Final answer:
Cosette's distress when separated from her father suggests she is experiencing normal 'stranger anxiety' in line with developmental milestones, not an avoidant attachment behavior as described by Ainsworth.
Step-by-step explanation:
The changes in behavior that Wyatt has noticed in his 10-month-old daughter, Cosette, following her development of crawling skills, can be linked to various attachment styles and developmental milestones described by researchers in developmental psychology like Mary Ainsworth and Jean Piaget. For instance, Cosette's distress when Wyatt leaves her with a babysitter likely illustrates the concept of stranger anxiety, which often coincides with the development of object permanence—understanding that objects (and people) continue to exist even when they're not visible. This is a sign of a typical developmental stage rather than an avoidant attachment style. In the case of avoidant attachment, the child typically would not exhibit distress upon the caregiver's departure. Instead, it's more characteristic of such infants to show little to no preference between a caregiver and a stranger, which is not what is described in the question.