(. 14-2) , . , , . (Leonard Bickman, 1975, 1977, 1979) , . , , , . , , , , . . , : , . . , . ( .) ( ): . . . , .
. (Robert Foss, 1978) , , ( ), , - . (Leonard Jason & others, 1984) , , , , , . , . (Mark Snyder & others, 1974) , , , , . , , .
(1978; Solomon & others, 1981) . , , , , , . , -, , , , , , , -