Personality Type - Heredity or Environment?

[Mindsabre]

Personally I believe some traits may be hereditary while others are not. Even then I'm skeptical about the hereditary part in more non-physical factors. So... environment I guess.

 

[INTP]

Personally I believe some traits may be hereditary while others are not. Even then I'm skeptical about the hereditary part in more non-physical factors. So... environment I guess.

Human body/mind is 100% physical..

 

[tkae.]

No? It's entirely environmental. Cognitive processes aren't hereditary unless they involve a physical, neurological component.

Example: Red/green colorblindness could be hereditary because it involves a physical defect. The mental representation you have for a tree is not hereditary, even if it's highly personalized based on environmental factors that are as unique to you as your genetic code. Both are extremely complex, but genes aren't the modern world's crystal ball. You can't treat it like palm reading and say, "I see in your genetic code that you will be an INFP and live a happy life as a doctor."

Human body/mind is 100% physical..

In response to this, another example:

You losing three fingers in a chainsaw accident is not hereditary, even if it's physical. Your genetics didn't chart out your future and put you in that exact place at that exact time to lose that exact number of fingers. You can argue that since the information you process in your brain changes the physical structure of your brain at the neuron level, that genetics determine how your brain will change and is the same as genetics determining your height. But that's a false argument.

Post-birth environmental factors influencing your development and cognitive abilities are not hereditary. Nothing in the process of learning is hereditary. How you learn could be hereditary. What you learn the fastest and enjoy the most could be hereditary. But the things you're exposed to that shape your development is literally the definition of an environmental factor. Similarly, the life experiences you have at critical parts of developmental stages is what determines particular aspects of your personality. It's why you can't accurately determine an MBTI type until the late teens or early twenties. Your personality is still developing and fortifying itself, as much as a fluid identity can fortify.

 

[INTP]

In response to this, another example:

You losing three fingers in a chainsaw accident is not hereditary, even if it's physical. Your genetics didn't chart out your future and put you in that exact place at that exact time to lose that exact number of fingers. You can argue that since the information you process in your brain changes the physical structure of your brain at the neuron level, that genetics determine how your brain will change and is the same as genetics determining your height. But that's a false argument.

Post-birth environmental factors influencing your development and cognitive abilities are not hereditary. Nothing in the process of learning is hereditary. How you learn could be hereditary. What you learn the fastest and enjoy the most could be hereditary. But the things you're exposed to that shape your development is literally the definition of an environmental factor. Similarly, the life experiences you have at critical parts of developmental stages is what determines particular aspects of your personality. It's why you can't accurately determine an MBTI type until the late teens or early twenties. Your personality is still developing and fortifying itself, as much as a fluid identity can fortify.

Everything is nature via nurture(you can read this from any serious book in psychology that deals with heredity). Environment effects how our genes express themselves.

Introduction

Animals, including humans, are born with in-built instincts to perform adaptive behaviors. These instincts include many reflexes and relatively straightforward behaviors, such as food-seeking behavior. But, as animal behavior gets more complex, there are in-build instincts which are correspondingly more complex (e.g., food storing behaviors). Thus, personality in humans is considered, from an evolutionary perspective, not be qualitatively different in origin than the drive in dogs, for example, to bury their bones, or squirrels to store acorns. It's just that human personality is even more complex.

The evolutionary perspective of personality probably makes most sense when considered in conjunction with other perspectives. Evolutionary psychology can seen, for example, as a theoretical platform which underlies the human personality. At birth, everyone starts from scratch, with a unique genotype, some inbuilt instincts (including a temperament), and a pre-wired capacity to learn certain kinds of behaviors. Biological processes, psychodynamics proceses, behavioral processes, social shaping processes, etc. then unfold, interacting with the individual's genotype, to dynamically create the unique psychological characteristics of the individual. All the time, however, this shaping occurs within certain parameters layed down by the genotype, which itself is a synthesized expression of the knowledge of human evolution about what seems to be adaptive, stored and conveyed through genetic code.

The evolutionary perspective is closely related to all other perspectives of personality. Freud, for example, was ultimately famous for being the father of psychology, by revealing that human behavior was driven by unconscious, instinctual forces. Freud understood personality as arising from the way in which humans were able to resolve these instinctual impulses (such as for pleasure, sex, food, etc.) with societal constraints, and the long-term needs of the individual. Indeed, there is evidence that Freud was influenced by the writings of Darwin and that he greatly admired Darwin's work (Sulloway, 1979, cited in McAdams, 1994).

Skinner, the famous advocate for behavioral understandings of the human behavior, also understood their to be a role played by evolutionary forces, although he saw this as not being as important as environmental reinforcement:

"We can trace a small part of human behavior...to natural selection and the evolution of the species, but the greater part of human behavior must be traced to the contingencies of reinforcement, especially to the very complex social contingencies we call cultures. Only when we take those histories into account can we explain why people behave the way they do."
- Skinner, 1989, p. 18, cited in Feist & Feist (2002, p. 281)

Rather than see the various perspectives in opposition from one another, as Skinner seems to do here, I think it is more useful and productive to understand how they all work together in various ways to create the multi-faceted reality of human personality.

