A surface level explanation of psychoneuroimmunology, a discipline that looks at the connection between the immune system and social behavior. Through a study in rats in the 1970s, it was discovered that an immune response could be manipulated and conditioned. Specifically, a particular molecule that is activated in response to a pathogen attack, however in a number of animals, the molecule is also activated when they engage in social behavior. The findings could point to a connection between immune system deficiency and diagnosable social disorders, though at this point the full extent of these connections are unknown.