Caveat Emptor – let the buyer beware. Good advice for almost anything from buying cars or houses or making investments and, for that matter, in trying to make sense out of the nature–nurture debates. As is true about anything within the academic disciplines, the nature–nurture debates rest on certain basic assumptions about theory, methodology, and analysis. What is the subject matter? How is it defined and measured? How are data collected? How are they analyzed? How are they interpreted? These are not, in fact, questions unique to the nature–nurture debates but rather are generic to all aspects of the study of human development. Nevertheless, the nature–nurture debates often serve as the primary battleground for skirmishes between opposing sides on each of these issues. It is in this sense that I define one of the nature–nurture debates as the “proxy debate.”

This chapter is mostly about the proxy debate because it is these questions and assumptions on which they rest that speak to the heart and soul of human development as a discipline. These questions and assumptions can perhaps best be grouped together in two, admittedly overlapping, broad categories. The first refers to issues related to the question of the most appropriate level of analysis one should use in the study of human development, and it is this issue that serves to differentiate the classic debate from, for the most part, the new debate. The second broad category relates to a host of issues concerning research design and analysis, and it is this issue that most often serves to put the two sides of the classic debate at odds with each other.

Here is a riddle for you. What has been solved over and over again and yet still remains unsolved? The answer – the nature–nurture debate. Admittedly not a very good riddle, but nevertheless a true statement. The question is like one of those candles we used to have on our birthday cakes when we were children, the ones we would blow out and they would just light again and we would blow them out again and once more they would relight. Eventually we caught on that the problem wasn't with our blowing but with the candle. The focus of this book reflects the same sentiment. The problem isn't in the answer; it is in the question. We need some new candles to light.

The Nature–Nurture Debates: Bridging the Gap reviews both contemporary and historical approaches to the problem, from the perspective of both theory and method and the implications of each of these approaches. Without giving too much of the plot away, suffice it to say that the candle that needs replacing is the reductionist model. An approach that partitions variance into independent main effects will never resolve the debate because, by definition, it has no choice but to perpetuate it. The “new candle” is one consistent with the emerging perspective of a true developmental science, a multidisciplinary concept that is a worthy successor to the all-too-often static perspective of child psychology.

There is no question but that one's genotype significantly influences one's course of development. And there is no question but that one's environment significantly influences one's course of development. But there is now also no question that the way that the classic debate has attempted, for more than 100 years, to explain the role of each has done more harm than good, both in terms of our conceptual understanding of the course of development and in terms of the inappropriate policy and practice recommendations that have flowed from such a flawed perspective. As I said earlier, it really is incredible.

The classic debate's reliance on main-effects statistical models simply no longer reflects what we understand about the interdependence of nature and nurture. A statistical model not only needs to be mathematically accurate; it needs to accurately model the phenomenon of interest as well. The main-effects model may pass the first test, but it no longer passes the second test. In fact, it may never have passed the second test because partitioning variance is at heart an illusion. There is in reality no such thing as an independent effect.

It's really incredible when you think about it. Here we are, well into the twenty-first century, and we are still fighting over the role of nature and nurture in human development. And it isn't even a new fight; it's not even a twentieth-century fight. It actually goes back to the nineteenth century and probably even before that. So why is it that we cannot get this question answered and move on to a new one? Is it because we haven't yet gotten the necessary data to make a conclusion one way or the other? Do we not yet have a powerful enough computer to sort everything out? Have we not identified the best method and statistics to collect and analysis the relevant data? One answer to these questions is, of course, “yes” to all these possibilities, but there is also another possibility. It may also be that we are having trouble coming up with the answer because we continue to ask the wrong questions.

