A comparative approach to the behavior called "learned helplessness'.

The phenomenon of 'learned helplessness' is seen broadly across the animal kingdom. The basic characteristics of this behavior are similar in intact mammals, lower vertebrates and invertebrates. In fact, the basic characteristics even are seen in an isolated thoracic ganglion of an insect. The brain is evidently not essential either in mammals or in invertebrates for demonstrating this behavior. A neutral terminology is suggested that allows for investigation of this behavior and its underlying mechanisms in both intact and surgically simplified preparations of both vertebrates and invertebrates. Thus, its phylogeny can be investigated. In addition, simpler systems such as the insect ventral nerve cord with its large neurons and its ease of pharmacological manipulation may have important contributions to make to understanding the neuropharmacology underlying it. The ubiquity of the phenomenon in different phyla suggests that while in the laboratory it may appear maladaptive, this may not necessarily be the case in a natural ecological context. Because of increasing governmental regulations in both Europe and the US on mammalian studies involving shock and distress, such as that associated with 'learned helplessness', it may be prudent to consider other systems that may offer insight into its underlying mechanisms.