At one point, while she's reliving her memories at Hawkins Lab, Eleven has a series of conversations with One in which her English-speaking skills seem to be far more advanced compared to the skills she had when she first met Mike and the gang in season one. At that point in 1983, she communicated in only one or two words at a time.
In an interview with Variety before volume two's release, the Duffer Brothers alluded to the scene in episode eight where Eleven wakes up from her coma with Dr. Brenner at her bedside having no memory of the massacre at Hawkins Lab. Dr. Brenner's obsessive protection caused him to raise her in isolation, which further diminished her speech and socialization skills that fans remember from season one. But even with this background from the creators, Eleven's level of communication remains one of the most consistent inconsistencies throughout "Stranger Things."
