and interesting.

What these results suggest is that both the slow and fast strategies have their respective strengths and weaknesses. This is consistent with the idea that each one may be adaptive under some circumstances, yet maladaptive under others. On the other hand, the results appear to contradict the notion that one strategy is globally better than the other. Furthermore, in terms of personality traits expressed, neither strategy appears to fit in with the notion of a general factor of personality which combines all socially desirable traits in a uniform way. Participants who demonstrated a slow strategy could be described as agreeable, conscientious, and honest, yet also introverted and to a certain extent neurotic. On the other hand, those who demonstrated a fast strategy showed the opposite pattern of disagreeableness, dishonesty, and low conscientiousness, but were also more extraverted and emotionally stable. The fast life history strategy also seems consistent with a group of socially undesirable traits known as the “dark triad” of psychopathy, Machiavellianism, and narcissism. One study found that people who are high in “dark triad” traits tend to manifest a pattern of being selfish, disagreeable and low in conscientiousness, yet also extraverted, confident and socially dominant (Jonason, Li, & Teicher, 2010). This particular pattern of traits may allow people to successfully exploit others for selfish reasons and yet escape social punishment due to their social skills and charms. The authors of this paper compared this personality configuration to James Bond. Another real life example is the Italian adventurer Casanova. This fascinating fellow, notorious for his many love affairs, was noted as a sparkling conversationalist who stated that the chief business of his life was cultivating sensory pleasure. He also admitted to swindling people who he managed to convince that he had magical powers.  

Why do bad boys have all the fun?

Researchers have argued that “dark triad” traits may have evolved to facilitate short-term mating. Evidence for this comes from a study which found that women rated men with dark triad traits as having more attractive personalities than men who were low in these traits (Carter, Campbell, & Muncer). Another study found that men who were high in psychopathic traits (one of the components of the dark triad) were rated by female observers as being more physically attractive than men who were low in these traits (Visser, Pozzebon, Bogaert, & Ashton, 2010). Perhaps, these findings might help to explain why so many people are so fascinated by “dark” characters both from fiction and real life. Casanova for example was not the most moral person but he knew how to live in style!

What these findings suggest that the traits associated with the slow life history strategy represent a “good” personality in the traditional sense of being unselfish and of respecting society’s rules of good behaviour but not in a global sense of being generally better implied by JP Rushton. However, people who follow a slow strategy seem to be less socially skilled and may not experience as much immediate pleasure as their more selfish fast strategy counterparts, who are more focused on having a good time, often at the expense of other people. One of the differences that emerged between the two strategies, is that people with the slow style appear over-controlled and lacking expressiveness, whereas those with the fast style are more lively and impulsive. This suggests that one of the key differences may be in how much people inhibit expression of their impulses. Some people may be overly concerned with not doing anything that might give offense to others, whereas other people are more focused on expressing themselves, being less anxious about what other people might think.

The findings from Sherman et al. suggest that neither a fast nor a slow life history strategy is associated with a complete set of desirable traits that a general factor of personality would entail. In my previous post, I suggested that a general factor of personality might not represent a unitary dimension underlying all personality traits, but instead a particular cluster of separate traits combined in a way that maximises a person’s well-being. Perhaps this entails a personality type that can strike a balance between the conflicting demands of expressing the self on the one hand and exercising the self-control needed to comply with social expectations and rules for getting along with other people.


[1] Another minor difference from the Big Five is that in the HEXACO model neuroticism is replaced with “emotionality”. 
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This article also appears on Psychology Today on my blog Unique - Like Everybody Else.

© Scott McGreal. Please do not reproduce without permission. Brief excerpts may be quoted as long as a link to the original article is provided. Any version of this article appearing on sites other than Eye on Psych or my blog at Psychology Today has been ripped off without my consent.

Further reading: 
What is an Intelligent Personality? - discusses the relationship between personality and various concepts of intelligence, particularly in regard to claims that a general factor of personality is correlated with general intelligence. 

