In designing this study, Ainsworth and her colleagues reasoned that if attachment had developed well, infants and toddlers should use their parents as a secure base from which to explore their environments. In addition, when a parent leaves the room for a brief period of time, the child should show separation anxiety, and an unfamiliar adult should be less comforting than the parent. This concept has been supported by studies that measure infants' reactions in the Strange Situation, which closely resemble their use of the parent as a secure base and their response to the separation in the home environment (Blanchard & Main, 1979).