All bonds are not alike: A psychoendocrine evaluation of infant attachment.

Characteristics of attachment were assessed in peer- and object-reared lambs, and compared to mothered subjects by taking into consideration distress, proximity seeking, and exploration during two separation-reunion tests in both the familiar and a novel environment. Plasma cortisol and oxytocin were assayed as physiological indicators of stress and being comforted during the separation-reunion test. Rewarding properties of the familiar figures were also determined in a conditioned place preference-like paradigm.