Mnemonic
Martha is studying the chapter on personality for her psychology exam. In order to make it easier to remembering the Big Five traits (openness, conscientiousness, extroversion, agreeableness, and neuroticism) she uses the first letter of each trait to spell "OCEAN." Martha is using a(n) device.

The correct answer is : mnemonic

Explanation:

It refers to a learning technique or method that a person uses in order to retain important information in human memory. The memorization process allows associating ideas easier. This visual or auditory aid helps an individual to recall something in a much better way. It is also used to make a shortcut when presenting the information.