The Apes and Us: Brain and Emergent Processes
Duane M. Rumbaugh
Departments of Psychology and Language Research Center
Georgia State University
Atlanta, Georgia USA 30303
Within the order Primates, it is clear that the degree of both
biological and psychological continuity is a function of genetic relatedness. We are more
closely related to the chimpanzee/bonobo apes than they are, in turn, to any other
primates, including the gorilla. Although biological continuity between animals and humans
has been long recognized, psychological continuity has not * primarily because of the
long-standing beliefs that animals cannot think or even feel and that human language
results in a psychology that is quite different from that of animals. But now, at the dawn
of a new millennium, we have solid evidence for significant psychological continuity
between apes and humans. Apes are capable of complex learning, symbolic thought, speech
comprehension, basic dimensions of language, basic numeric skills, and planning. Rhesus
monkeys (Macaca) also have advanced skills and competencies, revealed by research with
computers that requires of them facile use of a joystick that controls a cursor on a
monitor. Although apparently not as adroit in symbolic processes, and probably with far
less capacity to acquire language than the great apes, they nonetheless are impressive.
They can predict events, estimate confidence in making choices, and learn equivalencies
and ordinal relationships between arrays of items and Arabic numerals. Like us, they do
significantly better when they can choose tasks on which to work, and they prefer to work
at their computers rather than to get food "for free."
Great apes and humans are noted for their large brains and
protracted stages of development and maturation. Sensitive periods of early years have
comparable effects, for better or worse, upon both infant ape and child. The effects can
be extreme and life long.
A comprehensive study with 12 primate species' (total N = 121)
ability to transfer learning in relation to brain evolution yielded important insights
that pertain to the evolution of humans. In an object-discrimination learning situation,
transfer of learning was studied in relation to levels of mastery. A slight increment in
the amount initially learned resulted in a remarkable decrease in transfer of learning
proficiency in the prosimians and in some small bodied monkeys. By striking contrast, the
larger monkeys and the great apes' transfer of learning increased. This shift, which is
qualitative in its effect (i.e., from negative to positive transfer), is believed to
reflect a shift from stimulus-response associative learning in the more primitive and
small-bodied monkeys to a more rational/relational learning process, particularly in the
great (but not lesser) apes.
It is proposed that
intelligence (e.g., facile learning and transfer of learning to an advantage rather than a
disadvantage) increased fortuitously in its association with both brain size and body
size. Such would have occurred if new primate species tended to be selected for having
large bodies. (Large-bodied primates tend to have access rights over others.) But
selection for intelligence based on body size, because of high metabolic demand, was
surely constrained to the great apes. Selection of intelligence based upon brain
enlargement apart from body size perhaps was contingent upon some early hominid becoming
bipedal. An erect posture would have served to enhance use of the hands and facilitated
manual interaction with objects of the environment. Inventions thus became more probable.
Cumulatively, inventions would have served to enrich the rearing contexts for the
offspring and to direct their cognitive development toward relational learning and
facilitated applications of even small amounts of experience to meet new challenges.
Offspring were thus prepared to make even greater gains in technological development than
did their parents--and the rate of cultural development was accelerated.
Here we will emphasize both the evolution and maturation of the
primate brain as an information-sensitive structure that is particularly responsive to
early rearing. The role of technology in research also will be emphasized.(HD-06016)
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