thinking explained

thinking explained! (see sketch)

The above sketch is loosely based on Piaget's TGE. While I believe his theory plausibly describes the issues, I don't think it holds up in explaining how the stages develop. Its application to nonhuman primates can be useful in organizing results and relationships among primates but there is no reason to rule out parallel or convergent evolution for any similarities or deficits in behaviors. Finally, I doubt very much that all behaviors start out as unspecialized movements -- with all creatures 're-inventing the wheel" one after another.... not to mention those that are unable to move normally.

tool use

6. technology: tool use in primates

the importance of tool use

practical and theoretical,

Human culture and behavior is synonymous with tool use. The practical value of tools --from clubs, knives, and needles to computers and science -- even language --needs no comment.
The obvious differences between the universal use of tools by humans and their sparse use by NHPs suggests understanding tool use may reveal much about human nature and its origins.

mythology of tool-use

One might get the impression from some recent writers that NHP use of tools was a recent and surprising--even dismaying discovery. Savage-Rumbaugh (1995) says, for example, "The belief that man alone can make tools had gone by the wayside in the first years of Jane Goodall's observations in the field. p. 201"
Despite such suggestions to the contrary, tool use in NHPs has been known at least since Darwin. He noted, for example,:
It has often been said that no animal uses any tool; but the chimpanzee in a state of nature cracks a native fruit, somewhat like a walnut, with a stone. [37] Rengger [38] easily taught an American monkey thus to break open hard palm-nuts; and afterwards of its own accord, it used stones to open other kinds of nuts, as well as boxes. It thus also removed the soft rind of fruit that had a disagreeable flavour. Another monkey was taught to open the lid of a large box with a stick, and afterwards it used the stick as a lever to move heavy bodies; and I have myself seen a young orang put a stick into a crevice, slip his hand to the other end, and use it in the proper manner as a lever. The tamed elephants in India are well known to break off branches of trees and use them to drive away the flies; and this same act has been observed in an elephant in a state of nature. [39] I have seen a young orang, when she thought she was going to be whipped, cover and protect herself with a blanket or straw. In these several cases stones and sticks were employed as implements; but they are likewise used as weapons. Brehm [40] states, on the authority of the well-known traveller Schimper, that in Abyssinia when the baboons belonging to one species (C. gelada) descend in troops from the mountains to plunder the fields, they sometimes encounter troops of another species (C. hamadryas), and then a fight ensues. The Geladas roll down great stones, which the Hamadryas try to avoid, and then both species, making a great uproar, rush furiously against each other. Brehm, when, accompanying the Duke of Coburg-Gotha, aided in an attack with firearms on a troop of baboons in the pass of Mensa in Abyssinia. The baboons in return rolled so many stones down the mountain, some as large as a man's head, that the attackers had to beat a hasty retreat; and the pass was actually closed for a time against the caravan. It deserves notice that these baboons thus acted in concert. Mr. Wallace [41] on three occasions saw female orangs, accompanied by their young, "breaking off branches and the great spiny fruit of the Durian tree, with every appearance of rage; causing such a shower of missiles as effectually kept us from approaching too near the tree." As I have repeatedly seen, a chimpanzee will throw any object at hand at a person who offends him; and the before-mentioned baboon at the Cape of Good Hope prepared mud for the purpose.
In the Zoological Gardens, a monkey, which had weak teeth, used to break open nuts with a stone; and I was assured by the keepers that after using the stone, he hid it in the straw, and would not let any other monkey touch it. Here, then, we have the idea of property; but this idea is common to every dog with a bone, and to most or all birds with their nests.
The Duke of Argyll [42] remarks, that the fashioning of an implement for a special purpose is absolutely peculiar to man; and he considers that this forms an immeasurable gulf between him and the brutes. This is no doubt a very important distinction; but there appears to me much truth in Sir J. Lubbock's suggestion, [43] that when primeval man first used flintstones for any purpose, he would have accidentally splintered them, and would then have used the sharp fragments. From this step it would be a small one to break the flints on purpose, and not a very wide step to fashion them rudely. This latter advance, however, may have taken long ages, if we may judge by the immense interval of time which elapsed before the men of the neolithic period took to grinding and polishing their stone tools. In breaking the flints, as Sir J. Lubbock likewise remarks, sparks would have been emitted, and in grinding them heat would have been evolved: thus the two usual methods of "obtaining fire may have originated." The nature of fire would have been known in the many volcanic regions where lava occasionally flows through forests. The anthropomorphous apes, guided probably by instinct, build for themselves temporary platforms; but as many instincts are largely controlled by reason, the simpler ones, such as this of building a platform, might readily pass into a voluntary and conscious act. The orang is known to cover itself at night with the leaves of the Pandanus; and Brehm states that one of his baboons used to protect itself from the heat of the sun by throwing a straw-mat over its head. In these several habits, we probably see the first steps towards some of the simpler arts, such as rude architecture and dress, as they arose amongst the early progenitors of man.
(Descent of Man,1871, Ch.III)
Some of the earliest experimental work including that of Kohler and others documented considerable tool-using capability in the laboratory, supplementing the anecdotal observations from performing apes and early naturalistic observations (Garner, 189x).
Recent research --Goodall's observations on chimpanzees' use of sticks in ant fishing, detailed accounts of nut-cracking-- as well as experimental work demonstrate and more imortantly refine both the degree and limitations of tool-use in NHPs. This research does not radically change our conception of the primate order--except perhaps for those who were ignorant of prior work.
The more sophisticated recent analysis, do however, raise subtle and important questions about how individuals and social groups come to utililize tools.

