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Personality Development: Intentional Strategy or Automatic Adaptation?

Personality development, like many aspects of phenotypic development seen across species, can be viewed within the framework of flexible ontogeny (Hagen & Hammerstein, 2005). An individual’s behavioral patterns across time represent that individual’s context-dependent adaptive strategy for coping with the unique environmental challenges he or she faces. Development and expression of a given strategy involves a complex interplay between latent genetic dispositions and conditional learning; individuals can have evolved the capacity to implement a given strategy (i.e., encoded in their genes) and can flexibly employ this strategy only when inhabiting an environment in which the strategy will lead to adaptive outcomes (i.e., conditional learning). Indeed, personality theorists have increasingly begun to view traits as context-dependent reaction norms which are implemented through similar interactions between genetic predispositions and environmental triggers (Penke, Denissen, & Miller, 2007), and emerging evidence suggests that variation in state personality (i.e., a momentary instance of trait-relevant behavior) is explained in part by extant situational pressures (Fleeson, 2007).

The concept of conditional learning raises the issue of whether adaptive strategies are consciously implemented or whether they automatically arise due to environmental pressures to promote an individual’s survival. Consider the recent finding that individuals who enter military service after high school show relatively little increases in agreeableness over the subsequent six years compared to individuals who enter community service (Jackson, Thoemess, Jonkmann, L├╝dtke, & Trautwein, 2012). Stated differently, high school graduates generally increase in agreeableness in the six years following high school, but those who enter the military do not show this developmental trend. The flexible ontogeny framework suggests that, whereas all individuals have the latent capacity to act in an agreeable manner as they enter young adulthood, environmental pressures of military service (e.g., the need to show callousness toward enemies in combat) curb this capacity and cause individuals to adopt a less agreeable strategy. Again, however, we do not know whether these individuals a) consciously chose to act less agreeable given the knowledge that such behavior would increase their likelihood of survival; or b) less agreeable behavior merely emerged due to day-to-day situational pressures inherent in the military. While consideration of these two possibilities risks rekindling the debate on whether behavior is more attributable to persons or situations, a better understanding of the mechanisms driving flexible ontogeny would help elucidate the how and why of personality development.

Discussion (5 Comments)


Hey Aaron,

Whereas the examples from the Hagen and Hammerstein paper were more discrete in nature, personality seems to be more of a continuous kind of thing, I think. From what the authors describe, the water flea Daphnia either grows a protective helmet or doesn’t grow a protective helmet based on the presence or absence of a cue in the environment which when present flips a genetic switch. So, I think any argument for a strategic (in the evolutionary sense of the word) view of personality may be more complicated than an argument for the same view in the helmet development of a water flea (surprise surprise!).

I think the following and more would have to be disentangled:

a) whether we are talking about genetic switches, and if we are, how this leads to continuous rather than discrete change,
b) whether there is a sensitive or critical period for certain aspects of personality or whether malleability remains throughout the lifespan (if certain aspects of personality or more or less malleable you might as why, under this strategic framework), and
c) whether strategic dispositional flexibility is encoded a priori into the nervous system as a form of learning.

Maybe I misunderstand but I’m not sure I would attempt to separate conscious processes from more “automatic” or unconscious processes by classifying them as different types of adaptation. In other words, while consciousness and reasoning probably make thinking about adaptation more complex, in my mind conscious processes can reflect the workings of adaptations and unconscious processes can reflect byproducts or noise and vice versa.

One way to view the question you are asking is whether flexible disposition shows evidence of design and within our understanding of how genes shape and maintain nervous systems/behavior, etc.


hey guys–great issue! i don’t have much to add, except to note that there is evidence for a genetic ‘switch’ in determining personality differences that clearly occur in response to environmental events. I’m thinking of the Caspi & Moffitt Science paper from some years back (perhaps one of you can dig it up) showing that a certain allele (i believe on a dopamine receptor gene) that was previously thought to underlie a genetic propensity for depression in fact leads to depression ONLY among people who grow up in a tough environment (e.g., abuse, poverty). In such cases, one could argue (and these authors, among others, have) that it’s adaptive to display the behaviors associated with depression–holing up and conserving what you got, rather than exploring, etc. I believe that in later work this same gene was found to predict the opposite kinds of behaviors, for individuals growing up in positive environments–but this i might be mis-remembering–I’m thinking of a talk Shelly Taylor gave here a few years back. Anyway, very cool stuff and a great example of gene-environment interaction.


I found two Caspi & Moffitt Science papers. Here are the take-home messages:

Caspi et al. (2002): The effect of childhood maltreatment (ages 3-11) on antisocial behavior (mid-20s) stronger for men with inhibited promoter for MAOA activity.

Caspi et al. (2003): Given the presence of stressful life events between ages 21 and 26, individuals carrying at least one “s” allele of the 5-HTT gene show steeper increases in depression and greater likelihood of onset of depression than individuals carrying no “s” alleles.

Okay, this is cool. Regarding a couple of Conor’s points, they are both good examples of continuous, rather than dichotomous, genetic switches, and the first one is a nice example in which behavior is shaped largely in a critical period of childhood.

I think they largely point to unconscious processes driving personality development. The explanation for the 2002 paper is that individuals with low MAOA activity are less able to withstand the neural system damage & stress that results from childhood maltreatment, and thus are more likely to become antisocial. The explanation for the 2003 paper is that possessing an “s” allele on the 5-HTT gene increases an individual’s overall reactivity to stressors (acute or prolonged), and thus these folks have a propensity to be more stressed out and become depressed.

I can’t think of a good post-hoc explanation for why either of these findings would represent a conscious personality development strategy. Maybe maltreated children intentionally become antisocial to fight back against their crummy, dangerous home environments? Maybe naturally stressed & reactive people act more depressed to elicit sympathy and support from others in times of significant life challenges? Those types of explanations seem to be a stretch; they require us to invert our thinking about what shades of personality are adaptive. Conscientiousness and self-control are adaptive, not impulsivity and antisocial behavior, right? Emotional stability is adaptive, not depression, right?

What do you guys think?


Hey Aaron,

If you’re going to be thinking about potentially maladaptive traits from an evolutionary perspective I recommend the following stuff as a brief introduction:

If it interests you further I have Nesse and Williams’ book on Darwinian medicine that offers some ways in which to look at potentially crappy things, e.g., antisocial behavior from an evolutionary perspective (although behavior etc is given a relatively small amount of space in the book).


Also, if you’ve been maltreated in childhood, becoming antisocial probably is a pretty adaptive strategy–essentially it means you’re going to be a jerk to get the things you need to survive, in this case, b/c you have to.

But I also agree with Conor that Nesse has come up with nice evolutionary explanations for the adaptiveness of depression and similarly maladaptive seeming traits. Why we Get Sick is a great book.

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