Table Of ContentThe Lopsided Ape
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The
Lopsided
Ape
Evolution of the
Generative Mind
MICHAEL C. CORBALLIS
Department of Psychology
University of Auckland
Auckland, New Zealand
OXFORD UNIVERSITY PRESS
New York Oxford
Oxford University Press
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Copyright © 1991 by Oxford University Press, Inc.
First published in 1991 by Oxford University Press, Inc.,
198 Madison Avenue, New York, New York 10016-4314
First issued as an Oxford University Press paperback, 1993
Oxford is a registered trademark of Oxford University Press
All rights reserved. No part of this publication may be reproduced,
stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, recording, or otherwise,
without the prior permission of Oxford University Press, Inc.
Library of Congress Cataloging-in-Publication Data
Corballis, Michael C.
The lopsided ape / Michael C. Corballis
p. cm. Includes bibliographical references and index
ISBN 0-19-506675-8
ISBN 0-19-508352-0 (Pbk.)
1. Laterality. 2. Human evolution
3. Brain—Evolution. I. Title.
QP385.5.C67 1991 152.3'35—dc20
90-22905
2 4 68 10 9753
Printed in the United States of America
Preface
In the 1950s, when I was an undergraduate, basic psychology
seemed to be built very largely on work with animals. We spent a
good deal of time discussing whether rats in mazes learned which
turns to make or which places to go to, or discussing how the rates at
which they pressed bars depended on the pattern of rewards they
received. The dominant figure of the time was the behaviorist B. F.
Skinner. I remember also the excitement of the ideas proposed by D.
O. Hebb, in many ways the founder of modern neuroscience as it
pertains to psychology. In all of this, it seemed to be taken for
granted that the same principles of behavior applied to humans as
to other animals, an idea that seemed at the time to have a vaguely
subversive quality to those of us with conventional upbringings.
Indeed, I am afraid it was probably the whiff of heresy that attracted
me away from mathematics and to psychology.
But how things have changed! In my own department animals are
slowly but surely disappearing, and mainstream psychology is now
based primarily on research with humans. No longer are we comfort-
able with the assumption that results based on animals can be ex-
trapolated to our own species. This change was due in part to the
classic confrontations of the late 1950s and early 1960s between
Skinner and Noam Chomsky, a linguist who revived the dualistic,
Cartesian idea that there is an unbounded quality to the human
mind that is not to be found in other animals. But change may have
been in the wind anyway, since the behaviorism of the 1950s and
1960s had seemed to place a straitjacket on the study of the mind. A
new sense of the special nature of humanity emerged, and such
human-based topics as memory, attention, language, and conscious-
ness moved to center stage.
This switch from an animal-based to a human-based science re-
flects an age-old tension in the way we view ourselves. For much of
our history we have seen ourselves as closer to God (or gods) than to
the animals, but there has always been a heretical and often sup-
vi Preface
pressed sense of our animal nature. This was reinforced by the
growth of secular science, which provided mechanistic accounts of
the way our bodies worked, and indeed revealed close parallels be-
tween the workings of our own bodies and those of other animals.
For some time, scholars such as Descartes were still able to preserve
at least a part of the human mind for some higher realm. The ulti-
mate challenge, of course, came from that mild but far-seeing En-
glishman, Charles Darwin. At first reticent over the implications of
his theory of natural selection, he eventually made clear his view
that we are indeed a part of the animal kingdom, and share a com-
mon ancestry, not so remote, with the apes.
Even in a secular age, it still seems reasonable to some to insist on
a fundamental discontinuity between humans and other animals. In
part, the issue has focused on the supposedly special nature of hu-
man language, and this is discussed in some detail in the following
chapters. It has also been argued that humans are endowed with a
special kind of consciousness, including self-consciousness, that is
not possessed by other animals. This has proven a more intractable
argument, partly because consciousness has proven peculiarly diffi-
cult to define. The notion of consciousness seems to depend on our
own subjective sense of what it is to be conscious, and so long as this
is so, other animals are placed at a distinct disadvantage .
