title: Two-to-one versus one-to-one student-teacher ratios in the operant verbal training of retarded children.
mesh_terms: D002648:Child; D003216:Conditioning, Operant; D004495:Education of Persons with Intellectual Disabilities; D004526:Efficiency; D006126:Group Processes; D006801:Humans; D013663:Teaching / Q000379:methods*; D014706:Verbal Learning