there is no widely recognized psychological concept or term called "Default mood." It's possible that new terms or concepts may have emerged or that "Default mood" is specific to certain fields or subcultures.
However, in psychology, there are related concepts such as "baseline mood" or "baseline emotional state," which refer to an individual's typical or average emotional state in the absence of specific stimuli or events. This baseline mood can vary from person to person and can be influenced by factors such as personality, genetics, life experiences, and mental health.
If "Default mood" has gained significance or popularity , I would not be aware of it. I recommend checking more recent sources or consulting with a mental health professional or psychologist for the latest information on this topic.