intelligence-98 perspectives

Intelligence: the main themes

intelligence: a touchy topic!

Discussions of intelligence can be counted on to offend one group, race, species or another! As Stephen Gould suggested in his Mismeasure of Man, -- a critique of nineteenth century efforts to relate brain size to intelligence -- the topic tends to bring out the prejudices of those working on the problem.

Herbert Spencer on brain and intelligence

Spencer <a href="">(1820-1903)</a> was a very original thinker, with many ideas on evolution is sometimes credited with founding sociology.
...well developed nervous systems will display a relatively marked premeditation--an habitual representation of more various possibilities of cause, and conduct, and consequence--a greater tendency to suspend judgments and an easier modifiction of judgments that have been formed. Those having nervous systems less developed, and with fewer and simpler sets of connexions among their plexuses, will show less of hesitation--will be prone to premature conclusions difficult to change. Unlikenesses of this kind appear when we contrast the larger brained races with the smaller brained races--when from the comparatively judicical intellect of the civilized man, we pass to the intellect of the uncivilized man, sudden inferences , incapable of balancing evidence, and adhering obstinately to first impressions. And we may observe a difference similar in kind but smaller in degree between the modes of thought of men and women; for the women are the more quick to draw conclusions, and retain more pertinaciously the beliefs once formed......

Galton on Intelligence

Francis Galton,
<a href="">(1822-1911)</a> was Darwin's cousin and a prominent scientist, who among other accomplishments invented the concept of linear regression in his effort to understand the heredity of traits as well as actually try to quantify intelligence. He was also a founder of the widespread eugenics movement to improve the human race. By 1931, thirty states in the US had passed sterilization laws.
"I propose to show in this book that a man's natural abilities are derived by inheritance, under exactly the same limitations as are the form and physical features of the whole organic world. Consequently, as it is easy, notwithstanding those limitations, to obtain by careful selection a permanent breed of dogs or horses gifted with peculiar powers of running, or doing anything else, so it would be quite practicable to produce a highly gifted race of men by judicious marriages during several consecutive marriages."
Galton, F. (1869). Hereditary genius, an inquiry into its laws and consequences .

perspectives on intelligence

adaptive ability?

Darwin, Piaget .... almost everyone supposes intellect or reason helps the organism adapt! But Descartes earlier made an often neglected point -- if an accomplishment is too easy maybe its NOT done by intelligence ("reason") at all -- but instead it's just an instinct. The adaptation has already been accomplished in evolution and the individual just does it! This issue has resurfaced, for example, in criticism of Piaget and other theorists who presume abilities are constructed or learned without innate domain specific "assistance."

not just capability for such and such..

Descartes (1596-1650) responding to Montaigne's "Essays" on abilities of animals, argues that automatic ability in animals does not show reason; instead it shows none!
"nature makes them behave as they do according to the disposition of their organs; just as a clock, composed only of wheels and weights and springs can count the hours and measure the time more accurately than we can with all our intelligence. Descartes, R. (1641) Discourse on Methods, Fifth Part.

perhaps intelligence is related to LACK of specialization?

This of course is consistent with the extreme neotenous condition of humans. Recall our discussion of the ontogeny of primate forelimbs-- also very unspecialized compared to other mammals.

While Descartes' argument comes out of a cultural, scientific, linguistic, and religious environment quite remote from our own, it provides a high contrast background against which to evaluate human and animal abilities. Just because, for example, human children acquire language much more rapidly than home-raised apes, are the humans more intelligent? Not if -- as Descartes put it "nature makes them (children) behave as they do according to the disposition of their organs.." The same is true regarding bipedalism.
We cannot assess the "intelligence" of an organism by observing it in its natural environment for which we suppose it is already well-adapted. The question is whether or how much of this adaptation is due to the "intelligence" of the individual rather than inheritance from its ancestors (ontogeny vs phylogeny, nurture vs nature). Thus it's conceivable that a well-adapted organism, highly specialized for its niche, is quite stupid!
The bottom line here is that comparisons among species on behavior that is "natural" to one of them makes conclusions about their respective "intelligence" very doubtful. If adaptive intelligence has any useful meaning, it must be applied assessed in situations where generalization or transfer to new settings is involved and innate factors do not weigh heavily on performance.

