Brain and socio-cultural environment - Luciano Mecacci

J. Social Biol. Struct. 1981 4, 319-327
Brain and socio-cultural environment
Luciano Mecaccit
Istituto di Psicologi.a de/ Consiglio Nazionale de/le Ricerche, Roma, Italy
The human brain is currently studied as a natural object working in a world of
natural stimuli. Brain functional organization depending on the socio-cultural
environment is not sufficiently considered. Research perspectives are outlined in
order to verify the hypothesis of the social and cultural influences on brain
functioning.
In early physiology textbooks, the study of the nervous system was called the 'physiology
of relational life' to indicate the fact that in studying the nervous system the relations
between the animal or human organism and the environment were to be investigated. The
present paper sets out to examine certain characteristics of the concept of environment as
it is used in neurophysiology as well as the critical aspects displayed by this concept when it
is extended to the study of the human brain.
Brain as a natural object
What was meant in classical neurophysiology by the term environment is comparatively
easy to establish. Suffice it to mention the reflex arc model which dominated neurophysiological
research up to the mid-twentieth century. In explaining reflex mechanisms, Descartes
in his Treatise of Man (1972) gave several illuminating examples, e.g. the well known figure
of the boy burning his foot in the fire and withdrawing it immediately. The reflex action is
a response to a stimulus from the environment, i.e. the fire in the above example (Fig. 1).
Several centuries later, in his fundamental work on neurophysiology, Sherrington (1906)
cited the processes that occur when we look at the sun as an effective example of the interaction
between organism and environment. Fire and sun are the natural equivalents of the
environment stimuli used in neurophysiology laboratories, i.e. heat, light, sound and touch
stimuli etc., which are nevertheless still stimuli belonging to the natural environment, that is
to say, which may be described by physics and quantified by mathematics.
The first criticism that could be made is, of course, the one levelled against the behaviorists
in their study of animal behavior, i.e. the artificiality of the environmental situation reproduced
in the laboratory. This criticism is known to be quite justified when it is claimed that
the elementary mechanisms studied in the laboratory may be used as the basis for an
explanation of molar behavior in the natural environment. This criticism is less justified
tRequests for reprints should be addressed to Luciano Mecacci, lstituto di Psicologia del CNR, Via dei
Monti Tiburtini 509, 00157 Roma, Italy.
0140-1750/81/040319 +. 09 $02.00/0 © 1981 Academic Press Inc. (London) Limited

320 L. Mecacci
Fig. 1. The boy burning and withdrawing his foot is the classical illustration from
Descartes' Treatise of Man of the idea of reflex. The stimulus (fire) affects the
receptors of the foot: the impulse is transmitted along the centripetal nerves to the
brain from which the response is ordered and transmitted along the centrifugal
nerves again to the foot. The figure is yet another example of the traditionally
naturalistic view of the brain. It is worth of noting that this famous figure was not
of Descartes himself and was inserted by the editor in the posthumous publication
of the book according to the text
when applied to a neurophysiology having a more limited scope, i.e. the study of the elemen
tary mechanisms of the nervous system as such.
A much more serious problem in our opinion is the one connected with the stimuli
used in neurophysiology to reproduce the environmental situation. Recent studies of the
neurophysiology of vision have shown that the stimuli used in the laboratory are often not
those most suitable for the nervous system. The stimuli chosen by the neurophysiologist are
those corresponding to the output, i.e. to the end result of the inner, nervous transformations
undergone by the true, suitable stimuli. For instance, although the triangle we perceive is the
final output of our brain's activity, the cells of the visual system have not actually 'seen' a
triangle as such, but only a set of physical and structural properties. Consequently, if it is
our aim to study the elementary mechanisms of the visual system according to a neurophysiological
method, the suitable stimulus is not the one that immediately springs to the
researcher's mind, nor those with which he has a daily familiarity; the suitable stimulus
consists of the underlying physical and structural properties. This critical observation is all
the more applicable in the case of neurophysiological research into such complex processes
as perception, memory, language etc., where an anthropomorphic or perhaps an unconsciously
phenomenological type of approach may be found: in studying the brain, the
researcher makes use of those stimuli that, in his experience, i.e. according to how things
appear to him as subject, the stimuli are activating brain activity.
