There have been several studies conducted on twins who were raised in different environments and these studies all revealed that the basic intelligence of the two humans from the same egg were almost the same. Back when IQ tests were given, the such twins tested were no more than 3 IQ points apart. For instance, when one twin who was deprived of stimuli that the other the twin had been exposed to, the first twin appeared less intelligent, but the natural intelligence was yet there, according to intelligence tests. [One studied involved a twin who remained in an orphanage while another was adopted by a college-educated couple.] Thus, it seems that there is no substitute for genetics. While educated and more intelligent parents usually create an environment in which motivation for improvement of one's mind and character are fostered, the intelligence is inherited.
Just because a child comes from a bad environment, the environment cannot be perceived as the cause of lack of intelligence. While, cases of prison inmates often indicate the negative effects of environment, they do not conclusively prove that a person is intellectually less because of this environment. In one particular case of an inmate in federal prison in a federal institution some years ago, when Pell Grants could be given to inmates, he went to two colleges, one by correspondence and another via of the professors from a local colleges coming into the institution. This student-inmate became valedictorian of the local college (he was not permitted to be called so, however), and he earned a 4.0 from the correspondence university. Later, he told one of the employees in the Education Department of the institution, "Had I received an education when I was younger, I may not have ended up here. Having an education has opened up new avenues of thinking for me." Obviously, he was at a disadvantage in his old environment, but he was of no intellectual disadvantage.
Nature vs. Nurture is the never-ending debate that intends to explain whether our behaviors are a result of upbringing or genetic inheritance. Research shows that, in the end, they are both intertwined. If you look in the profiles of some serial killers, you will find that some of them did not come from sick families who also killed. Some even come from very respectful families who are church-going and not dysfunctional. Hence, no question about social influence here.
However, what about the myriad of mental illnesses that happen as a result of exposure to the wrong meds, or as a result of an ill development of the frontal lobe cortex, which is the brain area that deals with emotions? What if the answer is: Neither nature nor nurture decide it all? What if the final answer is simply that each person's brain develops without a specific pattern and social experience increases or decreases the chances of bad behavior.
Unfortunately we may not ever get the final answer, but it is worthy to wonder whether it is possble to admit that development is so unique to each individual that it is completely unpredictable to imagine what will happen next.
I do agree with previous posters that intelligence is, without a doubt, partially biologically inherited. Genes are a strong, strong force. As exhibited by those separated twin studies mentioned earlier in the discussion, some things are just born into us.
That being said, as an educator who has taught both at-risk urban youth and middle/upper class kids, I can attest that the environment does have a huge impact in developing or stunting students' natural born potential. I have met so many kids who can obviously think quickly and critically, but they don't develop the same academic vocabulary and ability over time in comparison to their privileged counterparts. When students spend years coming to school hungry from homes where no adult cares whether they come or go, when kids are worried that they could get jumped at the bus stop, when kids have nobody in their lives to reinforce that education matters, it makes it very hard for them to develop into what they were meant to be. Think about it--are localized, low standardized test scores in big cities a symptom of a "bad genetics zone"? Absolutely not. A symptom of kids given a drastically different playing field to begin with? I think so. (Not to generalize overly so--I have met many highly involved, caring urban parents as well. But many kids cannot claim this happy situation.)
I guess I think of it this way: A palm tree seed will grow into a palm tree no matter what. But it's only going to survive and flourish in warm sandy soil. If you plant one in Chicago, it is still meant to be a palm tree, but it's just not going to make it unless it has someone to give it specialized shelter, provisions, and care.
While I, too, feel that both nature and nurture affect intelligence, I have read some research summarizing studies of twins, research that suggests that nature is a little more important than we would like to think it is. Twins raised in very different kinds of environments tend to have fairly close IQs, I recall.
Another comment I would like to make on this issue is that intelligence comes in many forms, not simply in the form measured by standardized IQ tests. Howard Gardner is the seminal source of the idea of multiple intellligences. What I do not know is how much research has been done on nature versus nurture on different kinds of intelligences, for example, musical or kinesthetic. Of interest also is a book by Malcolm Gladwell, The Outliers, in which he addresses not so much intelligence per se, but the factors that promote proficiency and success. The book is fascinating because it discusses not simply nature and nurture, but also factors such as birth date and birth year, which surprisingly seem to affect outcomes.
