Final answer:
Baby Joseph is demonstrating an avoidant attachment pattern, which is characterized by a lack of responsiveness to the parent, minimal distress upon separation, and indifference upon reunion.
Step-by-step explanation:
Based on the behaviors described, Baby Joseph is displaying an avoidant attachment pattern during the Strange Situation. In this attachment style, children seem unresponsive to their parent before the parent leaves and are not particularly bothered when the parent departs. Joseph's engagement with the stranger, along with his lack of a positive reaction when his mother returns, supports this attachment pattern. Avoidant attachment tends to develop with caregivers who are insensitive or unattentive to the child's needs, as theorized by Ainsworth.