Endoself contagion

Contagion here is environmental rather than imitative. Nobody catches endoself behaviour by copying it. What happens is that the routes to primary anima are closed off, and a person who cannot obtain energy through connection has only the other supply left, so the behaviour follows from necessity rather than from influence or corruption. Marsh gives the mechanism at the scale of a single gesture. An altruistic act attempted across an endosocial barrier that the recipient wishes to maintain will be rejected, either by repulsion at the gesture or by an immediate reciprocal action converting the act into trade, which is what happens across endosocial boundaries. That rejection blocks the conduit, and repeated often enough it produces endoself contagion. The implication is that an exosocial person surrounded by endoselves is not safe by virtue of their own disposition. Every attempt at connection is rebuffed or converted, the conduits stay closed and the tendency spreads through a population without anyone intending to spread it. This is also why the framework treats the endoself state as reversible and environmental rather than as a fixed character. If closing the routes produces the behaviour, opening them should reduce it, which is the reasoning behind Marsh's preference for structural remedies over the identification and exclusion of bad individuals.

Social contagion is well documented for behaviours from smoking to obesity to emotional states, following the work of Christakis and Fowler, and the usual mechanisms proposed are imitation, norm shift and homophily. Research on burnout and compassion fatigue in caring professions describes something closer to Marsh's account, in which the environment depletes the capacity rather than transmitting a behaviour. Zimbardo's situationist argument that circumstances produce conduct sits nearby. What Marsh adds is a specific pathway. Her contagion works by the removal of an alternative rather than by transmission of anything, which means the population does not need to influence the newcomer at all for the newcomer to end up behaving like them.