does tool-use imply intelligence? (Bryne, 1996))

We can imagine Descartes' answer to the question --only if it is a flexible general usage with some understanding of cause-effect relationships.
Bryne says: "single, isolated cases of object manipulation give little confidence that the perpetrators have a general understanding of cause and effect relations among objects; a wider repertoire of tool use, showing some flexibilty, would point more clearly to intelligent usage....for a few species of primates....a picture of animals that can use a range of tools for a range of purposes, animals that can choose between methods. This suggests real intelligence 88-9."

(capuchins (cebus) monkeys)

These have relatively large brains and are generally thought quite intelligent for monkeys. Bryne suggests their success stems from their great activity rather than insight into why an object makes a useful tool. 93 This was Thorndike's (1901) conclusion as well. T&C describe much recent research on this question and come to similar conclusions:
"..the majority of monkeys..manipulate objects..but not interested in the effects their interactions produce...The two major exceptions are capuchins, (South American monkeys often used in circuses, etc.) and baboons...(They are ..prolific tool users).p62. I (JL) also add they have relatively large brains.

tools as temporary adaptations

primates as generalists

hand (and eye/brain) as basic adaptations

tools as artifactual specializations

3 contexts in wild




common chimps most noted tool users in wild

minimal tool construction

all seem capable in captivity

shows role of natural environment

Only the western chimps systematically crack nuts; this reflects availability and possibly some natural selection at work.

shows role of cultural environment

Orangs are the most obvious example. They apparently can do anything chimps do in captivity but seem to little in the wild.

acquisition of tool use (2 videos, Tomasello)

social learning: priming, or imitation?

The basic point here is that humans clearly can acquire knowledge from others by observation and instruction. Apes surely benefit from the presence of others with solutions to problems but exactly how remains unclear as Tomasello's (1994) experiments suggest.
For example, Tomasello (1994, p.304) says "it is possible in all the reported cases of the rapid spread of a tool-use behavior ..that one creative individual has made discovery and, as a result, propitious learning conditions and stimulus enhacement facilitate the individual discovery of others. This process is different from true 'imitative learning', in which the learner actually copies another's behavior or behavioral strategy." See Bryne (1995) for a thorough discussion.
Also see Nagell, K., Olguin, R. S., & Tomasello, M. (1993). Processes of social learning in the tool use of chimpanzees (Pan troglydytes) and human children (Homo sapiens). Journal of Comparative Psychology, 107, 174-186. (video data)

wild western chimps


unique in perception of intent or goals?

Bryne (1995), following Tomasello (1990) distinguishes "emulation" from other types of social priming in that the goal of the observed animal is emulated. Tomasello (1994) compares chimps with humans on this dimension.
"I believe these studies suggest that chimpanzees and human children understand the tool-using behavior of conspecifics in different ways. For human children, the goal or intention of the demonstrator is a central part of what they perceive and, thus, her actual methods of tool use--the details of the way she is attempting to accomplish that goal become salient. For chimpanzees, the tool, the food, and their physical relation are salient; the intentional states of tahe demonstrator and her preceise methods, on the other hand, are either not perceived or seem less relevant. p. 305"

universal social learning

universal tool building

significance of ape tool use in captivity?

