Final answer:
Babies become more interested in objects and less self-preoccupied in the sensorimotor substage of cognitive development. They develop object permanence between 5 and 8 months, indicating an awareness that objects continue to exist even when not seen, which is a key cognitive milestone.
Step-by-step explanation:
When babies initially become less self-preoccupied and more interested in objects, they are most likely in the sensorimotor substage. During the sensorimotor stage of cognitive development, which lasts from birth to about 2 years old, children learn about their world through their senses and motor behaviors. By around 5 to 8 months, infants develop object permanence, which is the awareness that objects continue to exist even when they cannot be seen. This development marks the transition from self-focus to an engaging interest in external objects and is a crucial cognitive milestone within Piaget's framework of development. Babies exhibit a range of behaviors that reflect their cognitive growth in this stage. For example, they may explore objects by putting them in their mouths or by shaking them to understand cause and effect. Additionally, when babies reach out for a toy that has been covered up, they are indicating their understanding of object permanence. These actions demonstrate that even in early infancy, children are engaged in complex cognitive processes and are not as limited in understanding as previously thought.