Resolving the debate on innate ideas:
Learnability constraints and the evolved
interpenetration of motivational and
conceptual functions
John Tooby§ and Leda Cosmides§
Short title: Motivational unlearnability
§
Center for Evolutionary Psychology,
University of California, Santa Barbara, CA 93106-3210
Corresponding author:
John Tooby
Co-Director, Center for Evolutionary Psychology,
University of California
Santa Barbara, CA 93106-3210
tooby@anth.ucsb.edu
phone: 805 899-0067
Center fax: 805 965-1163
Center Web Page: http://www.psych.ucsb.edu/research/cep/
Key Words: innateness, motivation, learnability, evolution, induction, Hume, evolutionary
psychology
Overview
Plato says...that our “necessary ideas” arise from the preexistence of the soul, are not
derivable from experience—read monkeys for preexistence.
Charles Darwin, M Notebook
For almost a century the consensus among mainstream scholars has been that general learning
abilities, intelligence, and the capacity for culture insulates almost all human behaviour and
mental content from regulation by adaptively specialized neural circuitry. One common view is
that the evolution of a culture-absorbing brain was accompanied by the erasure of specialized
circuitry, turning the human mind effectively into a blank slate. On this view, our evolved
neurocognitive architecture resembles a tape recorder in that it is designed to register
environmental signals – ambient culture or direct experience – without introducing any content
of its own. Evolved procedures are considered to be free of content-like elements, to operate
uniformly regardless of the content they receive as input (i.e., to be content-independent), and to
be designed to operate on extremely general categories of information (i.e., to be domaingeneral). Aside from perceptual systems, models of learning mechanisms that are considered
plausible are those whose elements are abstract, global in scope, and content-independent (e.g.,
co-occurrence, contingency, contiguity, non-contradiction). On this view, the concepts and
contents that inhabit the mind reflect the world (to the extent that they do) because our learning
system is powerful enough to internalize the patterns present in experience. (These, of course,
may include false social communications and cultural conventions as well). There is no great
distance between modern neo-associationists, for example, and Aquinas when he said “There is
nothing in the mind that was not first in the senses.”
Evolutionary psychologists, beginning with Darwin, realized that, in addition to the senses, there
is a second possible route through which content could enter the mind, and come to reflect the
real structure of the world: Natural selection. Random mutations in the instructions for
constructing the brain could introduce design features which induce the development of a diverse
array of innate content. Those that induced the formation of content that that helped guide
behavior towards more effective reproduction would spread to become part of the standard
species design – that is, it would become part of the species’ genome. In short, genetic
inheritance (interacting with stable features of the world) could build into the reliably developing
neurocomputational architecture of the organism what once would have been called innate ideas
– that is, content-like concepts, specialized inferences, data formats for certain contents that
impose specific conceptual organization, and so on. Indeed, it is difficult to see how this would
not lead to something resembling a Kantian state of affairs – certain a priori or seemingly
necessary ideas would play a central role in organizing experience and thought, without their
being cognitively derived from something earlier.
Hence, an evolutionary psychological viewpoint is as follows. (i) The neurally based learning
and decision-making capacities of humans include specializations that evolved among our
foraging ancestors to solve the specific adaptive problems posed by the statistical and causal
structure of the ancestral world. (ii) These evolved because circuitry that includes specialized
content-like design features tailored to the distinct properties of an adaptive problem domain can
routinely outperform problem-solving strategies that are restricted to using the same procedures
on all problems regardless of their structure. (iii) Because these specializations constitute at least
part of the circuitry through which learning and development proceed, they introduce evolved
content into the mind (motivations, concepts, regulatory variables, etc.) that predispose the
individual to think, feel, and behave in ways that would have been adaptive given the recurrent
statistical structure of the ancestral world. (iv) Moreover, these specializations influence the
content of cultural elements that are acquired from and transmitted to other individuals in a way
that reflects, to some extent, the design and operation of these evolved problem-solving circuits.
Advocates of the environmentalist position dominated the intellectual world for almost a century,
and without much of an empirical foundation simply considered it self-evidently implausible that
there might be evolved circuitry that includes as part of its structure the modern
neurocomputational equivalent of innate ideas or evolved content. However, with the rise of
modern cognitive science, the debate between environmentalists and nativists became
transformed into a debate between computational nativism and computational environmentalism.
