The 'Batman Effect': How having an alter ego empowers you (2020)
The definitive book on this is ‘The Alter Ego Effect’ by Todd Herman (there’s also a bunch of extra resources on his website https://alteregoeffect.com )He goes into great detail about the method and the science of what’s happening in your brain when you use it.It’s helped me go from  introverted engineer to successful start-up founder that just exited.