Chapter 14 Flashcards
eugenics
People with disabilities came to
be viewed as a threat to the moral and intellectual fibre of society; the growing eugenics movement called for segregation, sterilization, the restriction of marriages, and institutionalization to protect society from this threat
stereotypy
(the repetition of meaningless gestures or movements).
challenges of assessing intelligence
- when people have had sheltered or
limited experiences because of their disability or when they have lived in isolated institutions, their testing performance may be biased because the test environment is unnatural
and unfamiliar, and the examining situation may be overwhelming - it is questionable whether scores on the lower end of the scale are valid because the major intelligence
tests such as the Wechsler Scales and early editions of the Stanford-Binet were not standardized on people with IQ scores lower than 70
cloak of competence
Edgerton, an anthropologist, noted the tendency to overestimate higher functioning individuals with disabilities by their “normal” appearance and verbal abilities.
- He emphasized the stigma of the disability and the need that disabled
persons felt to deny their cognitive handicap and attempt to pass as normal in society; he referred to this phenomenon as the “cloak of competence.”
acquiescence
the tendency of individuals with developmental disorders to answer affirmatively or agree in interviews
possibly because of:
- social desirability
- motivational and personal factors
- cognitive and linguistic limitations
Behavioural phenotypes
(the pattern of social, cognitive, and behavioural abnormalities) have been described for a particular number of
disabilities.
causes of developmental disorders
Developmental disorders may be caused by single or multiple genes alone or in association with environmental factors.
Three types of inheritence:
- dominant - if one parent of either sex has a defective gene, that gene
“assumes ‘control’
- recessive - genes “in a sense ‘recede’ when paired with a dissimilar mate and therefore only are influential when matched with another recessive gene” carrying the same trait
sex-linked or X-linked - the abnormal gene is carried on the X chromosome. In females, the gene is generally recessive and will operate only when it appears on both X chromosomes. Disorders transmitted in this way therefore primarily affect males, who have only one X chromosome;
the Y chromosome is not able to dominate or override the trait
Down syndrom
The best-known chromosomal abnormality associated with intellectual disability is Down syndrome
The most common is trisomy 21, which
occurs in 95 percent of cases of Down syndrome. Whereas the normal human cell has 23 pairs of chromosomes, one
chromosome in each pair provided by each parent, in Down syndrome there is an extra chromosome on pair 21. Thus, persons with Down syndrome have 47 rather than 46 chromosomes
translocation - part of the twenty-first chromosome breaks off and attaches to another
mosaicism - cell division occurs unevenly, so that some cells have 45 chromosomes and some have 47.
Amniocentesis
is a procedure conducted between the
eleventh and eighteenth weeks of pregnancy. With the assistance of ultrasound, a needle is inserted into the amniotic sac via the pregnant woman’s abdomen. A small amount of
amniotic fluid is withdrawn, and cells contained in the fluid are then cultured in the lab.
chorionic villus sampling (CVS)
involves obtaining cells from the placenta. Minor complications such as cramping or vaginal bleeding occur more frequently following CVS than amniocentesis and the overall
miscarriage rate is somewhat higher (2 to 5 percent) than after amniocentesis.
Phenylketonuria (PKU)
the best known of several rare metabolic disorders that can cause
intellectual disability. PKU has been described as an “inborn error of metabolism.” It is caused by an autosomal recessive gene
Maternal Infections
- Rubella during the first three months of pregnancy can lead to intellectual disability, visual defects, deafness, heart disease, and other problems.
- HIV - Developmental delays
or disabilities occur in 75 to 90 percent of children with HIV who do not receive appropriate treatment
Fetal Alcohol Spectrum Disorder (FASD) - Prenatal and postnatal growth retardation and central nervous system dysfunction are common. - shows the typical facial features of a child with
fetal alcohol syndrome disorder (FASD), including short eye openings, an elongated, flattened area between the mouth and nose, thin upper lip, and flattened cheeks and nasal bridge. Head circumference is frequently below the third percentile. Cleft palate, heart and kidney damage, and vision defects are also found
POSTNATAL ENVIRONMENTAL FACTORS: PSYCHOSOCIAL DISADVANTAGE
- Psychological and social deprivation due to lack of stimulation and care can impair intellectual development. Poverty, poor nutrition, large family size, lack of structure in
the home, and low expectations for academic success may
all be contributing factors.
They are found more frequently
within lower socio-economic groups, and commonly have at
least one parent and possibly one or more siblings with developmental delays
diagnostic overshadowing
perceiving mood changes or maladaptive behaviours to be solely a function of the developmental disorder might cause real psychiatric
disorders to be missed
dual diagnosis
In North America, the co-occurrence of serious behavioural or psychiatric disorders in people with intellectual
disability has been labelled dual diagnosis
