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Before launching into a review article on the research that my students and I have done in my laboratory on the behavioral and physiological effects of exposing rats to various types of stress-producing odors, I think that it is worth mentioning how it was that I first found odor emissions to be an important topic for further scientific investigation. Some time ago, I was doing research in my lab on the phenomenon of "learned helplessness." This research usually involved using the traditional triadic experimental design in which separate groups of rats initially received one of three conditions in a wheel-turn box: escapable shock, yoked-inescapable shock, or no shock. On the next day, these groups were tested in another room to determine how well they could learn an escape response from shock in a shuttlebox that required 5 trials of single crossing followed by 25 trials of two crossings. In some of these studies, but certainly not in all of them, I found the "learned helplessness effect" (LHE) in which the previously yoked group of rats did not learn to escape in the shuttlebox in contrast to good escape learning shown by the escape and the no-shock groups. The question that concerned me, as well as others, was why were the results from such studies so equivocal in terms of demonstrating the LHE? Upon further investigation, I consistently noted that when the odors of previously tested rats were present (often inadvertently) in the shuttlebox, there was a greater chance of demonstrating the LHE. From these exploratory studies, I hypothesized that the odors emitted from previously shocked rats (i.e., con specifics) probably played a significant role in determining the magnitude to which the LHE might be found. Much of the research that I will be describing in this article is derived from the notion that specific odors emitted by various animals, often in combination with the subject's previous experimental history, have a major impact on behaviors that reflect changes in motivational, sensory, and cognitive systems.