Image Credits

Darth Vader by Dualspades at DeviantArt

Sacrifice poster created at using image from Flickr

Sean Connery as James Bond from Wikia


Carter, G. L., Campbell, A. C., & Muncer, S. The Dark Triad personality: Attractiveness to women. Personality and Individual Differences(0). doi:
Jonason, P. K., Li, N. P., & Teicher, E. A. (2010). Who is James Bond? The Dark Triad as an Agentic Social Style. Individual Differences Research, 8(2), 111-120.
Musek, J. (2007). A general factor of personality: Evidence for the Big One in the five-factor model. Journal of Research in Personality, 41(6), 1213-1233.
Rushton, J. P., & Irwing, P. (2011). The General Factor of Personality: Normal and Abnormal. In T. Chamorro-Premuzic, S. v. Stumm & A. Furnham (Eds.), The Wiley-Blackwell Handbook of Individual Differences ( First ed.): Blackwell Publishing Ltd.
Sherman RA, Figueredo AJ, & Funder DC (2013). The behavioral correlates of overall and distinctive life history strategy. Journal of personality and social psychology, 105 (5), 873-88 PMID: 23915038
Visser, B. A., Pozzebon, J. A., Bogaert, A. F., & Ashton, M. C. (2010). Psychopathy, sexual behavior, and esteem: It’s different for girls. Personality and Individual Differences, 48(7), 833-838. doi:

Thursday, December 5, 2013

Atheism, Openness to Experience and Dogmatism: A Puzzling Relationship
Dogmatism has usually been related in research to low levels of openness to experience, a personality dimension associated with interest in new and non-traditional ideas. Dogmatism has mostly been studied in relation to religious beliefs but some recent research has looked at dogmatism among non-religious people. One surprising finding was that among self-identified atheists, higher levels of openness to experience were actually associated with greater dogmatism, contrary to the usual pattern. This suggests that the personality dimension openness to experience might not be a marker of open-mindedness as such but more of a preference for unconventional and complex ideas. Perhaps there needs to be a distinction made between humble versus arrogant forms of openness to experience.

Some people do not respond well to disagreement. 

Dogmatism refers to rigid certainty about the correctness of one’s views, along with refusal to consider alternatives and a conviction that any intelligent person who has thought things through would agree with one’s own opinions. The opposite of this is the willingness to consider that one’s own views are not the only reasonable way of looking at things and that it is possible that one could be proven wrong. This does not mean that a non-dogmatic person must be wishy-washy, only that they are willing to consider that other people might have good reasons for believing what they do and that it is alright for intelligent people to disagree.

Dogmatism and openness to experience: polar opposites?
People can be dogmatic about any subject, e.g. political and lifestyle views, but dogmatism has mostly been studied among religious believers. Religious beliefs in general tend to be held more dogmatically than other kinds of beliefs, and people with fundamentalist beliefs are generally the most dogmatic of all, virtually by definition. Not surprisingly, religious fundamentalism tends to be associated with low openness to experience (Saroglou, 2010). Openness to experience is a broad and somewhat heterogeneous dimension of personality that refers to the breadth and complexity of a person’s mental life (McCrae & Sutin, 2009). People low in openness to experience tend to prefer rather black-and-white views of the world that are not too complex or intellectually demanding. In contrast, people high in openness prefer more nuanced ways of looking at things, and feel comfortable with complex ideas. Openness to experience encompasses a diverse number of narrower traits, and one of these traits, openness to values, refers to readiness to “re-examine social, political and religious values” and has even been considered to represent “the opposite of dogmatism” (Costa & McCrae, 1992, cited in) (Smith, Johnson, & Hathaway, 2009).

Some atheists can’t stand disagreement
While it seems generally true that people high in openness to experience, particularly in the values facet, are least likely to be dogmatic, there may be some notable exceptions. Re-examining traditional values, for example, does not necessarily guarantee that one will not become tolerant of differences in opinion. Some people might reject traditional values and then become dogmatic adherents of non-traditional ones. One example that I believe fits this description is an online movement called “Atheism Plus”. This movement, which emerged just over a year ago in the atheist blogging community, bills itself as a “positive” approach that aims to combine atheism/scepticism with a variety of left-liberal political causes associated with the term “social justice.” Responses to this movement in the atheist/sceptical community have been less than totally positive. Atheism Plus has been criticised by other atheists as a divisive movement, and a commonly expressed concern is that members of this group have demonstrated intellectual arrogance and intolerance of dissent, even on minor matters.[1] They would seem to be high in openness to values yet appear very dogmatic in their views. A recent research study may sheds some light on when and why high openness to experience and dogmatism sometimes go together.

Parody of Atheism Plus. See here for another good parody.