Can we do without a concept of intelligence?

Apparently some behaviorist psychologists thought so in that they believed the general principles of behavior could be discovered using almost any species and that the only differences were in sensory-motor processes and perhaps size of memory. Although much of what they had to say about behavior in general seems now misguided, we might consider that the idea of "intelligence" is an intuitive concept better understood in terms of differential component processes including sensori-motor and memory processes, processing rates, motivation, domain-specific abilities, and the self-organizing characteristics of the brain as it develops in particular environments.

psychometric approaches (within humans)

Psychologists' efforts to measure intelligence, general to compare within species: Galton, Binet, Terman, Yerkes... Lots of problems, some success.

standardized norms, reliability, validity

The serious problems come on establishing validity; Binet and others focussed on schooling potential --with specific types of schools in mind!

general vs multiple specific intelligences

Is there just one factor in "intelligence" or is a concept with many diverse parts, more or less independent of each other? Or both?

domain general vs domain specific

Similar to the above distinction, this terminology arises in developmental studies concerned with the origins of "modular" abilities, i.e. the extent to which different skills or abilities are interrelated or correlated or exchange information. (e.g Tomasello & Call, 1997, sec, 12)

animal learning comparisons

Learning arbitrary rules, e.g. which container has the food. There's evidence that, if properly controlled to eliminate sensory or motor advantages, relatively larger brains learn arbitrary rules, generally to get food (adapt?) more quickly. (HP)
Harlow developed the concept of "learning set" to express this idea of "learning to learn" -- i.e. become increasingly effective in problem solving problems of a certain type with experience.

home-raised apes vs children

This proved a useful test of the role of environment; Kohts, Kelloggs', Hayes' and recent studies of human "enculturated" apes show some important similarities and limits of apes vs. children. (See "social/cultural" below.)


Studies of brain size, structure, processes, nutrition and various social deficits on intelligence.


The role of environment and social structure in modulating intelligent behavior is one focus of Bryne's book. Recently it has been observed that IQ scores on standardized tests have been rising across generations --the so-called "Flynn effect." Extrapolating across the 100 years of these tests, an individual scoring in the top 10% in 1900 would be in the bottom 10% today with the very same performance. This is quite a change that must be due to social/cultural factors -- schooling, parenting, health and nutrition factors.

other factors comprise/enhance intelligence

In addition to sensory-motor abilities and memory, such factors as temprament, curiosity, attention, and motivation determine intelligent behavior. IS there any need for the concept of intelligence itself?

evolutionary factors in intelligence

Anything leading to larger brains, e.g. social structure (Dunbar); foraging (Milton); neoteny and related factors (Gould), throwing (Calvin), tools, language.........

assessment of human intelligence

assessment of human intelligence

Galton, Binet, Terman, Yerkes.....WISC, Stanford-Binet

Many psychometric measures devised to measure differences in human intelligence over the last 100 years.
Intelligence tests today tend to have a combination of general and specific factors, with debates on every dimension --theoretical and applied.

Some of the varying perspectives on intelligence

Piaget's TGE

Intelligence is the general apparatus that governs one's adaption to one's environment by generating structures (schemes, concepts) in interaction with that environment. It is more or less constant across members of a species.

knowledge of the physical world

space, objects, time, causality, quantity, etc.

Intelligence aids the child in constructing the concepts fundamental to knowledge of the world out of basic sensorimotor reflexes and interactions with the world. Much of this is achieved in the first two years -- the "sensorimotor period."

knowedge of the social world

This same intelligence is applied to the social world.

self, egocentricism, language and logic, morality

The early Piaget studied these topics, then turned to the infant's sensorimotor beginnings upon which in TGE, socialization depends.
Recent research based on new methods of working with infants has cast doubt some of Piaget's conclusions in that rudiments of knowledge in various specific domains like object permanence, language, and even number are present in the first year.

