DANIEL J. POVINELLI
University of Louisiana at Lafayette
in collaboration with
JAMES E. REAUX, LAURA A. THEALL
AND STEVE GIAMBRONE
OXFORD UNIVERSITY PRESS
2000
CONTENTS
An initial word about 'folk physics' page vii
Preface page ix
1 Folk physics cannot be assumed page 1
2 Escaping the argument by analogy page 9
3 Causality, tool use, and folk physics: a comparative approach page 73
4 The trap-tube problem page 108
5 The trap-table problem page 132
6 The inverted- and broken-rake problems page 149
7 The flimsy-tool problem page 163
8 The tool-insertion problem: the question of shape page 173
9 The rope, hook, touching-stick, and related problems: the question of
physical connection page 206
10 The support problem: physical connection revisited page 254
11 The bendable-tool and tool-construction problems: the question of tool
modification page 271
12 Toward a folk physics for chimpanzees page 297
References page341
Appendix I page 365
Appendix II page 369
Appendix III page375
Index page 385
A QUOTE FROM THE INTRODUCTORY MATERIAL
'Honored Members of the Academy!
You have done me the honor of inviting me to give your Academy an account
of the life I formerly led as an ape.
I regret that I cannot comply with your request to the extent you desire.
It is now nearly five years since I was an ape, a short space of time,
perhaps, according to the calendar, but an infinitely long time to gallop
through at full speed as I have done, more or less accompanied by excellent
mentors, good advice, applause and orchestral music, and yet essentially
alone...
In revenge, however, my memory of the past has closed the door against me
more and more. I could have returned at first, had human beings allowed it,
through an archway as wide as the span of heaven over the earth, but as I
spurred myself on in my forced career, the opening narrowed and shrank
behind me; I felt more comfortable in the world of men...'
from Franz Kafka, A Report to an Academy
AN INITIAL WORD ABOUT 'FOLK PHYSICS'
physics (fiz'iks) n 1. (used with a sing. v.) The science of
matter and energy and of interactions between the two, grouped in
traditional fields such as acoustics, optics, mechanics, and
thermodynamics, as well as modern extensions including atomic and nuclear
physics, cryogenics, and particle physics.'
Physics is the most basic of the sciences, concerning itself with
the interactions of energy, matter, space, and time, and especially with
questions of what underlies every phenomenon.2
Surely chimpanzees and other apes do not possess scientific theories about
matter and energy, let alone group them into academic sub-disciplines?
Indeed, the idea that they have any kind of science at all seems a bit
preposterous. So, why have we invoked the term 'physics' in the title of
this book?
The reason is simple: chimpanzees, like us, must confront the
world of matter and energy every moment of their waking lives. And so, like
us, they must possess some kind of understanding or knowledge about the
movements and interactions of the objects that surround them. This
knowledge may not constitute a science, of course, but it may well be a
body of knowledge that is, to some extent or another, organized and
coherent. To make the point clearly, think for a moment about our own
infants and children. Modern psychological research has revealed that they
know a surprising amount about how and why the physical world works the way
it does. Indeed, from a very early age infants and children are already
constructing quite sophisticated ideas about concepts such as gravity,
force, mass, and shape. And yet we would not want to say that these infants
and children have developed a science of physics. Of course, there may be
striking parallels between how children come to discover the regularities
of the world and the methods that scientists use (observation,
experimentation, revising one's ideas in the light of new evidence, etc.),
but to describe this as a formal science of physics may be too far a
stretch for most readers.
On the other hand, we might be perfectly comfortable talking about
infant's and children's 'folk physics', that is, their common-sense
understanding of how the world works, as well as why it works in the way
that it does. Likewise, chimpanzees and other nonhuman species may possess
a kind of folk physics as well. However, short of simply guessing, there is
no principled way of knowing ahead of time how similar or different the
ape's folk physics is to our own.
Of course, it is possible simply to suppose from the outset that
because chimpanzees are so closely related to us, and because they must
confront more or less the same physical universe as we do, they understand
the world in a very similar manner. We adopt a different approach. The
purpose of the research reported in this book is to break down this general
supposition of similarity into a series of specific, testable hypotheses
concerning chimpanzees' understanding of concepts such as gravity, force,
mass, shape, and physical connection (to name just a few), and then to
subject these hypotheses to serious experimental scrutiny.
1. The American Heritage College Dictionary, (3rd edn, 1993), p. 103 1.
Houghton Mifflin, Boston.