Because the capacities of proposed computational architectures can be actually dissected,
analyzed, emulated, and field tested, broad and vague claims about the computational power of a
proposed general learning rule can be evaluated and often falsified. Chomsky was the first to
make use of this new analytic power to demonstrate that the finite state grammars that
underwrote behaviorism were incapable of explaining language.
Logically, Chomsky’s arguments and (for example) Pinker’s learnability theory analyses
demonstrate the need for “innate ideas” in the acquisition of grammar. Sociologically, however,
this argument has failed persuade the majority of cognitive and behavioral scientists of nativism
in grammar, much less that there is a rich, complexly textured innate structure for many domains
of human mental content and cognitive competence. One reason for this failure to persuade is
that grammatical patterns in human language are objectively present in the world, tempting
researchers to speculate that they might eventually find some kind of cognitive architecture that
could detect such patterns without any assistance from computational machinery specialized for
the task. This same property of (apparent) objective truth applies to many other domains for
which nativist psychologists have claimed to see evidence for innate ideas or specialized
competences: Objects are permanent and solid; agents seem to really exist and have beliefs;
faces exist and differentiate identities; life forms really do fall into a hierarchical taxonomic
structure; people regularly engage in social exchanges. For most cognitive and social scientists,
traditional pretheoretical commitments make it seem more attractive to assume that hypothesized
general learning systems of undetermined structure are responsible for the mind building
conceptual reflections of the objective properties of the world, even if we do not have any model
of how this actually happens.
However, if it can be shown that organisms need to acquire – and do develop – competences
based on patterns that are not objectively present in the external world, then no possible contentindependent learning architecture could acquire those competences unassisted by “innate ideas”.
If a pattern is not in the external world, then it cannot be observed in or learned from the external
world. The impossibility of learning things that are not present in the world to be learned would
demonstrate conclusively the reality of innate ideas, resolving the issue sociologically (one
hopes) as well as analytically. Hume’s argument that one cannot derive an ought from an is
suggests one major class of such competences fitting this precondition: motivational
competences. Although Hume was discussing the impossibility of deriving moral deliverances
from sets of facts, his argument generalizes to the (im)possibility of deriving any value-based or
motivationally based conclusion simply from states of affairs. After all, a computational
architecture could be designed to adopt any of an infinite number of motivational stances (or
none at all) with respect to any given state of affairs. From the point of view of the designs of
organisms’ neurocomputational architectures, motivational systems evolved to cause the
organism to pursue ends that, on average, under ancestral conditions, would have promoted its
own or its relative’s reproduction. The solution of various adaptive tasks requires the valuing of
a large and irreducibly heterogenous set of outcomes, such as copulation, status, offspring
welfare, predator avoidance, mate valuation, contagion avoidance, incest avoidance, ingestion of
food, friendship or alliance maintenance, and so on. Evolved motivations must be packaged with
conceptual machinery that makes the motivation meaningful and targeted on the appropriate set
of adaptive outcomes. The desire to avoid eating disgusting things requires conceptual
machinery for specifying what entities are disgusting. The desire for a mate depends on the
specification of an adult conspecific of a particular gender and threshold of attractiveness. The
desire to avoid having sex with one’s parent requires conceptual machinery that links certain
conditions or anticipated outcomes to certain motivational responses.
In short, the value of a behavioral outcome is not objectively present in the external world, and
so cannot be learned from the external world through content-independent means without the
assistance of innate ideas (that is, some kind of evolved, content-specific neurocomputational
circuitry). Therefore, any concept or category necessary for adaptively specifying a goal state
required for the successful functioning of an organism’s adaptations must be, in some way,
innately (that is, evolutionarily) specified. Such categories are numerous, and so innate ideas
necessarily exist and must be numerous as well. Environmentalists might discount learnability
arguments that center on the acquisition of knowledge in the external world, assuming that some
hypothetical 99999
To pick an exotic but illuminating example, infanticide of nursing infants by newly dominant
males has evolved in a number of mammalian species, including primates, carnivores, and
rodents. The adaptive function for the new male of killing the infants is that the infant’s mother
ceases to lactate, since the dead infant no longer nurses. Lactation inhibits ovulation, so when
lactation ceases, the female rapidly becomes fertile again – far earlier than she would have if her
infant had survived to weaning. Males with motivational circuits that cause them to kill nursing
infants leave more descendants than males who are indifferent to nursing infants, and who
therefore must wait many months before weaning naturally occurs. That is why the infanticide
motivational circuit spread in these species, displacing non-infanticidal designs. Of course, the
motivational circuit cannot be designed to kill all nursing infants – after the male has been in
residence for a period longer than pregnancy, the infants that begin to be born are his offspring.
