How to test the threat-simulation theory

Malcolm-Smith, Solms, Turnbull and Tredoux [Malcolm-Smith, S., Solms, M.,Turnbull, O., & Tredoux, C. (2008). Threat in dreams: An adaptation? Consciousness and Cognition, 17, 1281-1291.] have made an attempt to test the Threat-Simulation Theory (TST), a theory offering an evolutionary psychological explanation for the function of dreaming [Revonsuo, A. (2000a). The reinterpretation of dreams: An evolutionary hypothesis of the function of dreaming. Behavioral and Brain Sciences, 23(6), 877-901]. Malcolm-Smith et al. argue that empirical evidence from their own study as well as from some other studies in the literature does not support the main predictions of the TST: that threatening events are frequent and overrepresented in dreams, that exposure to real threats activates the threat-simulation system, and that dream threats contain realistic rehearsals of threat avoidance responses. Other studies, including our own, have come up with results and conclusions that are in conflict with those of Malcolm-Smith et al. In this commentary, we provide an analysis of the sources of these disagreements, and their implications to the TST. Much of the disagreement seems to stem from differing interpretations of the theory and, consequently, of differing methods to test it.