Dogmatism and openness to experience among the non-religious
Studies on non-religious people have found that they are generally considerably higher in openness to experience than those who are religious (Galen & Kloet, 2011). People who are non-religious vary greatly in how they define their lack of religiosity so it can be useful to make broad distinctions. A recent study did this by comparing people with “no beliefs in particular” (which I will call “nones” for convenience) and those self-identifying as atheists (Gurney, McKeown, Churchyard, & Howlett, 2013). Those who describe themselves as atheists are more likely to identify themselves as members of a specific group, whereas nones have no particular group identity. Membership of a group tends to promote a sense of loyalty to the values of the group along with a sense of separateness from outsiders, and this can foster dogmatism about the beliefs and values of one’s group to some extent. A distinguishing feature of an atheist identity is that qualities associated with openness to experience, such as challenging traditional beliefs and appreciation of intellectual activity, are highly valued. This is in contrast to a religious identity, which is more likely to emphasise conformity to tradition and submission to authority in matters of belief. Individuals atheists vary in how central atheism is to their identity overall. Some regard their atheism as simply an absence of belief in gods, and one attitude among many others they may have. For others though, being an atheist is a more central and defining part of their self-concept tied to their core values, such as a belief in the social importance of scepticism and reason. Gurney et al. therefore argued that insofar as atheists have a social identity that values high openness to experience, dogmatism among them may be positively correlated with openness to experience, as opposed to religious social identities that devalue such openness. They performed a survey to confirm this, so let’s look at what they found.

The survey compared a group of atheists, nones, and Christians on measures of dogmatism and openness to experience. Additionally, atheists and Christians were asked to rate how strongly they identified with their respective groups. (Nones have no clear group membership, so this question would not be meaningful to them.) The number of atheists in the sample (37) was on the small side, so the study should be seen as a preliminary investigation rather than something definitive. The measure of dogmatism (the DOG scale) used is content neutral in that it includes generic statements like “The things I believe in are so completely true, I could never doubt them” and “It is best to be open to all possibilities and ready to evaluate all your beliefs” (the latter indicates low dogmatism). The openness to experience measure provides an overall score and scores on the subscales of inquisitiveness, aesthetic appreciation, creativity, and unconventionality. The three groups scored similarly on overall openness, although atheists scored significantly higher than Christians on inquisitiveness and unconventionality. Considering atheists’ particular interests, this result is as expected. The Inquisitiveness measure refers to intellectual curiosity, such as interest in science, history and political discussion. Items used to measure it also suggest that is particularly associated with intelligence, e.g. “have a rich vocabulary” and “avoid difficult reading material” (the latter indicating the low end of the trait). Unconventionality indicates non-conformity with social expectations. Unconventionality appears somewhat similar to openness to values as it includes items such as “rebel against authority” and “swim against the current” but also includes several items referencing unusual characteristics, e.g. being eccentric and odd, which may not be quite as relevant to dogmatism though.

On the dogmatism measure, atheists did score slightly higher than nones, although they were substantially lower than Christians. The graph below depicts dogmatism scores for the three groups.

Dogmatism levels among atheists, nones and Christians. Error bars represent standard deviations.

Dogmatism was also positively correlated with group identification in both atheists and Christians. That is the more strongly a person identified as either an atheist or a Christian, the more dogmatic they were about their respective beliefs. So atheists who do not attach much significance to their unbelief were less rigid in their views than those who see atheism as more central to their identity. Additionally and as expected, correlations between dogmatism and openness to experience differed among the three groups. Dogmatism was negatively correlated with openness to experience among nones, and to a lesser extent among Christians. In the latter group, inquisitiveness in particular was significantly negatively correlated with dogmatism, indicating that among Christians, the more dogmatic they were, the less interest they had in intellectual pursuits. This pattern was reversed among atheists, as overall openness to experience, and the facets of inquisitiveness, unconventionality, and creativity were positively associated with dogmatism. That is, atheists who considered themselves more intellectual, more non-traditional, and more creative even, were more dogmatically certain about the correctness of their views and presumably less tolerant of dissenting ones.

Open to experience does not always mean open-minded
The association among atheists between higher dogmatism and higher openness to experience, especially the inquisitiveness facet, is in a way rather surprising. As previously noted, people high in inquisitiveness are comfortable with complex concepts so would be expected to have the cognitive flexibility to steer away from black-and-white thinking usually associated with dogmatism. They also tend to express an interest in science, and one of the guiding principles of science is that one should be willing to question one’s preferred theories rather than cling to them rigidly. Nevertheless, even great scientists sometimes become overly attached to their pet theories and may defend them dogmatically. Furthermore, the unconventionality scale refers to being an unusual person with off-beat ideas but says nothing about the flexibility or rigidity of one’s beliefs. Perhaps it would be fair to say that high openness to experience indicates a preference for complex and unusual ideas, but this does not always mean that one will not be receptive to challenges to these ideas.

