After reading the description of Alana's reactions to her brother hiding under a blanket, we can say that the developmental concept being illustrated is:
Object permanence.
- Object permanence refers to a child's ability to understand that an object continues to exist even if it cannot be seen.
- Young children often cry when we hide a toy, for example, under a blanket. That happens when object permanence has not developed yet.
- As they grow older, children begin to understand that an object's disappearance does not mean it does not exist any longer.
Learn more about the topic here:
https://brainly.com/question/25097828