This book focuses the question of human discontinuity on lat-
erality. Although I was fearful that evidence on animal asymmetries
would overtake me, it still seems to be the case that right-
handedness and cerebral asymmetry are unique to humans—
unique not so much in their presence as in their extent, pattern, and
population bias. Moreover it is not laterality per se that is critical so
much as the nature of functions that are lateralized, which them-
selves seem to capture much of the essence of what it is to be human.
Handedness is related to our extraordinary ability to manufacture
and manipulate, and cerebral asymmetry is most pronounced with
respect to that putatively unique faculty, language.
In order to develop my themes, I have been obliged to cover mate-
rial from a range of disciplines, some outside my own areas of exper-
tise. I have therefore tried to avoid excessive jargon and to write in a
way that is understandable to nonspecialists. Since my own exper-
tise is in cognitive psychology and neuropsychology, I am aware that
my attempts to do this are uneven. I am also aware that much of the
material, especially that on human evolution, is highly controver-
sial, and that my conclusions may be seen by some as biased or
wrong. I have simply tried to make the best sense of the material
that I could.
I have also tried to make each chapter as autonomous as possible,
Preface vii
so that readers familiar with some material can skip chapters. No
chapter is immune from my own interpretations, although I hope
the coverage is sufficiently broad to serve also as a general review,
even for those who disagree with my conclusions. The crux of my
argument for human uniqueness is developed in Chapter 9, and
knowledgeable readers avid for the message (or for blood) might
proceed directly there. My theme also suggests a revision of popular
notions of hemispheric duality, which is discussed in Chapter 10.
However, I have tried to organize the material in such a way that the
case is built up in logical sequence, so that readers with widely
ranging backgrounds can follow it.
I have used notes at the end of each chapter rather than references
in the text so as not to interrupt the flow of the text, and technical
details are sometimes covered in the notes. I have nevertheless pro-
vided a fairly comprehensive list of references. In this, I was mindful
of a colleague who once wrote to me to say how much he appreci-
ated an earlier book I wrote—because he found the references use-
ful. Anything to please.
I could not have finished this book had I not been granted Re-
search and Study Leave from the University of Auckland in 1989.I
am grateful to Professor Francesca Simion of the University of
Padua, Italy, Dr. Alan Baddeley of the MRC Applied Psychology Unit
in Cambridge, England, and Dr. Justine Sergent of the Montreal
Neurological Institute, Montreal, Canada, for arranging for me to
spend time in each of their institutions. All three visits were produc-
tive for me, and I am sorry that I was so obsessed with writing that I
neglected to contribute much to their endeavors. Countless col-
leagues have contributed, but I should like to single out for special
mention Marian Annett, Irving Biederman, Daniel Bub, Martha
Farah, Philip Johnson-Laird, Wayne P. Lawrence, John Macnamara,
Tony Marcel, Paula Marentette, Brenda Milner, Jenni Ogden, Isa-
belle Peretz, Gill Rhodes, Tim Shallice, Lynette Tippett, and Robert
Zatorre—although I expect none of them is in complete agreement
with me. I am also grateful to the students in my 1990 graduate
seminar in "Mind and Brain," who discussed the chapters in class
and made several useful suggestions. A special thanks, too, to Jeffrey
House of Oxford University Press for his friendly advice and en-
couragement.
Finally I thank my wife Barbara and sons Paul and Tim, who put
up with me while we traveled to glorious places, while all I could
think about was The Book.
Auckland M. C. C.
August 1990
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Contents
I. Are Humans Unique? 3
2. Human Evolution, 30
3. The Human Condition, 52
4. Human Handedness, 80
5. Human Language, 109
6. The Evolution of Language, 136
7. Language and the Brain, 168
8. Praxis and the Left Brain, 191
9. The Generative Mind, 218
10. The Duality of the Brain, 247
I1. The Plastic Brain, 280
12. Conclusions, 305
References, 315
Index, 353
Description:Most people are right-handed, though with a substantial minority of left-handers: this is such a familiar feature of human existence that we rarely think about it at all (especially if we are right-handed), and now that schools no longer try to force left-handers to write with the right hand, the ps