Intellectual arrogance versus intellectual humility
Another possibility is that there are different varieties of openness to experience that might be relevant to whether or not a person is dogmatic. Openness to experience comprises a broad array of traits, some of which combine features of openness with traits from other distinctive personality dimensions (Johnson, 1994). For example, openness combined with introversion defines the trait of introspectiveness, whereas openness combined with extraversion defines a preference for variety and originality. Dogmatism implies a lack of humility about the rightness of one’s views, an arrogant assumption that one cannot possibly wrong and that anyone who disagrees is either stupid or evil. There does not appear to be any research that has explored what a combination of high openness to experience with low humility might be, but it sounds like this combination of traits would describe intellectual arrogance. Perhaps openness to experience in atheists who are also dogmatic involves a blend of unconventionality and lack of humility that facilitates an unusual form of dogmatism.

Well, I can think of much more arrogant beliefs...

A limitation of the Gurney et al. study was that it did not address whether identity strength (how strongly a person identified as an atheist) and openness to experience were equally important as predictors of dogmatism or whether one was more crucial than the other. That is, does openness to experience still predict dogmatism in atheists when taking into account identity strength or does it become non-significant? Or conversely, does identity strength still predict dogmatism when taking openness to experience into account? This could be tested statistically with a larger sample of atheists. A more difficult question to answer is why some people have a stronger atheist identity than others. There was a positive correlation between identity strength and openness to experience. Do people identify more strongly as atheists because they are high in openness to experience or does having a strong identity increase openness to experience? And what is the relationship, if any between low humility and identity strength? Does adopting a strong identity lead to an arrogant dismissive attitude towards people who disagree (which I believe to be a problem with Atheism Plus)? Or is it the case that arrogant people are drawn to a polarizing identity? Perhaps it is a combination of both, where adopting such an identity reinforces pre-existing tendencies towards arrogance? Longitudinal research studies would be needed to answer these questions.

I want to make it clear that I have no problem with people having a strong atheist identity, or even people combining atheism with particular political views or an interest in social justice. What I am concerned about is when people hold their views in a dogmatic and arrogant manner. One Atheism Plus blogger claimed that atheism implies not just disbelief in gods but a view of reality in which highly specific political and economic beliefs are to be regarded as certain and inconvertible truths. Even in the hard sciences, theories are open to debate, so I find it incredible he would claim to have certain knowledge in highly complex and soft disciplines where experts disagree. I think it is definitely possible for people to have strong well-defined views about things and yet also realise that their own beliefs are ultimately provisional and subject to change according to new evidence. Finally I want to acknowledge that I am aware of many good examples of atheist bloggers[2] who do acknowledge that people who disagree with them are not necessarily stupid or evil and who do understand the meaning of being reasonable. 

[1] Well known blogger PZ Myers stated for example that critics of Atheism Plus should call themselves “asshole atheists.” He is also notorious for banning dissenting commenters from his blog, among other things
[2] For example, Triangulations, Atheist Revolution, and The A-Unicornist have all been non-dogmatic in my experience. 

Note on layout: Please accept my apologies for any inconsistencies in the appearance of the text. Blogger does strange and unpredictable things to text copied from Word. 

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© Scott McGreal. Please do not reproduce without permission. Brief excerpts may be quoted as long as a link to the original article is provided. 

This article also appears on Psychology Today on my blog Unique - Like Everybody Else.

Other posts about the psychology of (non-)belief

Image credits
Snarling dog image care of The Daily Telegraph
Poster created at
The creator of the A+ parody is currently unknown.
Atheism galaxy poster from Atheist Pictures.

Galen, L. W., & Kloet, J. (2011). Personality and Social Integration Factors Distinguishing Nonreligious from Religious Groups: The Importance of Controlling for Attendance and Demographics. Archive for the Psychology of Religion, 33(2), 205-228. doi: 10.1163/157361211x570047
Gurney, D. J., McKeown, S., Churchyard, J., & Howlett, N. (2013). Believe it or not: Exploring the relationship between dogmatism and openness within non-religious samples Personality and Individual Differences DOI: 10.1016/j.paid.2013.07.471
Johnson, J. A. (1994). Clarification of Factor Five with the help of the AB5C Model. European Journal of Personality, 8(4), 311-334. doi: 10.1002/per.2410080408
McCrae, R., & Sutin, A. R. (2009). Openness to Experience. In R. H. H. Mark R. Leary (Ed.), Handbook of Individual Differences in Social Behavior (pp. 257-273). New York/London: The Guildford Press.
Saroglou, V. (2010). Religiousness as a Cultural Adaptation of Basic Traits: A Five-Factor Model Perspective. Personality and Social Psychology Review, 14(1), 108-125. doi: 10.1177/1088868309352322
Smith, C. L., Johnson, J. L., & Hathaway, W. (2009). Personality Contributions to Belief in Paranormal Phenomena. Individual Differences Research, 7(2), 85-96.