In addition to the naturalness or artificiality of stimuli, another important aspect of the

Brain and socio-cultural environment 321
concept of environment in neurophysiology is the problem of environmental influences on
neurones and brain activity. Up to a few decades ago it was believed that the environment
and the nervous system interacted and that a stimulus activated the nervous system and that
the latter responded to the stimulus, without the mechanisms involved in the response being
modified by the stimulus. Only the response was believed to vary as a function of the
stimulus and not the mediation mechanisms. About ten years ago this conception began to
be challenged. Here we are concerned not only with research on changes in brain chemistry
produced by the environment in which the animals live (Horn, Rose & Bateson, 1973;
Bennett, Diamond, Krech & Rosenzweig, 1964), but above all with visual deprivation
studies. The first sensational experiments were reported in 1970 and the one by Blakemore
and Cooper had the significant title of 'Development of brain depends on the visual environment'
(Blakemore & Cooper, 1970; Hirsch & Spinelli, 1970). Basing their work on previous
literature concerning the selectivity of visual cortex neurones to orientation, the authors
raised kittens from birth in a cylinder, the walls of which were lined with black and white
bars. They found that the adult cats had only neurones that were particularly responsive
to the vertical bars, if the animals had only been exposed to vertical bars, and only neurones
that were particularly responsive to the horizontal bars in the case of exposure only to the
latter. These experiments were repeated many times and also came in for harsh criticism
(Blakemore, 1978; Maffei & Mecacci, 1979, chapter VII). However, two important facts
were established: the brain mechanisms and organization genetically acquired by the animal
at birth may be extensively modified by environmental stimuli and thus not produce normal
responses; secondly, this effect is possible only in certain critical post-natal periods. By
means of this type of experiments, modem neurophysiology investigates the relations
between brain and environment in a plastic fashion, as a set of interactions that may have
a direct effect on the brain processes governing the interactions themselves. Although these
studies have so far only been carried out using animals, it is believed that the results could
be extended to a description of the properties of the human brain.
The main workers in the field of contemporary neurophysiology, following a tradition
handed down from master to disciple, have investigated the elementary processes of the
nervous system, reflex activity, synapses and receptors, as well as the wider significance
of their research for an understanding of the human brain (Sherrington, 1940; Adrian,
1947; Eccles, 1970; Granit, 1977). The human brain is believed to have basically the same
functional characteristics as the animal brain, which neuroscientists have investigated directly,
as well as certain peculiar properties, to which Sherrington and Eccles have given a purely
spiritualistic connotation: where the brain described by neurophysiology is found to
be wanting, they tum to the soul, an entity that can only be defined in fanciful, nonneurophysiological
terms. The soul or some other spiritualistic explanation is made use of
wherever the problem is raised of the relations between brain and consciousness, between
the brain and man's higher intellectual activities. Taking as one's starting point a physicalistic
and naturalistic conception of the environment with which man's brain supposedly interacts,
i.e. the environment studied by classical neurophysiology, leads directly to the dualistic
solution of Sherrington or Eccles: on the one hand, the brain with its laws described by
neurophysiology, surrounded by a world of light, sound and tactile stimuli; on the other,
'something' on which the value, the consciousness and the cultural products of an individual
living in human society are dependent.
History of the brain
This situation changes as the human brain is considered in the context of a different conception
of man and of the relationship between man and nature. The nature with. which

322 L. Mecacci
man interacts is not just a collection of abstract physical phenomena but a nature transformed
by man during the history of production and the history of science and culture. In
the context of our discussion of environmental stimuli, the pure physical stimuli belong to
an abstract nature produced by the mind of the neuroscientist. They do not correspond to
the environment on which the development of human history is based. This does not mean
that these abstract stimuli do not activate nervous and brain processes. All would probably
agree that by varying light wavelengths or sound frequencies it is possible to explain the
fundamental processes the human brain shares with other animal species but not its specific
characteristics. The problem is that these stimuli are not the stimuli which activate the
nervous and brain processes at a level of complexity of the responses displayed by the
highly developed brain of the human species.
Stimulus abstractness is not, however, the most difficult aspect to clarify in brain research.
There is another, more ticklish problem. The nature man has changed is not only the nature
of the surrounding environment, but also the very nature of man himself, his body and
above all his brain.
A comparatively little known theoretical approach which may prove useful in tackling
this problem was proposed by the Soviet psychologist Lev S. Vygotsky (1978) in the early
thirties and elaborated systematically by Aleksandr R. Luria, who was also responsible for
the most valid and best known extension of this theory to experimental and clinical research
(Luria, 1973; Mecacci, 1979). Vygotsky introduced an expression which represented a
complete novelty in the traditional theories of the brain-namely 'history of brain functions'.