The evolutionary perspective, then, views personality as the product of a long history during which it was advantageous for humans to adopt particular characteristic ways of thinking and behaving. Evolutionary forces are most useful for understanding some of the broad trends in apparently instinctual drives. It is also seems that although we have been shaped as a species by the challenge of survival, understanding individual's personalities is often best approached from other perspectives, particularly because the evolutionary perspective currently seems to offer little in the way of practical intervention or assistance in dealing with personality problems.

Variation in human characteristics as adaptive for the species

An important principle of natural selection is that a species will exhibit variations in various physical and behavioral characteristics. In this way, over time, individuals with physical and behavioral characteristics which are most adaptive for survival will be more likely to survive and pass on their characteristics to their off-spring. Over a long period of time, this leads to eventually to entirely different species, or the gradual shaping (evolution) of a species to have some characteristics and not others.

In this light, then, observations of the wide variations in human personality can be understood as the process of evolution throwing up variations of the human psyche which allows the most adaptive personalities to survive more often and procreate.

In a complex species, such as humans, it is also important to realize that quite different personalities may prove adaptive in different ways. For example, highly aggressive behaviors can be adapative in that they allow a person to stand up for themselves and fight for their share, or more, of available resources. However, this also makes a person vulnerable to the aggression of others. So, it is also understandable that more submissive or passive personalities can be adaptive. By avoiding conflict with others, the individual is less likely to suffer direct harm from the aggression of others, but may find that it is difficult to get access to the resources for survival.

For some aspects of personality, there appear to be convincing evolutionary explanations; for other aspects, for other aspects of personality, evolutionary perspectives are less useful. Evolutionary perspectives are probably most useful for explaining general societal behavior trends.

An example of such a trend is that males are greater perpetrators of violence than women.

During human history, it seems males evolved with particular tendencies and capacities that were advantageous for hunting and physical defence of tribes. This underlying predisposition of males seems to also predispose males to also being more likely to have overly violent behaviors. This may be due to higher than normal levels, for example, of particular hormones and neurochemicals (testosterone, for example). Other behavioral sex differences which have attracted evolutionary explanations include the higher rates of promiscuity for males, and the higher rates of rape by males.

Behavioral genetics

Behavioural genetics studies the way inherited biological material i.e. genes, can influence patterns of behaviour.

Behavioural genetics has sometimes been called �trait� genetics as it examines the way our genes influence our personality traits.

The basic methodology of behavioural genetics is to compare similarities in personality between individuals who are and are not genetically related, or who are related to different degrees.

Humans are highly similar to each other genetically. About 90% of human genes are identical from one individual to another. Behavioural genetics concentrates on the approximately 10% of the human genome that does vary.

Behavioural genetics, like trait psychology, focuses exclusively on aspects of personality that differ from one individual to another. The inheritance of species-specific traits or traits that all humans share is examined later in evolutionary psychology.

The basic assumption of behavioural genetics is that if a trait is influenced by genes then it ought to be more highly correlated across pairs of identical (monozygotic:MZ) twins than across pairs of fraternal (dyzygoticZ) twins, and more highly correlated across closer genetic relatives than across more distant genetic relatives.

Across many personality traits the average correlation across MZ twins is .50 and across DZ twins is .30 (e.g. Bouchard & McGue, 1990; Loehlin & Nichols, 1976). Thus according to twin studies average heritability of most personality traits is .40. This is interpreted to mean that the proportion of behavioural variance that can be explained by genetic variance is 40%. (This is a heritability coefficient i.e. a percentage not a correlation coefficient).

Heritability of the Big Five personality factors

Are the Big 5 traits influenced by our genes? A number of twin studies have explicitly examined the heritability of C, A, O, N, and E.
Evidence of heritability for conscientiousness(Jang, McCrae, Angleimer, Riemann, & Livesey, 1998)
Evidence of heritability for agreeableness (Jang, Livesey, & Vernon, 1996)
Evidence of heritability for openness to experience (Loehlin, 1992)
Strong and consistent evidence of heritability for neuroticism
Strong and consistent evidence of heritability for extraversion

Twin studies suggest that heritability and environmental factors equally influence all five factors to the same degree.[56] Among four recent twin studies, the mean percentage for heritability was calculated for each personality and it was concluded that heritability influenced the five factors broadly. The self-report measures were as follows: openness to experience was estimated to have a 57% genetic influence, extraversion 54%, conscientiousness 49%, neuroticism 48%, and agreeableness 42%.[57]

Here is some basics discussed relating to development of temperament:

I havent watched that video in quite a while, but as far as i remember it has some good info in it.

Now you might say that big 5 is different, if so, feel free to tell me how/why you think it is so different regarding to this, so that i can tell you why it is not so.

Also read the first post i made on this topic