There are several reasons why we may forget information. Encoding failure occurs when information is not properly encoded into long-term memory in the first place, such as when our attention shifts away during encoding. Motivated forgetting is when we actively work to forget traumatic or disturbing memories through unconscious repression or conscious suppression. According to decay theory, memory traces fade over time if the information is not rehearsed or remembered. Interference theory suggests that similar memories can compete with and interfere with each other, making some memories harder to recall.