Chapter 16: Sirois, S. & Karmiloff-Smith, A. Ontogenetic
development matters (pp. 312-334).
Historical Preformationism: the
notion that egg and/or sperm
contained a little preformed human
(homunculus) which over time
became grew into adult.
Modern preformationism: ideas that
genes or sets of genes encode for
specific cognitive functions which
simply emerge with maturation
(called the “canonical view.”)
Problems with canonical view:
• Genetic (lossy) compression: Too few genes – too many connections.
Given that there are around 30,000 genes in human genome, and over
100 billion neurons in brain connecting to upto 10,000 others, the wiring
complexity problem is beyond having genes specifically code for neural
circuits. Data compression – gene instructions can only utilize very general
heuristics (e.g. over-wire and cut back)
• The fallacy of innate knowledge: Evolutionary continuity dictates that if
other animals have inborn innate knowledge (specified genetically), then
humans should too. Reply: Continuity is not in the presence of innate
knowledge, it is in the presence of behavioral biases. Ex: newborn geese
do not know who their mother is and therefore imprint on here. They are
bias to follow a signal with certain physical/sensory characteristics.
Similarly, human infants are behaviorally biased to attend to face-like
visual signals, though they know nothing of human faces.
• Failures of parsimony: Studies claiming to show that infants “understand”
certain properties of physics, theory of mind, or language can all be
challenged by simpler interpretations based on behavioral biases.
Problems with the canonical view
• Important implication of overturning canonical view:
• “…brains of atypically developing infants should not be
conceptualized as normal brains with parts intact and
parts impaired. Rather, they should be viewed as brains
that have developed differently throughout
embryogenesis and postnatal development” (p. 325).
• Not a normal brain minus …. But a different brain
because…
• Canonical view: brain as
pre-specified cognitive
modules, some intact
some deficient
• Authors’ view: brain as
interactive collection of
parts where a genetic
defect with be variably
expressed across a
number of different
cognitive functions (ripple
effects; rather than
modular knockout).
Example: Development of face processing.
• Given adaptive significance a dedicated face processing model seems
likely. But such is not the case.
• Progressive modularization:
• First few months: face processing associated with wide areas of brain
across both hemispheres
• Six months: face processing more restricted to right hemisphere, where
certain biases in info processing make the processes more efficient.
• End of first year: increasingly specialized face processing in temporal lobe
of right hemisphere which continues to be refined for many years to
come.
Face processing
• No pre-specified face model, but
• Behavioral biases (attention to
face-like stimuli; maybe
subcortically driven recall Johnson
chapter)
• linking to general but variable
patterns of computational
processing in brain (right deals
better with general
configurational patterns)
• leading to predicable patterns of
brain specialization (fusiform face
area receives inputs from visual
system and hippocampus for
efficient recognition and storage
of face patterns.).
Effect of genetic disorder: Williams Syndrome
Symptoms
Delayed speech that may later turn into
strong speaking ability and strong
learning by hearing
Developmental delay
Easily distracted, attention deficit
disorder (ADD)
Mild to moderate mental retardation
Personality traits including being very
friendly, trusting strangers, fearing loud
sound
Short stature
Unusual appearance of the face
• Cause: deletion of 28 genes on one copy of chromosome 7
• Effect: low IQ; hypersociality including normal to better face recognition.
• On the surface this seems to support the pre-specified modular view;
intact face processing module but defective “intelligence” module
Williams Syndrome: evidence for modularity?
• Authors argue face processing is not unaffected by
Williams Syndrome, face recognition is different and
affected by genetic disorder.
• WS: more bilateral face processing; more holistic and
featural processing; same brain areas used for
recognizing cars as faces.
• Typically developing controls: processing in typical RH
face area; configurational processing (assessing
differences in featural locations; how wide apart the
eyes, how far mouth from nose, etc); different brain
areas for face and cars.
Possible lesson:
• brains of atypically developing children may remain more
“interconnected” than normal. Less evidence of the same degree of
progressive modularization. Or, as in autism, may commit too
quickly to specialized areas of processing.
• New view of developmental process:
• Development is not a special case of learning
• Development is a trajectory toward a certain type of processing
state. Critical question is what is controlling or influencing the
developmental trajectory and how might it be modified?