tool use by captive primates

Kohler and others, Wright (1972) in HP, 232,, and Kanzi (video) all show skills at tools use--not to mention hundreds of imaginable circus acts and the achievements of the home-raised chimps.

evolution of tool use

hominid tool users

Homo habilis (handy man)

prerequisites to tool use

Much of this is captured in the descriptive features of the stages in Piaget's sensori-motor period.

causal understanding of the world

object permanence etc.

dexterity: timing and coordination

foresight and planning

Human tool use is not only universal; so is the culture of tool making.

positive feedback relating tool use to brain

size of brain

brain specialized circuits

especially coordination of eye-hand activity with planning for future

the importance of environmental stress

This sort of feedback is only likely when there are extreme advantages to using tools. In the rainforest environments, these advantages may not be great.

availability of hand, cerebral asymmetry etc.

Indeed the unique human hand, with its opposable thumb and precision grip may have been shaped by the increasingly important tool use of our ancestors. Susman (1994, 1995) argues that tool use shows up in the fossil record of the hominid hand about 2 million years ago, about 500,000 years after the earliest stone tools have been dated.

handedness in primates

While there are many reports of hand preference in primates, only humans as a species consistently show a right hand preference across many tasks.
Annett (19xx, 1991) has argued handedness is a genetic trait related to language.
MacNeilage (19xx) argues in his "postural origins" theory that handedness has its roots back in ancient prosimians who clung to branches with their right hand and reached for food with the left. One implication from this theory is that to really evaluate handedness, the animal has to be put in certain situation for a handedness tendency to reveal itself.
Overall species, there appear to be three general tendencies. The prosimians, like their ancestors, still display a left hand preference. whereas apes in varying degrees and situations and of course humans , prefer their right hand. In m
McGrew and Merchant, 1992, for example found no handedness in termite fishing but a right hand bias in reaching. Hopkins, Bard, Jones, and Bales, 1993 found an interesting relationship between throwing hand, position, and sex. Captive females were more likely to throw with the right hand in both four and two legged positions; while males used their right side much more when bipedal.
This raises some interesting speculation about the possible interrelationship of human lateralized function, language, and bipedality.

the "problem" of over capacity in primates

"Evolution could not supply an animal with mental or physical equipment of which it has no need, because there can be no selection pressure if the equipment is of no value in promoting survival. 222 HP"

possible answers to the "problem"

causal factors: "insight" or trial & error?

While different species may seem to use tools comparably, perhaps the development of those skills differed --much as earlier "learning set" studies showed that while many species could learn the rule to find food in the WGTA, primates did it quickly as some relative brain size measures would predict.

competence vs motivation

T&C suggest some apes have little or no motivation in their natural habitat to use tools. Of course this is why experimentalists want to use arbitrary tasks like rule learning or cooperative activities to determine abilities or "intelligence."

The environment

Everyone notices how chimps and orangs pick up many of human tool using skills to some extent when living with humans. This may be due to many factors including "enculturation" effects on attention, motivation, etc.

video scenes of NHP tool use

chimps nutcracking in the Tai forest

lots of ant fishing in Goodall

Tomasello's raking experiment: child vs ape

Galdikas' orangs

Kortlandt's throwing chimps

Kohler's tasks

Miles orang

Kanzi stone chipping

video (Primate imitation and cognition in lab)

video (Primate imitation and cognition in lab)

week xx

week xx


video "Language"--please read the video notes!

project topics


discuss language, a bit on evolution of language

exam questions?

video on mind in apes (30 minutes)?

week 13

4/09 exam 3

4/11 videos

Can chimps Talk? (Nova)

Kanzi starring in "Can chimps talk?" See the <a href="kanzi.html">transcript </a>in video notes. Note the following points:

relations among humans, bonobo, chimps

training of Kanzi

his language performance


interpretation/comparison of performance

interspecies communication
comprehension MUST precede production
a "pidgin" for here and now activities

"Pidgins" are based on bits and pieces of languages used by individuals who do not share a common language. Recall the discussion of the pidgins developed in the slave colonies in the 17th century in the Language video. Typically they do not have any syntax and few function words. Utterances are just a few "content" words --nouns, verbs, modifiers.

what's missing?

reference to mental states, epistemology,
Kanzi and dogs mostly produce requests, but very few questions, etc.
little or no evidence of syntax; no complement clauses, etc. Indeed the entire projective, creative aspect of human language (Limber, 1977) seems unique to human use of human language.

chimp aggression toward (fake) leopard

(This is video clip of an experiment mentioned in HP. Note the following points in the film.)

chimps use of "weapons"

innate fear?

mutual support during "attack"

role of habitat in response to leopard

(tree vs savannah chimps responses)

week 14


return exams

Consciousness conference report

Interspecies communication (apes, dolphins, Alex, dogs and apes. See abstracts by Limber, Reiss, Pepperberg, and Savage-Rumbaugh, on primate page.)


