The history of Atlantic Migration has provided scholars with exhaustive source material for examining the emergence, maturation, peak and decline of large-scale migration systems. As such, it has been fundamental in allowing theories of migration to be explored, codified, and tested. Alongside the long-term migration systems that developed between Europe and the Americas, Atlantic migration history is also replete with anomalous events – migration ‘fevers’ sitting somewhat outside of well described norms in migratory dynamics. Such events are further opportunity for historians to examine the processes that have driven human mobility. This paper examines the behavioural dynamics of two well documented and historically significant emigration ‘fevers’ between central Europe and North America during the 18th and 19th centuries, subjecting available migrant testimony to the behaviours described by prospect theory and cascade effects. It finds the risk-seeking behaviour described by prospect theory to be both a compelling pre-condition for these migration events, and a fertile condition for subsequent cascade effects, creating a social dynamic of ‘irrational’ migration. In doing so, it hopes to provide a testable framework for understanding why and how these short-lived migration episodes acquired the force that they did, whilst also exploring the broader applicability, especially of prospect theory, to accepted decision-making structures in migration analysis.