The Nature–Nurture Debates: Bridging the Gap is an attempt to make sense out of the nature–nurture debate, to explain why this debate is still even a debate. I mean, after all, how many other topics in any of the sciences have been debated for more than 150 years without any resolution? Making sense out of the debate requires an examination of several issues and questions. For starters, what in fact are we talking about when we talk about nature and nurture? How is each measured, and how is its relative contribution assessed? What is the history of the debate? Have there been solutions that we now no longer accept? What were they? Why were they rejected? What has changed in our understanding of the course of human development? How has this change redefined the debate? What difference does it really make anyway how much nature and nurture influence our development? Is this essentially an academic debate that may never be answered to everyone's satisfaction, or are there important practical implications as well? What are the major theoretical positions in the debate? What does each have to offer? What claims does each make? What data does each provide?

One of the things that all students of human development are taught in their research methodology and statistics classes is that methodology and statistics are designed to be neutral, that is, the results of an experiment should reflect the data collected rather than how the data were collected or analyzed. This is the bedrock, the basis on which we claim our work to be objective, to be scientific. However, at least with respect to nature and nurture, and, in particular, the early history of the classic debate, this fundamental assumption simply doesn't appear to be true. In fact, most of the research methods and statistics used in the debate, then and now, evolved out of a desire of those whom we would now recognize as nativists to have an “objective” way of demonstrating the dominant position of nature over nurture rather than an objective means to assess the relative importance of the two.

Like just about everything in Western thought, this brief history lesson goes all the way back to the ancient Greek philosophers, Plato (437–347 b.c.e.) and Aristotle (384–322 b.c.e.). Today we would call Plato a nativist (Simpson et al. 2005), although it was not a term he made use of. Nevertheless, Plato argued that experience was simply insufficient to account for all the knowledge and abilities humans possess. Because these things cannot be taught, they must instead be present at birth, that is, they are innate. On the other hand, Aristotle, Plato's student, might have been the first empiricist, more precisely, possibly the first epigeneticist. As Anandalakshmy and Grinder (1970) explain it,

One of the major – if not the major – points of this book is that the nature–nurture debate continues to be fought along two battlefronts and that these two fronts represent different levels of analysis, that is, different metatheories. One metatheory reflects a belief that the life sciences, including the study of human development, can best be modeled using the same principles as those that work so well for the physical sciences, that is, a belief that complicated phenomena can best be understood as reflecting the cumulative effects of several antecedents each acting essentially independent of each other. The design and use of methodology allowing for the partitioning of variance into independent main effects is consistent with this worldview.

Scholars working within this reductionist metatheoretical tradition, such as those involved in the classic debate, typically reject the notion that there is a metatheoretical value reflected in their work. Rather, they argue that as empirical researchers (whether the focus is on nature or nurture), they are simply capturing what there is to be found with respect to the causes of human development and, further, that their research methods are neutral, that is, if the data show that it is possible to partition nature and nurture, it is so because it is possible to partition nature and nurture, not because the methodology artificially creates such a result. And finding evidence for such main effects, they report them, to both the scholarly community and to the general public. And so people picking up their morning papers (or iPads, as might be the case), read that scientists have found the God gene (Wade 2009), that bad driving might be genetic (McHughen et al. 2010), that political orientation might be genetic (Alford et al. 2005), and of course that the poor may not only be poorer than the rest of us but in some way might be genetically different as well (Rowe 2005).

This chapter and the next examine the four relatively distinct approaches to the nature–nurture debate. In this chapter, we look at models favoring a reductionist approach to the issue, that is, models that attempt to examine the influence of variables independently of each other. In the next chapter, we look at models favoring a systems approach, that is, models that see variables in constant interaction with each other. The reductionist approach is the classic debate; the systems approach, the new debate.

The classic debate is just that, a classic. It seems to have been going on forever and, given the elements of the debate, is likely to continue going on forever. The players change periodically as do the particular statistics, but the fundamental question is always the same: What percentage of the variance is caused by nature and what percentage of the variance is caused by nurture? The fact that there seems to be no end in sight to the classic debate is perhaps one reason why many have abandoned reductionist approaches to development and have moved on to the more integrative, systemic ones.