The answer is Substage 3: Secondary circular reactions.
This substage involves infants beginning to coordinate separate actions into single, integrated activities. However, these actions are primarily focused on the infant's own body and are not yet directed towards external objects.
This substage involves infants beginning to show intentionality and goal-directed behavior, such as using one object to obtain another. Jimmy's actions are more exploratory and not yet goal-directed.
This substage involves the use of innate reflexes, such as sucking and grasping, which are not yet coordinated with external objects in a purposeful way.
This substage involves infants beginning to interact with the external environment, repeating actions that produce interesting effects. Jimmy's exploration of the rattle and his enjoyment of the sounds it makes fit this description.
The answer is spoken language.
While important, memory strategies are not the primary tool Vygotsky emphasized for cultural transmission.
Written language is significant but is typically acquired after spoken language and builds upon it.
Vygotsky emphasized spoken language as the most crucial tool for transmitting cultural knowledge and cognitive development. It is through spoken language that children learn to think and solve problems in culturally relevant ways.
Numbers are important for cognitive development but are not the primary tool Vygotsky highlighted for cultural transmission.