Summary Prepared by Spencer Payne (comments and additions by Frawley
The class began with a brief discussion on heredity and heritability. Heredity, loosely defined as those characterisics which are passed on from one generation to another, can be derived both internally and externally. Factors considered as external to the individual would include culture, customs, style, etc. Internal factors can be broken down into two subcategories: specified (what we start with) and developmental (characterisitics which arise from interaction).
Note: heritability, the idea that some traits found in one generation are also found in the next, is popularly thought of as a property traceable to internal (genetic?) factors. But it is technically a calculation derived from the relative influence of internal and external factors. Something might thus be heritable if derived entirely from external factors -- say, pony tails on boys in the 60s and on their children in the 80's and 90's -- because the external conditions reproduce the phenomenon across generations. And, of course, something might be heritable from purely internal factors, like blood type, which is entirely traceable to genetic specification. The tricky ones (most?) are those that draw on both factors: it is important to be specific about how much influence the internal or external has on the calculation of heritability.
In discussing heritability we must be careful to distinguish between internal and external while also taking care not to endow individuals of populations with "average" characteristics.
Note: again on heritability. It is technically a feature of populations, not individuals. So even if something is heritable -- for whatever reason, internal or external -- it is not true that it is inherited by all the individuals or even fully in any single individual in the population.A major point here is the meaninglessness of race, a term most social and biological anthropologists do not sees as discrete. What is there to race that distinguishes people from others? True there are differences in skin color (and skin color is genetic) but the other factors stem from external cues such as culture. Furthermore, upon examination, racial lines blur. Since there exists such a varied mix of physical properties, the idea of race becomes a very low level construct of low worth. (Similar agruments can be made for the construct of IQ.)
The purpose of the lecture was to focus on those heritable traits which are specified by the genetic code, or rather, where they go awry. By studying those individuals or conditions by which various cognitive faculties are hindered or disrupted due to genetic causes, a greater idea of what amount of cognitive ability stems from a hard or wet-wired configuration of the brain. The four major disorders mentioned wre Williams syndrome, Turner syndrome, autism and spina pifida (with hydrocephalus). Due to time restrictions, the discussion focused on Williams syndrome.
Those with Williams syndrome are typically short, with flat chests, and elfin appearance.The cognitive manifestations of the condition are quite interesting. Williams children have a hyperextended lexicon and language ability. When asked to give the names of ten animals responses include emu, llama, and kiwi, when most children's answers would include cow, dog or cat. Additionally, as conversationists, they are nonstop, often offering a barrage of questions or statements which may be loosely tied together.
However, while they have a more than adequate language and auditory ability, their visual/spatial integration is lacking. When presented with a task of copying a somewhat askew letter or to arrange blocks to form a given pattern, they fail, providing exploded representations which are not very close to the original at all. Contrarily, when presented with a face and asked to pick the most similar face out of a group, they have no problem, peforming better than average. It is also seen that as children, they do not point at objects. Pointing in children encompasses two things in pre-speaking children (1) communication of some desire and (2) object recognition. Clearly Williams kids have object recognition involving their tremendous lexicon, but their communicative tasks are lacking due to their random statements when speaking freely. Moreover, they do well on tests of theory of mind, unlike, say, autistic children. From this information three major inferences can be made with relation to cognitive domains:
Oddly, the cause for this condition was found to be a deletion of DNA withing a 83 kbp region of chromosome 7. This area of the chromosome is responsibile for the genetic coding of a protein known as elastin whose function is to allow stretch in blood vessels. Hence this deletion is what gives rise to the blood vessel and cardiac problems in Williams children. But since elastin is not expressed in the brain, there must be something else in this chromosomal area that gives rise to the cognitive profile. Smaller deletions in the region (53 kbp) than others seem to reduce the severity of the affect on personality but the spatial integration is not regained. This suggests that also in this area is the specification for spatial integration.
The deletion occurs spontaneously in 99% of the cases, and it appears to be a dominant condition. Offspring of Williams individuals have a greater than 50% chance of inheriting the disorder, so it can be passed on via internal specified factors.
Note: Williams syndrome is a design disorder, a way that Nature cuts the mental architecture at its joints. The cognitive and behavioral effects of the syndrome are support for a modular architecture.