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.
Twin Observations: What Psychology Can Learn from Twins They're mirror images, but twins can be astoundingly different. How twins have helped psychology address the nature vs. nurture debate. Despite obvious similarities, their differences can be astounding: One twin is right-handed, and the other is a lefty. One is outgoing, and the other is reserved. Some of the differences are apparent early in age, whereas others develop over time as genes and the environment interact.