Saturday, November 30, 2013

The Forgotten Role of Individual Differences in the Stanford Prison Experiment

The Stanford Prison Experiment did NOT show that strong situations overpower personality.
The Stanford Prison experiment (SPE) is one of the most famous, or indeed infamous, studies in the history of psychology. The dramatic and horrifying result of the SPE have been used to draw rather sweeping conclusions about human nature and the psychology of evil. For example, the SPE supposedly illustrates the power of an abusive situation to induce good people to do evil things. In particular, Phil Zimbardo has argued that the study shows that strong situational forces can override individual differences in personality and moral values so that the latter count for very little. Indeed he has even claimed that virtually anybody at all who was put into a situation where they had power over others, such as guards have over prisoners, would act in a tyrannical and abusive way. Furthermore, the results of the SPE have been applied to prisoner abuse in Abu Ghraib. The influence of the SPE on psychology is all the more remarkable considering the obvious limitations of the study, such as its small sample size and the ad hoc way in which the experiment was conducted. Closer examination shows that the design of the SPE did not provide an adequate test of the role of individual differences in a simulated prison, and that no satisfactory account of the individual differences in behaviour shown by participants has been offered. Therefore, the popularly accepted conclusion that the SPE shows that “situational power triumphs over individual power in certain contexts” (Zimbardo, 2007) is quite unfounded.

Prisoner abuse at Abu Ghraib has been compared to events at Stanford. What are the real lessons? 

Dispositions vs. situations - opposed or complementary?
 The details of the SPE are fairly well-known and are explained in detail on Zimbardo’s website. Susan Krauss Whitbourne also provides a nice accessible summary of the study on her blog. When the study was first published, the stated rationale was to critique the “dispositional hypothesis” of why prison life is so deplorable (Haney, Banks, & Zimbardo, 1973). Briefly, the “dispositional hypothesis” supposedly blames the “nature” of the people who administer the prison system (e.g. the guards) and the “nature” of the people who populate it (the prisoners). That is, when guards act in a brutal manner it is because they are brutal people. Alternatively, prisoners are seen as naturally aggressive people unable to control their impulses, and therefore repressive measures are needed to control them. According to Haney et al., this dispositional hypothesis has been invoked both by those who defend the status quo (poor conditions in prisons are due to evil prisoners) and by critics of the system (poor conditions in prisons are due to sadistic guards). Supposedly, such simplistic explanations draw attention away from the complex social, economic, and political causes that really underlie this deplorable situation, and which are too difficult to change without radical social upheaval. A few years ago, a research paper proposed that self-selection might have influenced the outcomes of the SPE, because the sort of people who would willingly volunteer for a study on prison life might have distinctive personality traits that might predispose them to abusive behaviour (Carnahan & McFarland, 2007).[1] Haney and Zimbardo (2009) responded to this by attacking the influence of what they call “persistent dispositionalism” in psychology – “explaining context-driven socially problematic behavior in largely individualistic, trait-based terms, no matter how much evidence has been amassed to the contrary”.

The alternative hypothesis that Haney et al. present is a “situationist” one, which is the claim that powerful and oppressive social situational forces, such as occur in a prison, over-ride individual differences in personality and moral values, and induce ordinary decent people to act in abhorrent ways. Haney et al. (1973) attacked the idea that prisoner abuse is due to “bad seeds” and alternatively suggested that the prison system consists instead of “bad soil” that can corrupt anyone. In a more recent talk, Zimbardo has explained his belief about prisoner abuse at Abu Ghraib “I believed our soldiers were good apples that someone had put into a very bad barrel in that prison dungeon.”

Prisoner abuse at Abu Ghraib: good apples in a bad barrel? Did they not choose to behave the way they did? 

