Imagining Science: Thought experiments in the physical sciences

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Most of the thought experiments in this blog, either created by myself or cited from others, typically involve ethics and politics. However, thought experiments have been used (and still are) by scientists and philosophers of science. The most popular thought experiments cited in philosophy are Galileo’s falling objects (’s_experiment); Shrodinger’s cat (,devised%20by%20Austrian%20physicist%20Erwin%20Schr%C3%B6dinger%20in%201935.); Maxwell’s demon (,a%20small%20door%20between%20two%20chambers%20of%20gas.); and so on. However, contemporary thought experiments used in science by scientists seem to not get the same amount of attention.

However, whilst rereading some of my undergraduate literature on the nature/nurture debate. The nature/nuture debate, roughly, is the debate between whether human behaviour is best attributed to nature or nurture. Nature being physical characterists such as genetics, and nurture being environmental characteristics such as upbringing, social circles, and so on. Of course, many philosophers and scientists have pointed out that this is a false dichotomy. Human behaviour can be explained by a mixture of genetics and environment. This postion is known as interactionism.

Interactionism seems to be the most attractive among laypeople and the scientific community, which includes myself. That said, it is a mistake to assume that interactionsim says that it is 50% nature/genetics and 50% nurture/environment. It could be 90% nature/genetics and 10% nurture/environment and anywhere within the spectrum.

These beliefs typically are associated with individuals. So, what would an interactionist believe about groups of individuals? On face value, it seems contradictory to say that there is a 100% genetic/environmental explanation for the behaviour of groups whilst also saying that individual behaviour must be on the spectrum between genetics and environment. However, a thought experiment was made by Richard Lewontin (David S. Moore & David Shenk, 2016) to show how someone can consistently believe that traits inherited by individuals is a mixture of genetics and environment, but the traits inherited between groups is 100% environmental. This is Lewontin’s thought experiment:

“Imagine that we plant a handful of normal seeds in an environ-mental context in which each developing plantreceives the identical amount of light and the identical amount of nutrients, and furthermore, thatthe amount of light and nutrients each plantreceives is adequate to support normal growth. In this case, the variation in height that we ultimately see in theseplants can be accounted for by referencing genetic variation alone (because all of the plants are grown in the same environment, meaning there is no environmental variation at all); in this situation, the heritability of height would be calculatedto be 100%. Next, imagine that we plant another handful of normal seeds in an environmental context in which each developing plant again receives the identical amount of light and the identical amount of nutrients—but now imagine that each plant is provided with a less-than-adequate amount of light and nutrients. In this situation, too, the heritability of height would be calculated to be 100%, because again, we have carefully controlled the environment in which this second group of plants has grown, so all of the variation in the plants’ heights can be accounted for by referencing genetic variation alone. However, even though heritability in each of these subpopulations would be calculated to be 100%, we would still find that on average, the nutrient-deprived plants wind upshorter than the plants grown in adequate environmental conditions. Thus, finding that the heritability of a characteristic is 100% still does not mean that environmental factors cannot powerfully influence the development of that characteristic.” (David S. Moore & David Shenk, 2016).

Of course, this thought experiment does not allow us to conclude that if there are different traits between groups then it must be 100% environmental, only that it can be. And this remains possible even if it is true that the traits possessed by individuals within that group are a product of both genetics and environment. The take home message of the thought experiment is that if we see one group possessing a trait significantly different than other groups, this observation does not allow us to make further assumptions about whether this is caused by genetics, environment, or a mixture of the two.


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Andrew Tulloch

I have a Bachelor of Arts majoring in Philosophy and Sociology, with a Political Science minor. I also have an honours degree in Philosophy. I am currently studying for my PhD in Philosophy.

2 thoughts on “Imagining Science: Thought experiments in the physical sciences”

  1. A great piece, Andrew. I have lean towards environmental factors as a dominating factor when it comes to groups, especially social beings like humans.
    I’m not sure I can explain my stand, but it feels right—social pressures can really influence people. I’ve experienced this because I’ve lived a nomadic life, and I notice that within a few months of moving to a new place, I begin to speak and think like the people there (no matter how much I tried to rebel). Does that make sense?

    Liked by 1 person

    1. Thanks Saurab,
      Yes I tend to agree. Since the human genome project, the consensus of scientists seems to be that environment would be the best explanation for group differences since there is more genetic variation within groups than between groups. But not being a philosopher and not a scientist all I can do is appeal to their authority.


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