The discussion as to whether nature or nurture were the driving force shaping our cognitive abilities, was for a long time considered interminable. In the 18th century, Locke and the English empiricists claimed that individuals were born with a tabula rasa and only experience could establish mind, consciousness and the self. On the continent, Leibniz envisaged the self as a monad carrying with it some knowledge of a basic understanding of the world. Until the 1960s, this dispute was still very vivid in the behavioral sciences: B.
F. Skinner’s school of behaviorism in the USA postulated (as reflexology did earlier) general rules for all types of learning, neglecting innate differences or predispositions. K. Lorenz was one of the protagonists of ethology in Europe, focusing on the inherited aspects of behavior. It was Lorenz who ended the antagonistic view of behavior in showing that there indeed are innate differences and predispositions in behavior where only little learning occurs.
Today, it is largely agreed upon that nature and nurture are intimately cooperating to bring about adaptive behaviors. Probably only in very few cases ontogenetic programs are not subjected to behavioral plasticity at all. Conversely, the possibility to acquire behavioral traits has to be genetically coded for. Today, realising that genes and environment cooperate and interact synergistically, traditional dichotomy of nature vs. nurture is commonly seen as a false dichotomy.
Especially operant conditioning, i. e. e learning of the consequences of one’s own behavior can lead to positive feedback loops between genetic predispositions and behavioral consequences that render the question as to cause and effect nonsensical. Positive feedback has the inherent tendency to exponentially amplify any initial small differences. For example, an at birth negligible difference between two brothers in a gene affecting IQ to a small percentage, may lead to one discovering a book the will spark his interest in reading, while the other never gets to see that book.
One becomes an avid reader who loves intellectual challenges while the other never finds a real interest in books, but hangs out with his friends more often. Eventually, the reading brother may end up with highly different IQ scores in standardized tests, simply because the book loving brother has had more opportunities to train his brain. Had both brother received identical environmental input, their IQ scores would hardly differ.
Judging from just one IQ-test and a genetic analysis, one would come to the conclusion, that the effect of this one little genetic difference created that big difference in IQ-scores. However, knowing the background and history of the two brothers, it is obvious that only the interaction between the genetic difference and the environent created that difference. In theory, one way of quantifying environmental and genetic influences would be to calculate the genetic differences in % basepairs and compare it to the phenotypic difference. However, the question of scale seems amost insolvable.