In a prior study of family interactional variables associated with language learning, major differences in parenting (i.e., time, attention, and talking) were found to be associated with differences in child productive vocabulary between 7 to 36 months of age, and child IQ, favoring higher-SES parents.

Lower-SES children were exposed less often than higher-SES children to diverse vocabulary through their parents' attention and talking, and they were prohibited from talking more often.