THE MOSS-HARlOW EFFECT IN YOUNG CHILDREN: REPLICATION

Summary.-3- to 4- and 7- to 8-yr.-old children were given a series of 6trial discrimination problems involving 2 objects after receiving either a rewarded or nonrewarded single-object information trial. During the discrimination, 2 other variables were investigated, fixed vs varying formboard position and near vs far object separation. No main effect was strong, but the age x information-trial reward condition was significant; younger Ss displayed the Moss-Harlow effect but older Ss did not. This finding supports the results of Cross and Vaughter (1966) but not those of Vaughter (1968). Other differences were anticipated on the basis of While's (1965) notions regarding a temporal learning hierarchy. White (1965) has advanced a provocative explanation of changes in learning observed in children between the ages of 5 and 7 yr. He contends that a system of primitive associative responses is gradually overlaid by a "cognitive" mode, characterized by an increasing capacity to inhibit the temporally prior associative patterns. Cross and Vaughter (1966) found that younger children were more able to inhibit responses to previously nonrewarded stimuli than were older children. Such improved performance following nonrewarded informarion trials has often been found in studies with infrahuman primates and is known as the Moss-Harlow effect (1947). The observation of the MossHarlow effect in young but not in older children appears, superficially at least, to be at variance with White's position. The "inhibition mechanism" invoked by White presumably works to check simpler mechanisms of reaction and allow more complex strategies, but the finding that inhibition of any sort is less pronounced wich age seems to bear upon White's position. The recent failure of Vaughter (1968) to replicate the MossHarlow effect in young children also calls fot further study. An additional test of White's view was afforded by the inclusion of fixed vs varying formboard position and near vs far object separation. White has maintained that variation in the learning procedure, as in a changing stimulus pattern, may hinder the performance of younger while actually benefitting older children. Method.-Normal children, 11 boys and 11 girls, ranging in age from 4 to 7 yr., served as Ss. Nine 4-yr.-old Ss were enrolled in che Grace Tarum Nursery of Springfield, Ohio, and 13 Ss were from the second grade at Garfield Elementary School located two blocks from the nursery. A WGTA for children (Vaughter & Cross, 1965) was modified to permit not only a center-information foodwell but 24 additional foodwells located in four parallel columns of 6 foodwells each. The two outside columns were 12 in. apart and were designated "far." The "near" columns were 6 in. distant. Foodwells within a column were 2 in. apart. Multidimensional and multicolored "junk objects were used as stimuli and M & M candy served as the reinforcement. On a given problem, S was initially presented the formboard with only the rewarded or nonrewarded stimulus object positioned over the center foodwell. This single trial was rewarded or nor rewarded depending upon the stimulus employed. Following this "information trial," there were six discrimination trials involving the simultaneous presen