Personality is revealed rather than suppressed by situations

Note the apparent dichotomy here. A person’s behaviour in a situation such as a mock prison or even a real one is supposed to be due either to their internal dispositions or the external features of the situation, but not both. I think this a false dichotomy that has led to extreme and unfounded conclusions. Furthermore, it appears to be a straw man argument. When Haney et al. (1973) originally discussed the “dispositional hypothesis” they did not cite any references to show that this is a real hypothesis taken seriously by any genuine scholars. Perhaps certain naïve laypeople believe in it, but whether actual social scientists and psychologists do is not clear. Similarly, when Haney and Zimbardo (2009) attack “persistent dispositionalism” they seem to invoke a decades-old misconception that personality psychologists believe that behaviour can be understood primarily as a function of a person’s traits without serious consideration of the context of the person’s behaviour. On the contrary, personality psychologists have long maintained that a person’s behaviour is a function of both the features of the person and the features of the situation, not just one or the other. That is, personality psychologists argue that people generally make choices about how to behave in order to meet their needs within the constraints and opportunities inherent in particular situations.[2] Regarding the SPE in particular, the authors who argued that self-selection could have influenced the SPE’s outcome responded to the criticism of Haney and Zimbardo that they supposedly preferred “dispositionalist” explanations over situational ones, by acknowledging that features of the situation had a powerful influence on the behaviour of the participants (McFarland & Carnahan, 2009). What they were arguing was that traits might influence a person’s decision to participate in such a situation in the first place. Furthermore, they also argued that being in such a situation with people with similar personality traits would tend to amplify whatever tendencies one already had to be abusive. However, Zimbardo (2007) has argued for a more extreme situationist view, claiming that “a large body of evidence in social psychology supports the concept that situational power triumphs over individual power in certain contexts” and that bad situations can cause “good” people to do “evil” things. However an alternative view of the power of situations is that they provide opportunities that can reveal rather than suppress individual differences (Krueger, 2008). That is, put two different people with different desires in the same situation, and they will respond in accordance with their personal preferences, within whatever constraints are imposed by the demands of the situation. Let’s examine the actual findings of the SPE and see which view of situational power finds more support.

What really happened at Stanford

The SPE study sample consisted of 21[3] men who had been selected from a large pool of 75 volunteers based on psychological assessments to ensure their mental stability and lack of criminal history. One day prior to the study these 21 were assessed on ten different personality trait tests and then randomly assigned to the role of guard or prisoner – 11 to the former, 10 to the latter. On the whole it seems, the guards were pretty mean, and the prisoners became demoralised by their situation, and five of the latter had such adverse psychological reactions that they had to be released early. So far, sounds like a big win for the situationist account right? Participants acted the way they did based on their situationally defined roles, so the situation had a strong influence on their behaviour. However, I don’t think anyone is actually denying that situations influence behaviour. Zimbardo’s claim is that “situational power triumphs over individual power.” If this was the case, then we would expect that there was little or no variation in the way participants behaved in their respective roles as prisoners or guards. Did this really happen though?

According to the original report by Haney et al. there actually were notable individual differences in how the prisoners and guards behaved.
“Some guards were tough but fair (“played by the rules”), some went far beyond their roles to engage in creative cruelty and harassment, while a few were passive and rarely instigated any coercive control over the prisoners” (p. 81).
Apparently about a third of the guards (so about 3 or 4) were actively cruel, while those described as “passive” by Haney et al. have been described elsewhere as “good guards from the prisoner’s point of view since they did them small favors and were friendly”. Furthermore, although five prisoners broke down under the stress of being abused, the other five were more resilient.

Clothes make the man? (Image Source)

The role of personality traits - at first acknowledged, then later dismissed

The original report by Haney et al. does acknowledge that personality traits could moderate the effect of social situational variables, allaying or intensifying the latter’s effects. That is, individual differences in participants could influence how they respond to the perceived demands of their assigned role. When discussing the limitations of their study they even go so far as to admit that they could not adequately test whether a dispositional or a situational account provides a better explanation of their results and state that “We cannot say that personality differences do not have an important effect on behavior in situations such as the one reported here.” They acknowledge that a stronger test would involve comparing two conditions where participants were pre-selected for having more extreme personality traits. I suppose one way to do this would to set up two mock prisons for comparison, one featuring people selected for above-average kindness and compassion, the other one populated only with narcissists and psychopaths. If there were no differences in the behaviour shown in the two conditions (!) this would provide strong evidence that personality traits are not an important influence on behaviour in such a situation. However, they lacked the resources to perform such an experiment, which (hardly surprisingly) has not been done to this day.

