Tag Archives: language

Hacking almost helps us see what Hacking overlooks

The Social Construction of What? (Harvard UP, 2000) by philosopher of science, Ian Hacking, critically reviews the possible meanings of social construction in the context of scientific knowledge and technology.  However, there is one meaning of construction that he does not consider, perhaps the most obvious one to the common person, namely, the process of building a structure from diverse materials, as in the foundations, frames, walls, roof, plumbing and electrical circuits, and so on. (2011 post)

A 1975 book of Hacking’s, What does language matter to philosophy?, almost allows us to see what he overlooked at that time and still did in the 2000 book, namely, that knowing always involves engaging [*] or acting as if the world were like our explicit and implicit theories and representations of it. Continue reading

What you thought you understood about the meaning of heritability

A quick comment by a colleague about how she teaches students to think about the meaning and limitations of the concept of heritability led me to explore her example of coming to speak the language of one’s country of origin.

Consider English-speaking families in the USA and families that have children when they immigrate to the USA from a place where English is not spoken.  We know that language “runs in the family” in that children will speak the language of their families.  Of course, we suspect that is all about the environment parents provide for the children, but let us examine the heritability of English-speakingness anyway.

We can conduct a classic twin study of 10-year olds to estimate heritability by comparing the similarity of identical (monozygotic or MZ) twins and fraternal (dizygotic or DZ) twins.  What we would expect to find is that if one twin speaks English so does the other, whether MZ or DZ.   And if one twin doesn’t speak English neither does the other, again whether MZ or DZ.  No math is needed to conclude that the heritability is zero.  Notice that this result holds even if the twins in some immigrant families have gone to schools that enable them to become bilingual but the twins from other families have not learned English, at least not by age 10.

Suppose however that we go back to the foundations of heritability estimation as it is conceived of in trials of plant varieties grown in a number of locations.  Growing in a number of locations for humans requires the thought experiment that identical twins are separated and raised one in an English-speaking family and one in a non-English-speaking family.  (Perhaps they could be raised in different countries.)

Suppose that the data looked like Table 1, where 1 = speaks English at 10 y.o., 0 = does not.

Table 1

raised in an English-speaking family raised in a non-English-speaking family
Twin pair 1 1 0
Twin pair 2 1 1
Twin pair 3 1 0

The heritability estimate for the data in Table 1 is .25.

(The math are as follows: Means for the twin pairs = .5, 1., .5.  Variance of those means = 1/18.  Variance for the trait over the whole data set = 2/9.  Heritability = ratio of those variances. [Any statistician worrying about sample versus population variance can simply imagine that this pattern in the data is repeated many times so that the two estimates converge.])

Why is the estimate not zero this time?  After all, nothing changed about the way the world works in relation to language acquisition.   We might suspect that the data point for Twin Pair 2 raised in a non-English-speaking family is recorded incorrectly and should be 0.  But suppose we have asked for this to be checked and it is correct.  What needs to be understood is that the estimate of 0 from the original twin study corresponds to a partial snapshot of the phenomenon compared to the separated twins study, as indicated in Table 2.

Table 2

raised in an English-speaking family raised in a non-English-speaking family
MZ or DZ twin pair 1 raised together 1 n.a.
MZ or DZ twin pair 2 raised together n.a. 0
MZ or DZ twin pair 3 raised together Etc. Etc.

What does it mean that the heritability estimate is not zero?  If the data were from plants not people (and the trait was some plant trait!), then non-zero heritability means that the breeder could expect to increase the average value of the trait in the population by selectively breeding the variety that has higher average value across the locations (i.e., the Twin Pair 2 variety).   The plant breeder might be curious about the factors underlying the observed trait values, but would not have to discover those factors before proceeding.

But these are human data; selective breeding is not possible.  So the next way to look at the non-zero heritability would be to investigate what the underlying factors are.  It turns out, once a sociologist looked deeper at the twins in their families that, for twin-pair 2, the twin raised in a non-English-speaking family watched a lot of English-language TV and learned English even though it wasn’t spoken by the family.

Watching a lot of English-language TV sounds like an environmental factor, so how do we understand that factor resulting in non-zero heritability? From the plant breeder’s point of view, we now have to make sure that the locations have that factor—the families need to have TV with English-language shows and let the child view them—if the heritability value is still to lead us expect to increase the average value of the trait in the population by selectively breeding the variety that has higher average value across the locations.  In short, understanding non-zero heritability does not require that we have exposed underlying genetic factors.