In college, I was fully in favor of nurture over nature. I was convinced that the right kind of boundary enforcement, goals, and rewards, could essentially motivate a person to do almost anything.
Now that I have my own children, I am much more of a believer in nature over nurture. I fully believe humans are born with a personality and genetic tendencies already in place. This is evidenced by behavioral quirks seen in very young babies and children which seem to carry out throughout their adult lives. While nurture can teach humans to use their powers for good rather than evil, so to speak, I personally believe there is a pre-written genetic code which guides far more than any environmental factors.
I would say that both factors have a role in intelligence. I do feel that the nurture side plays a bigger role than heredity. As mentioned above I have seen many students who come from very well educated parents that struggle with academics and I have also seen some very bright students who have parents with less education do quite well. I feel that parents who nurture and value learning from a very early age have the biggest impact on the children and their academic growth.
Excellent post above by the scarlet pimpernel. I tend to agree that nature and nurture are pretty evenly balanced. As a teacher, I have seen both sides of the debate, and I have taught many unmotivated, seemingly slow-witted children whose parents were doctors and professors. Likewise, many children whose parents were poorly educated showed high intelligence and high motivation.
Levitt and Dubner's book Freakonomics has an interesting chapter on this much-debated topic. The authors compile the results of several surveys and studies to discuss whether environmental factors such as a child growing up with a lot of books in his or her home makes a difference in academic achievement or perceived intelligence. What the surveys/studies imply is that other factors related to a child's mother are much more important. For example, children that are born to mothers who waited until later in life (30-years-old and up) to have children overwhelmingly do better in school. In contrast, a child who is adopted has a much higher chance of struggling academically (according to the surveys). While these results are thought-provoking, they served only to cause me to form the opinion that nature and nurture seem to be about blananced when it comes to their influence on intelligence. For if you really think about it, is a mother who has children later in life just a naturally intelligent person who chose a career which demanded her full-time attention (such as preparing to be a doctor)? If she is, then she most likely passed on that natural intelligence to her children. Or, is the woman who has children later in life better able to provide a stable environment for her child, thus fostering intellectual growth?
I would argue that both factors must surely be involved, but I would argue that experience and socialization matter more than biology. Of course, I have no solid proof of this. I simply feel that so much of what seems like intelligence depends on the degree to which children are exposed to reading and to the idea that constantly learning new ideas and facts is fun.
However, I think personality has something to do with it as well. A kid who is, by nature, inclined to like to think about things is going to seem more intelligent and is going to absorb much more book learning than a kid who is inclined to always be out running around and doing physical things.
A good read about Nature vs. Nurture is Lord Of The Flies.
I believe that Nature always wins in the battle between the two. For example, you can take a baby gorilla away from its mother the second it's born, and keep it as a pet, treating it as you would a human baby. But, when the gorilla grows up, it's natural instincts will kick in. suddenly, your pet is a danger. Just because you try to raise something against it's core nature, doesn't mean that you are erasing it. Take serial killers, for example. Some people are born with the urge to kill; a mental disorder of sorts. Some people are more likely than others. If you took two people who were likely to do this, and put one of them into a good home, and one into a bad home, and let them grow up, you would find that they are both likely to exhibit the urge to kill still. Some environmental settings are easier for nature to come about, but in the end, you cannot change a person's core insinct simply by nurture. People, and animals, are born with insincts and these insincts will be shown, no matter how you nuture them. You cannot change the core of a human being simply by showing them love.
Though Nature and Nurture might seem to be evenly balanced, when you really think about it, it comes down to almost entirely Nature.
To begin with, you of course have Nature, as in whatever talents and abilities you're born with, and subject to not being born with any handicaps.
Then comes the nurturing by the parents. But this, you see, is also Nature. The kind of nurturing you'll receive is based on the Nature of the parents. If you're exceptionally intelligent, chances are you got that from one, or both, of the parents. In which case, they will provide exceptional Nurture.
In education, again the same thing applies. The quality of the schools you attend, the quality of the teachers you get, will depend on where you live, what financial level your parents are at, etc. Again, it's determined by Nature.
There are the freak cases of geniuses being born to mediocre parents; outstanding achievements from poor areas; and so on. But they're rare enough that they can't be applied as the rule.
So, ultimately, it's Nature. Coming from a Fatalist, as you can see.