Longitudinal studies of children s intelligence
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Longitudinal Studies of Children’s Intelligence. IQ appears to be relatively stable from age 3 through adulthood. Overall, retest correlations tend to be higher when: The interval is shorter. The older the children.

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Longitudinal studies of children s intelligence
Longitudinal Studies ofChildren’s Intelligence

  • IQ appears to be relatively stable from age 3 through adulthood.

  • Overall, retest correlations tend to be higher when:

  • The interval is shorter.

  • The older the children.

  • Correlation between IQ in latter preschool and grade school ranges from .6 to .8. Between adolescents, it increases to ~ .8.

Possible reasons for iq stability
Possible Reasons for IQ Stability

  • Overlap hypothesis - IQ is cumulative.

  • Overlap between current and past knowledge.

  • Environmental stability - People tend to remain in the same environments across the developmental life span.

  • Prerequisite Learning Skills –

  • Individual retains the same learning tools (e.g., problem-solving methods) from year to year.

  • Neurological Consistency-The pattern of neurological development remains relatively constant.

Evidence for the instability of iq
Evidence for the Instability of IQ

  • While overall IQ remains constant across large groups of individuals, specific individuals may exhibit large changes in IQ.

  • This may be due to changes such as dramatic shifts in environment or individual factors.

Instability of iq continued
Instability of IQ(continued)

  • California Guidance Study (1948-12 year period):

  • 59% of children exhibited changes of > 15 points

  • 37% > 20 or more point

  • 9% > 30 or more points.

Instability of iq continued1
Instability of IQ (continued)

  • Garber Study (1988)

  • Generally, children in culturally disadvantaged environments lose IQ points whereas people in culturally enriched environments gain IQ points.

  • Specifically, examined the relationship between children reared in environments with mothers who had IQ’s either >80 or <80.

  • No difference, from 13-35 months (avg IQ = 95) but by 14, > 80 mothers = 90, whereas, < 80 mothers = 67.

Instability of iq continued2
Instability of IQ (continued)

  • Instability attributable to changes in:

  • Parental concern re: education.

  • Also, home environments characterized by “encouragement…structure” associated with increases in IQ.

  • Emotional dependency on parents was another factor responsible for IQ loss in childhood.

  • During school years, IQ increases were associated with high achievement drive, competitive striving, and curiosity about nature.

Iq in early childhood
IQ in Early Childhood

  • Preschool tests have moderate predictive validity in predicting future IQ.

  • Between ages 2 and 14, the correlation is about .3.

  • Infant tests have little predictive validity (best for concurrent validity - relative status now).

  • Little correlation in scales even with intervals as small as 3 months.

  • The reason for these low correlations is the change in the construct of IQ.

Iq in infancy continued
IQ in Infancy(continued)

  • The construct of IQ in infancy is made up of largely motor development and visual-perceptional skills.

  • This differs from how intelligence is defined in school aged children.

  • In infancy, parental education and other characteristics of home environment are better predictors of subsequent IQ.

Early childhood iq continued
Early Childhood IQ (continued)

  • This speaks to the importance of early intervention programs that provide training in the prerequisite learning skills and the need for parental involvement.

  • Beyond 18 months, prediction of IQ is improved if tests are combined with family SES information.

  • However, infant tests may have higher predictive validities within non-normative samples.

Typical iq instruments
Typical IQ instruments

  • Bayley Tests of Infant Development- 0-42 months.

  • Stanford-Binet V (2 through adulthood).

  • Wechsler Preschool and Primary Scales of Intelligence (2.5 years to 7.25 years).

  • Wechsler Intelligence Scale for Children-IV

  • (6 through 16-11 months).

Issues in the assessment of adult iq
Issues in the Assessment of Adult IQ

Findings re: Age and IQ

  • In Cross-sectional designs, such as that used in Wechsler's standardization samples, IQ declines with age.

  • Possible explanations include:

    • Less education

    • Poorer health

    • Less familiarity with the information age.

Issues in iq assessment continued
Issues in IQ Assessment (continued)

  • Longitudinal designs involve testing one cohort (same individuals) at different times.

  • In contrast to cross-sectional designs, using longitudinal designs, IQ increases with age.

  • Explanation includes exposure to more information as one grows older.

Issues in iq assessment continued1
Issues in IQ Assessment (continued)

  • In Cross-sequential designs, combination of longitudinal and cross-sectional using a time-lag design.

  • A time-lag design provides that same-age cohorts are tested at different time periods (e.g., 40-year-olds tested at 1970 and 1980).

  • That is, 20 years tested in 1940 are compared to themselves in 1970 and 20 year olds tested in 1970.

Cross sequential findings
Cross-Sequential Findings

  • Older cohorts have higher IQ's from when they were tested earlier (IQ increases over time).

  • However, when different age groups were compared to one another at times (20 y.o. in 1950 vs. 20 y.o. in 1970), no significant differences emerged.

  • This suggests that experiential factors, not age itself, leads to changes in IQ.

Conclusions re changes in adult iq
Conclusions re: Changes in Adult IQ

  • True age decrements do not begin until well after age 60.

  • One exception is speeded tests which do decrease with age.

  • Overall changes in IQ in older age are largely related to health status.

  • That is, elderly individuals in poorer health do less well on tests of intelligence.

Conclusions continued
Conclusions (continued)

  • Test norms require frequent updating.

  • Experiential, cultural, variables must be taken into account in interpreting test scores.

  • IQ scores do measure cultural factors.