Four objections might arise:

  1. Given that selective breeding is not possible, why then are we interested in heritability for humans?   Answer: There is no need to be.
  2. Is the analysis of Table 1 correct given that being raised in a non-English-speaking family is not being raised in the same location if some children can watch a lot of English-language TV and others can’t?  Answer: We don’t know that the others couldn’t watch English-language TV.  But, even if that were the case, it was through analysis of the data that we decided to look more deeply at the families (locations).  If we had known in advance what all the relevant underlying factors were we wouldn’t have bothered with the twin study.
  3. It is possible that all the twins were allowed to watch English-language TV in the non-English-speaking families, but only in Twin Pair 2 did the twin learn English by the age of 10.  The underlying factor is no longer having English-language TV to watch, but choosing to watch it and learning from that.   That no longer sounds like an environmental factor.  Response: a. From the plant breeder’s point of view, nothing has changed; the label is unimportant; b. From the human sociologist’s point of view, the situation has become more interesting: What leads a child to choose to watch and learn from the English-language TV when it is not spoken in the family?  This is an interesting question, but not one that demands that the factors we investigate are genetic.
  4. What if we learned that, contra the twin study described at the start, DZ twins are less similar than MZ twins in choosing to watch and learn from English-language TV in the non-English-speaking families?  That is, the heritability estimate is non-zero.  Answer: We shouldn’t be any more likely to search for underlying genetic factors than we would based on the non-zero estimate based on Table 1 (which, as noted earlier, is a complete not partial snapshot of the situation).

The impulse to look for the underlying factors is understandable if we are interested in changing the situation (in this case, to produce English-language speakers even in non-English-speaking families).  What heritability estimation does not warrant is taking values of heritability as an indication that the factors to look for are genetic.  Indeed, heritability estimation is a snapshot of a situation at one point of time, so it does not warrant a subsequent search for underlying factors at all.

When breeders use the estimates to make predictions about advances under selection they know from experience that the outcomes do not always match the predictions.  If they care enough about the discrepancy, they might go on to investigate a) the underlying genetic factors and how they are getting recombined through bi-parental matings (unless they are cloning offspring); b) the underlying environmental factors to see whether they are truly reproducing the locations from generation to generation; and c) the ways that those genetic and environmental factors combine to influence the trait.

A clear understanding that heritability does not measure the relative influence of genetic versus environmental factors may lead us not to teach students to think about the meaning and limitations of the concept of heritability through human examples that involve modifying underlying factors.  (The classic case of this approach involves not language learning, but the high heritability human trait height.  One points to the increase in average height of Japanese from the pre-WWII to the post-WWII generation and suggests that changes in the quality of diet led to the change.  The problem with this approach is that it invites us to imagine that the explanation is probably genetic factors if we encounter a trait in which there is a large average difference between groups but no obvious single environmental factor explains the difference.)

On the metaphor of transmission

Transmission might seem to entail some tangible thing that is being passed from sender to receiver.  For example, inheritance is some property or money that parents leave for–or transmit to–their offspring.  However, people now also speak of heredity as a transmission of traits or characteristics, even though the egg and the sperm, which are transmitted, have none of traits in question, e.g., height, aggression, blue eyes, etc.

In my writing about nature-nurture science, I usually note something to the effect that

as a starting point, the potential for confusion in the varying uses of the term “genetic” diminishes if genetic is reserved as an adjective in reference to factors that are transmitted from parents to offspring and whose presence can, in principle, be observed.  In a similar spirit, “environmental” can be taken to refer to measurable factors, which can range widely, say, from average energy intake to maltreatment as a child.

I use factor in a colloquial sense as a bland word with few connotations.  Read: “thing” or “entity.”  But I have often had readers ask why I don’t talk about “traits” or “characteristics.”  They are quite comfortable with the idea that physical traits and personality traits can be transmitted.  My guess is that the term became metaphorical — heredity is like transmission in that a germ cell is transmitted and it contains all the potential or instructions or information for the resulting organism that does show the traits.  And then it became sufficient to think of the heredity being the transmission of the information and not to unpack just how information becomes, through development, the organism that does show the traits.  (This has been the subject of Susan Oyama’s critiques such as the Ontogeny of Information.)

Nature, a conversation II

Each person takes one of the three roles: Partovo (“Humans are a Part Of nature”); Separata (“Humans have become Separate from nature”); or Interpreta (“Interpret Socially views about nature and what is natural”) (see Preamble).

Begin the conversation as scripted, but call time out to discuss among yourselves any comment that you do not understand or that you would like to rewrite.  If the group agrees to the rewrites and they diverge far from the script, record the new conversation you generate.

