Endnote for Lecture 3: The Teachings Concerning Heredity and the Environment in Pedology
As Vygotsky made clear in the first two lectures, child development is holistic. By that, Vygotsky
doesn’t simply mean that it is the whole body or even the whole mind which grows. On the contrary,
as he noted in the first lecture, different parts grow at very different rates. What he means is that
development includes not only growth but also differentiation into a complex whole, and that it is only
by understanding how these functionally and now structurally very different products work together in
systems that we can hope to understand development. For the next two lectures, Vygotsky wants to
show how two very different endowments of the child work together: biological heredity on the one
hand, and the cultural environment on the other. In this lecture, Vygotsky’s focus is the hereditary
endowment, although as we shall see, his main concern is differentiating it from the sociocultural one,
hence the twofold title of this lecture.
This lecture, like the first two, may be divided into three parts. In his introduction, Vygotsky shows four
ways in which the study of heredity in pedology differs from its study in other fields and from the study
of heredity for its own sake (3-1~3-18). Next, Vygotsky shows us, through the method of the
comparative study of twins, how traits which are more dependent on heredity may be distinguished
from traits which are more dependent on the environment (3-19~3-30). Finally, Vygotsky generalizes
the results of these studies into four propositions or laws: greater dependence of elementary functions
on heredity, non-linearity of the transition from heredity-based to cultural-based functions, the
possibility that dependence upon heredity may change during development, and, consequently, the
lack of general law which can permanently define the role of heredity in development. Elaborating on
the last two laws, Vygotsky points out that on the one hand, there are general traits having to do with
growth which do not seem to vary at all (e.g. the components and structure of the eye as opposed to
their color). On the other hand, where there are traits which do vary, we can never definitively say that
the trait is purely hereditary or purely environmental, or even explicable to the mechanical
combination of contributions from heredity and the environment according to fixed ratios. (3-31~3-49)
I Introduction: Vygotsky begins by saying that this lecture will provide concrete examples of the
holistic, clinical, and comparative-genetic method that he outlined last time: Vygotsky means that it will
study heredity in connection with the environment, it will study it clinically rather than symptomatically,
and it will use a comparative method. This will distinguish the pedological approach to heredity from a
general biological one in four ways (3-1~3-5).
A) In the general biological approach, the geneticist is interested in simple, univariate traits (e.g.
height in bean-stalks, or color in flower blossoms), since these are most likely to reflect the laws of
heredity (e.g. the Mendelian laws of dominance) in a pure form. The pedologist, in contrast, is most
interested in complex traits where the mechanisms of heredity must interact with other mechanisms
(3-6~3-7).
B) In the general biological approach, the geneticist is interested in traits that are maximally
dependent on heredity (e.g. eye color). The pedologist, in contrast, is most interested in mixed traits
where the interaction of heredity with environmental factors can be observed (e.g. vision). (3-8~3-9)
C) In the general biological approach, the geneticist is interested in traits which clearly distinguish
children, rather than in those traits which different children have in common (e.g. eye color as
opposed to eye structure). The pedologist, in contrast, is most interested in the shared traits which
contribute to development in all children. (3-10~3-12).
D) In the general biological approach, the geneticist is interested in traits that by and large do not
change over time. In contrast, the pedologist is most interested in traits such as school marks, or
juvenile delinquency which vary from generation to generation. Vygotsky notes that a recent studies in
Germany showing that school marks and juvenile delinquency appear to vary less within families than
they do between families have been misinterpreted: a lack of variation in school marks or juvenile
delinquency within a family may be due to environmental factors and not simply hereditary ones. this
then raises the question of how the two different types of factors can be separated. (3-13~3-18).
II Comparative-Genetic Studies in Twins. In this section, Vygotsky lays out the method of
comparing monozygotic and dizygotic twins and applies it to a simple example: determining whether
speech acquisition or musicality is more dependent upon heredity.
A) Vygotsky explains the key difference between monozygotix twins and dyzygotic ones, and notes
that while the former are entirely identical in their genetic make up, the latter are no more closely
related than normal siblings (and may even be different genders). The problem, then, is to quantify the
difference between the pairs of twins of different types on a given trait. (3-19~3-20)
B) Vygotsky suggests, for example, that a pair of monozygotic twins and a pair of dizygotic twins could
be given tests of speech ability and tests of musical ability (the tests are, unfortunately, not described)
and correlation co-efficients (in this case, percentages of agreement) are calculated separately for the
different pairs of twins. The difference between the correlation coefficient of the monozygotic twins
and that of the dizygotic twins on tests of speech ability (0.96 vs. 0.89) is then compared to the
difference between the correlation coefficient of monozygotic twins and that of dizygotic twins on tests
of musical ability (0.93 vs. 0.67), and it is discovered that the difference is greater in the case of
musical ability (3-21~3-24).
