Panglossian

Optimism is a mental attitude—a happy belief that the outcome of some specific endeavor, or outcomes in general, will be good. A common idiom used to illustrate optimism versus pessimism is a glass with water at the halfway point, where the optimist is said to see the glass as half full and the pessimist sees the glass as half empty.

The term derives from the Latin optimum, meaning "best". Being optimistic, in the typical sense of the word, is defined as expecting the best possible outcome from any given situation. This is usually referred to in psychology as dispositional optimism. It thus reflects a belief that future conditions will work out for the best.

Theories of optimism include dispositional models, and models of explanatory style. Methods to measure optimism have been developed within both theoretical systems, such as various forms of the Life Orientation Test, for the original definition of optimism, or the Attributional Style Questionnaire designed to test optimism in terms of explanatory style.

Variation in optimism and pessimism is somewhat heritable and reflects biological trait systems to some degree. It is also influenced by environmental factors, including family environment, with some suggesting it can be learned. Optimism may also be linked to health.

Researchers operationalize the term differently depending on their research. As with any trait characteristic, there are several ways to evaluate optimism, such as the Life Orientation Test (LOT).

Dispositional optimism and pessimism are typically assessed by asking people whether they expect future outcomes to be beneficial or negative (see below). The LOT returns separate optimism and pessimism scores for each individual. Behaviourally, these two scores correlate around r = 0.5. Optimistic scores on this scale predict better outcomes in relationships, higher social status, and reduced loss of well-being following adversity. Health preserving behaviors are associated with optimism while health-damaging behaviors are associated with pessimism.

...
Wikipedia