Final answer:
The question pertains to resistant attachment in psychology, where the child displays sullenness and sadness during reunion with the mother, indicative of an inconsistent caregiving environment.
Step-by-step explanation:
The type of attachment where a child is sullen and sad during a reunion with their mother after a separation suggests the presence of resistant attachment. Developed from the work of Ainsworth and Bell, resistant attachment is characterized by clingy behavior during the parent's presence, followed by rejection of the parent upon interaction attempts, usually due to the caregivers' inconsistent response levels to their child. During a reunion, these children can be difficult to comfort and may exhibit anger or indifference towards the caregiver.
Children with avoidant attachment appear unresponsive to the parent and do not use the parent as a secure base. In contrast, children with disorganized attachment may display confused or odd behaviors upon a caregiver's return, which is often linked to past abuse or trauma. On the healthier spectrum is secure attachment, where the child is happy to see the parent during the reunion and uses them as a secure base.