C) Vygotsky explains that this means that heredity makes less difference in the case of speech than in
the case of musical ability. If heredity were a more important essential component of speech, then the
difference between hereditarily identical twins and that hereditarily non-identical twins would be large.
But in fact, the difference is small than with the trait of musical ability, and Vygotsky thus assumes that
musical ability is more dependent upon heredity. (3-25~3-28)
D) The problem of non-hereditary influence within families which marred the interpretation of the
German studies has now apparently been taken into account because monozygotic twins will have no
hereditary variation and only non-hereditary variation, while dizygotic twins will have both types of
variation. But Vygotsky notes that it is still necessary to take many pairs to study, because in fact twins
are sometimes treated quite differently and this may cause variations that can be confused for
hereditary variations. (3-29~3-30)
III Results. Vygotsky now sets us the task of generalizing these results into general laws, or
“propositions”. He proceeds inductively: In each case, he discusses the result of the study, sometimes
in an abstract logical form, and then “formulates” the proposition. This will be his procedure
throughout the lectures.
A) The first result is more elementary, lower functions tend to show larger differences in the
coefficients of similarity between monozygotic and dizygotic twins and higher, cultural functions tend
to show smaller differences. (Thus it would appear Vygotsky believes that in the eighteenth-century
debate between Rameau, who believed that speech evolved before musical ability, and Rousseau,
who believed that musical ability evolved before speech, Vygotsky does indeed take the side of
Rousseau!) Vygotsky concludes that the lower functions form, historically, a foundation for the
development of higher functions, which arise relatively late in sociogenesis (3-31~3-33).
B) The second result is that if we examine many functions synchronically and then attempt to array
the functions in order of their dependence upon heredity, we find that an equal-interval scale is
impossible (3-34~3-37). We will find that difference between twin-type correlation coefficients is quite
large in one group of functions (the lower, elementary ones) and quite small in another (the higher,
cultural-historical ones). Vygotsky then draws two conclusions from this result:
1. Lower-level functions (e.g. eye color) tend to be unmediated and they have a very short
path of development. This does not allow much time or scope for their modification by the
environment. Higher-level functions (e.g. reading ability) in contrast require mediation (the acquisition
of literacy) and thus offer a great deal of time and scope for modification and for the emergence of
something new (3-38).
2. Heredity itself has a different relationship to life in the case of the lower level functions and
the higher level ones. The relationship of heredity to lower level functions, it is a more or less direct
cause of development. But in the case of the higher functions, it is merely a precondition (3-39).
C) The third result is that if we examine the same function diachronically, at different moments of the
child’s life, we find that degree of heritability appears to change over time. This apparently nonsensical
conclusion is not simply due to the increase in the power of the environment over time, because the
influence of the environment may actually decrease. There are some functions, e.g. psychosexuality,
where hereditary inclinations may actually become more compelling over time (3-40~3-42).
D) This leads Vygotsky to his fourth result: There can be no general law of which defines the role of
heredity for all traits and at all times. Variation in the role of heredity takes place not only
synchronically, between traits, but also diachronically, in a single trait, as the power of the
environment waxes or wanes (3-43~3-45). Vygotsky concludes with two “corrollaries” drawn from the
last two results (that is, from synchronic and diachronic variation in heretibility).
1. The method of comparative study of twins applies only to traits which vary, and not to the
traits which all children have in common. We may easily observe that there is a difference in the
coefficient of similarity in eye color between monozygotic twins (where eye color is identical) and
dizygotic ones (where it may vary) and we surmise correctly that this large difference means that the
trait is hereditary. But we also observe that there is no difference at all in non-varying traits such as
eye structure, and we cannot draw the conclusion that this is not hereditary. Similarly, we may note
strong similarities in body type in both monozygotic twins and dizygotic twins that are not based on
varying traits, and we cannot thereby conclude that they are not hereditary (3-47).
2. Because pedology is interested in varying traits, we find that the it is never the case that a
trait is entirely heritable, with no environmental component, or that a trait is entirely environmental,
with no hereditary component at all. Nor is it the case that development can be calculated according
to a mechanical formula which suggests an unvarying relationship between heredity and the
environment. Like other aspects of growth, differentiation makes this quite impossible. Vygotsky
promises to study the other side of this problem, the environment, in the next lecture. (3-48~3-49).