In their more recent article though, Haney and Zimbardo (2009) summarily dismissed the role of individual differences, arguing that the precautions and controls they used in their original study were sufficient to lay to rest “any trait-based explanations of our findings” (emphasis added). Specifically, participants were assessed on a number of personality traits and found to score within the normal range for the general population. Additionally, guards and prisoners did not differ on any of these traits. And finally, these personality measures did not predict variations in behaviour within either the prisoner group or the guard group. Supposedly, these precautions should be enough to settle the matter for good.

On its face, such an assertion that the results from a single study of 21 people can permanently lay to rest “any” trait-based explanations seems to me like a breathtakingly bold dismissal that flies in the face of usual scientific practice. Such a small single study like this would normally be considered by most scientists just the beginning of enquiry into the matter not the end of it. Haney and Zimbardo offer no explanation of why individual differences occurred in people who were exposed to the same situation, yet claim that they have enough evidence to dismiss “any” trait-based explanation at all based on their statistical analysis of 21 people. Let’s examine the merits of their “precautions and controls.”

Weak arguments about strong situations

The first argument is that participants did not differ from the general population on their personality traits, and were therefore a fair sample of “normal” individuals. Eight of these measures comprised the Comrey Personality scales. According to a critique by McFarland and Carnahan (2009) none of these traits have ever been linked to abusive and aggressive behaviour. If this is correct, they would have been of no use in assessing whether the participants were “normal” with respect to their propensity to be abusive in a situation where they held power over others. The other two traits measured were authoritarianism and Machiavellianism (the propensity to manipulate others for one’s own gain), which would appear to be theoretically relevant to abusive behaviour. The original report by Haney et al. is actually silent on how their participants compared to the normal population on these measures. For some reason that is not made clear, the researchers used a non-standard scoring method for Machiavellianism that makes comparisons with the general population not possible. Carnahan and McFarland (2007) pointed out that participants actually did score higher on authoritarianism than the general population and their scores were actually comparable to those found in a study of actual prisoners in San Quentin. Haney and Zimbardo argued that the actual difference from the norm was fairly small, so whether it was enough to contribute to the actual behaviour of participants in their study was a moot point. Still, the matter has hardly been “laid to rest.” 

The second argument is that participants assigned to the prisoner and guard roles did not differ significantly on their personality traits. Apart from the miniscule sample size involved, which I will address shortly, I am tempted to respond “So, what?” Prisoners and guards were effectively in two different situations with differing opportunities and faced different challenges. For example, some of the guards disturbed the prisoners’ sleep by banging on their cell doors. The prisoners obviously did not have the opportunity to reciprocate this treatment, because the guards went home at the end of their shifts. So the prisoners could not engage in such abusive behaviour even if they had felt inclined to do so, because the opportunity was simply not there. As I have argued earlier, personality theorists propose that individual differences are relevant to how people respond to their circumstances, not that individual differences somehow allow people to transcend these circumstances and behave however they feel like.

Haney and Zimbardo’s third argument is that the behaviour of individuals within their respective roles of prisoner or guard could not be predicted from their personality scores. They do not deny that there were individual differences in behaviour, just that they could not predict them. I think this is their weakest argument of all. Remember that there were 11 guards and 10 prisoners. The guards’ behaviour in particular sorted them into three distinct types – good guards, tough but fair, and mean guards. So this means that in order to perform a statistical analysis we would have to compare three subgroups consisting of 3 – 4 individuals to determine if there were significant differences in their personality traits. Statistically this is laughable. A basic principle of statistics is that significant differences between groups can only be detected if the sample sizes are adequately large, and the sample sizes in the SPE are so small as to be completely inadequate for the purpose. Now, let’s say that I was a researcher who wanted to test the hypothesis that individual differences in personality traits could predict behaviour in an experimental situation such as an in a mock prison. (Let’s also assume that I knew in advance what personality traits were relevant to the outcomes concerned.) I could actually estimate in advance what sort of sample size I would need in order to have a reasonable chance of finding a significant result, if a real effect existed. Using a procedure known as power analysis, I can calculate that if personality traits had a medium-sized effect on behaviour (i.e. about average compared to most effects in psychology) resulting in three different behavioural subgroups I would need about 50 or so participants per subgroup (so 150 in total) to have an 80% chance of detecting a statistically significant effect if one actually existed. Even if the effects of personality were actually much larger than average, I would still need about 22 participants per subgroup, so 66 in total. Remember, that these numbers refer only to the number of guards. Presumably we would need an equivalent number of prisoners as well. This means that I could anticipate in advance that I would need a sample of between 132 to 300 participants to have a reasonable chance of getting a significant result. If for some reason I then decided to settle for a grand sample of 21 people - which would give me less than a 9% chance of finding a statistically significant result assuming a medium sized effect, and about a 15% chance assuming a large one - I would look rather foolish as such a tiny sample would not allow me to test my hypothesis in anything like a conclusive way. Haney et al. quite obviously did not have anywhere near enough statistical power to predict individual behavior from measured personality traits, so the fact that they could not do so reflects a defect in their methodology rather than some deep truth about the power of situations to overwhelm individual differences.

