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Now this is a topic I honestly don't prefer because it has no realistic answer but was given as a bonus question for my psychology final.

Nature vs Nurture what is your opinion?

Me, I believe you can't have one without the other. The option of free will is usually a factor I would have to consider in this case, since free will would guide the method of Nurture. But the supporters of the Lucifer Gene may think otherwise. I really don't know that much about the Lucifer Gene short of generic inheritance of evil. If you can inherit evil then why not good. But lack of good Google results don't help me here, and honestly, I don't bother or even trust Wiki if Google doesn't pull up an official page of some sort.

Exactly my point, you can't have one without the other. I don't see how one can function without the other, except to say there is no such thing as freewill.

I would have to disagree. A person's life is filled with points of no return, past which, if they don't learn something by then, they will never learn it.
For example, there are children who (sadly) are abused or abandoned in such a way that they grow up basically feral. These children missed the window during which they could have learned to speak like normal adults, or even like children. They will never learn to properly converse with other people. Kittens raised seeing only vertical stripes will be unable to see horizontal stripes.

Aside from drastic examples like that that, there are many aspects to nature- Albert Einstein born in a backwater hick town with an absent dad, teenage mom, and lead piping will likely grow up completely different than Albert Einstein born into a caring upper-middle class family with two PhD parents in the suburbs. The genes will be the same, but all of the aspects of nurture- parental care, family and community values, available opportunites, nutrition, etc.- will be different. The genes will be the same, but those effects of nurture will never go away, short of a Phineas Gage-like catastrophe.

My opinion is that nature decides how far we can go, Nurture determines how far we will go. I include everything that can happen in life as nurture- from being born premature, to having vitamin deficiencies, to having a broken home, to having the life that is the envy of everyone.

Some have all the right materials, and all the right tools. They meet or almost meet their potential.
Some have all the right materials, and inadequate tools. They may meet most of their potential.
Some have inadequate materials, and all the right tools. They may meet a decent portion of their potential, with luck.
Some have inadequate materials and inadequate tools. They lucked out in the game of life.

The problem, I think, is that you and I are defining nature and nurture differently. I define nature as genetics- when the sperm hits the egg, the nature is defined because the genetics are defined. Nurture, then corresponds to every modification imposed by the environment. You define, if I am not mistaken, nature as what is written in the brain.
The problem with that definition, though, is that there would be no use describing nurture. When something is experienced, it is written in the brain as connections between neurons. Repeated similar experiences will strengthen those connections, making that experience easier to recall and harder to forget. Likewise, experiences that are not repeated will atrophy. Think of it like paths through a field- if you keep on walking a similar route, you will see a line of dirt surrounded by grass. If you take a diffent route, the path will grow over again. If you continue, a rut may develop. Every moment you live, your brain is changing, and so your nature would thus also be continually changing.

In regards to Pavlov's dogs, even if the dogs had not associated the bell with the prospect of food for a while, once the association was repeated, it would take much less time for the response to resume. At no point did the association disappear- but it had lessened. As for the phobias, they are not "easily" reversed. Neither does classical conditioning (like Pavlov's dogs) fully account for the range of phobias experienced. Many people have phobias, but have had no negative experiences relating to the object or situation of which they are phobic. Furthermore, the prevalence of different phobias is out of proportion to what we are exposed to- animal phobias are the most prevalent, yet there are far more accidents involving motor vehicles than there are animals. People can recognize that they have a phobia, but feel powerless to control their fear. While one incident may cause a phobia, it may take several sessions of different therapies to extinguish it. Quoting Wikipedia's article on phobia, "Gradual desensitisation treatment and CBT are often successful, provided the patient is willing to endure some discomfort and to make a continuous effort over a long period of time."- a situation far from "easily reversed". There is also some evidence that phobias are to some extent genetically caused. People fear snakes (potentially dangerous) much more readily than flowers (not dangerous), as shown by experiments performed by Martin Seligman. People with a first degree relative who is agoraphobic are twice as likely to also have agoraphobia. However, there is also evidence that phobias are passed on by social learning, which is supported by the fact that small children who develop animal phobias are around age five and whose mothers also are zoophobic (children see their mothers freak out, and model those same reactions).

As for twin studies, I would have to say that the similaries you named are trivial, likely the result of confirmation bias, and just as meaningful as the similarities between Lincoln and Kennedy (interesting article here.) Taking from wikipedia again, here are two graphs showing the heritability of different traits. Heritability is the percent of difference that can be attributed to genes, so a heritability of 1.0 for a trait means that any difference would be purely genetic.




