Graziano and Raulin (8th ed)Graziano & Raulin
Research Methods (8th edition)

Abbreviations

Abbreviations, if used at all in a research report, should be used sparingly. In general, excessive use of abbreviations makes it very hard to read the paper, because the reader is constantly trying to decode the meaning of the abbreviations. 

If abbreviations are used, they should be defined for the reader when first introduced. Abbreviations are defined by placing them in parentheses immediately after the term they represent as shown in the following example.

The reaction time (RT) data were collected automatically for all trials in which the target stimulus appeared.

Although abbreviations should generally be avoided, there are some exceptions to this rule. Abbreviations that are accepted as words by the general public, such as AIDS, ESP, or IQ, are acceptable. Terms that have come into general use by psychologists, such as MMPI, CS, or GABA, are also acceptable. Standard Latin abbreviations, such as e.g., i.e., or vs., can be used without defining them. There are also several standard scientific definitions that should be used routinely, such as ms for millisecond or or Hz for hertz. Other than these exceptions, it is best to avoid using abbreviations in your research papers.