See course description. All papers (6-8 pages) need an approved outline, at least 2 references 1994 or later unless Oked by my, and must connect to the relevant course materials as well as relate to human behavior.

human language origins discussion

prerequisites and timing

bipedalism, increase in brain size and reorganization (laterality, >neocortex, radial projections from thalamus, special circuits for language), vocal tract
role of glacial cooling 2-3 mya (Calvin)
one origin theory?

Follows precisely the mDNA story--one small group in Africa were the ancestors of all humans, maybe 200,000-300,000 years ago. All human languages are essentially dialects of each other, just as we know the Romance languages (French, Italian, Spanish, etc.) are dialects descended from the language of the Romans.

Indo-European (IE)

English belongs to this family which includes nearly all European languages and some northern Indian and Asian dialects as well. IE was spoken around what today is Turkey and Armenia perhaps 5 to 10,000 years ago --before writing was invented less than 5000 years ago.

conditions leading to human language

These include the large brain, etc. above, high degree of pair bonding between M & F, increasingly sophisticated culture where there is a great fitness advantage in early acquisition of the communication system, and the several neotenous features characteristic of human evolution. (See Limber, 1982; Gould, 1977))
Bryne suggests, p.233, cognitive precursors to language-- especially attribution of intentions and beliefs to others, etc.

synergy between brain, culture, and language.

The human brain evolved and incorporated human language into it (the "Baldwin effect" Limber, 1982).
Human language is a clever compromise with instinctive components dealing with structure and an "open" component -the lexicon-- enabling new topics to be immediately discussed with the introduction of new words into the existing structures.


overview of remaining topics

sex , reproduction, and parenting

social structures in primates

See <A HREF="">Bonobo Sex and Society</A> (by Frans de Waal)<p>

aggression and competition

broad picture of human evolution

Tooby and Devore

ethical issues in primate research


Why sex?

It provides the necessary variation for natural selection to work upon-- whether size and shape of the beaks of Darwin's finches or the diversity of immune systems to protect the species against new strains of bacteria or viruses. Survival of species lies in variation. (It has also been suggested that two copies of each gene offers a backup in case one is not copied correctly.)

Social sexual differences among apes (deWaal)

(See <A HREF="">Bonobo Sex and Society</A> (by Frans de Waal)</a><br>

Sexual reproduction and differentiation in mammals (class notes)

Sexual dimorphism (differences in M/F bodies)

Sexual selection (Darwin)

week 15

4/23 video (de Waal Family of chimps)

These animals were the basis for deWaal's Chimpanzee Politics. One very important point to remember about this video is how much the zoo environment impacts the behavior of these chimps. For example, a steady food supply probably gives them more time to engage in other activities in addition to better health, more rapid maturity, and even larger in size. The environment also might allow the dominant male, Nikki, much greater control over the behavior of others who cannot escape into the woods for a little unsupervised fun! (Group size also may be important, too.)

synergy of prematurity, nursing, diet, MPI, and reproductive rates

synergy of prematurity, nursing, diet, MPI, and reproductive rates

We have already discussed the importance of diet in intelligence --both direct effects and indirect effects. Diet also plays a varied and critical role in fertility. (See the Ackerman interview of Ellison in readings.)
All of the issues below contribute to a primate species rate of reproduction.

sexual maturity--genes and diet

fertility a function of nursing frequency and body fat

prematurity and nursing aided by high MPI

lactation demands

A normal 2000 calorie woman requires double that when nursing. Coupled with the extreme helplessness of a human infant, male parental investment (MPI) seems critical in early Homo sapiens survival.

summary of human "reproductive strategy"

4/25 video (goodall) get study guide for exam 4

week 16

4/30 video (New Chimps)

aggression and reconciliation

parenting, attachment, socialization

modelling evolution (read about it!)

some points from Tooby & Devore, Small, and Bryne

ethical implications of research (ditto!)

5/02 last exam

week 17

5/07 last class

week 18

5/15 papers due