Let us now pause and dwell on what Harvard University has to say regarding the subject matter:

“I tried finding out if there’s such a 75-year longitudinal study correlating success in life with childhood chores.

Answer: Yes — but it’s not a single “Harvard chores study”. The claim comes from 2 different Harvard-affiliated sources that get mixed up:

1. The Harvard Study of Adult Development / Grant Study

This is the 80+ year longitudinal study people usually mean.