The term was used to indicate that the human brain has a history of its own, not only in the
sense that it represents the product of a biological evolution, but also in the sense that the
human brain develops as a function of human and social history. In our interpretation, this
theory asserts that the human brain is genetically equipped with a complex of structures as
a functional organization, the maturation of which may take place at different times after
birth. However, brain functional organization does not depend only on genetically preset
maturation. It also depends on the interaction between the individual and his social and
cultural environment and, as the latter is determined historically, it ultimately depends on
history itself.
To use Luria's terminology, human psychological processes consist of an integrated system
of simpler processes, each of which is a function of a specific brain structure. These integrated
systems are called 'functional systems' (Luria, 1973). They develop during ontogenesis under
the influence of social and cultural variables. For instance, color perception in human
beings consists of a system of neural functions which is more complex than in the other
animal species. Indeed, in human beings, color perception not only involves the structures
(and their functions) connected with the wavelength decoding as in other animals (i.e.
retina, lateral geniculate body and other brain structures), but also a functional connection
with the language brain centres. The connection between specifically visual coding and
verbal coding, which are mediated by different brain centres, is achieved during ontogenesis
along with the child's language acquisition. Thereafter color perception consists of a functional
system integrating visual and verbal functions. However, this brain organization is not
the same in the brain of all the human beings as it is affected by socio-cultural variables, as
shown by cross-cultural studies on color naming (Bornstein, 1973). Fabrega (1977) has
pointed to other research areas where a cultural differentiation may be perceived in the
universally physiological processes of the human species (e.g. pain perception). Crosscultural
psychological research can therefore also prove useful as an indirect demonstration
of the effects of social and cultural influences on brain organization. Special mention must
be made in this connection of the approach by Cole and co-workers (Cole & Scribner,
·

Brain and socio-cultural environment 323
1974), which takes account of Vygotsky's and Luria's theory of the higher psychological
functions as brain functional systems and culturally determined processes.
The question arises of whether there is any chance of verifying these hypothetical social
and cultural influences on brain functional organization by studying directly the brain
functions. Two hitherto comparatively unexploited lines of approach appear to be particularly
interesting. The first of these consists of the investigation of the functional differences
in the brain of individuals belonging to different cultures, and the second is
concerned with the brain of individual human beings. The study of the brain of individuals
of different cultures may be understood in two, albeit complementary, ways. One approach
would be to study the brain of individuals having lived in different periods of human history.
The investigation of the brain of hominids has reached a high methodological level. However,
the scope of neuropaleoanthropological research has so far been the ascertaining of
constant features rather than variations in the structural and functional organization of the
human brain (Holloway, 1974; Washburn, 1978). The possibility of studying the development
of the functional organization of the human brain in more recent historical ages would
be enhanced by the availability of indirect evidence provided by archeology and historical
documents. No systematic research has been carried out on this subject. One interesting
example of indirect reconstruction is the ascertainment of the dominance of the right hand.
Art documents have made it possible to establish that for at least fifteen thousand years the
right hand has been dominant in various human activities (hunting, working, writing etc.)
(Coren & Porac, 1977). The second type of approach is concerned with the brain functional
organization in living populations of different cultures. This type of investigation
could make an important contribution to the verification of the socio-cultural hypothesis.
No systematic investigations have been carried out in this area either. A distinction must be
made between research comparing populations at roughly the same level of civilization (i.e.
an area which could be defined as cross-cultural neuropsychology) and research on populations
at a primitive level (neuroanthropology). One highly promising line of investigation
in the area of cross-cultural neuropsychology is the comparison of the degree of hemisphere
specialization in different populations. One large body of data concerns right-hand preference
as an index of brain lateralization (Dawson, 1977) or the differences in lateralization
effects in visual and verbal tasks found by comparing, for instance, Jewish and English
people (Orbach, 1967), Spanish-English bilinguals and monolinguals (Walters & Zatorre,
1978), English and Japanese people (Hatta, 1979).
