the nature and nurture of language development Flashcards
lecture 8
equation for heritability
2(rMZ - rDZ) = heritability
twin studies
compare resemblance of MZ and DZ twins on a specific trait by looking at correlation
cheesman et al - twin study and genetics
80% of height and weight is genetic
whereas cognitive ability such as maths, language and IQ are less affected by genetic factors
highest percentage 58% - reading
twins studies of language ability
is a beritable trait
age 2 - hertiability for vocab is 26% and grammar is 52%for boys and 43% for girls
this further increase between 2 and 4 and increase again between 4 and 6
convergent evidence for moderate to high heritability was obtained at age 16
environmental influences also play a role
limitations of twin studies for studying language ability
large sample sizes are required
population-based samples are preferred to avoid over-representation of MZ pairs
language phenotypes are often limited and lacking in metrics interpretable for comparisons to singleto age peers
possible twinning effect
FOXP2 gene - Lai et al 2001
FOXP2 gene is the gene that is responsible for the speech and language disorder in the KE famility
A single mutation in the KE family leads to a loss of function of one copy of the FOXP2 gene and that the one copy that remains is insufficient for normal brain development leading to the speech and language disorder
KE family
the first family to be examined with genetic testing to look at their speech development due to half them suffering with dyspraxia
behavioural phenotype - for every test administered the family was on average significantly impaired in relation to the unaffected group
neural phenotype - morphometry analyses showed some areas of reduced grey matter in the family
evolution of the FOXP2 gene
a comparison of the FOXP2 gene of humans, other primates and other placental mammals shows that FOXP2 is amongst the most highly conserved 5% of proteins, indicting that it has a fundamental role in mammals
- enard et al 2002