2. Paul Peter Urone ( 1998), College physics. Brooks/Cole, Pactfic Grove.
FROM CHAPTER 1
Folk Physics Cannot Be Assumed
Daniel J. Povinelli
This book is the result of a five-year project designed to explore how
chimpanzees conceive of the physics that underlies their use and
construction of simple tools. The project was designed to use experimental
techniques to explore what chimpanzees understand about why tools produce
the specific effects that they do. In doing so, the project begins with a
clear recognition that chimpanzees naturally make and use simple tools in
the wild, and that in captivity these activities may be even further
elaborated and refined (see Chapter 3). However, our project seeks not so
much to document tool use and manufacture by chimpanzees, but to elucidate
the nature of the mental representations that guide this behaviour. In
short, we want to explore their 'folk physics' of tool use and manufacture.
Although it may seem like an odd way of introducing our work, we
are quite fond of reflecting on what our most dogged skeptic might say
about this project, and in particular, whether it is even necessary in the
first place: 'Look,' the skeptic might begin, 'isn't it obvious that
chimpanzees and other great apes understand the physical principles
governing simple tool use in just about the same manner that we do? Haven't
we all seen enough National Geographic specials to know that chimpanzees
make and use tools spontaneously and naturally? They crack nuts open using
hammer stones and they construct simple fishing-wands to extract termites
from their mounds. So why do we need to bring them into the laboratory and
test them on their ability to use tools? Anyhow, didn't some famous German
psychologist-Kohler, maybe?-demonstrate almost a century ago that captive
chimpanzees can use tools in remarkable ways, such as stacking boxes on top
of one another to gain access to bananas suspended out of reach?' As we
mentioned, starting with this skeptical voice may seem odd to some readers,
suggesting that we have accepted a defensive posture from the outset.
Nothing could be further from the truth. After all, on our very best days
as scientists, this skeptical voice repeats over and over in our minds,
reminding us of the fact that our project is a difficult one indeed.
But where does this skeptical voice come from? We believe it
derives from an assumption about animals that is very difficult to escape.
It is an assumption that the eighteenth-century philosopher, David Hume,
found to be unassailable; it is an assumption that was present over a
century ago when the field of comparative psychology was being founded by
Charles Darwin; and it is an assumption that was even explicitly stated
when the field was formally codified by Darwin's champion, George John
Romanes. Even today, the invisible tentacles of this assumption run deep
and tangled through our efforts to understand the minds of other species.
The assumption, quite simply, is that when it comes to trying to compare
the mental lives of humans and other species, analogous behaviors imply
analogous minds. For over three centuries, philosophers and scientists
alike have, to greater and lesser degrees, assumed that when we see animals
behave in ways that look very similar to ours, they must be thinking in
ways that are very similar to ours. As we shall see, this idea has come to
be known as the argument by analogy-so-named because the argument relies on
an analogy of sorts between what we believe to be the causal connection
between our own thoughts and behaviors (namely, that our thoughts cause our
behaviors) on the one hand, and the behavior and (inferred) thoughts of
nonhuman species, on the other. Simply put, since we know that some
particular thought (let us call it 'thought X') caused some particular
behavior ('behavior Y') in us, then if we see behavior Y in an animal, it
must have been caused by something very much like thought X.
As should be obvious by now, it is precisely the argument by
analogy that gives rhetorical force to the skeptical outlook we introduced
earlier. Recall that, in the case of tool use and tool making, the
skeptic's position is that when we see chimpanzees cracking nuts using
hammer stones and anvils in the same manner that humans do, it is a safe
bet to assume that they understand the physical principles in the same
manner we do.
Thus, the intuitively persuasive appeal of the argument by analogy
forces us to ask whether we really need to proceed with carefully
controlled, laboratory-based tests of chimpanzees' understanding of tool
use. We have come to believe that the answer is a resounding 'yes.' and, as
we shall see, the reason for this answer is that there is an alternative to
the skeptic's position-an alternative to the conclusion dictated by the
argument by analogy. As we shall explain more fully and clearly in Chapter
2, it is possible that similar behavior-even among closely related
species-does not guarantee a comparable degree of psychological similarity.
Indeed, escaping the argument by analogy allows us to take a fresh look at
the mental lives of other species, a look which may one day allow us to see
them without the fog of our own way of thinking about the world shrouding
their true natures.
ABOUT THE AUTHOR
Daniel Povinelli received his undergraduate degree in physical anthropology
from the University of Massachusetts at Amherst in 1986, and his PhD. from
Yale University in 1991. He is currently an Associate Professor at the
University of Louisiana at Lafayette where he conducts his comparative
studies of the mental lives of chimpanzees and children.
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