Final answer:
Abigail has developed object permanence.
Step-by-step explanation:
Object permanence is the understanding that objects continue to exist even when they are out of sight. At around 8 months old, infants begin to grasp this concept. When Nancy moves Abigail's toys out of her crib, Abigail's search for them demonstrates her newfound awareness that the toys still exist even though she can't see them. This cognitive milestone is crucial in a child's development, marking the beginning of their ability to mentally represent objects in their absence. It enables them to anticipate, search for, and understand the world around them more comprehensively. As Abigail engages in this search, she's actively learning about the permanence of objects, a significant step in her cognitive growth.
Abigail has developed object permanence, which is the understanding that objects exist even when they're out of sight.