WJEC A2 Psychology PY4 - Role of Environmental Factors in the Development of Intelligence

4 Environmental Factors in the Development of Intelligence

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Prenatal Factors: Alcohol

1. Prenatal Factors: Alcohol

  • research has suggested prenatal factors are thought to be biggest cause of biologically caused learning difficulties and lowered IQ
  • known prenatal teratogens (causes abnormality in developing foetus) include infections (eg rubella), drugs in the mother's body (heroine, cocaine, alcohol, tobacco), radiation, pollutants and toxins produced by mother's faulty metabolism
  • Streissguth et al (1989) found mothers who reported consuming more than 1.5oz (shot of 40% spirits) of alcohol daily during pregnancy had children who scored 5 IQ points below controls (other children) at age 4 (even when maternal and paternal education was accounted for). Prenatal exposure to aspirin + antibiotics had similar negative effects in study, suggesting alcohol during pregnancy affects intelligence. But was it effects of the alcohol?

(-) difficult to isolate prenatal factors in order to see which affect IQ, and also to separate them from postnatal factors that may have effect before IQ is measured (eg mother who drank during pregnancy may treat child differently or create different environment for child after birth than those who didn't drink)

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Prenatal Factors: Alcohol

(?) Eriksen et al (2012)

  • tested 1628 Danish women and their children, found no differences in average IQ between children (aged 5) whose mothers consumed between 1 - 4 and 5 - 8 drinks per week at some point during pregnancy, compared with children of mothers who abstained
  • alcohol may not have any impact on a child's intelligence during pregnancy

(-) Kelly et al (2010)

  • found (using sample of 11,513 UK children) children born to light drinkers achieved higher cognitive scores at age 5 than those whose mothers had abstained from alcohol while pregnant
  • completely contradicts the idea that alcohol can be damaging to child's IQ level

(?) although, differences in these studies' findings to Streissguth's study could be due to confounding variables such as amount or type of alcohol consumed; accuracy of mother's self-reporting of alcohol use; characteristics/IQ of mothers or IQ test used

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Postnatal Factors: Nutrition/Diet

2. Postnatal Factors: Nutrition/Diet

  • prolonged malnutrition during childhood does appear to have long-term detrimental intellectual effects
  • Pollitt et al (1993) gave preschoolers in two Guatemalan villages (where undernourishment is common) access to protein dietary supplement for several years. Decade later, many of these children scored significantly higher on school-related achievement tests than comparable controls
  • suggests nutrition does have impact on intelligence but, a lack of it can be overcome with supplements and consequently, increase levels of achievement (therefore intelligence?)


(-) effects of poor nutrition on intelligence may well be indirect. Malnourished children are typically less responsive to adults, less motivated to learn, and less active in exploration than their more adequately nourished counterparts, not necessarily less intelligent?

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Postnatal Factors: Nutrition/Diet

(-) many other unfavourable socioeconomic conditions are often associated with chronic malnutrition, so it is difficult to single out nutrition as the cause of the differences in IQ

(+) Benton and Cook (1991)

  • found that when vitamin and mineral supplements were given to 6 year olds over a 6 week period, their IQs increased by an average of 7.6 points
  • supports the idea that intelligence is affected (positively) by diet

3. Postnatal Factors: Breastfeeding

  • a meta-analysis (of 11 different studies) by Anderson et al (1999) found that breastfed infants tested 5.2 IQ points higher than formula fed infants
  • calculated that difference in IQ in breastfed and formula fed infants was 40% due to mother-infant bonding and 60% due to nutritional benefits of human milk (eg the presence of Omega-3 fatty acids that may aid brain development and are prevalent in breast milk but absent in infant formula)
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Postnatal Factors: Breastfeeding

(-) some researchers believe link is based on the fact well-educated, wealthier women breastfeed far more than poor and less educated women. Consequently, breastfed children found to test better for same reasons that wealthier children from high social classes test better on standardised tests

(+) however, Anderson et al identified 15 factors including maternal education, birth weight, order and family income that could affect IQ. After factors removed, researchers still found breastfed babies tested 3.1 IQ points higher than formula fed babies

(-) Caspi et al (2007) found benefits of breastfeeding on intelligence may actually be mediated by a single gene (instead of purely environmental factors like breastfeeding)

  • children with one version of FADS2 gene scored 7 IQ points higher if breastfed but breastfeeding had no effect on IQ of children with different version
  • gene helps break down fatty acids from dietlinked with brain development, estimated 90% of population possess it
  • contradicts Anderson's research because may mean that instead of breastfeeding increasing intelligence based on nutritional value, actually due to genetic factors that cause breastfeeding to have any benefit on intelligence
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Postnatal Factors: Cultural Factors

4. Postnatal Factors: Cultural Factors

  • Stevenson et al (1990) suggests effects of socioeconomic status (SES) on intelligence is overridden in some groups by attitudes to hard work. Asian cultures (notorious for intelligence success) tend to have incremental rather than entity theory of intelligence
  • Dweck (2002) found students who held incremental theory about intelligence (that it can be increased through hard work) went on to improve their grades more than those who held an entity theory (intelligence is fixed)


(+) identification of effect that a child's attitudes to development of intelligence actually has on its development has led to creation of intervention programmes that appear to increase children's intelligence. These teach children about plasticity of brain and discourage them to see intelligence as fixed

(+) Dweck also suggested children should be praised for effort rather than for level of intelligence as encourages them to have incremental view of intelligence eg

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Postnatal Factors: Cultural Factors

(+) Dweck's research questions value of labelling children as 'gifted and talented' or streaming pupils according to perceived ability as it may encourage them to see their intelligence as an entity that they possess rather than something to be developed through hard work

(-) further research may be needed to identify how people develop their attitude towards intelligence and the role that family peers, society and formal education play in this, perhaps in order to raise educational standards

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tom sage


thanks for the notes Zo! i achieved 95% in my exam. any more to come?

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