Recent studies on the 'Japanese brain' (Tsunoda) deserve special mention. Research on
the brain organization of speech (Tsunoda, 1973, 1976) have evidenced a different functional
specialization of the two brain hemispheres in the Japanese with respect to Western
populations. This seems to be due to a special language acquisition process in the Japanese,
to a special interaction between verbal coding and external verbal and non-verbal information
and to the verbal mediation of the culturally learned 'meanings' given to the external
stimuli. For instance, a human voice, an animal's noise, (e.g. the barking of a dog, birds
singing) or the sound of Japanese instrumental music are processed by the left hemisphere
in the Japanese brain, while in Western populations it is the right hemisphere which is
dominant in the processing of this information. According to Sanches (1979), these stimuli
are processed in the left hemisphere because they are full of a communicative value
unknown to Westerners. This communicative value, these meanings, are obviously learned
in the iapanese socio-cultural environment in which the young Japanese is reared. Closely
related to Tsunoda's and Sanches' data on the relations between brain and speech in the
Japanese is the literature on brain organization underlying writing and reading. There are
two writing systems in Japanese-a logographic system (kanji) and a phonetic system (kana)

324 L. Mecacci
kana
kanji
Fig. 2. Kana and kanji writing systems are used in the same text. To process the
two systems Japanese brain has a special function organization
(Fig. 2). Research on Japanese aphasics indicates that these two systems are mediated by
different brain structures (Sasanuma, 1975), while experiments on normal subjects have
shown that the right hemisphere is dominant in recognizing kanji characters and the left
hemisphere in recognizing kana characters (Hirata & Osaka, 1967; Sasanuma, Itoh, Mori &
Kobayashi, 1977; Hatta, 1977). These results are confirmed by the performance in reading
in the two systems of Japanese patients after partial commissurotomy. The Japanese can
read written material presented in the left visual field and projected into the right hemisphere
when this material is in kanji characters. In the case of kana material (phonetic type),
deficiencies are observed which are similar to those found in Western 'bisected brain' patients
(Gazzaniga, 1970) for whom verbal material, in order to be read, must be presented in the
right visual field and projected into the left hemisphere (Sugishita, Iwata, Toyokura, Yoshioka
& Yamada, 1978). This interaction between brain hemispheres in the Japanese in reading
and writing is once again a historical phenomenon due to the superimposition of the Chinese
script (from which kanji derived) on the Japanese spoken language in about the fifth century.
Ever since then, the brain functional organization in the Japanese which is involved in writing
and reading processes has had a different development than in Western populations. The
processing of Chinese language and writing in the Chinese does not appear to require the
brain organization typical of the Japanese (Tzeng, Hung, Cotton & Wang, 1979; Naeser
& Chan, 1980), while the decoding of the two writing systems in Korean appears to
require differentiated processing and probably also differentiated brain processes (Park
& Arbuckle, 1977).
The question of whether it was possible to set up a neuroanthropological study was raised
by Paredes & Hepburn (1976) who used the principle of the functional asymmetry of the
two cerebral hemispheres to explain the cross-cultural characteristics of cognitive processes.
Variations between populations are thought to depend on a different lateralization of the

Brain and socio-cultural environment 325
cognitive processes in the two hemispheres, on the predominance of one of the hemispheres
in overall brain organization, which would be dependent on the specific types of interaction
with the environment according to the means of production, social relations and culture of
the populations involved. To our knowledge there has been no systematic investigation of
hemisphere specialization in primitive populations. In addition to experiments on normal
subjects, it would also be necessary to investigate disorders of the cognitive processes produced
by brain lesions in individuals belonging to such populations. The discussion aroused
by the article of Paredes & Hepburn (1976) has revealed the need for a rigorous study of
hemisphere asymmetry in Western and Eastern populations, both primitive and not, before
making overgeneralizing extrapolations of the type: the Westerner's analytical ant'l logical
mind is indicative of left hemisphere dominance, while the synthetic and mystical Eastern
mind is due to right hemisphere dominance.
The other main line of research is based on the study of the brain of single individuals.
