We conducted a longitudinal study of intentional communication and cognitive prerequisites for mentally retarded infants. A total of 27 cases were observed for their intentional communicative acts in daily care settings. The items in cognitive-adaptive scale of The Kyoto Scale of Psychological Development were used for the evaluating development of cognitive and manipulative behavior when the new intentional communicative act emerged in each case. With those data, we searched for cognitive prerequisites for actions used in intentional communication.
The cases were divided into five groups according to the main act used in intentional communication. We examined and classified items in cognitive-adaptive scale by the criterion of whether or not all subjects passed in each group.
We also analyzed the cognitive prerequisites for the acts used for intentional communication in the process of language acquisition. The results were as follows :
1. Reaching and grasping objects, paying attention to two objects, knowing the relationship between two objects, using the secondary circular reactions and understanding the system of indices preceded the emergence of intentional communicative acts such as looking at an adult while making an effort to reaching the goal, vocalizations and alternating eye contact between the goal and adults.
2. By the time the emergence of communication by taking hands of an adult and pushing it to the goal, showing, giving and pointing behavior, several cognitive behaviors (such as the attainment of object permanence, understanding of means-ends relations, using tertiary circular reactions, unsuccessful inferior scissors grasping and approaching a pellet with the index finger) were developed. And the ability of putting things into a container was prerequisite for development of pointing behavior.
3. The development of representation, conventional use of objects, exploration for objects with the index finger, attempts to build cube towers and undestanding the goal of tasks and persisting with them preceded the intentional communication with using words.
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