A headgear for placing sensors on a subject's head includes a centerpiece； a plurality of arms attached to and radiating outward and generally downward from the centerpiece； and sensor tips attached to the dorsal ends of at least some of the arms. At least one of the plurality of arms is a lower arm that is elastic and/or spring-like. When the headgear is placed on a subject's head, the at least one lower arm is so disposed in relation to the maximum circumference of the subject's head that the at least one lower arm must be bent outward for placement of the headgear on the subject's head and thereby provide a reactive force toward the head that causes the at least one lower arm to grasp at least a portion of the head that is at and/or below the maximum circumference of the head.