In spite of these limitations, the original report on the SPE does note a number of non-significant trends for personality traits to predict behaviour. Specifically, prisoners who stayed until the end of the study, compared to the five who left early, scored higher on extraversion, conformity, empathy, and authoritarianism (Haney, et al., 1973). A reasonable interpretation of this finding is that personality traits deserve further investigation with a larger sample to determine if these trends are robust or not. Haney et al. admitted in 1973 that the SPE was not actually designed to test the hypothesis that personality traits would predict individual differences in behaviour. Yet in spite of these inadequacies in the study design, Haney and Zimbardo argued in 2009 that “any trait-based explanations” of why participants behaved the way they did can be dismissed without any further consideration. This seems disingenuous as well as unreasonable.

Conclusions: the importance of choice
In summary, the purpose of the SPE was supposed to be to demonstrate that powerful situational forces could over-ride individual dispositions and choices, leading good people to do bad things simply because of the role they found themselves in. If this were true, then participants in the study should have acted in a uniform way depending on their role. However, this was not the case, participants acted like individuals, showing that they still had the capacity to make choices within the constraints of their situations. Furthermore, the study was not even designed to provide a fair assessment of the influence of personality traits in such a situation because the sample size was nowhere near large enough to justify any definite conclusions. Far from demonstrating that individual differences do not matter in how people behave in a strong situation, the study’s results illustrate that even in undeniably tough situations people still have the capacity to make choices and that these choices matter.


[1] This blog post mentions some interesting results of this study regarding self-selection.
[2] To be fair, Zimbardo has stated, for example on his blog, that be believes that behaviour is a function of both individual differences and situational factors. However, many of his published remarks indicate that he sees dispositional and situational factors as competing with each other to explain behaviour. Personality psychologists see this “competition” hypothesis as being based on a false dichotomy. See this blog post by David Funder for example for an explanation of why this dichotomy is not valid.
[3] The sample was originally 24. Two were asked to remain on standby and one withdrew before the study began. 

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This article also appears on Psychology Today on my blog Unique - Like Everybody Else.

© Scott McGreal. Please do not reproduce without permission. Brief excerpts may be quoted as long as a link to the original article is provided. Any version of this article appearing on sites other than Eye on Psych or my blog at Psychology Today has been ripped off without my consent.

Follow up articles critiquing situationism that discuss the SPE
Challenging the "Banality" of Evil and of Heroism, Part 1 and Part 2. This pair of articles refutes Zimbardo's claim that heroic and evil acts are equally "banal" outcomes of situational factors and that qualities within a person are of no real importance. 

Further interesting reading
Don’t blame Milgram by David Funder – debunks the popular claim that Milgram’s obedience studies show that the “power of the situation” overwhelms the “power of the person”.

Carnahan T, & McFarland S (2007). Revisiting the Stanford prison experiment: could participant self-selection have led to the cruelty? Personality & social psychology bulletin, 33 (5), 603-14 PMID: 17440210
Haney, C., Banks, C., & Zimbardo, P. G. (1973). Interpersonal dynamics in a simulated prison. International Journal of Criminology and Penology, 1, 69-97.
Haney, C., & Zimbardo, P. G. (2009). Persistent Dispositionalism in Interactionist Clothing: Fundamental Attribution Error in Explaining Prison Abuse. Personality and Social Psychology Bulletin, 35(6), 807-814. doi: 10.1177/0146167208322864
Krueger, J. I. (2008). Lucifer's last laugh. The American Journal of Psychology, 121, 335-341.
McFarland, S., & Carnahan, T. (2009). A Situation's First Powers Are Attracting Volunteers and Selecting Participants: A Reply to Haney and Zimbardo (2009). Personality and Social Psychology Bulletin, 35(6), 815-818. doi: 10.1177/0146167209334781
Zimbardo, P. G. (2007). The Lucifer Effect: Understanding How Good People Turn Evil (1st ed.). New York: Random House.