Also in this case several methodological approaches are possible. Firstly, with reference to
the above-mentioned studies on hemisphere specialization, there have been several recent
experiments which have evidenced individual differentiation in the effects of lateralization
and manual preference. The degree of hemisphere specialization correlates with various
indexes of cognitive style (Pizzarniglio, 1974) and of personality (Charman, 1979), while
professional activity, for instance in artists (Mebert & Michel, 1980), has been found to
affect manual preference. Individual variations in brain activity have been subjected to
systematic research by Soviet workers ranging from the Pavlovian conception of types of
nervous system to current studies correlating psychophysiological differences with cognitive
performance and personality proftles (Mecacci, 1976; Powell, 1979). A further approach is
concerned with the effects of brain damage on psychological processes. The latter approach
is preferred by Luria who has devoted several works to the detailed description of clinical
cases (e.g. the classical case of aphasia analysed in Luria, 1972). The clinical approach, in
its peculiarities, differs from the experimental approach based on a comparison between
different individual cases. What is significant in the clinical approach is the subject's previous
history, his culture and his personality which has been damaged by the brain lesion. In the
. experimental approach it is attempted to find a correlation between psychological disorders
and damage to specific brain structures which is valid above and beyond any peculiar individual
manifestations (Luria & Majovski, 1977). The history of brain functions is thus more
than the mere development of the human brain through human history. The development of
the brain functions interacts with the environmental variables and the functional organization
is dependent upon this interaction. A man's brain thus consists of a functional organization
that has developed in a specific social and cultural environment and any damage to this brain
will have an effect which varies from one individual to another. Also, in verifying this
hypothesis, the studies carried out on the brain organization of subjects who learnt a second
language early in life are extremely significant. The 'bilingual brain' is found to have a functional
organization which differs from the 'monolingual brain' and this organization varies
according to the languages involved (Albert & Obler, 1978). Also subjects having suffered
from deprivation in their emotional and social relationship in early life and who have not
acquired language in the normal way are thought to have a different brain functional organization
according to experimental evidence, as is indicated by the interesting case of Nadia,
an autistic little girl with extraordinary drawing ability (Selfe, 1977), and Genie, a little girl
whose lilte acquisition of language is thought to have been mediated by the right hemisphere
(Curtiss, 1977). Individual variations in brain functions (and thus in behavior) may be
considered as due to anatomic differences. Research on the anatomy and cytoarchitectonics
of the brain of 'normal' and 'eminent' persons has revealed a wide range of individual

326 L. Mecacci
variability {Sarkisov, 1966; Meyer, 1977). Apart from the methodological problems involved
in research of this kind, it must be considered that the results are often interpreted as the
proof of the 'inborn' nature of individual psychological differences, the latter being apparently
based on differences in brain structure. Until such time as more systematic data become
available on brain structure from birth to adulthood, when it will be possile to verify
whether this structure remains constant in time from one individual to another, or whether
it changes, the opposite interpretation, according to which the individual variations found
post mortem in both normal and eminent adult brains are due to specific interactions
between their brain and the environment, will continue to be valid.
Conclusion
The human brain is not just a vessel or an instrument at the service of values or of a culture
imposed from outside. It is the brain itself which, in its interaction with the social and
cultural environment and in its individual variety manifested over the human history, produced
and yet produces values and cultures. However, in both current neurophysiology and
neuropsychology, the aim of research is to detect resemblances rather than differences in
brain functions. In view of this approach, an abstract environment has been created for the
purpose of studying the responses of a brain that shares many features with that of other
animal species, but has little in common with the human brain. Neurophysiological and
neuropsychological research is not to be rejected in the study of the human brain and the
latter is to be entrusted to psychologists, sociologists, and philosophers. It is a matter of
changing the direction of the lines of research when we want to appreciate the significance
of man's biosocial dimension at the level of his most important structure-his brain.
References
Adrian, E. D. (1947). The Physical Background of Perception. Oxford: Clarendon Press.
Albert, M. L. & Ohler, L. K. (1978). The Bilingual Brain: Neuropsychological and Neurolinguistic
Aspects of Bilingualism. New York:.Academic Press.
Bennett, E. L., Diamond, M. C., Krech, D. & Rosenzweig, M. R. (1964). Science 146, 610.
Blakemore, C. (1978). Maturation and modification in the developing visual system. In
(R. Held, H. W. Leibowitz & H. -L. Teuber, Eds) Perception. Berlin: Springer.
Blakemore, C. & Cooper, G. F. (1970). Nature 228, 477.
Bornstein, M. H. (1973). Psycho/. Bull. 80, 257.
Charman, D. K. {1979). Cortex 15, 655.
Cole, M. & Scribner, S. (1974). Culture & Thought: A Psychological Introduction. New
York: Wiley.
Coren, S. & Porac, C. (1977). Science 198, 631.
Curtiss, S. (1977). Genie: A Psycholinguistic Study of a Modem-day "Wild Child". New
York: Academic Press.