Application to non-human primates

the sensori-motor stages

See Chevalier-Skolnikoff, S. (1977). A Piagetian model for describing and comparing socialization in monkey, ape, and human infants.
Tomasello and Call (1997) apply these concepts to foraging and social cognition.


TGE itself is undergoing much criticism in regard to its claims on human development, especially in regard to human language and its demand that all abilities be derived from a small set of sensori-motor processes and general "intelligence."
Recent research on infants suggests they come equipped with much more specific structure than Piaget believed.
Piaget was also concerned with "consciousness" and how various abilities interact and are extended by human culture, e.g. science.

learning and conditioning models

These are usually based on animal research

Thorndike, E. L (1874-1949)

Thorndike, student of William James and teacher of Yerkes(?), was perhaps the first psychologist to experimentally explore the nature of intelligence in animals. He is known for his "law of effect."
In his research on cebus monkeys and other birds and mammals, Thorndike proposed there was only associative trial and error activity; success on a trial increased its probability of use. There is an important truth here; the problem lies in characterizing how "trials" come about are and are evaluated. In addition, successes and/or errors must be somehow taken account of. He suggested several behavioral differences corresponding to differences in intelligence -- the rapidity that error trials were inhibited and "imitation" that served to elevate one "trial" over another. Few animals other than humans showed evidence of imitation. This remains a controversial issue today.
Thorndike, E. L. (1901). The mental life of the monkeys. Psychological Monographs, 3, 1-57.

Kohler, Wolfgang (18xx-19xx)

Argued some apes used "insight" based on his observation of their manner of solutions. He contrasted this with trial and error processes developed by Thorndike. "the insight of the chimpanzee shows itself to be principally determined by his optical comprehension of the situation..p. 277 in many cases in which the chimpanzee stops acting with insight, it may have been simply that the lie of the land was too much for his visual grasp (relative "weakness of shape perception"). Thus "insight" seems to involve an ability to manipulate in one's head the visual scene imagining a solution.
Kohler, W. (1925). The mentality of apes. New York: Harcourt, Brace and Co.

Yerkes, Robert (1876-1956) and students

See PC, e.g. Tinklepaugh.

Harlow , Harry (190x-1980)-- "learning sets" and the WGTA

Harry Harlow pioneered methods of evaluating "learning set" ability -- the ability to form and use a rule -- across species using his Wisconsin General Testing Apparatus (WGTA).
Passingham (1982) summarizes much of the research in the figure below, showing performance of various species on a two-choice visual discrimination task in which the organism picks one of two objects with a hidden reward under it. Essentially the subject must learn a rule --that the food is under a certain type of object despite other changes in position or features of the objects--and follow that rule in choosing.

Sketched from Fig. 5.8 in Passingham (1980).
Passingham concludes from these data that when mammals are ranked in terms of their improvement over a series of these problems, their rank is predicted by Jerison's (1973) measure of surplus brain cells.

brain and other biological factors (see 1996 intelligence notes)

brain size (suitably relativized)

Relative brain size has been shown to predict rule -learning (above) and even "curiosity (below)."
Passingham notes that relative brain size predicts well the responsiveness ("curiosity") of zoo animals to novel objects over time. Suppose animals just get bored after exhausting their repertoire of responses to the object. Perhaps brain size indirectly reflects the variety of responses available to various species. Primates have the obvious handling advantage over carnivores, for example. And humans have a linguistic repertoire far exceeding that of any other primate.

Responsive of zoo animals to novel objects
Sketched after Fig. 5.10, Passingham (1980)

factors in brain size


Obviously if brain size evolved due to natural selection, there must be heritable component. Recent estimates in terms of correlation indicate an r about .5 or so.


early experiences

Darwin, Harlow, Bowlby and attachment


a complex synergistic relationship (see figure below) between nutrition and intelligence

what created the primates' (and humans) large brains?

foraging and nutrition?