DZ stands for dizygotic or fraternal twins, MZ is for monozygotic (identical) twins.
As you can see, there is no trait that is close to being 100% heritable, though intelligence comes close (and still leaved 14% open). Aspects such as memory are not even 50% heritable. As no trait is pure "nature", then it must be safe to assume that nuture does indeed play a significant role in a person's development.
It is also important to note that heritability is not a one hundred percent measure of genetic similarity- environment also plays a role, and so heritability charts may overestimate the role of genetics. If the mother of twins smokes, it would be almost impossible for one fetus to get all the side effects and the other to be perfectly fine. Twins are not assigned at random to foster or adoptive homes either. New homes are selected so that the family matches the child. Twin studies in the 60's are also susceptible to problems during number crunching. Again quoting wikipedia, "Using the statistical models published in Loehlin and Nichols (1976), the narrow heritability’s of HR of responses to the question “did you have your back rubbed” has been shown to work out to .92 heritable for males and .21 heritable for females, and the question “Did you wear sunglasses after dark?” is 130% heritable for males and 103% for females."
Using IQ as another method for showing that nurture does play a large role, a 1997 study showed that whites scored an average of 1.6 standard deviations higher than blacks on IQ tests. But, blacks raised in white families scored similarly to whites.

And now for the kittens.
I might have been overstating a bit when I said that kittens couldn't see horizontal stripes, but the portions of their brains devoted to seeing such things were markedly smaller. As I stated at the beginning, changes in brain structure do reflect changes in experience. I found a site about that experiment and similar, and it also showed that kittens with one eye sewn shut at birth ultimately had no ability to see with that eye, because there was no area devoted to being able to see with that eye. Quoting from the end of that site,



Sources:

Wikipedia.org, articles on Twin Studies and Heritability

http://wilderdom.com/personality/L4-1IntelligenceNatureVsNurture.html

http://hubel.med.harvard.edu/b57.htm (under "Further studies in Neural Plasticity", but the rest is good too, if a bit technical)

http://www.snopes.com/history/american/lincoln-kennedy.asp


Small edit: I was partially wrong about the impossibility of identical twins having the same prenatal conditions. While two-thirds of identical twins do share the same placenta, one-third of identical twins seperate at a certain point so that they have different placentas, and are therefore subject to different amounts of horomones, etc., much like fraternal twins.
source: The Dependent Gene: The Fallacy of Nature Vs. Nurture By David S. Moore, p 57 (found through google)

I really don't know what else can be said that already hasn't.

Your definition of Nature and Nurture are flawed. Nature is genetics. Nurture is everything else. Those are the accepted uses of the terms, that is how everyone else uses them. Replace the terms you are using with the more conventional definitions where applicable; the two of you will find that you agree on everything except your definitions.

It looks as though there is a problem properly defining nature and nurture.

(The following is surfing through Answers.com)

The concept of instinct is an attempt to explain why some kinds of behaviour develop consistently in a given species across a wide range of environments. Each species of animal exhibits some characteristic forms of behaviour that have this developmentally robust quality. Bees, for example, dance to indicate the location of pollinating flowers, and they do this with no formal instruction. When a type of behaviour develops in this way, without the need for learning or any other environmental input beyond the bare minimum for physical survival, it is usually attributed to a strong internal force that pushes development in certain directions rather than in others. It is to this idea of a strong internal force that the notion of instinct refers.

Chomsky pointed out that learning a language would be impossible without some predispositions to learn certain things. The distinction between learning and instinct was once again shown to be more subtle than the way in which it was often presented. Language is a good example, because, although it has to be learned, the learning is guided by innate rules, unlike, say, learning to play chess. In Darwin's apt phrase, the ability of humans to learn language is ‘an instinctive tendency to acquire an art’. The psychologist Steven Pinker has made this point vividly in his book The Language Instinct (1994).

The concept of instinct does not, therefore, entail an inflexible notion of development. On the contrary, it is quite compatible with the idea that developmental outcomes are contingent on environmental conditions, and with the idea that learning plays an important part in development. In contemporary cognitive science, developmental outcomes are seen as the result of a complex interplay of innate programs and environmental inputs. The innate programs do not take the form ‘Thou shalt’, but rather specify disjunctive rules such as ‘if … then …’. The environmental inputs determine whether the rules are applied or not. In this model of development, the disjunctive rules correspond to instincts.

To sum it up humans have an instinct, or nature, to learn. But to learn would be the influence of the environment.[/edit]

Humans tend to be a social animal. Though I have noticed when many animals group they tend to ignore or overlay some of their instincts with social behaviors. We still have the drive to learn but when grouped we lack the drive to find out on our own. This is where I believe nurture steps in.

After I reread it earlier today I wanted to edit that part out, just didn't sound right. But there was some kind of server problem and I couldn't access Gaia. I'll leave it as is but I still don't like it.