Brain size, evolution and expertise capacity

["Dr. John R. Skoyles" <skoyles@GLOBALNET.CO.UK>]

Clinical neuropsychologists might be interested in a paper that links
clinical neuropsychological findings about brain size and human evolution.
The paper is in the commentary ejournal Psycoloquy [run by Steven Harnad of
Behavioural and Brain Sciences fame] and called 'HUMAN EVOLUTION EXPANDED
BRAINS TO INCREASE EXPERTISE CAPACITY, NOT IQ'.

http://www.cogsci.soton.ac.uk/cgi/psyc/newpsy?10.002


    HUMAN EVOLUTION EXPANDED BRAINS TO INCREASE EXPERTISE CAPACITY, NOT IQ

                Dr. John R. Skoyles
                skoyles@globalnet.co.uk
                http://www.users.globalnet.co.uk/~skoyles/index.htm

ABSTRACT: Why do modern humans have larger brains than earlier
    people such as Homo erectus? As large brains cause problems in
    childbirth, infancy and locomotion, the advantage they offer must
    be substantial. This advantage might be associated with increased
    IQ, but there is a problem: evidence from MRI volumetric surveys,
    microcephaly and hemispherectomy shows that there exist individuals
    with psychometrically normal IQ but Homo-erectus-sized brains. Why
    did evolution increase brain size (with its associated costs) when
    humans (as these individuals demonstrate) can have normal IQ
    without bigger brains? I propose that the advantage may be related
    to increased capacity for an aspect of intelligent behaviour not
    measured by IQ tests but critical to the survival of our simple
    hunter-gatherers ancestors: the capacity to develop expertise.

    KEYWORDS: brain size, brain imaging, evolution, expertise,
    hemispherectomy, Homo erectus, individual differences,
    intelligence, IQ, language, microcephaly, MRI volumetrics,
    psychometrics.


    RATIONALE FOR SOLICITING COMMENTARY:  A 1998 Medline search at
    http://www4.ncbi.nlm.gov/pubmed/ using keywords "microcephaly,"
    "normal intelligence" and "normal IQ," would retrieve abstracts of
    about 22 papers describing contemporary people with brains no
    bigger than that of Homo erectus yet exhibiting normal
    intelligence. Recent MRI volumetric surveys also support these
    findings. How can this be? Surely evolution expanded human brain
    size (at some cost) to increase our intelligence -- but the
    existence of these small-brained individuals of normal intelligence
    seems to suggest that this may not have been unnecessary.
    Palaeoanthropologists do not attach much weight to such anomalous
    reports, but I propose a possible explanation: brain size expansion
    may not be associated with what IQ tests measure but with another
    aspect of intelligent behaviour: the capacity to develop
    expertise. This is supported by data from a number of diverse
    domains (from clinical to palaeoanthropological) that are not
    normally seen as related in any way. Expert interdisciplinary
    commentary may accordingly be especially fruitful on this topic.
    Neuropsychologists and brain imaging specialists are invited to
    consider the evidence about individuals with small but nonretarded
    brains. Evolutionary psychologists, sociobiologists,
    psychometricians and palaeoanthropologists are invited to consider
    whether expertise capacity rather than psychometric IQ might have
    been what drove early hominid brain size expansion. Social
    psychologists, linguists and motor control scientists might
    contribute ideas about how aspects of our sociality, language and
    tool making could be related to increased expertise capacity and
    brain size.

-----------------------------------------------------------------------
psycoloquy.99.10.002.brain-expertise.1.skoyles          Tue Jan  5 1999
ISSN 1055-0143       (42 paragraphs, 45 references, 2 notes, 784 lines)
PSYCOLOQUY is sponsored by the American Psychological Association (APA)
                Copyright 1999 John R. Skoyles
The URL of Psycoloquy is
http://www.princeton.edu/~harnad/psyc.html