Dawson, J. L. M. (1977). An anthropological perspective on the evolution and lateralization
of the brain. In (S. J. Dimond & D. A. Blizard, Eds) Evolution and Lateralization of the
Brain. Ann. N. Y. A cad. Sci. 299, 4 24.
Descartes, R. (1972). Treatise of Man. Cambridge, Mass.: Harvard University Press. (Originally
published 1662.)
Eccles, J.C. (1970). Facing Reality. New York: Springer.
Fabrega, H. Jr. (1977). Ann. Rev. Anthrop. 6, 419.
Gazzaniga, M. S. ( 1970). The Bisected Brain. New York: Appleton-Century-Crofts.
Granit, R. (1977). The Purposive Brain. Cambridge, Mass.: MIT Press.
Hatta, T. (1977). Neuropsychol. 15, 685.
Hatta, T. (1979). Percept. Mot. Skills 48, 917.
Hirata, K. & Osaka, R. (1967). Psychologia 10, 7.

Brain and socio-cultural environment
327
Hirsch, H. V. B. & Spinelli, D. N. (1970). Science 168, 869.
Holloway, R. L. (1974). Scient. Am. 231(1),106.
Horn, G., Rose, S. P.R. & Bateson, P. G. (1973). Science 146, 610.
Luria, A. R. ( 1972). The Man with a Shattered World . New York: Basic Books.
Luria, A. R. ( 1973). The Working Brain. Harmondsworth: Penguin.
Luria, A. R. & Majovski, K. V. ( 1977). Am. Psycho!. 32, 959.
Maffei, L. & Mecacci, L. (1979). La Visione: Dalla Neurofisiologia alla Psicologia. Milano:
EST Mondadori.
Mebert, C. J. & Michel, G. F. (1980). Handedness in artists. In (J. Herron, Ed.) Neuropsychology
of Left-handedness. New York: Academic Press.
Mecacci, L. ( 1976). Pavlovian J. biol. Sci. 2, 93.
Mecacci, L. (1979). Brain and History: The Relationship between Neurophysiology and
Psychology in Soviet Research. New York: Brunner/Maze!.
Meyer, A. ( 1977). The search for a morphological substrate in the brains of eminent persons
including musicians: A historical review. In (M. Critchley & R. A. Henson, Eds) Music
and the Brain: Studies in Neurology of Music. London: Heinemann.
Naeser, M.A. & Chan, S. W. -C.(1980). Neuropsychol. 18, 389.
Orbach, J. (1967). Neuropsychol. S, 127.
Paredes, J. A. & Hepburn, M. J. ( 1976). Cur. Anthrop. 17, 121.
Park, S. & Arbuckle, T. Y. (1977). J. exp. Psychol.: Hum. Learn. Mem. 3, 631.
Pizzamiglio, L. (1974). Percept. Mot. Skills 38, 700.
Powell, G. E. (1979). Brain and Personality. Westmead: Saxon House.
Sanches, M. (1979). Lang. Sci. 1, 35.
Sarkisov, S. A. (1966). The Structure and Function of the Brain. Bloomington, Ind.: Indiana
University Press.
Sasanuma, S. (1975). Brain Lang. 2, 369.
Sasanuma, S., Itoh, M., Mori, K. & Kobayashi, Y. (1977).Neuropsychol. IS, 547.
Selfe, L. (1977). Nadia: A Case of Extraordinary Drawing Ability in an Autistic Child.
London: Academic Press.
Sherrington, C. S. (1906). The Integrative Action of the Nervous System. New York:
Scribners.
Sherrington, C. S. ( 1940). Man on his Nature. London: Cambridge University Press.
Sugishita, M., Iwata, M., Toyokura, Y., Yoshioka, M. & Yamada, R. (1978). Neuropsychol.
16,417.
Tsunoda, T. (1973). Proc. Japan Acad. 49, 643.
Tsunoda, T. (1976). Proc. Japan Acad. 52, 528.
Tzeng, 0. J. L., Hung, D. L., Cotton, B. & Wang, W. S. -Y.(1979). Nature 282, 499.
Vygotsky, L. S. (1978). Mind in Society: The Development of Higher Psychological Processes.
Cambridge, Mass.: Harvard University Press.
Walters, J. & Zatorre, R. (1978). Brain Lang. 6, 158.
Washburn, S. L. (1978). Scient. Am. 239 (3), 146.