With an emphasis on procedural fundamentals, the original behavior-analytic equivalence experiments and the equivalence paradigm are described briefly. A few of the subsequent developments and implications are noted, with special reference to the possible significance of the findings with respect to language and cognition. (Contains 9 figures.)

In a study to determine whether or not culturally deprived children develop at progressively greater deficits in intellectual functioning during the ages of 15 months to 3 years, tutors provided 15-month-old infants with intellectual and verbal stimulation one hour daily, five times a week until they were 36 months old. The subjects consisted of…