The simplest definition of narcissism is “narrow or reduced interpretation(s) of psychological signs.”
This is a functional definition that provides insight into a wide range of human psychological reactions.
A broad example of psychological narcissism using the above definition is alcoholism which reduces sign interpretation due both to inebriation and toxicity.
Notice this definition does not presuppose anything psychological about the alcoholic. Alcoholism reduces sign interpretation due to the chemical properties of ethanol.
Alcoholism damages and simplifies the brain’s capacity to entertain multiple interpretations of signs. This is the core reason why so many alcoholics display narcissistic behaviors.
Somewhat similarly, small children can be functionally “narcissistic” because their brains are not developed. Like an alcoholic on the other side of life, a small child simply does not have the brain complexity to entertain multiple interpretations.
Narcissism is a simple and very basic operating system. This is why it is a normal option for both undeveloped and alcoholic brains.
The cure for narcissism is help the narcissist see multiple interpretations.
I believe that most if not all psychological analyses of individuals should be applicable to groups of people and vice versa.
Thus, a group with a reduced interpretation of signs will probably be a narcissistic group.
Groups that insist on a single interpretation of the past or the present are examples of this.