Matching is one term in connection with experiments that refers to the procedure whereby pairs of subjects are matched on the basis of their similarities on one or more variables, and one member of the pair is assigned to the experimental group and the other to the control group.

Matching is attempting to make different groups of subjects equivalent based upon subject char acteristics or scores on tests; the infant and the caregiver are involved in similar behaviors or states at the same time. Matching is also a term used when research participants in the experimental and control groups are "matched" or similar on variables, examples, age, sex, that may affect the outcome of the research; the assignment of individuals to groups so that a specific variable is balanced or matched across the groups.