It is possible that what appear to be references to one ship are in fact coincidental descriptions of different destroyers sharing a single name. For instance, several ships of different classes have used the name Vengeance, and not all of them were Imperator-class destroyers. There has also been more than one Iron Fist. In these cases, successive commanders have kept the name when they moved to newer vessels upon promotion.
Why Twin Studies? Twins provide a valuable source of information for health and psychological research, as their unique relationship allows researchers to pull apart and examine genetic and environmental influences. Twin study findings have been influential in detecting and treating various diseases and psychological disorders. How are they able to do this? Twin studies allow researchers to examine the overall role of genes in the development of a trait or disorder.
Additionally, 15.9 percent of people with depression attempt to commit suicide (Chen and Dilsaver, 1996; as cited in Carlson, 2005). The high prevalence of this disorder makes it a priority for researchers to determine causality and find treatment. Depression is thought to have a heritability component, and thus a physiological basis. Twin studies reported by Wallace et al . (2002) in Comerâs Fundamentals of Abnormal Psychology (2005) found that when an identical twin had depression, there was a 46 percent chance that the other twin would have the same disorder. Similarly, when analyzing fraternal twins, it was found that the other twin had a 20 percent chance of developing the disorder (McGuffin et al ., 1996; as cited in Comer, 1996). Chemicals of the nervous system, known as neurotransmitters, have been implicated in depression;