Compare and contrast: Contemporary and historical approaches to individual differences

The study of differences between individuals is as old as recorded history.  These differences could pertain to aspects of personality, interests, physical traits, talents, etc.  Only during the last few centuries has this field of inquiry attained a more scientific and methodological approach; for prior to it, theories were constructed based on select observations and limited understanding.  In other words, the fields of inquiries of human psychology and human physiology have only been devised during the last few centuries and theories and methods employed previous to that remain deficient to that extent.  It is fair to say that the Renaissance was a crucial period in the advancement of robust theories pertaining to individual differences among humans.  At the outset, it is important to note that human behaviour and personality is much more difficult to understand than that of animals.  And more than any other species, human behaviour is subject to interpretation and conjecture, not always leading to easy inferences.  Studying individual differences is further thwarted by the fact that human behaviour is an emergent reality and not a fixed one.  As our species is provided with an ever increasing repository of knowledge, its behaviour too simultaneously evolves to fit the new reality. Hence, Wilson’s following observation is pivotal to understanding differences among humans:

“Today, the greatest divide within humanity is not between races, or religions, or even, as widely believed between literate and illiterate. It is the chasm that     separates scientific from pre-scientific cultures….Without the instruments and accumulated knowledge of the natural sciences–physics, chemistry, and biology–humans are trapped in a cognitive prison. They invent ingenious speculations and myths about the origin of the confining waters, of the sun and the sky and the stars above, and the meaning of their own existence. But they are wrong, always wrong, because the world is too remote from ordinary experience to be merely imagined.” (Lubinski, 2000)

A proven theoretical framework of analysing individual differences is the one based on evolutionary biology.  Within this broad framework is the specialized study of human infant intelligence.  Since the nature of early intelligence is nonverbal, it is closely linked to primate evolution, and hence helps us gain insights into the origins of individual differences in human intelligence. Within the ontogeny of infant intelligence, variation between individuals is restricted by ‘canalization’ and also by ‘common human environments’.  Scientists were able to observe from the common behavioural elements among members of our species, an abstract pattern which differs from that of other species.  It must be noted however, that “what exists are individuals, each different from the other; a species-typical pattern is an abstraction from reality. The development of infant intelligence has both a species-typical pattern and individual variation.” (Lubinski, 2000)

Since the time of Mendel’s discovery of genes as the basic codes of information, a substantial body of scholarship has been devoted to this area of study.  While genes are said to create ‘variation’ within the population, “environmental differences within and between families, social class, and ethnic groups try to account for portions of the variance in IQ scores and personality compositions as well” (Scarr, 1991).  While studies relating genetic factors to variation in IQ scores have proven to be controversial, the role of genes in physiological differentiation among individuals is well established.  Darwin’s theory of evolution by natural selection is the foundation upon which genetic variation exists.  It is the general principle of natural selection that those features and characters that are “close to reproductive fitness and viability are allowed only limited differences within the species” (Scarr, 1991).  A classic example of this principle is the birth-weight of the human baby, which has a narrow range.  Similarly, “it is likely that many gene loci for normal intellectual development also has little polygenic variability within the species and that a minority of regulatory genes control most of the individual variation in the normal range”. (Lubinski, 2000)

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