Final answer:
An infant who does not show distress when a caregiver leaves and does not seek interaction upon the caregiver's return is said to have an avoidant attachment style.
Step-by-step explanation:
Research on attachment using Mary Ainsworth's Strange Situation has identified different types of attachment styles between infants and their caregivers. The situation you are describing, where an infant is generally not distressed when the caregiver leaves and does not acknowledge the caregiver upon return, is indicative of an avoidant attachment style. This type of attachment is characterized by the child's unresponsiveness to the parent, lack of use of the parent as a secure base, and little to no preference between the parent and a stranger. It is theorized to result from having a caregiver who is insensitive and inattentive to the infant's needs.