FORMATION OF THE PREPARATORY SET IN THE MENTALLY RETARDED CHILDREN : ON THE ACQUISITION OF THE ROLE OF THE WARNING SIGNAL THROUGH PRELIMINARY VERBAL INSTRUCTION

Abstract

In most of the studies concerned with the reaction time (RT) in the mentally retarded children, it was not seriously considered whether the meaning of the warning siganl (WS) could be effectively understood by subjects through experimenter's instruction. One of features in the mentally retarded children appears in the retardation or instability in the verbal regulation of behavior (Luria 1961). If a child does not acquire the role of WS as a regulator of its behavior, the main problem for the child in the RT situation with WS might only become the selective motor response to the reaction signal (RS) differentiating from WS. In order to investigate the formation of the preparatory set in the mentally retarded children, the present study examined the effectiveness of preliminary instructions about the role of WS as well as the level of selectivity of the motor response to RS differentiating from WS. Subjects were 55 normal children (CA: 4-9 years old) and 20 mentally retarded children (CA: 8-15 years old, IQ: 40-80). A white noise (1 sec, 65dB) was presented as WS, and a tone-pip (50ms, 1000Hz, 75dB) was used as RS. The experiment was composed of three conditions (Fig. 1). (1) "non WS" condition: RS stimuli were presented to a subject at an irregular interval of 7-10 sec. A subject was previously instructed to press the button to RS as quick as possible. (2) "WSa" condition: A white noise stimulus was presented 2-5 sec before RS. A subject was instructed, "Press the button to a tone-pip but don't press it to a noisy sound." (3) "WSb" condition: Both stimuli were presented in the same sequence as in "WSa" condition. However, the instruction was, "In a short time after the noisy sound, a tone-pip comes. Then, you must press the button as quick as possible." Results were as follows: (1) There were those subjects in both groups who showed longer RT in "WSa" condition than that in "non WS" condition, and such normal subjects were of younger ages (Fig. 3). (2) In those subjects, RT in "WSb" condition was longer than that of "nonWS" condition or remained almost unchanged. Such a tendency of RT elongation in "WSb" condition was not observed in other subjects whose RT was shortened or changed little in "WSa" condition (Fig. 4, 5). From these results, it was pointed out that in some younger normal children and some mentally retarded children the preliminary instruction of WS was not effective and WS had only a meaning as a negative signal to be discriminated in the selective motor response situation. Before a child can form the preparatory set through the preliminary instruction, at least two conditions might have to be prepared. Namely one is the selective motor response to RS and the other is the understanding of the instruction about WS. Some mentally retarded children might stay at the stage in which these necessary conditions are not satisfactorily established yet.