Obtaining food plays a double role.
In phylogeny of a species, it drives evolution of the necessary mental capacities for obtaining food as well as in ontogeny of an individual, nutrition plays a complex role in maximizing the intelligence of the organism. (See diagram below adapted from Brown and Pollitt (1996) on the complex effects of malnutrition.)
Adequate nutrition is also fundamental to fertility thus linking foraging to the spread of "intelligence" in the population. Thus foraging involves a syergetic combination of factors relating to intelligence.

social factors?

Humphries (1976) and others have suggested that social cognition is so important in primate society, that big brains are needed to deal with this social complexity, e.g. facial recognition, keeping tabs on dominance, communication, etc.

a result of shrinking body size?

a variety of heterochronous factors might be involved. There are many ways to skin a cat!

throwing and hunting?

Throwing and a variety of tool-using activities might have conspired to increase brain size.

human language?

It seems possible that human language requires a specialized and large brain to deal with the phonology, syntax, huge lexicon, and semantic structures involved.

all of the above?

Several factors, acting synergistically, may be involved.

none of the above?

Might this just be a correlated result of selection for some other factor like body size alone?

social cognition

How "well" do organisms' represent and interact with conspecifics and other relevant species?


faces, calls, smells



(human language, human-based codes)

A human-based code (HBC) is a means of communication between humans and animals that is based on a human language though without its complexity in most cases. The signs, tokens, and sign-boards used in various research projects are HBCs.

predict others behavior

cues from behavior]

represent others beliefs ("theory of mind")

ontogenetic ritualization

A pair of individuals "essentially shape one another's behavior in repeated instances of a social interaction. PC 301" In this way a behavior that initially was not a signal becomes one as each of the pair can use the behavior by virtue of the expected response of the other. Think of humans interacting in familiar settings, e.g. ordering in a favorite restaurant or a potential sexual encounter with an intimate partner.

manipulate and deceive others?

Lots of anecdotes, but hard to show reliably in non-humans as a result of representations of other minds.

learning from others -- social learning?

While it is natural to think of apes "aping" one another, the actual state of affairs in most natural settings is not clear. There are several ways knowledge can be transmitted from verbal instruction, modelling and imitation, to various combinations of trial and error facilitated by a social presence. See Tomasello and Call (1997, p. 279) on chimp tool use, for example. Bryne (1996)

modeling social influences that affect existing brain records

social priming of existing "brain records"

From Fig. 5.2 in Bryne, p.62. A classification of the various explanations of social influences on learning related to the idea of priming brain "records" by observing another organism.

What are characteristics of "intelligent" creatures?

Data from Gould (1977), Passingham (1980) and reflection suggest a complex of interrelated characteristics are observed in intelligent creatures. Many of these derive from the neotenous condition of primates but can be expected to reflect "intelligence" in other species who happen to have similar characteristics.

large brain and "surplus" neurons

This probably is important in representing experience and "working memory."

long life

The more experience to accumulate.

high parental investment

small numberof offspring (reproductive strategy)

long period of immaturity and degree of immaturity at birth

The better to shape the brain for new circumstances and to learn from experienced adults.

high manipulative ability

Manipulating a limb or vocal tract requires a brain capable of representing, planning, and transmitting information. These manipulations themselves may be useful or their brain space might be used for other intelligent activity.

dexterity in hand, paw, claw, bill, trunk, tentacle, and vocal tract

The puppetmeister metaphor is useful here; how may strings and how often must you pull them gives a rough indication of the sophistication of the system. Generally speaking, more degrees of freedom require greater information flow per unit time.
The most complex example is probably speech, where Darley, F. L., Aronson, A. E., & Brown, J. R. (1975). Motor speech disorders . Philadelphia: Saunders estimate 14,000 muscles must be controlled and at a very rapid rate!

reafferent affects on CNS
decreases boredom factor (increase curiosity?)

complex vocal communication

Both brain requirements and social functions are important.

complex social organization

high visual acuity

Vision requires a sophisticated nervous system that can be used for "intelligent" actions--vision thus is perhaps a useful preadaption for intelligence. It may be particularly important enabling the use of visual imagery in problem solving. See Piaget's "figurative intelligence" and Kohler's "insight", etc.

summary on intelligence, TGE -- humans and apes