Partovo:  Humans are living organisms.  As such they are part of nature.  Therefore, everything they do is natural.

Separata:  People have lost touch with nature and that is why our environment and our society are in trouble.

Interpreta:  When I hear people draw lessons from nature, I hear them really telling me something about their views on society.

Separata:  You’ll have to explain this interpretation to me, because, without a sense of what is natural and what is unnatural, anything is acceptable.

Interpreta:  But Partovo has a sense of what is natural that tells him everything is acceptable.

Separata:  Is that right?

Partovo:  Yes.

Separata:  So you mean mad cow disease, polio, AIDS, and so on are acceptable?

Partovo:  Um, yes.  We could look at them as forms of population control for the human species.

Separata:  So you wouldn’t invest in research for AIDS treatments?

Partovo:  No.  And I don’t think the government should either.  AIDS affects mostly gays and IV drug users.  Their practices do not meet widely held community standards and so they don’t deserve society’s help.

Separata:  I think you are out of date about who gets AIDS.  But, putting that aside, I thought you said anything humans do is natural and thus acceptable.

Partovo:  Well, not everything.

Separata:  So, what is and what is not?

Partovo:  Look, I overstated my position.  What I do know is that it is not consistent for environmentalists to argue that draining wetlands disturbs the balance of nature, while putting out forest fires to keep a national park scenic is OK.

Separata:  I think that the National Park Service is reconsidering its fire policy — whether it is better to do preventative control burning or not; whether to allow lightning fires to burn or not.

Partovo:  So humans get to decide what kind of (non-human) nature is the one they want?

Separata:  Not in any arbitrary way; forest ecologists use the best science available to advise the NPS on this.

Partovo:  “Scientists know best”  — I thought your line was that we’d lost touch with nature, not that we needed to listen more to scientists.  But now I think about it, you did support research for an AIDS vaccine, right?  So you don’t mind if scientists intervene to limit interaction between humans and (non-human) nature in the case of the HIV virus.  In what ways exactly do you want us to regain touch with nature?

Separata:  I guess I also overstated my position.  Basically what I want to say is that we have to remember that we’re dependent on foodchains for much of our food, plants for our planet’s oxygen, microorganisms inside us to digest our food well, and..

Partovo:… microorganisms for our beer, bread, sewerage treatment works, and thus clean water.  Or do you think these processes are unnatural because humans have harnessed them for our own purposes?

Interpreta:  Can I interrupt here? (continued in the next post)

Nature, a conversation

Preamble

Ideas of nature underlie a great deal of social thought and have done so through recorded history.  The changing meanings of “nature” and the tensions among co-existing meanings have been analyzed brilliantly by the English cultural analyst Raymond Williams; he shows us a history readable in terms of the social order being defended or promoted [Williams 1980].  The romantic ideal, for example, of a unspoiled places and sentiments (i.e., nature separate from “man”) arose at a time when industrialization was rapidly escalating exploitation of people and natural resources (i.e., producing unprecedented interdependencies among peoples and nature), exploitation underwritten by the removal of traditional checks in the name, ironically, of the natural principles of individual autonomy and of unconstrained pursuit of utility in social transactions.  Following Williams, whenever we hear the environment and its conservation being talked about we should factor into our interpretations the social concerns and social-historical location of those who hold those ideas.  The recent literature on conservation efforts in colonial Africa and India, for example, has been revealing vividly how policies and actions to preserve species and habitats were greatly motivated by anxieties about changes back in the metropole and by the need to assign “primitive” peoples some less threatening place in the colonial order.

Taylor, P. and R. García-Barrios. 1995. “The social analysis of ecological change.” Social Science Information, 34: 5-30, referring to Williams, R. 1980. “Ideas of Nature,” in Problems of Materialism and Culture. London: Verso, 67-85

Suppose we want students to consider how, for example, the valorization by the romantics of untouched (non-human) nature might be interpreted in terms of the romantics’ need to turn the attention away from the industrialization and colonial exploitation of which many of them were beneficiaries.  It’s too much to ask students to jump straight into advancing their own social interpretations of claims about “nature.”  First they have to get comfortable with the very idea of exposing what is not literally stated—what people state only when prodded, and then not all the time.  The conversation starting in the next post: i) develops this idea of interpretation in a dialogue—or trialogue because there are three voices; ii) allows students to go through and mark where they don’t understand the response given or where different responses could be given; and iii) provides a start—the first five statements—from which students could write their own trialogues.