amentia arrested development babyishness backwardness blithering idiocy childishness cretinism half-wittedness idiocy idiotism imbecility immaturity insanity mental defectiveness mental deficiency mental handicap mental retardation mongolianism mongolism mongoloid idiocy moronism moronity profound idiocy puerilism puerility retardation retardment simple-wittedness simplemindedness simpleness simplicity subnormality