Sources

Wechsler, D. (1949). Wechsler Intelligence Scale for Children: Manual. New York: The Psychological Corporation. WISC data

Wechsler, D. (1955). Wechsler Adult Intelligence Scale: Manual. New York: The Psychological Corporation. WAIS data

Wechsler, D. (1974). Wechsler Intelligence Scale for Children: Revised. New York: The Psychological Corporation. WISC-R data

Wechsler, D. (1981). Wechsler Adult Intelligence Scale: Revised. New York: The Psychological Corporation. WAIS-R data

Wechsler, D. (1989). Wechsler Preschool and Primary Scale of Intelligence: Revised. San Antonio, TX: The Psychological Corporation. WPPSI-R data

Wechsler, D. (1992). Wechsler Intelligence Scale for Children – Third Edition: Manual (Australian Adaptation). San Antonio, TX: The Psychological Corporation. WISC-III data

Wechsler, D. (1997). Wechsler Adult Intelligence Scale – Third Edition: Manual. San Antonio, TX: Pearson. WAIS-III data

Wechsler, D. (2002). Wechsler Preschool and Primary Scale of Intelligence – Third Edition: Manual. San Antonio, TX: Pearson. WPPSI-III data

Wechsler, D. (2003). Wechsler Intelligence Scale for Children – Fourth Edition: Manual. San Antonio, TX: The Psychological Corporation. WISC-IV data

Wechsler, D. (2008). Wechsler Adult Intelligence Scale – Fourth Edition: Manual. San Antonio, TX: Pearson. WAIS-IV data

The analysis of this subtest will be prefaced by a step-by-step description of how the method works. The method takes you from the data presented in the age tables (for a particular subtest) to conclusions about the extent to which family or common environment influences performance on whatever ability the subtest measures, and at what age (if any) that influence disappears. Since the method is fundamentally the same throughout, it will not be repeated for other subtests; which is to say, all other prefatory remarks will refer you back to this description.

The Age-Table Method: its assumptions

1. (1) Those whose performance puts them at +2 SD above the median come from homes whose cognitive quality will extend far below that level. As long as family environment persists, they will be at a disadvantage when compared to whatever age the lingering effects of family environment fade in favor of a match between genes and current environment (where it becomes a null factor). The same is true, although to a lesser degree, for those at +1 SD above the median.