The article retraces the shifting conceptualizations of psychological trauma in experimental psychopathological research in the middle decades of the twentieth century in the United States. Among researchers studying so-called experimental neuroses in animal laboratories, trauma was an often-invoked category used to denote the clash of conflicting forces believed to lead to neurotic suffering. Experimental psychologists, however, soon grew skeptical of the traumatogenic model and ultimately came to reject neurosis as a disease entity. Both theoretical differences and practical circumstances, such as the technical challenge of stabilizing neurotic symptoms in rats, led to this demise. Yet, despite their reservations, experimental psychologists continued to employ traumatic stimuli to produce psychopathological syndromes. In the 1960s, a new understanding of trauma evolved, which emphasized the loss of control experienced by traumatized animal subjects. These shifting ideas about trauma, I argue, reflect both varying experimental cultures, epistemic norms as well as changing societal concerns.