Killing them would select that male’s design out of the population. So the circuit must be
indifferent to infants when the male has no prospect of becoming the dominant resident male; it
must become motivated to kill the infants immediately after becoming the dominant male; it
must stay on until all the previous males nursing infants are dead or weaned; it must continue to
motivat the male to kill infants born after he took over the group, but that were conceived before
he took over the group; it must turn off around the time that the infants being born are likely to
be his. It must not waste effort on killing weaned infants, since their deaths will have no impact
on his reproduction. And so on.
This example illustrates a number of key points. The first is that it is possible to pair any
motivational goal to any stimulus – the environment does not and cannot supply the information
about what motivational stance to adopt toward a stimulus. The mother of the infant (and the
infant’s aunts and grandmother, as well as the infant) are strongly motivated to defend the life of
the infant. The male is motivated to kill the infant. Predators frequently attack, kill, and carry
off infants – to them, the infant is relevant to the hunger system. Secondly, this motivation in the
male is incommensurate – it cannot be derived from any other motivational system: The male
expends considerable effort; the male is often injured in the course of this behavior. Ordinary
pain and effort avoidance systems would not generate this behavior. There must be some innate
conceptual apparatus in the evolved architecture of the infanticidal male that individuates
“unweaned infants in a newly dominated social group” from other categories, and couples this
category to a motivation to kill (which must therefore also be innate). Similarly, for snake and
spider fears to be innate, there must be some neurocomputational description of snakeness and
spider-ness, connected to the fear system.
A possible counterargument is to accept the premise, but to argue that there only needs to be a
small number of motivations – pleasure-seeking, pain-avoidance, hunger, thirst – and accept the
small number of innate concepts they are embedded in. The claim would then be, backward
induction from a few drives would produce the diversity of human motivation. Behaviorists held
this view, and predicted, for example, that mother love would simply be the folk term for
motivated proximity through conditioned food reward. (This was falsified accidentally by
Harlow’s work, showing that that the emotional attachment was elicited by fur-affordances,
rather than food.) The key to working out how many motivational systems must be innate is
identifying the number of motivational tasks that are incommensurate – that is, where one
motivation cannot be derived from another through the organism discovering that one is a factor
that contributes to attaining the other as a goal state. If, for a class of events, what defines
successful behavior (or “value”) cannot all be derived from a common computational procedure, then
two or more motivational incommensurate motivational domains are involved. Analytically, the
number of innate (evolved) conceptual-motivational systems needs to be at least as numerous as
the number of incommensurate motivational tasks the organism was designed to face in the
course of a lifetime of successful reproduction under natural (ancestral) conditions.
Environmentalists, generally unfamiliar with the natural history of most organisms, often seem to
consider this number to be small. Evolutionary researchers are familiar with a great diversity of
incommensurate motivational problems that organisms, including humans, routinely face.
Discovering the boundaries and properties of the innate ideas embedded in motivational systems
requires empirical study. Indeed, detailed empirical research shows that, in a number of cases,
human motivational categories accomplish evolved functions that are significantly at variance
with the general reward structure of the ontogenetic environment. That is, a few major
motivational goals, such as pain avoidance, resource accrual, and social approval, are insufficient
to explain the richness of human motivation. Drawing on our own recent work, we consider the
impossibility of acquiring through content-independent learning procedures the empirically
documented patterns of aversion found in human incest avoidance or the prosocial sentiments of
family altruism; punitive sentiments towards free riders; patterns of cheater detection reasoning;
intuitive membership assignment to coalitions; and anger. We will also quickly review many
other documented examples. These are also cases where the motivation cannot be derived from
simpler motivations, such as hunger, thirst, or sexual desire.
One section of the paper will deal with apparent and real counterarguments, such as:
(1) values are sensory properties that instruct you how to connect value to concept.
(2) values are sometimes socially supplied.
Another section will deal with the large array of conceptual-motivational elements in the human
psychological architecture that humans are actively socialized against. This presents a
particularly interesting
Finally, we will address the issue of how to define innateness evolutionarily, given that
everything is the result of gene-environment interaction; and we will address how concepts could
plausibly be innate, given the apparent developmental plasticity of the human neocortex.